diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/Kconfig | 13 | ||||
| -rw-r--r-- | drivers/lguest/Makefile | 10 | ||||
| -rw-r--r-- | drivers/lguest/core.c | 573 | ||||
| -rw-r--r-- | drivers/lguest/hypercalls.c | 186 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 160 | ||||
| -rw-r--r-- | drivers/lguest/io.c | 626 | ||||
| -rw-r--r-- | drivers/lguest/lg.h | 194 | ||||
| -rw-r--r-- | drivers/lguest/lguest.c | 1108 | ||||
| -rw-r--r-- | drivers/lguest/lguest_asm.S | 93 | ||||
| -rw-r--r-- | drivers/lguest/lguest_bus.c | 218 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 376 | ||||
| -rw-r--r-- | drivers/lguest/lguest_user.c | 161 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 361 | ||||
| -rw-r--r-- | drivers/lguest/segments.c | 76 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 581 | ||||
| -rw-r--r-- | drivers/lguest/x86/switcher_32.S (renamed from drivers/lguest/switcher.S) | 78 |
16 files changed, 1601 insertions, 3213 deletions
diff --git a/drivers/lguest/Kconfig b/drivers/lguest/Kconfig index 41e2250613a1..7eb9ecff8f4a 100644 --- a/drivers/lguest/Kconfig +++ b/drivers/lguest/Kconfig @@ -1,7 +1,6 @@ config LGUEST tristate "Linux hypervisor example code" - depends on X86 && PARAVIRT && EXPERIMENTAL && !X86_PAE && FUTEX - select LGUEST_GUEST + depends on X86_32 && EXPERIMENTAL && !X86_PAE && FUTEX && !(X86_VISWS || X86_VOYAGER) select HVC_DRIVER ---help--- This is a very simple module which allows you to run @@ -18,13 +17,3 @@ config LGUEST_GUEST The guest needs code built-in, even if the host has lguest support as a module. The drivers are tiny, so we build them in too. - -config LGUEST_NET - tristate - default y - depends on LGUEST_GUEST && NET - -config LGUEST_BLOCK - tristate - default y - depends on LGUEST_GUEST && BLOCK diff --git a/drivers/lguest/Makefile b/drivers/lguest/Makefile index e5047471c334..5e8272d296d8 100644 --- a/drivers/lguest/Makefile +++ b/drivers/lguest/Makefile @@ -1,10 +1,12 @@ -# Guest requires the paravirt_ops replacement and the bus driver. -obj-$(CONFIG_LGUEST_GUEST) += lguest.o lguest_asm.o lguest_bus.o +# Guest requires the device configuration and probing code. +obj-$(CONFIG_LGUEST_GUEST) += lguest_device.o # Host requires the other files, which can be a module. obj-$(CONFIG_LGUEST) += lg.o -lg-y := core.o hypercalls.o page_tables.o interrupts_and_traps.o \ - segments.o io.o lguest_user.o switcher.o +lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \ + segments.o lguest_user.o + +lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o Preparation Preparation!: PREFIX=P Guest: PREFIX=G diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index a0788c12b392..cb4c67025d52 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -11,58 +11,20 @@ #include <linux/vmalloc.h> #include <linux/cpu.h> #include <linux/freezer.h> +#include <linux/highmem.h> #include <asm/paravirt.h> -#include <asm/desc.h> #include <asm/pgtable.h> #include <asm/uaccess.h> #include <asm/poll.h> -#include <asm/highmem.h> #include <asm/asm-offsets.h> -#include <asm/i387.h> #include "lg.h" -/* Found in switcher.S */ -extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; -extern unsigned long default_idt_entries[]; - -/* Every guest maps the core switcher code. */ -#define SHARED_SWITCHER_PAGES \ - DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE) -/* Pages for switcher itself, then two pages per cpu */ -#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS) - -/* We map at -4M for ease of mapping into the guest (one PTE page). */ -#define SWITCHER_ADDR 0xFFC00000 static struct vm_struct *switcher_vma; static struct page **switcher_page; -static int cpu_had_pge; -static struct { - unsigned long offset; - unsigned short segment; -} lguest_entry; - /* This One Big lock protects all inter-guest data structures. */ DEFINE_MUTEX(lguest_lock); -static DEFINE_PER_CPU(struct lguest *, last_guest); - -/* FIXME: Make dynamic. */ -#define MAX_LGUEST_GUESTS 16 -struct lguest lguests[MAX_LGUEST_GUESTS]; - -/* Offset from where switcher.S was compiled to where we've copied it */ -static unsigned long switcher_offset(void) -{ - return SWITCHER_ADDR - (unsigned long)start_switcher_text; -} - -/* This cpu's struct lguest_pages. */ -static struct lguest_pages *lguest_pages(unsigned int cpu) -{ - return &(((struct lguest_pages *) - (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]); -} /*H:010 We need to set up the Switcher at a high virtual address. Remember the * Switcher is a few hundred bytes of assembler code which actually changes the @@ -73,9 +35,7 @@ static struct lguest_pages *lguest_pages(unsigned int cpu) * Host since it will be running as the switchover occurs. * * Trying to map memory at a particular address is an unusual thing to do, so - * it's not a simple one-liner. We also set up the per-cpu parts of the - * Switcher here. - */ + * it's not a simple one-liner. */ static __init int map_switcher(void) { int i, err; @@ -132,90 +92,11 @@ static __init int map_switcher(void) goto free_vma; } - /* Now the switcher is mapped at the right address, we can't fail! - * Copy in the compiled-in Switcher code (from switcher.S). */ + /* Now the Switcher is mapped at the right address, we can't fail! + * Copy in the compiled-in Switcher code (from <arch>_switcher.S). */ memcpy(switcher_vma->addr, start_switcher_text, end_switcher_text - start_switcher_text); - /* Most of the switcher.S doesn't care that it's been moved; on Intel, - * jumps are relative, and it doesn't access any references to external - * code or data. - * - * The only exception is the interrupt handlers in switcher.S: their - * addresses are placed in a table (default_idt_entries), so we need to - * update the table with the new addresses. switcher_offset() is a - * convenience function which returns the distance between the builtin - * switcher code and the high-mapped copy we just made. */ - for (i = 0; i < IDT_ENTRIES; i++) - default_idt_entries[i] += switcher_offset(); - - /* - * Set up the Switcher's per-cpu areas. - * - * Each CPU gets two pages of its own within the high-mapped region - * (aka. "struct lguest_pages"). Much of this can be initialized now, - * but some depends on what Guest we are running (which is set up in - * copy_in_guest_info()). - */ - for_each_possible_cpu(i) { - /* lguest_pages() returns this CPU's two pages. */ - struct lguest_pages *pages = lguest_pages(i); - /* This is a convenience pointer to make the code fit one - * statement to a line. */ - struct lguest_ro_state *state = &pages->state; - - /* The Global Descriptor Table: the Host has a different one - * for each CPU. We keep a descriptor for the GDT which says - * where it is and how big it is (the size is actually the last - * byte, not the size, hence the "-1"). */ - state->host_gdt_desc.size = GDT_SIZE-1; - state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); - - /* All CPUs on the Host use the same Interrupt Descriptor - * Table, so we just use store_idt(), which gets this CPU's IDT - * descriptor. */ - store_idt(&state->host_idt_desc); - - /* The descriptors for the Guest's GDT and IDT can be filled - * out now, too. We copy the GDT & IDT into ->guest_gdt and - * ->guest_idt before actually running the Guest. */ - state->guest_idt_desc.size = sizeof(state->guest_idt)-1; - state->guest_idt_desc.address = (long)&state->guest_idt; - state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; - state->guest_gdt_desc.address = (long)&state->guest_gdt; - - /* We know where we want the stack to be when the Guest enters - * the switcher: in pages->regs. The stack grows upwards, so - * we start it at the end of that structure. */ - state->guest_tss.esp0 = (long)(&pages->regs + 1); - /* And this is the GDT entry to use for the stack: we keep a - * couple of special LGUEST entries. */ - state->guest_tss.ss0 = LGUEST_DS; - - /* x86 can have a finegrained bitmap which indicates what I/O - * ports the process can use. We set it to the end of our - * structure, meaning "none". */ - state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); - - /* Some GDT entries are the same across all Guests, so we can - * set them up now. */ - setup_default_gdt_entries(state); - /* Most IDT entries are the same for all Guests, too.*/ - setup_default_idt_entries(state, default_idt_entries); - - /* The Host needs to be able to use the LGUEST segments on this - * CPU, too, so put them in the Host GDT. */ - get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; - get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; - } - - /* In the Switcher, we want the %cs segment register to use the - * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so - * it will be undisturbed when we switch. To change %cs and jump we - * need this structure to feed to Intel's "lcall" instruction. */ - lguest_entry.offset = (long)switch_to_guest + switcher_offset(); - lguest_entry.segment = LGUEST_CS; - printk(KERN_INFO "lguest: mapped switcher at %p\n", switcher_vma->addr); /* And we succeeded... */ @@ -247,86 +128,15 @@ static void unmap_switcher(void) __free_pages(switcher_page[i], 0); } -/*H:130 Our Guest is usually so well behaved; it never tries to do things it - * isn't allowed to. Unfortunately, Linux's paravirtual infrastructure isn't - * quite complete, because it doesn't contain replacements for the Intel I/O - * instructions. As a result, the Guest sometimes fumbles across one during - * the boot process as it probes for various things which are usually attached - * to a PC. - * - * When the Guest uses one of these instructions, we get trap #13 (General - * Protection Fault) and come here. We see if it's one of those troublesome - * instructions and skip over it. We return true if we did. */ -static int emulate_insn(struct lguest *lg) -{ - u8 insn; - unsigned int insnlen = 0, in = 0, shift = 0; - /* The eip contains the *virtual* address of the Guest's instruction: - * guest_pa just subtracts the Guest's page_offset. */ - unsigned long physaddr = guest_pa(lg, lg->regs->eip); - - /* The guest_pa() function only works for Guest kernel addresses, but - * that's all we're trying to do anyway. */ - if (lg->regs->eip < lg->page_offset) - return 0; - - /* Decoding x86 instructions is icky. */ - lgread(lg, &insn, physaddr, 1); - - /* 0x66 is an "operand prefix". It means it's using the upper 16 bits - of the eax register. */ - if (insn == 0x66) { - shift = 16; - /* The instruction is 1 byte so far, read the next byte. */ - insnlen = 1; - lgread(lg, &insn, physaddr + insnlen, 1); - } - - /* We can ignore the lower bit for the moment and decode the 4 opcodes - * we need to emulate. */ - switch (insn & 0xFE) { - case 0xE4: /* in <next byte>,%al */ - insnlen += 2; - in = 1; - break; - case 0xEC: /* in (%dx),%al */ - insnlen += 1; - in = 1; - break; - case 0xE6: /* out %al,<next byte> */ - insnlen += 2; - break; - case 0xEE: /* out %al,(%dx) */ - insnlen += 1; - break; - default: - /* OK, we don't know what this is, can't emulate. */ - return 0; - } - - /* If it was an "IN" instruction, they expect the result to be read - * into %eax, so we change %eax. We always return all-ones, which - * traditionally means "there's nothing there". */ - if (in) { - /* Lower bit tells is whether it's a 16 or 32 bit access */ - if (insn & 0x1) - lg->regs->eax = 0xFFFFFFFF; - else - lg->regs->eax |= (0xFFFF << shift); - } - /* Finally, we've "done" the instruction, so move past it. */ - lg->regs->eip += insnlen; - /* Success! */ - return 1; -} -/*:*/ - -/*L:305 +/*H:032 * Dealing With Guest Memory. * + * Before we go too much further into the Host, we need to grok the routines + * we use to deal with Guest memory. + * * When the Guest gives us (what it thinks is) a physical address, we can use - * the normal copy_from_user() & copy_to_user() on that address: remember, - * Guest physical == Launcher virtual. + * the normal copy_from_user() & copy_to_user() on the corresponding place in + * the memory region allocated by the Launcher. * * But we can't trust the Guest: it might be trying to access the Launcher * code. We have to check that the range is below the pfn_limit the Launcher @@ -338,148 +148,27 @@ int lguest_address_ok(const struct lguest *lg, return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); } -/* This is a convenient routine to get a 32-bit value from the Guest (a very - * common operation). Here we can see how useful the kill_lguest() routine we - * met in the Launcher can be: we return a random value (0) instead of needing - * to return an error. */ -u32 lgread_u32(struct lguest *lg, unsigned long addr) -{ - u32 val = 0; - - /* Don't let them access lguest binary. */ - if (!lguest_address_ok(lg, addr, sizeof(val)) - || get_user(val, (u32 __user *)addr) != 0) - kill_guest(lg, "bad read address %#lx", addr); - return val; -} - -/* Same thing for writing a value. */ -void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val) -{ - if (!lguest_address_ok(lg, addr, sizeof(val)) - || put_user(val, (u32 __user *)addr) != 0) - kill_guest(lg, "bad write address %#lx", addr); -} - -/* This routine is more generic, and copies a range of Guest bytes into a - * buffer. If the copy_from_user() fails, we fill the buffer with zeroes, so - * the caller doesn't end up using uninitialized kernel memory. */ -void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes) +/* This routine copies memory from the Guest. Here we can see how useful the + * kill_lguest() routine we met in the Launcher can be: we return a random + * value (all zeroes) instead of needing to return an error. */ +void __lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) - || copy_from_user(b, (void __user *)addr, bytes) != 0) { + || copy_from_user(b, lg->mem_base + addr, bytes) != 0) { /* copy_from_user should do this, but as we rely on it... */ memset(b, 0, bytes); kill_guest(lg, "bad read address %#lx len %u", addr, bytes); } } -/* Similarly, our generic routine to copy into a range of Guest bytes. */ -void lgwrite(struct lguest *lg, unsigned long addr, const void *b, - unsigned bytes) +/* This is the write (copy into guest) version. */ +void __lgwrite(struct lguest *lg, unsigned long addr, const void *b, + unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) - || copy_to_user((void __user *)addr, b, bytes) != 0) + || copy_to_user(lg->mem_base + addr, b, bytes) != 0) kill_guest(lg, "bad write address %#lx len %u", addr, bytes); } -/* (end of memory access helper routines) :*/ - -static void set_ts(void) -{ - u32 cr0; - - cr0 = read_cr0(); - if (!(cr0 & 8)) - write_cr0(cr0|8); -} - -/*S:010 - * We are getting close to the Switcher. - * - * Remember that each CPU has two pages which are visible to the Guest when it - * runs on that CPU. This has to contain the state for that Guest: we copy the - * state in just before we run the Guest. - * - * Each Guest has "changed" flags which indicate what has changed in the Guest - * since it last ran. We saw this set in interrupts_and_traps.c and - * segments.c. - */ -static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages) -{ - /* Copying all this data can be quite expensive. We usually run the - * same Guest we ran last time (and that Guest hasn't run anywhere else - * meanwhile). If that's not the case, we pretend everything in the - * Guest has changed. */ - if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) { - __get_cpu_var(last_guest) = lg; - lg->last_pages = pages; - lg->changed = CHANGED_ALL; - } - - /* These copies are pretty cheap, so we do them unconditionally: */ - /* Save the current Host top-level page directory. */ - pages->state.host_cr3 = __pa(current->mm->pgd); - /* Set up the Guest's page tables to see this CPU's pages (and no - * other CPU's pages). */ - map_switcher_in_guest(lg, pages); - /* Set up the two "TSS" members which tell the CPU what stack to use - * for traps which do directly into the Guest (ie. traps at privilege - * level 1). */ - pages->state.guest_tss.esp1 = lg->esp1; - pages->state.guest_tss.ss1 = lg->ss1; - - /* Copy direct-to-Guest trap entries. */ - if (lg->changed & CHANGED_IDT) - copy_traps(lg, pages->state.guest_idt, default_idt_entries); - - /* Copy all GDT entries which the Guest can change. */ - if (lg->changed & CHANGED_GDT) - copy_gdt(lg, pages->state.guest_gdt); - /* If only the TLS entries have changed, copy them. */ - else if (lg->changed & CHANGED_GDT_TLS) - copy_gdt_tls(lg, pages->state.guest_gdt); - - /* Mark the Guest as unchanged for next time. */ - lg->changed = 0; -} - -/* Finally: the code to actually call into the Switcher to run the Guest. */ -static void run_guest_once(struct lguest *lg, struct lguest_pages *pages) -{ - /* This is a dummy value we need for GCC's sake. */ - unsigned int clobber; - - /* Copy the guest-specific information into this CPU's "struct - * lguest_pages". */ - copy_in_guest_info(lg, pages); - - /* Set the trap number to 256 (impossible value). If we fault while - * switching to the Guest (bad segment registers or bug), this will - * cause us to abort the Guest. */ - lg->regs->trapnum = 256; - - /* Now: we push the "eflags" register on the stack, then do an "lcall". - * This is how we change from using the kernel code segment to using - * the dedicated lguest code segment, as well as jumping into the - * Switcher. - * - * The lcall also pushes the old code segment (KERNEL_CS) onto the - * stack, then the address of this call. This stack layout happens to - * exactly match the stack of an interrupt... */ - asm volatile("pushf; lcall *lguest_entry" - /* This is how we tell GCC that %eax ("a") and %ebx ("b") - * are changed by this routine. The "=" means output. */ - : "=a"(clobber), "=b"(clobber) - /* %eax contains the pages pointer. ("0" refers to the - * 0-th argument above, ie "a"). %ebx contains the - * physical address of the Guest's top-level page - * directory. */ - : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir)) - /* We tell gcc that all these registers could change, - * which means we don't have to save and restore them in - * the Switcher. */ - : "memory", "%edx", "%ecx", "%edi", "%esi"); -} /*:*/ /*H:030 Let's jump straight to the the main loop which runs the Guest. @@ -489,22 +178,16 @@ int run_guest(struct lguest *lg, unsigned long __user *user) { /* We stop running once the Guest is dead. */ while (!lg->dead) { - /* We need to initialize this, otherwise gcc complains. It's - * not (yet) clever enough to see that it's initialized when we - * need it. */ - unsigned int cr2 = 0; /* Damn gcc */ - - /* First we run any hypercalls the Guest wants done: either in - * the hypercall ring in "struct lguest_data", or directly by - * using int 31 (LGUEST_TRAP_ENTRY). */ - do_hypercalls(lg); - /* It's possible the Guest did a SEND_DMA hypercall to the + /* First we run any hypercalls the Guest wants done. */ + if (lg->hcall) + do_hypercalls(lg); + + /* It's possible the Guest did a NOTIFY hypercall to the * Launcher, in which case we return from the read() now. */ - if (lg->dma_is_pending) { - if (put_user(lg->pending_dma, user) || - put_user(lg->pending_key, user+1)) + if (lg->pending_notify) { + if (put_user(lg->pending_notify, user)) return -EFAULT; - return sizeof(unsigned long)*2; + return sizeof(lg->pending_notify); } /* Check for signals */ @@ -542,144 +225,20 @@ int run_guest(struct lguest *lg, unsigned long __user *user) * the "Do Not Disturb" sign: */ local_irq_disable(); - /* Remember the awfully-named TS bit? If the Guest has asked - * to set it we set it now, so we can trap and pass that trap - * to the Guest if it uses the FPU. */ - if (lg->ts) - set_ts(); - - /* SYSENTER is an optimized way of doing system calls. We - * can't allow it because it always jumps to privilege level 0. - * A normal Guest won't try it because we don't advertise it in - * CPUID, but a malicious Guest (or malicious Guest userspace - * program) could, so we tell the CPU to disable it before - * running the Guest. */ - if (boot_cpu_has(X86_FEATURE_SEP)) - wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); - - /* Now we actually run the Guest. It will pop back out when - * something interesting happens, and we can examine its - * registers to see what it was doing. */ - run_guest_once(lg, lguest_pages(raw_smp_processor_id())); - - /* The "regs" pointer contains two extra entries which are not - * really registers: a trap number which says what interrupt or - * trap made the switcher code come back, and an error code - * which some traps set. */ - - /* If the Guest page faulted, then the cr2 register will tell - * us the bad virtual address. We have to grab this now, - * because once we re-enable interrupts an interrupt could - * fault and thus overwrite cr2, or we could even move off to a - * different CPU. */ - if (lg->regs->trapnum == 14) - cr2 = read_cr2(); - /* Similarly, if we took a trap because the Guest used the FPU, - * we have to restore the FPU it expects to see. */ - else if (lg->regs->trapnum == 7) - math_state_restore(); - - /* Restore SYSENTER if it's supposed to be on. */ - if (boot_cpu_has(X86_FEATURE_SEP)) - wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); + /* Actually run the Guest until something happens. */ + lguest_arch_run_guest(lg); /* Now we're ready to be interrupted or moved to other CPUs */ local_irq_enable(); - /* OK, so what happened? */ - switch (lg->regs->trapnum) { - case 13: /* We've intercepted a GPF. */ - /* Check if this was one of those annoying IN or OUT - * instructions which we need to emulate. If so, we - * just go back into the Guest after we've done it. */ - if (lg->regs->errcode == 0) { - if (emulate_insn(lg)) - continue; - } - break; - case 14: /* We've intercepted a page fault. */ - /* The Guest accessed a virtual address that wasn't - * mapped. This happens a lot: we don't actually set - * up most of the page tables for the Guest at all when - * we start: as it runs it asks for more and more, and - * we set them up as required. In this case, we don't - * even tell the Guest that the fault happened. - * - * The errcode tells whether this was a read or a - * write, and whether kernel or userspace code. */ - if (demand_page(lg, cr2, lg->regs->errcode)) - continue; - - /* OK, it's really not there (or not OK): the Guest - * needs to know. We write out the cr2 value so it - * knows where the fault occurred. - * - * Note that if the Guest were really messed up, this - * could happen before it's done the INITIALIZE - * hypercall, so lg->lguest_data will be NULL, so - * &lg->lguest_data->cr2 will be address 8. Writing - * into that address won't hurt the Host at all, - * though. */ - if (put_user(cr2, &lg->lguest_data->cr2)) - kill_guest(lg, "Writing cr2"); - break; - case 7: /* We've intercepted a Device Not Available fault. */ - /* If the Guest doesn't want to know, we already - * restored the Floating Point Unit, so we just - * continue without telling it. */ - if (!lg->ts) - continue; - break; - case 32 ... 255: - /* These values mean a real interrupt occurred, in - * which case the Host handler has already been run. - * We just do a friendly check if another process - * should now be run, then fall through to loop - * around: */ - cond_resched(); - case LGUEST_TRAP_ENTRY: /* Handled at top of loop */ - continue; - } - - /* If we get here, it's a trap the Guest wants to know - * about. */ - if (deliver_trap(lg, lg->regs->trapnum)) - continue; - - /* If the Guest doesn't have a handler (either it hasn't - * registered any yet, or it's one of the faults we don't let - * it handle), it dies with a cryptic error message. */ - kill_guest(lg, "unhandled trap %li at %#lx (%#lx)", - lg->regs->trapnum, lg->regs->eip, - lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode); + /* Now we deal with whatever happened to the Guest. */ + lguest_arch_handle_trap(lg); } + /* The Guest is dead => "No such file or directory" */ return -ENOENT; } -/* Now we can look at each of the routines this calls, in increasing order of - * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(), - * deliver_trap() and demand_page(). After all those, we'll be ready to - * examine the Switcher, and our philosophical understanding of the Host/Guest - * duality will be complete. :*/ - -int find_free_guest(void) -{ - unsigned int i; - for (i = 0; i < MAX_LGUEST_GUESTS; i++) - if (!lguests[i].tsk) - return i; - return -1; -} - -static void adjust_pge(void *on) -{ - if (on) - write_cr4(read_cr4() | X86_CR4_PGE); - else - write_cr4(read_cr4() & ~X86_CR4_PGE); -} - /*H:000 * Welcome to the Host! * @@ -701,72 +260,50 @@ static int __init init(void) /* First we put the Switcher up in very high virtual memory. */ err = map_switcher(); if (err) - return err; + goto out; /* Now we set up the pagetable implementation for the Guests. */ err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES); - if (err) { - unmap_switcher(); - return err; - } + if (err) + goto unmap; - /* The I/O subsystem needs some things initialized. */ - lguest_io_init(); + /* We might need to reserve an interrupt vector. */ + err = init_interrupts(); + if (err) + goto free_pgtables; /* /dev/lguest needs to be registered. */ err = lguest_device_init(); - if (err) { - free_pagetables(); - unmap_switcher(); - return err; - } + if (err) + goto free_interrupts; - /* Finally, we need to turn off "Page Global Enable". PGE is an - * optimization where page table entries are specially marked to show - * they never change. The Host kernel marks all the kernel pages this - * way because it's always present, even when userspace is running. - * - * Lguest breaks this: unbeknownst to the rest of the Host kernel, we - * switch to the Guest kernel. If you don't disable this on all CPUs, - * you'll get really weird bugs that you'll chase for two days. - * - * I used to turn PGE off every time we switched to the Guest and back - * on when we return, but that slowed the Switcher down noticibly. */ - - /* We don't need the complexity of CPUs coming and going while we're - * doing this. */ - lock_cpu_hotplug(); - if (cpu_has_pge) { /* We have a broader idea of "global". */ - /* Remember that this was originally set (for cleanup). */ - cpu_had_pge = 1; - /* adjust_pge is a helper function which sets or unsets the PGE - * bit on its CPU, depending on the argument (0 == unset). */ - on_each_cpu(adjust_pge, (void *)0, 0, 1); - /* Turn off the feature in the global feature set. */ - clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); - } - unlock_cpu_hotplug(); + /* Finally we do some architecture-specific setup. */ + lguest_arch_host_init(); /* All good! */ return 0; + +free_interrupts: + free_interrupts(); +free_pgtables: + free_pagetables(); +unmap: + unmap_switcher(); +out: + return err; } /* Cleaning up is just the same code, backwards. With a little French. */ static void __exit fini(void) { lguest_device_remove(); + free_interrupts(); free_pagetables(); unmap_switcher(); - /* If we had PGE before we started, turn it back on now. */ - lock_cpu_hotplug(); - if (cpu_had_pge) { - set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); - /* adjust_pge's argument "1" means set PGE. */ - on_each_cpu(adjust_pge, (void *)1, 0, 1); - } - unlock_cpu_hotplug(); + lguest_arch_host_fini(); } +/*:*/ /* The Host side of lguest can be a module. This is a nice way for people to * play with it. */ diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index db6caace3b9c..b478affe8f91 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -25,17 +25,13 @@ #include <linux/mm.h> #include <asm/page.h> #include <asm/pgtable.h> -#include <irq_vectors.h> #include "lg.h" -/*H:120 This is the core hypercall routine: where the Guest gets what it - * wants. Or gets killed. Or, in the case of LHCALL_CRASH, both. - * - * Remember from the Guest: %eax == which call to make, and the arguments are - * packed into %edx, %ebx and %ecx if needed. */ -static void do_hcall(struct lguest *lg, struct lguest_regs *regs) +/*H:120 This is the core hypercall routine: where the Guest gets what it wants. + * Or gets killed. Or, in the case of LHCALL_CRASH, both. */ +static void do_hcall(struct lguest *lg, struct hcall_args *args) { - switch (regs->eax) { + switch (args->arg0) { case LHCALL_FLUSH_ASYNC: /* This call does nothing, except by breaking out of the Guest * it makes us process all the asynchronous hypercalls. */ @@ -51,7 +47,7 @@ static void do_hcall(struct lguest *lg, struct lguest_regs *regs) char msg[128]; /* If the lgread fails, it will call kill_guest() itself; the * kill_guest() with the message will be ignored. */ - lgread(lg, msg, regs->edx, sizeof(msg)); + __lgread(lg, msg, args->arg1, sizeof(msg)); msg[sizeof(msg)-1] = '\0'; kill_guest(lg, "CRASH: %s", msg); break; @@ -59,67 +55,50 @@ static void do_hcall(struct lguest *lg, struct lguest_regs *regs) case LHCALL_FLUSH_TLB: /* FLUSH_TLB comes in two flavors, depending on the * argument: */ - if (regs->edx) + if (args->arg1) guest_pagetable_clear_all(lg); else guest_pagetable_flush_user(lg); break; - case LHCALL_BIND_DMA: - /* BIND_DMA really wants four arguments, but it's the only call - * which does. So the Guest packs the number of buffers and - * the interrupt number into the final argument, and we decode - * it here. This can legitimately fail, since we currently - * place a limit on the number of DMA pools a Guest can have. - * So we return true or false from this call. */ - regs->eax = bind_dma(lg, regs->edx, regs->ebx, - regs->ecx >> 8, regs->ecx & 0xFF); - break; /* All these calls simply pass the arguments through to the right * routines. */ - case LHCALL_SEND_DMA: - send_dma(lg, regs->edx, regs->ebx); - break; - case LHCALL_LOAD_GDT: - load_guest_gdt(lg, regs->edx, regs->ebx); - break; - case LHCALL_LOAD_IDT_ENTRY: - load_guest_idt_entry(lg, regs->edx, regs->ebx, regs->ecx); - break; case LHCALL_NEW_PGTABLE: - guest_new_pagetable(lg, regs->edx); + guest_new_pagetable(lg, args->arg1); break; case LHCALL_SET_STACK: - guest_set_stack(lg, regs->edx, regs->ebx, regs->ecx); + guest_set_stack(lg, args->arg1, args->arg2, args->arg3); break; case LHCALL_SET_PTE: - guest_set_pte(lg, regs->edx, regs->ebx, mkgpte(regs->ecx)); + guest_set_pte(lg, args->arg1, args->arg2, __pte(args->arg3)); break; case LHCALL_SET_PMD: - guest_set_pmd(lg, regs->edx, regs->ebx); - break; - case LHCALL_LOAD_TLS: - guest_load_tls(lg, regs->edx); + guest_set_pmd(lg, args->arg1, args->arg2); break; case LHCALL_SET_CLOCKEVENT: - guest_set_clockevent(lg, regs->edx); + guest_set_clockevent(lg, args->arg1); break; - case LHCALL_TS: /* This sets the TS flag, as we saw used in run_guest(). */ - lg->ts = regs->edx; + lg->ts = args->arg1; break; case LHCALL_HALT: /* Similarly, this sets the halted flag for run_guest(). */ lg->halted = 1; break; + case LHCALL_NOTIFY: + lg->pending_notify = args->arg1; + break; default: - kill_guest(lg, "Bad hypercall %li\n", regs->eax); + /* It should be an architecture-specific hypercall. */ + if (lguest_arch_do_hcall(lg, args)) + kill_guest(lg, "Bad hypercall %li\n", args->arg0); } } +/*:*/ -/* Asynchronous hypercalls are easy: we just look in the array in the Guest's - * "struct lguest_data" and see if there are any new ones marked "ready". +/*H:124 Asynchronous hypercalls are easy: we just look in the array in the + * Guest's "struct lguest_data" to see if any new ones are marked "ready". * * We are careful to do these in order: obviously we respect the order the * Guest put them in the ring, but we also promise the Guest that they will @@ -134,10 +113,9 @@ static void do_async_hcalls(struct lguest *lg) if (copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st))) return; - /* We process "struct lguest_data"s hcalls[] ring once. */ for (i = 0; i < ARRAY_SIZE(st); i++) { - struct lguest_regs regs; + struct hcall_args args; /* We remember where we were up to from last time. This makes * sure that the hypercalls are done in the order the Guest * places them in the ring. */ @@ -152,18 +130,16 @@ static void do_async_hcalls(struct lguest *lg) if (++lg->next_hcall == LHCALL_RING_SIZE) lg->next_hcall = 0; - /* We copy the hypercall arguments into a fake register - * structure. This makes life simple for do_hcall(). */ - if (get_user(regs.eax, &lg->lguest_data->hcalls[n].eax) - || get_user(regs.edx, &lg->lguest_data->hcalls[n].edx) - || get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx) - || get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx)) { + /* Copy the hypercall arguments into a local copy of + * the hcall_args struct. */ + if (copy_from_user(&args, &lg->lguest_data->hcalls[n], + sizeof(struct hcall_args))) { kill_guest(lg, "Fetching async hypercalls"); break; } /* Do the hypercall, same as a normal one. */ - do_hcall(lg, ®s); + do_hcall(lg, &args); /* Mark the hypercall done. */ if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) { @@ -171,9 +147,9 @@ static void do_async_hcalls(struct lguest *lg) break; } - /* Stop doing hypercalls if we've just done a DMA to the - * Launcher: it needs to service this first. */ - if (lg->dma_is_pending) + /* Stop doing hypercalls if they want to notify the Launcher: + * it needs to service this first. */ + if (lg->pending_notify) break; } } @@ -182,76 +158,35 @@ static void do_async_hcalls(struct lguest *lg) * Guest makes a hypercall, we end up here to set things up: */ static void initialize(struct lguest *lg) { - u32 tsc_speed; - /* You can't do anything until you're initialized. The Guest knows the * rules, so we're unforgiving here. */ - if (lg->regs->eax != LHCALL_LGUEST_INIT) { - kill_guest(lg, "hypercall %li before LGUEST_INIT", - lg->regs->eax); + if (lg->hcall->arg0 != LHCALL_LGUEST_INIT) { + kill_guest(lg, "hypercall %li before INIT", lg->hcall->arg0); return; } - /* We insist that the Time Stamp Counter exist and doesn't change with - * cpu frequency. Some devious chip manufacturers decided that TSC - * changes could be handled in software. I decided that time going - * backwards might be good for benchmarks, but it's bad for users. - * - * We also insist that the TSC be stable: the kernel detects unreliable - * TSCs for its own purposes, and we use that here. */ - if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable()) - tsc_speed = tsc_khz; - else - tsc_speed = 0; - - /* The pointer to the Guest's "struct lguest_data" is the only - * argument. */ - lg->lguest_data = (struct lguest_data __user *)lg->regs->edx; - /* If we check the address they gave is OK now, we can simply - * copy_to_user/from_user from now on rather than using lgread/lgwrite. - * I put this in to show that I'm not immune to writing stupid - * optimizations. */ - if (!lguest_address_ok(lg, lg->regs->edx, sizeof(*lg->lguest_data))) { + if (lguest_arch_init_hypercalls(lg)) kill_guest(lg, "bad guest page %p", lg->lguest_data); - return; - } + /* The Guest tells us where we're not to deliver interrupts by putting * the range of addresses into "struct lguest_data". */ if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start) - || get_user(lg->noirq_end, &lg->lguest_data->noirq_end) - /* We tell the Guest that it can't use the top 4MB of virtual - * addresses used by the Switcher. */ - || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) - || put_user(tsc_speed, &lg->lguest_data->tsc_khz) - /* We also give the Guest a unique id, as used in lguest_net.c. */ - || put_user(lg->guestid, &lg->lguest_data->guestid)) + || get_user(lg->noirq_end, &lg->lguest_data->noirq_end)) kill_guest(lg, "bad guest page %p", lg->lguest_data); - /* We write the current time into the Guest's data page once now. */ + /* We write the current time into the Guest's data page once so it can + * set its clock. */ write_timestamp(lg); + /* page_tables.c will also do some setup. */ + page_table_guest_data_init(lg); + /* This is the one case where the above accesses might have been the * first write to a Guest page. This may have caused a copy-on-write - * fault, but the Guest might be referring to the old (read-only) - * page. */ + * fault, but the old page might be (read-only) in the Guest + * pagetable. */ guest_pagetable_clear_all(lg); } -/* Now we've examined the hypercall code; our Guest can make requests. There - * is one other way we can do things for the Guest, as we see in - * emulate_insn(). */ - -/*H:110 Tricky point: we mark the hypercall as "done" once we've done it. - * Normally we don't need to do this: the Guest will run again and update the - * trap number before we come back around the run_guest() loop to - * do_hypercalls(). - * - * However, if we are signalled or the Guest sends DMA to the Launcher, that - * loop will exit without running the Guest. When it comes back it would try - * to re-run the hypercall. */ -static void clear_hcall(struct lguest *lg) -{ - lg->regs->trapnum = 255; -} /*H:100 * Hypercalls @@ -261,16 +196,12 @@ static void clear_hcall(struct lguest *lg) */ void do_hypercalls(struct lguest *lg) { - /* Not initialized yet? */ + /* Not initialized yet? This hypercall must do it. */ if (unlikely(!lg->lguest_data)) { - /* Did the Guest make a hypercall? We might have come back for - * some other reason (an interrupt, a different trap). */ - if (lg->regs->trapnum == LGUEST_TRAP_ENTRY) { - /* Set up the "struct lguest_data" */ - initialize(lg); - /* The hypercall is done. */ - clear_hcall(lg); - } + /* Set up the "struct lguest_data" */ + initialize(lg); + /* Hcall is done. */ + lg->hcall = NULL; return; } @@ -280,12 +211,21 @@ void do_hypercalls(struct lguest *lg) do_async_hcalls(lg); /* If we stopped reading the hypercall ring because the Guest did a - * SEND_DMA to the Launcher, we want to return now. Otherwise if the - * Guest asked us to do a hypercall, we do it. */ - if (!lg->dma_is_pending && lg->regs->trapnum == LGUEST_TRAP_ENTRY) { - do_hcall(lg, lg->regs); - /* The hypercall is done. */ - clear_hcall(lg); + * NOTIFY to the Launcher, we want to return now. Otherwise we do + * the hypercall. */ + if (!lg->pending_notify) { + do_hcall(lg, lg->hcall); + /* Tricky point: we reset the hcall pointer to mark the + * hypercall as "done". We use the hcall pointer rather than + * the trap number to indicate a hypercall is pending. + * Normally it doesn't matter: the Guest will run again and + * update the trap number before we come back here. + * + * However, if we are signalled or the Guest sends I/O to the + * Launcher, the run_guest() loop will exit without running the + * Guest. When it comes back it would try to re-run the + * hypercall. */ + lg->hcall = NULL; } } @@ -295,6 +235,6 @@ void write_timestamp(struct lguest *lg) { struct timespec now; ktime_get_real_ts(&now); - if (put_user(now, &lg->lguest_data->time)) + if (copy_to_user(&lg->lguest_data->time, &now, sizeof(struct timespec))) kill_guest(lg, "Writing timestamp"); } diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 39731232d827..2b66f79c208b 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -12,8 +12,14 @@ * them first, so we also have a way of "reflecting" them into the Guest as if * they had been delivered to it directly. :*/ #include <linux/uaccess.h> +#include <linux/interrupt.h> +#include <linux/module.h> #include "lg.h" +/* Allow Guests to use a non-128 (ie. non-Linux) syscall trap. */ +static unsigned int syscall_vector = SYSCALL_VECTOR; +module_param(syscall_vector, uint, 0444); + /* The address of the interrupt handler is split into two bits: */ static unsigned long idt_address(u32 lo, u32 hi) { @@ -39,7 +45,7 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) { /* Stack grows upwards: move stack then write value. */ *gstack -= 4; - lgwrite_u32(lg, *gstack, val); + lgwrite(lg, *gstack, u32, val); } /*H:210 The set_guest_interrupt() routine actually delivers the interrupt or @@ -56,8 +62,9 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) * it). */ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) { - unsigned long gstack; + unsigned long gstack, origstack; u32 eflags, ss, irq_enable; + unsigned long virtstack; /* There are two cases for interrupts: one where the Guest is already * in the kernel, and a more complex one where the Guest is in @@ -65,8 +72,10 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) if ((lg->regs->ss&0x3) != GUEST_PL) { /* The Guest told us their kernel stack with the SET_STACK * hypercall: both the virtual address and the segment */ - gstack = guest_pa(lg, lg->esp1); + virtstack = lg->esp1; ss = lg->ss1; + + origstack = gstack = guest_pa(lg, virtstack); /* We push the old stack segment and pointer onto the new * stack: when the Guest does an "iret" back from the interrupt * handler the CPU will notice they're dropping privilege @@ -75,14 +84,16 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) push_guest_stack(lg, &gstack, lg->regs->esp); } else { /* We're staying on the same Guest (kernel) stack. */ - gstack = guest_pa(lg, lg->regs->esp); + virtstack = lg->regs->esp; ss = lg->regs->ss; + + origstack = gstack = guest_pa(lg, virtstack); } /* Remember that we never let the Guest actually disable interrupts, so * the "Interrupt Flag" bit is always set. We copy that bit from the - * Guest's "irq_enabled" field into the eflags word: the Guest copies - * it back in "lguest_iret". */ + * Guest's "irq_enabled" field into the eflags word: we saw the Guest + * copy it back in "lguest_iret". */ eflags = lg->regs->eflags; if (get_user(irq_enable, &lg->lguest_data->irq_enabled) == 0 && !(irq_enable & X86_EFLAGS_IF)) @@ -102,7 +113,7 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) /* Now we've pushed all the old state, we change the stack, the code * segment and the address to execute. */ lg->regs->ss = ss; - lg->regs->esp = gstack + lg->page_offset; + lg->regs->esp = virtstack + (gstack - origstack); lg->regs->cs = (__KERNEL_CS|GUEST_PL); lg->regs->eip = idt_address(lo, hi); @@ -113,7 +124,7 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) kill_guest(lg, "Disabling interrupts"); } -/*H:200 +/*H:205 * Virtual Interrupts. * * maybe_do_interrupt() gets called before every entry to the Guest, to see if @@ -165,7 +176,7 @@ void maybe_do_interrupt(struct lguest *lg) /* Look at the IDT entry the Guest gave us for this interrupt. The * first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip * over them. */ - idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq]; + idt = &lg->arch.idt[FIRST_EXTERNAL_VECTOR+irq]; /* If they don't have a handler (yet?), we just ignore it */ if (idt_present(idt->a, idt->b)) { /* OK, mark it no longer pending and deliver it. */ @@ -183,6 +194,47 @@ void maybe_do_interrupt(struct lguest *lg) * timer interrupt. */ write_timestamp(lg); } +/*:*/ + +/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent + * me a patch, so we support that too. It'd be a big step for lguest if half + * the Plan 9 user base were to start using it. + * + * Actually now I think of it, it's possible that Ron *is* half the Plan 9 + * userbase. Oh well. */ +static bool could_be_syscall(unsigned int num) +{ + /* Normal Linux SYSCALL_VECTOR or reserved vector? */ + return num == SYSCALL_VECTOR || num == syscall_vector; +} + +/* The syscall vector it wants must be unused by Host. */ +bool check_syscall_vector(struct lguest *lg) +{ + u32 vector; + + if (get_user(vector, &lg->lguest_data->syscall_vec)) + return false; + + return could_be_syscall(vector); +} + +int init_interrupts(void) +{ + /* If they want some strange system call vector, reserve it now */ + if (syscall_vector != SYSCALL_VECTOR + && test_and_set_bit(syscall_vector, used_vectors)) { + printk("lg: couldn't reserve syscall %u\n", syscall_vector); + return -EBUSY; + } + return 0; +} + +void free_interrupts(void) +{ + if (syscall_vector != SYSCALL_VECTOR) + clear_bit(syscall_vector, used_vectors); +} /*H:220 Now we've got the routines to deliver interrupts, delivering traps * like page fault is easy. The only trick is that Intel decided that some @@ -197,49 +249,43 @@ int deliver_trap(struct lguest *lg, unsigned int num) { /* Trap numbers are always 8 bit, but we set an impossible trap number * for traps inside the Switcher, so check that here. */ - if (num >= ARRAY_SIZE(lg->idt)) + if (num >= ARRAY_SIZE(lg->arch.idt)) return 0; /* Early on the Guest hasn't set the IDT entries (or maybe it put a * bogus one in): if we fail here, the Guest will be killed. */ - if (!idt_present(lg->idt[num].a, lg->idt[num].b)) + if (!idt_present(lg->arch.idt[num].a, lg->arch.idt[num].b)) return 0; - set_guest_interrupt(lg, lg->idt[num].a, lg->idt[num].b, has_err(num)); + set_guest_interrupt(lg, lg->arch.idt[num].a, lg->arch.idt[num].b, + has_err(num)); return 1; } /*H:250 Here's the hard part: returning to the Host every time a trap happens * and then calling deliver_trap() and re-entering the Guest is slow. - * Particularly because Guest userspace system calls are traps (trap 128). + * Particularly because Guest userspace system calls are traps (usually trap + * 128). * * So we'd like to set up the IDT to tell the CPU to deliver traps directly * into the Guest. This is possible, but the complexities cause the size of * this file to double! However, 150 lines of code is worth writing for taking * system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all - * the other hypervisors would tease it. + * the other hypervisors would beat it up at lunchtime. * - * This routine determines if a trap can be delivered directly. */ -static int direct_trap(const struct lguest *lg, - const struct desc_struct *trap, - unsigned int num) + * This routine indicates if a particular trap number could be delivered + * directly. */ +static int direct_trap(unsigned int num) { /* Hardware interrupts don't go to the Guest at all (except system * call). */ - if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR) + if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) return 0; /* The Host needs to see page faults (for shadow paging and to save the * fault address), general protection faults (in/out emulation) and * device not available (TS handling), and of course, the hypercall * trap. */ - if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY) - return 0; - - /* Only trap gates (type 15) can go direct to the Guest. Interrupt - * gates (type 14) disable interrupts as they are entered, which we - * never let the Guest do. Not present entries (type 0x0) also can't - * go direct, of course 8) */ - return idt_type(trap->a, trap->b) == 0xF; + return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY; } /*:*/ @@ -287,7 +333,7 @@ void pin_stack_pages(struct lguest *lg) * change stacks on each context switch. */ void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages) { - /* You are not allowd have a stack segment with privilege level 0: bad + /* You are not allowed have a stack segment with privilege level 0: bad * Guest! */ if ((seg & 0x3) != GUEST_PL) kill_guest(lg, "bad stack segment %i", seg); @@ -306,7 +352,7 @@ void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages) * part of the Host: page table handling. */ /*H:235 This is the routine which actually checks the Guest's IDT entry and - * transfers it into our entry in "struct lguest": */ + * transfers it into the entry in "struct lguest": */ static void set_trap(struct lguest *lg, struct desc_struct *trap, unsigned int num, u32 lo, u32 hi) { @@ -348,15 +394,11 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) * to copy this again. */ lg->changed |= CHANGED_IDT; - /* The IDT which we keep in "struct lguest" only contains 32 entries - * for the traps and LGUEST_IRQS (32) entries for interrupts. We - * ignore attempts to set handlers for higher interrupt numbers, except - * for the system call "interrupt" at 128: we have a special IDT entry - * for that. */ - if (num < ARRAY_SIZE(lg->idt)) - set_trap(lg, &lg->idt[num], num, lo, hi); - else if (num == SYSCALL_VECTOR) - set_trap(lg, &lg->syscall_idt, num, lo, hi); + /* Check that the Guest doesn't try to step outside the bounds. */ + if (num >= ARRAY_SIZE(lg->arch.idt)) + kill_guest(lg, "Setting idt entry %u", num); + else + set_trap(lg, &lg->arch.idt[num], num, lo, hi); } /* The default entry for each interrupt points into the Switcher routines which @@ -399,22 +441,35 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, /* We can simply copy the direct traps, otherwise we use the default * ones in the Switcher: they will return to the Host. */ - for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) { - if (direct_trap(lg, &lg->idt[i], i)) - idt[i] = lg->idt[i]; + for (i = 0; i < ARRAY_SIZE(lg->arch.idt); i++) { + /* If no Guest can ever override this trap, leave it alone. */ + if (!direct_trap(i)) + continue; + + /* Only trap gates (type 15) can go direct to the Guest. + * Interrupt gates (type 14) disable interrupts as they are + * entered, which we never let the Guest do. Not present + * entries (type 0x0) also can't go direct, of course. */ + if (idt_type(lg->arch.idt[i].a, lg->arch.idt[i].b) == 0xF) + idt[i] = lg->arch.idt[i]; else + /* Reset it to the default. */ default_idt_entry(&idt[i], i, def[i]); } - - /* Don't forget the system call trap! The IDT entries for other - * interupts never change, so no need to copy them. */ - i = SYSCALL_VECTOR; - if (direct_trap(lg, &lg->syscall_idt, i)) - idt[i] = lg->syscall_idt; - else - default_idt_entry(&idt[i], i, def[i]); } +/*H:200 + * The Guest Clock. + * + * There are two sources of virtual interrupts. We saw one in lguest_user.c: + * the Launcher sending interrupts for virtual devices. The other is the Guest + * timer interrupt. + * + * The Guest uses the LHCALL_SET_CLOCKEVENT hypercall to tell us how long to + * the next timer interrupt (in nanoseconds). We use the high-resolution timer + * infrastructure to set a callback at that time. + * + * 0 means "turn off the clock". */ void guest_set_clockevent(struct lguest *lg, unsigned long delta) { ktime_t expires; @@ -425,20 +480,27 @@ void guest_set_clockevent(struct lguest *lg, unsigned long delta) return; } + /* We use wallclock time here, so the Guest might not be running for + * all the time between now and the timer interrupt it asked for. This + * is almost always the right thing to do. */ expires = ktime_add_ns(ktime_get_real(), delta); hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS); } +/* This is the function called when the Guest's timer expires. */ static enum hrtimer_restart clockdev_fn(struct hrtimer *timer) { struct lguest *lg = container_of(timer, struct lguest, hrt); + /* Remember the first interrupt is the timer interrupt. */ set_bit(0, lg->irqs_pending); + /* If the Guest is actually stopped, we need to wake it up. */ if (lg->halted) wake_up_process(lg->tsk); return HRTIMER_NORESTART; } +/* This sets up the timer for this Guest. */ void init_clockdev(struct lguest *lg) { hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS); diff --git a/drivers/lguest/io.c b/drivers/lguest/io.c deleted file mode 100644 index ea68613b43f6..000000000000 --- a/drivers/lguest/io.c +++ /dev/null @@ -1,626 +0,0 @@ -/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest - * to talk to the Launcher or directly to another Guest. It uses familiar - * concepts of DMA and interrupts, plus some neat code stolen from - * futexes... :*/ - -/* Copyright (C) 2006 Rusty Russell IBM Corporation - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA - */ -#include <linux/types.h> -#include <linux/futex.h> -#include <linux/jhash.h> -#include <linux/mm.h> -#include <linux/highmem.h> -#include <linux/uaccess.h> -#include "lg.h" - -/*L:300 - * I/O - * - * Getting data in and out of the Guest is quite an art. There are numerous - * ways to do it, and they all suck differently. We try to keep things fairly - * close to "real" hardware so our Guest's drivers don't look like an alien - * visitation in the middle of the Linux code, and yet make sure that Guests - * can talk directly to other Guests, not just the Launcher. - * - * To do this, the Guest gives us a key when it binds or sends DMA buffers. - * The key corresponds to a "physical" address inside the Guest (ie. a virtual - * address inside the Launcher process). We don't, however, use this key - * directly. - * - * We want Guests which share memory to be able to DMA to each other: two - * Launchers can mmap memory the same file, then the Guests can communicate. - * Fortunately, the futex code provides us with a way to get a "union - * futex_key" corresponding to the memory lying at a virtual address: if the - * two processes share memory, the "union futex_key" for that memory will match - * even if the memory is mapped at different addresses in each. So we always - * convert the keys to "union futex_key"s to compare them. - * - * Before we dive into this though, we need to look at another set of helper - * routines used throughout the Host kernel code to access Guest memory. - :*/ -static struct list_head dma_hash[61]; - -/* An unfortunate side effect of the Linux double-linked list implementation is - * that there's no good way to statically initialize an array of linked - * lists. */ -void lguest_io_init(void) -{ - unsigned int i; - - for (i = 0; i < ARRAY_SIZE(dma_hash); i++) - INIT_LIST_HEAD(&dma_hash[i]); -} - -/* FIXME: allow multi-page lengths. */ -static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma) -{ - unsigned int i; - - for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) { - if (!dma->len[i]) - return 1; - if (!lguest_address_ok(lg, dma->addr[i], dma->len[i])) - goto kill; - if (dma->len[i] > PAGE_SIZE) - goto kill; - /* We could do over a page, but is it worth it? */ - if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE) - goto kill; - } - return 1; - -kill: - kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]); - return 0; -} - -/*L:330 This is our hash function, using the wonderful Jenkins hash. - * - * The futex key is a union with three parts: an unsigned long word, a pointer, - * and an int "offset". We could use jhash_2words() which takes three u32s. - * (Ok, the hash functions are great: the naming sucks though). - * - * It's nice to be portable to 64-bit platforms, so we use the more generic - * jhash2(), which takes an array of u32, the number of u32s, and an initial - * u32 to roll in. This is uglier, but breaks down to almost the same code on - * 32-bit platforms like this one. - * - * We want a position in the array, so we modulo ARRAY_SIZE(dma_hash) (ie. 61). - */ -static unsigned int hash(const union futex_key *key) -{ - return jhash2((u32*)&key->both.word, - (sizeof(key->both.word)+sizeof(key->both.ptr))/4, - key->both.offset) - % ARRAY_SIZE(dma_hash); -} - -/* This is a convenience routine to compare two keys. It's a much bemoaned C - * weakness that it doesn't allow '==' on structures or unions, so we have to - * open-code it like this. */ -static inline int key_eq(const union futex_key *a, const union futex_key *b) -{ - return (a->both.word == b->both.word - && a->both.ptr == b->both.ptr - && a->both.offset == b->both.offset); -} - -/*L:360 OK, when we need to actually free up a Guest's DMA array we do several - * things, so we have a convenient function to do it. - * - * The caller must hold a read lock on dmainfo owner's current->mm->mmap_sem - * for the drop_futex_key_refs(). */ -static void unlink_dma(struct lguest_dma_info *dmainfo) -{ - /* You locked this too, right? */ - BUG_ON(!mutex_is_locked(&lguest_lock)); - /* This is how we know that the entry is free. */ - dmainfo->interrupt = 0; - /* Remove it from the hash table. */ - list_del(&dmainfo->list); - /* Drop the references we were holding (to the inode or mm). */ - drop_futex_key_refs(&dmainfo->key); -} - -/*L:350 This is the routine which we call when the Guest asks to unregister a - * DMA array attached to a given key. Returns true if the array was found. */ -static int unbind_dma(struct lguest *lg, - const union futex_key *key, - unsigned long dmas) -{ - int i, ret = 0; - - /* We don't bother with the hash table, just look through all this - * Guest's DMA arrays. */ - for (i = 0; i < LGUEST_MAX_DMA; i++) { - /* In theory it could have more than one array on the same key, - * or one array on multiple keys, so we check both */ - if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) { - unlink_dma(&lg->dma[i]); - ret = 1; - break; - } - } - return ret; -} - -/*L:340 BIND_DMA: this is the hypercall which sets up an array of "struct - * lguest_dma" for receiving I/O. - * - * The Guest wants to bind an array of "struct lguest_dma"s to a particular key - * to receive input. This only happens when the Guest is setting up a new - * device, so it doesn't have to be very fast. - * - * It returns 1 on a successful registration (it can fail if we hit the limit - * of registrations for this Guest). - */ -int bind_dma(struct lguest *lg, - unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt) -{ - unsigned int i; - int ret = 0; - union futex_key key; - /* Futex code needs the mmap_sem. */ - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - - /* Invalid interrupt? (We could kill the guest here). */ - if (interrupt >= LGUEST_IRQS) - return 0; - - /* We need to grab the Big Lguest Lock, because other Guests may be - * trying to look through this Guest's DMAs to send something while - * we're doing this. */ - mutex_lock(&lguest_lock); - down_read(fshared); - if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) { - kill_guest(lg, "bad dma key %#lx", ukey); - goto unlock; - } - - /* We want to keep this key valid once we drop mmap_sem, so we have to - * hold a reference. */ - get_futex_key_refs(&key); - - /* If the Guest specified an interrupt of 0, that means they want to - * unregister this array of "struct lguest_dma"s. */ - if (interrupt == 0) - ret = unbind_dma(lg, &key, dmas); - else { - /* Look through this Guest's dma array for an unused entry. */ - for (i = 0; i < LGUEST_MAX_DMA; i++) { - /* If the interrupt is non-zero, the entry is already - * used. */ - if (lg->dma[i].interrupt) - continue; - - /* OK, a free one! Fill on our details. */ - lg->dma[i].dmas = dmas; - lg->dma[i].num_dmas = numdmas; - lg->dma[i].next_dma = 0; - lg->dma[i].key = key; - lg->dma[i].guestid = lg->guestid; - lg->dma[i].interrupt = interrupt; - - /* Now we add it to the hash table: the position - * depends on the futex key that we got. */ - list_add(&lg->dma[i].list, &dma_hash[hash(&key)]); - /* Success! */ - ret = 1; - goto unlock; - } - } - /* If we didn't find a slot to put the key in, drop the reference - * again. */ - drop_futex_key_refs(&key); -unlock: - /* Unlock and out. */ - up_read(fshared); - mutex_unlock(&lguest_lock); - return ret; -} - -/*L:385 Note that our routines to access a different Guest's memory are called - * lgread_other() and lgwrite_other(): these names emphasize that they are only - * used when the Guest is *not* the current Guest. - * - * The interface for copying from another process's memory is called - * access_process_vm(), with a final argument of 0 for a read, and 1 for a - * write. - * - * We need lgread_other() to read the destination Guest's "struct lguest_dma" - * array. */ -static int lgread_other(struct lguest *lg, - void *buf, u32 addr, unsigned bytes) -{ - if (!lguest_address_ok(lg, addr, bytes) - || access_process_vm(lg->tsk, addr, buf, bytes, 0) != bytes) { - memset(buf, 0, bytes); - kill_guest(lg, "bad address in registered DMA struct"); - return 0; - } - return 1; -} - -/* "lgwrite()" to another Guest: used to update the destination "used_len" once - * we've transferred data into the buffer. */ -static int lgwrite_other(struct lguest *lg, u32 addr, - const void *buf, unsigned bytes) -{ - if (!lguest_address_ok(lg, addr, bytes) - || (access_process_vm(lg->tsk, addr, (void *)buf, bytes, 1) - != bytes)) { - kill_guest(lg, "bad address writing to registered DMA"); - return 0; - } - return 1; -} - -/*L:400 This is the generic engine which copies from a source "struct - * lguest_dma" from this Guest into another Guest's "struct lguest_dma". The - * destination Guest's pages have already been mapped, as contained in the - * pages array. - * - * If you're wondering if there's a nice "copy from one process to another" - * routine, so was I. But Linux isn't really set up to copy between two - * unrelated processes, so we have to write it ourselves. - */ -static u32 copy_data(struct lguest *srclg, - const struct lguest_dma *src, - const struct lguest_dma *dst, - struct page *pages[]) -{ - unsigned int totlen, si, di, srcoff, dstoff; - void *maddr = NULL; - - /* We return the total length transferred. */ - totlen = 0; - - /* We keep indexes into the source and destination "struct lguest_dma", - * and an offset within each region. */ - si = di = 0; - srcoff = dstoff = 0; - - /* We loop until the source or destination is exhausted. */ - while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si] - && di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) { - /* We can only transfer the rest of the src buffer, or as much - * as will fit into the destination buffer. */ - u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff); - - /* For systems using "highmem" we need to use kmap() to access - * the page we want. We often use the same page over and over, - * so rather than kmap() it on every loop, we set the maddr - * pointer to NULL when we need to move to the next - * destination page. */ - if (!maddr) - maddr = kmap(pages[di]); - - /* Copy directly from (this Guest's) source address to the - * destination Guest's kmap()ed buffer. Note that maddr points - * to the start of the page: we need to add the offset of the - * destination address and offset within the buffer. */ - - /* FIXME: This is not completely portable. I looked at - * copy_to_user_page(), and some arch's seem to need special - * flushes. x86 is fine. */ - if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE, - (void __user *)src->addr[si], len) != 0) { - /* If a copy failed, it's the source's fault. */ - kill_guest(srclg, "bad address in sending DMA"); - totlen = 0; - break; - } - - /* Increment the total and src & dst offsets */ - totlen += len; - srcoff += len; - dstoff += len; - - /* Presumably we reached the end of the src or dest buffers: */ - if (srcoff == src->len[si]) { - /* Move to the next buffer at offset 0 */ - si++; - srcoff = 0; - } - if (dstoff == dst->len[di]) { - /* We need to unmap that destination page and reset - * maddr ready for the next one. */ - kunmap(pages[di]); - maddr = NULL; - di++; - dstoff = 0; - } - } - - /* If we still had a page mapped at the end, unmap now. */ - if (maddr) - kunmap(pages[di]); - - return totlen; -} - -/*L:390 This is how we transfer a "struct lguest_dma" from the source Guest - * (the current Guest which called SEND_DMA) to another Guest. */ -static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src, - struct lguest *dstlg, const struct lguest_dma *dst) -{ - int i; - u32 ret; - struct page *pages[LGUEST_MAX_DMA_SECTIONS]; - - /* We check that both source and destination "struct lguest_dma"s are - * within the bounds of the source and destination Guests */ - if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src)) - return 0; - - /* We need to map the pages which correspond to each parts of - * destination buffer. */ - for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) { - if (dst->len[i] == 0) - break; - /* get_user_pages() is a complicated function, especially since - * we only want a single page. But it works, and returns the - * number of pages. Note that we're holding the destination's - * mmap_sem, as get_user_pages() requires. */ - if (get_user_pages(dstlg->tsk, dstlg->mm, - dst->addr[i], 1, 1, 1, pages+i, NULL) - != 1) { - /* This means the destination gave us a bogus buffer */ - kill_guest(dstlg, "Error mapping DMA pages"); - ret = 0; - goto drop_pages; - } - } - - /* Now copy the data until we run out of src or dst. */ - ret = copy_data(srclg, src, dst, pages); - -drop_pages: - while (--i >= 0) - put_page(pages[i]); - return ret; -} - -/*L:380 Transferring data from one Guest to another is not as simple as I'd - * like. We've found the "struct lguest_dma_info" bound to the same address as - * the send, we need to copy into it. - * - * This function returns true if the destination array was empty. */ -static int dma_transfer(struct lguest *srclg, - unsigned long udma, - struct lguest_dma_info *dst) -{ - struct lguest_dma dst_dma, src_dma; - struct lguest *dstlg; - u32 i, dma = 0; - - /* From the "struct lguest_dma_info" we found in the hash, grab the - * Guest. */ - dstlg = &lguests[dst->guestid]; - /* Read in the source "struct lguest_dma" handed to SEND_DMA. */ - lgread(srclg, &src_dma, udma, sizeof(src_dma)); - - /* We need the destination's mmap_sem, and we already hold the source's - * mmap_sem for the futex key lookup. Normally this would suggest that - * we could deadlock if the destination Guest was trying to send to - * this source Guest at the same time, which is another reason that all - * I/O is done under the big lguest_lock. */ - down_read(&dstlg->mm->mmap_sem); - - /* Look through the destination DMA array for an available buffer. */ - for (i = 0; i < dst->num_dmas; i++) { - /* We keep a "next_dma" pointer which often helps us avoid - * looking at lots of previously-filled entries. */ - dma = (dst->next_dma + i) % dst->num_dmas; - if (!lgread_other(dstlg, &dst_dma, - dst->dmas + dma * sizeof(struct lguest_dma), - sizeof(dst_dma))) { - goto fail; - } - if (!dst_dma.used_len) - break; - } - - /* If we found a buffer, we do the actual data copy. */ - if (i != dst->num_dmas) { - unsigned long used_lenp; - unsigned int ret; - - ret = do_dma(srclg, &src_dma, dstlg, &dst_dma); - /* Put used length in the source "struct lguest_dma"'s used_len - * field. It's a little tricky to figure out where that is, - * though. */ - lgwrite_u32(srclg, - udma+offsetof(struct lguest_dma, used_len), ret); - /* Tranferring 0 bytes is OK if the source buffer was empty. */ - if (ret == 0 && src_dma.len[0] != 0) - goto fail; - - /* The destination Guest might be running on a different CPU: - * we have to make sure that it will see the "used_len" field - * change to non-zero *after* it sees the data we copied into - * the buffer. Hence a write memory barrier. */ - wmb(); - /* Figuring out where the destination's used_len field for this - * "struct lguest_dma" in the array is also a little ugly. */ - used_lenp = dst->dmas - + dma * sizeof(struct lguest_dma) - + offsetof(struct lguest_dma, used_len); - lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret)); - /* Move the cursor for next time. */ - dst->next_dma++; - } - up_read(&dstlg->mm->mmap_sem); - - /* We trigger the destination interrupt, even if the destination was - * empty and we didn't transfer anything: this gives them a chance to - * wake up and refill. */ - set_bit(dst->interrupt, dstlg->irqs_pending); - /* Wake up the destination process. */ - wake_up_process(dstlg->tsk); - /* If we passed the last "struct lguest_dma", the receive had no - * buffers left. */ - return i == dst->num_dmas; - -fail: - up_read(&dstlg->mm->mmap_sem); - return 0; -} - -/*L:370 This is the counter-side to the BIND_DMA hypercall; the SEND_DMA - * hypercall. We find out who's listening, and send to them. */ -void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma) -{ - union futex_key key; - int empty = 0; - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - -again: - mutex_lock(&lguest_lock); - down_read(fshared); - /* Get the futex key for the key the Guest gave us */ - if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) { - kill_guest(lg, "bad sending DMA key"); - goto unlock; - } - /* Since the key must be a multiple of 4, the futex key uses the lower - * bit of the "offset" field (which would always be 0) to indicate a - * mapping which is shared with other processes (ie. Guests). */ - if (key.shared.offset & 1) { - struct lguest_dma_info *i; - /* Look through the hash for other Guests. */ - list_for_each_entry(i, &dma_hash[hash(&key)], list) { - /* Don't send to ourselves. */ - if (i->guestid == lg->guestid) - continue; - if (!key_eq(&key, &i->key)) - continue; - - /* If dma_transfer() tells us the destination has no - * available buffers, we increment "empty". */ - empty += dma_transfer(lg, udma, i); - break; - } - /* If the destination is empty, we release our locks and - * give the destination Guest a brief chance to restock. */ - if (empty == 1) { - /* Give any recipients one chance to restock. */ - up_read(¤t->mm->mmap_sem); - mutex_unlock(&lguest_lock); - /* Next time, we won't try again. */ - empty++; - goto again; - } - } else { - /* Private mapping: Guest is sending to its Launcher. We set - * the "dma_is_pending" flag so that the main loop will exit - * and the Launcher's read() from /dev/lguest will return. */ - lg->dma_is_pending = 1; - lg->pending_dma = udma; - lg->pending_key = ukey; - } -unlock: - up_read(fshared); - mutex_unlock(&lguest_lock); -} -/*:*/ - -void release_all_dma(struct lguest *lg) -{ - unsigned int i; - - BUG_ON(!mutex_is_locked(&lguest_lock)); - - down_read(&lg->mm->mmap_sem); - for (i = 0; i < LGUEST_MAX_DMA; i++) { - if (lg->dma[i].interrupt) - unlink_dma(&lg->dma[i]); - } - up_read(&lg->mm->mmap_sem); -} - -/*M:007 We only return a single DMA buffer to the Launcher, but it would be - * more efficient to return a pointer to the entire array of DMA buffers, which - * it can cache and choose one whenever it wants. - * - * Currently the Launcher uses a write to /dev/lguest, and the return value is - * the address of the DMA structure with the interrupt number placed in - * dma->used_len. If we wanted to return the entire array, we need to return - * the address, array size and interrupt number: this seems to require an - * ioctl(). :*/ - -/*L:320 This routine looks for a DMA buffer registered by the Guest on the - * given key (using the BIND_DMA hypercall). */ -unsigned long get_dma_buffer(struct lguest *lg, - unsigned long ukey, unsigned long *interrupt) -{ - unsigned long ret = 0; - union futex_key key; - struct lguest_dma_info *i; - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - - /* Take the Big Lguest Lock to stop other Guests sending this Guest DMA - * at the same time. */ - mutex_lock(&lguest_lock); - /* To match between Guests sharing the same underlying memory we steal - * code from the futex infrastructure. This requires that we hold the - * "mmap_sem" for our process (the Launcher), and pass it to the futex - * code. */ - down_read(fshared); - - /* This can fail if it's not a valid address, or if the address is not - * divisible by 4 (the futex code needs that, we don't really). */ - if (get_futex_key((u32 __user *)ukey, fshared, &key) != 0) { - kill_guest(lg, "bad registered DMA buffer"); - goto unlock; - } - /* Search the hash table for matching entries (the Launcher can only - * send to its own Guest for the moment, so the entry must be for this - * Guest) */ - list_for_each_entry(i, &dma_hash[hash(&key)], list) { - if (key_eq(&key, &i->key) && i->guestid == lg->guestid) { - unsigned int j; - /* Look through the registered DMA array for an - * available buffer. */ - for (j = 0; j < i->num_dmas; j++) { - struct lguest_dma dma; - - ret = i->dmas + j * sizeof(struct lguest_dma); - lgread(lg, &dma, ret, sizeof(dma)); - if (dma.used_len == 0) - break; - } - /* Store the interrupt the Guest wants when the buffer - * is used. */ - *interrupt = i->interrupt; - break; - } - } -unlock: - up_read(fshared); - mutex_unlock(&lguest_lock); - return ret; -} -/*:*/ - -/*L:410 This really has completed the Launcher. Not only have we now finished - * the longest chapter in our journey, but this also means we are over halfway - * through! - * - * Enough prevaricating around the bush: it is time for us to dive into the - * core of the Host, in "make Host". - */ diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index 64f0abed317c..86924891b5eb 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -1,119 +1,25 @@ #ifndef _LGUEST_H #define _LGUEST_H -#include <asm/desc.h> - -#define GDT_ENTRY_LGUEST_CS 10 -#define GDT_ENTRY_LGUEST_DS 11 -#define LGUEST_CS (GDT_ENTRY_LGUEST_CS * 8) -#define LGUEST_DS (GDT_ENTRY_LGUEST_DS * 8) - #ifndef __ASSEMBLY__ #include <linux/types.h> #include <linux/init.h> #include <linux/stringify.h> -#include <linux/binfmts.h> -#include <linux/futex.h> #include <linux/lguest.h> #include <linux/lguest_launcher.h> #include <linux/wait.h> #include <linux/err.h> #include <asm/semaphore.h> -#include "irq_vectors.h" -#define GUEST_PL 1 - -struct lguest_regs -{ - /* Manually saved part. */ - unsigned long ebx, ecx, edx; - unsigned long esi, edi, ebp; - unsigned long gs; - unsigned long eax; - unsigned long fs, ds, es; - unsigned long trapnum, errcode; - /* Trap pushed part */ - unsigned long eip; - unsigned long cs; - unsigned long eflags; - unsigned long esp; - unsigned long ss; -}; +#include <asm/lguest.h> void free_pagetables(void); int init_pagetables(struct page **switcher_page, unsigned int pages); -/* Full 4G segment descriptors, suitable for CS and DS. */ -#define FULL_EXEC_SEGMENT ((struct desc_struct){0x0000ffff, 0x00cf9b00}) -#define FULL_SEGMENT ((struct desc_struct){0x0000ffff, 0x00cf9300}) - -struct lguest_dma_info -{ - struct list_head list; - union futex_key key; - unsigned long dmas; - u16 next_dma; - u16 num_dmas; - u16 guestid; - u8 interrupt; /* 0 when not registered */ -}; - -/*H:310 The page-table code owes a great debt of gratitude to Andi Kleen. He - * reviewed the original code which used "u32" for all page table entries, and - * insisted that it would be far clearer with explicit typing. I thought it - * was overkill, but he was right: it is much clearer than it was before. - * - * We have separate types for the Guest's ptes & pgds and the shadow ptes & - * pgds. There's already a Linux type for these (pte_t and pgd_t) but they - * change depending on kernel config options (PAE). */ - -/* Each entry is identical: lower 12 bits of flags and upper 20 bits for the - * "page frame number" (0 == first physical page, etc). They are different - * types so the compiler will warn us if we mix them improperly. */ -typedef union { - struct { unsigned flags:12, pfn:20; }; - struct { unsigned long val; } raw; -} spgd_t; -typedef union { - struct { unsigned flags:12, pfn:20; }; - struct { unsigned long val; } raw; -} spte_t; -typedef union { - struct { unsigned flags:12, pfn:20; }; - struct { unsigned long val; } raw; -} gpgd_t; -typedef union { - struct { unsigned flags:12, pfn:20; }; - struct { unsigned long val; } raw; -} gpte_t; - -/* We have two convenient macros to convert a "raw" value as handed to us by - * the Guest into the correct Guest PGD or PTE type. */ -#define mkgpte(_val) ((gpte_t){.raw.val = _val}) -#define mkgpgd(_val) ((gpgd_t){.raw.val = _val}) -/*:*/ - struct pgdir { - unsigned long cr3; - spgd_t *pgdir; -}; - -/* This is a guest-specific page (mapped ro) into the guest. */ -struct lguest_ro_state -{ - /* Host information we need to restore when we switch back. */ - u32 host_cr3; - struct Xgt_desc_struct host_idt_desc; - struct Xgt_desc_struct host_gdt_desc; - u32 host_sp; - - /* Fields which are used when guest is running. */ - struct Xgt_desc_struct guest_idt_desc; - struct Xgt_desc_struct guest_gdt_desc; - struct i386_hw_tss guest_tss; - struct desc_struct guest_idt[IDT_ENTRIES]; - struct desc_struct guest_gdt[GDT_ENTRIES]; + unsigned long gpgdir; + pgd_t *pgdir; }; /* We have two pages shared with guests, per cpu. */ @@ -141,9 +47,11 @@ struct lguest struct lguest_data __user *lguest_data; struct task_struct *tsk; struct mm_struct *mm; /* == tsk->mm, but that becomes NULL on exit */ - u16 guestid; u32 pfn_limit; - u32 page_offset; + /* This provides the offset to the base of guest-physical + * memory in the Launcher. */ + void __user *mem_base; + unsigned long kernel_address; u32 cr2; int halted; int ts; @@ -151,6 +59,9 @@ struct lguest u32 esp1; u8 ss1; + /* If a hypercall was asked for, this points to the arguments. */ + struct hcall_args *hcall; + /* Do we need to stop what we're doing and return to userspace? */ int break_out; wait_queue_head_t break_wq; @@ -163,28 +74,16 @@ struct lguest u32 pgdidx; struct pgdir pgdirs[4]; - /* Cached wakeup: we hold a reference to this task. */ - struct task_struct *wake; - unsigned long noirq_start, noirq_end; - int dma_is_pending; - unsigned long pending_dma; /* struct lguest_dma */ - unsigned long pending_key; /* address they're sending to */ + unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */ unsigned int stack_pages; u32 tsc_khz; - struct lguest_dma_info dma[LGUEST_MAX_DMA]; - /* Dead? */ const char *dead; - /* The GDT entries copied into lguest_ro_state when running. */ - struct desc_struct gdt[GDT_ENTRIES]; - - /* The IDT entries: some copied into lguest_ro_state when running. */ - struct desc_struct idt[FIRST_EXTERNAL_VECTOR+LGUEST_IRQS]; - struct desc_struct syscall_idt; + struct lguest_arch arch; /* Virtual clock device */ struct hrtimer hrt; @@ -193,19 +92,38 @@ struct lguest DECLARE_BITMAP(irqs_pending, LGUEST_IRQS); }; -extern struct lguest lguests[]; extern struct mutex lguest_lock; /* core.c: */ -u32 lgread_u32(struct lguest *lg, unsigned long addr); -void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val); -void lgread(struct lguest *lg, void *buf, unsigned long addr, unsigned len); -void lgwrite(struct lguest *lg, unsigned long, const void *buf, unsigned len); -int find_free_guest(void); int lguest_address_ok(const struct lguest *lg, unsigned long addr, unsigned long len); +void __lgread(struct lguest *, void *, unsigned long, unsigned); +void __lgwrite(struct lguest *, unsigned long, const void *, unsigned); + +/*H:035 Using memory-copy operations like that is usually inconvient, so we + * have the following helper macros which read and write a specific type (often + * an unsigned long). + * + * This reads into a variable of the given type then returns that. */ +#define lgread(lg, addr, type) \ + ({ type _v; __lgread((lg), &_v, (addr), sizeof(_v)); _v; }) + +/* This checks that the variable is of the given type, then writes it out. */ +#define lgwrite(lg, addr, type, val) \ + do { \ + typecheck(type, val); \ + __lgwrite((lg), (addr), &(val), sizeof(val)); \ + } while(0) +/* (end of memory access helper routines) :*/ + int run_guest(struct lguest *lg, unsigned long __user *user); +/* Helper macros to obtain the first 12 or the last 20 bits, this is only the + * first step in the migration to the kernel types. pte_pfn is already defined + * in the kernel. */ +#define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK) +#define pte_flags(x) (pte_val(x) & ~PAGE_MASK) +#define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT) /* interrupts_and_traps.c: */ void maybe_do_interrupt(struct lguest *lg); @@ -219,6 +137,9 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, const unsigned long *def); void guest_set_clockevent(struct lguest *lg, unsigned long delta); void init_clockdev(struct lguest *lg); +bool check_syscall_vector(struct lguest *lg); +int init_interrupts(void); +void free_interrupts(void); /* segments.c: */ void setup_default_gdt_entries(struct lguest_ro_state *state); @@ -232,28 +153,33 @@ void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt); int init_guest_pagetable(struct lguest *lg, unsigned long pgtable); void free_guest_pagetable(struct lguest *lg); void guest_new_pagetable(struct lguest *lg, unsigned long pgtable); -void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 i); +void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 i); void guest_pagetable_clear_all(struct lguest *lg); void guest_pagetable_flush_user(struct lguest *lg); -void guest_set_pte(struct lguest *lg, unsigned long cr3, - unsigned long vaddr, gpte_t val); +void guest_set_pte(struct lguest *lg, unsigned long gpgdir, + unsigned long vaddr, pte_t val); void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages); int demand_page(struct lguest *info, unsigned long cr2, int errcode); void pin_page(struct lguest *lg, unsigned long vaddr); +unsigned long guest_pa(struct lguest *lg, unsigned long vaddr); +void page_table_guest_data_init(struct lguest *lg); + +/* <arch>/core.c: */ +void lguest_arch_host_init(void); +void lguest_arch_host_fini(void); +void lguest_arch_run_guest(struct lguest *lg); +void lguest_arch_handle_trap(struct lguest *lg); +int lguest_arch_init_hypercalls(struct lguest *lg); +int lguest_arch_do_hcall(struct lguest *lg, struct hcall_args *args); +void lguest_arch_setup_regs(struct lguest *lg, unsigned long start); + +/* <arch>/switcher.S: */ +extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; /* lguest_user.c: */ int lguest_device_init(void); void lguest_device_remove(void); -/* io.c: */ -void lguest_io_init(void); -int bind_dma(struct lguest *lg, - unsigned long key, unsigned long udma, u16 numdmas, u8 interrupt); -void send_dma(struct lguest *info, unsigned long key, unsigned long udma); -void release_all_dma(struct lguest *lg); -unsigned long get_dma_buffer(struct lguest *lg, unsigned long key, - unsigned long *interrupt); - /* hypercalls.c: */ void do_hypercalls(struct lguest *lg); void write_timestamp(struct lguest *lg); @@ -262,7 +188,7 @@ void write_timestamp(struct lguest *lg); * Let's step aside for the moment, to study one important routine that's used * widely in the Host code. * - * There are many cases where the Guest does something invalid, like pass crap + * There are many cases where the Guest can do something invalid, like pass crap * to a hypercall. Since only the Guest kernel can make hypercalls, it's quite * acceptable to simply terminate the Guest and give the Launcher a nicely * formatted reason. It's also simpler for the Guest itself, which doesn't @@ -292,9 +218,5 @@ do { \ } while(0) /* (End of aside) :*/ -static inline unsigned long guest_pa(struct lguest *lg, unsigned long vaddr) -{ - return vaddr - lg->page_offset; -} #endif /* __ASSEMBLY__ */ #endif /* _LGUEST_H */ diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c deleted file mode 100644 index 3ba337dde857..000000000000 --- a/drivers/lguest/lguest.c +++ /dev/null @@ -1,1108 +0,0 @@ -/*P:010 - * A hypervisor allows multiple Operating Systems to run on a single machine. - * To quote David Wheeler: "Any problem in computer science can be solved with - * another layer of indirection." - * - * We keep things simple in two ways. First, we start with a normal Linux - * kernel and insert a module (lg.ko) which allows us to run other Linux - * kernels the same way we'd run processes. We call the first kernel the Host, - * and the others the Guests. The program which sets up and configures Guests - * (such as the example in Documentation/lguest/lguest.c) is called the - * Launcher. - * - * Secondly, we only run specially modified Guests, not normal kernels. When - * you set CONFIG_LGUEST to 'y' or 'm', this automatically sets - * CONFIG_LGUEST_GUEST=y, which compiles this file into the kernel so it knows - * how to be a Guest. This means that you can use the same kernel you boot - * normally (ie. as a Host) as a Guest. - * - * These Guests know that they cannot do privileged operations, such as disable - * interrupts, and that they have to ask the Host to do such things explicitly. - * This file consists of all the replacements for such low-level native - * hardware operations: these special Guest versions call the Host. - * - * So how does the kernel know it's a Guest? The Guest starts at a special - * entry point marked with a magic string, which sets up a few things then - * calls here. We replace the native functions various "paravirt" structures - * with our Guest versions, then boot like normal. :*/ - -/* - * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or - * NON INFRINGEMENT. See the GNU General Public License for more - * details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. - */ -#include <linux/kernel.h> -#include <linux/start_kernel.h> -#include <linux/string.h> -#include <linux/console.h> -#include <linux/screen_info.h> -#include <linux/irq.h> -#include <linux/interrupt.h> -#include <linux/clocksource.h> -#include <linux/clockchips.h> -#include <linux/lguest.h> -#include <linux/lguest_launcher.h> -#include <linux/lguest_bus.h> -#include <asm/paravirt.h> -#include <asm/param.h> -#include <asm/page.h> -#include <asm/pgtable.h> -#include <asm/desc.h> -#include <asm/setup.h> -#include <asm/e820.h> -#include <asm/mce.h> -#include <asm/io.h> - -/*G:010 Welcome to the Guest! - * - * The Guest in our tale is a simple creature: identical to the Host but - * behaving in simplified but equivalent ways. In particular, the Guest is the - * same kernel as the Host (or at least, built from the same source code). :*/ - -/* Declarations for definitions in lguest_guest.S */ -extern char lguest_noirq_start[], lguest_noirq_end[]; -extern const char lgstart_cli[], lgend_cli[]; -extern const char lgstart_sti[], lgend_sti[]; -extern const char lgstart_popf[], lgend_popf[]; -extern const char lgstart_pushf[], lgend_pushf[]; -extern const char lgstart_iret[], lgend_iret[]; -extern void lguest_iret(void); - -struct lguest_data lguest_data = { - .hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF }, - .noirq_start = (u32)lguest_noirq_start, - .noirq_end = (u32)lguest_noirq_end, - .blocked_interrupts = { 1 }, /* Block timer interrupts */ -}; -struct lguest_device_desc *lguest_devices; -static cycle_t clock_base; - -/*G:035 Notice the lazy_hcall() above, rather than hcall(). This is our first - * real optimization trick! - * - * When lazy_mode is set, it means we're allowed to defer all hypercalls and do - * them as a batch when lazy_mode is eventually turned off. Because hypercalls - * are reasonably expensive, batching them up makes sense. For example, a - * large mmap might update dozens of page table entries: that code calls - * paravirt_enter_lazy_mmu(), does the dozen updates, then calls - * lguest_leave_lazy_mode(). - * - * So, when we're in lazy mode, we call async_hypercall() to store the call for - * future processing. When lazy mode is turned off we issue a hypercall to - * flush the stored calls. - */ -static void lguest_leave_lazy_mode(void) -{ - paravirt_leave_lazy(paravirt_get_lazy_mode()); - hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0); -} - -static void lazy_hcall(unsigned long call, - unsigned long arg1, - unsigned long arg2, - unsigned long arg3) -{ - if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) - hcall(call, arg1, arg2, arg3); - else - async_hcall(call, arg1, arg2, arg3); -} - -/* async_hcall() is pretty simple: I'm quite proud of it really. We have a - * ring buffer of stored hypercalls which the Host will run though next time we - * do a normal hypercall. Each entry in the ring has 4 slots for the hypercall - * arguments, and a "hcall_status" word which is 0 if the call is ready to go, - * and 255 once the Host has finished with it. - * - * If we come around to a slot which hasn't been finished, then the table is - * full and we just make the hypercall directly. This has the nice side - * effect of causing the Host to run all the stored calls in the ring buffer - * which empties it for next time! */ -void async_hcall(unsigned long call, - unsigned long arg1, unsigned long arg2, unsigned long arg3) -{ - /* Note: This code assumes we're uniprocessor. */ - static unsigned int next_call; - unsigned long flags; - - /* Disable interrupts if not already disabled: we don't want an - * interrupt handler making a hypercall while we're already doing - * one! */ - local_irq_save(flags); - if (lguest_data.hcall_status[next_call] != 0xFF) { - /* Table full, so do normal hcall which will flush table. */ - hcall(call, arg1, arg2, arg3); - } else { - lguest_data.hcalls[next_call].eax = call; - lguest_data.hcalls[next_call].edx = arg1; - lguest_data.hcalls[next_call].ebx = arg2; - lguest_data.hcalls[next_call].ecx = arg3; - /* Arguments must all be written before we mark it to go */ - wmb(); - lguest_data.hcall_status[next_call] = 0; - if (++next_call == LHCALL_RING_SIZE) - next_call = 0; - } - local_irq_restore(flags); -} -/*:*/ - -/* Wrappers for the SEND_DMA and BIND_DMA hypercalls. This is mainly because - * Jeff Garzik complained that __pa() should never appear in drivers, and this - * helps remove most of them. But also, it wraps some ugliness. */ -void lguest_send_dma(unsigned long key, struct lguest_dma *dma) -{ - /* The hcall might not write this if something goes wrong */ - dma->used_len = 0; - hcall(LHCALL_SEND_DMA, key, __pa(dma), 0); -} - -int lguest_bind_dma(unsigned long key, struct lguest_dma *dmas, - unsigned int num, u8 irq) -{ - /* This is the only hypercall which actually wants 5 arguments, and we - * only support 4. Fortunately the interrupt number is always less - * than 256, so we can pack it with the number of dmas in the final - * argument. */ - if (!hcall(LHCALL_BIND_DMA, key, __pa(dmas), (num << 8) | irq)) - return -ENOMEM; - return 0; -} - -/* Unbinding is the same hypercall as binding, but with 0 num & irq. */ -void lguest_unbind_dma(unsigned long key, struct lguest_dma *dmas) -{ - hcall(LHCALL_BIND_DMA, key, __pa(dmas), 0); -} - -/* For guests, device memory can be used as normal memory, so we cast away the - * __iomem to quieten sparse. */ -void *lguest_map(unsigned long phys_addr, unsigned long pages) -{ - return (__force void *)ioremap(phys_addr, PAGE_SIZE*pages); -} - -void lguest_unmap(void *addr) -{ - iounmap((__force void __iomem *)addr); -} - -/*G:033 - * Here are our first native-instruction replacements: four functions for - * interrupt control. - * - * The simplest way of implementing these would be to have "turn interrupts - * off" and "turn interrupts on" hypercalls. Unfortunately, this is too slow: - * these are by far the most commonly called functions of those we override. - * - * So instead we keep an "irq_enabled" field inside our "struct lguest_data", - * which the Guest can update with a single instruction. The Host knows to - * check there when it wants to deliver an interrupt. - */ - -/* save_flags() is expected to return the processor state (ie. "eflags"). The - * eflags word contains all kind of stuff, but in practice Linux only cares - * about the interrupt flag. Our "save_flags()" just returns that. */ -static unsigned long save_fl(void) -{ - return lguest_data.irq_enabled; -} - -/* "restore_flags" just sets the flags back to the value given. */ -static void restore_fl(unsigned long flags) -{ - lguest_data.irq_enabled = flags; -} - -/* Interrupts go off... */ -static void irq_disable(void) -{ - lguest_data.irq_enabled = 0; -} - -/* Interrupts go on... */ -static void irq_enable(void) -{ - lguest_data.irq_enabled = X86_EFLAGS_IF; -} -/*:*/ -/*M:003 Note that we don't check for outstanding interrupts when we re-enable - * them (or when we unmask an interrupt). This seems to work for the moment, - * since interrupts are rare and we'll just get the interrupt on the next timer - * tick, but when we turn on CONFIG_NO_HZ, we should revisit this. One way - * would be to put the "irq_enabled" field in a page by itself, and have the - * Host write-protect it when an interrupt comes in when irqs are disabled. - * There will then be a page fault as soon as interrupts are re-enabled. :*/ - -/*G:034 - * The Interrupt Descriptor Table (IDT). - * - * The IDT tells the processor what to do when an interrupt comes in. Each - * entry in the table is a 64-bit descriptor: this holds the privilege level, - * address of the handler, and... well, who cares? The Guest just asks the - * Host to make the change anyway, because the Host controls the real IDT. - */ -static void lguest_write_idt_entry(struct desc_struct *dt, - int entrynum, u32 low, u32 high) -{ - /* Keep the local copy up to date. */ - write_dt_entry(dt, entrynum, low, high); - /* Tell Host about this new entry. */ - hcall(LHCALL_LOAD_IDT_ENTRY, entrynum, low, high); -} - -/* Changing to a different IDT is very rare: we keep the IDT up-to-date every - * time it is written, so we can simply loop through all entries and tell the - * Host about them. */ -static void lguest_load_idt(const struct Xgt_desc_struct *desc) -{ - unsigned int i; - struct desc_struct *idt = (void *)desc->address; - - for (i = 0; i < (desc->size+1)/8; i++) - hcall(LHCALL_LOAD_IDT_ENTRY, i, idt[i].a, idt[i].b); -} - -/* - * The Global Descriptor Table. - * - * The Intel architecture defines another table, called the Global Descriptor - * Table (GDT). You tell the CPU where it is (and its size) using the "lgdt" - * instruction, and then several other instructions refer to entries in the - * table. There are three entries which the Switcher needs, so the Host simply - * controls the entire thing and the Guest asks it to make changes using the - * LOAD_GDT hypercall. - * - * This is the opposite of the IDT code where we have a LOAD_IDT_ENTRY - * hypercall and use that repeatedly to load a new IDT. I don't think it - * really matters, but wouldn't it be nice if they were the same? - */ -static void lguest_load_gdt(const struct Xgt_desc_struct *desc) -{ - BUG_ON((desc->size+1)/8 != GDT_ENTRIES); - hcall(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES, 0); -} - -/* For a single GDT entry which changes, we do the lazy thing: alter our GDT, - * then tell the Host to reload the entire thing. This operation is so rare - * that this naive implementation is reasonable. */ -static void lguest_write_gdt_entry(struct desc_struct *dt, - int entrynum, u32 low, u32 high) -{ - write_dt_entry(dt, entrynum, low, high); - hcall(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES, 0); -} - -/* OK, I lied. There are three "thread local storage" GDT entries which change - * on every context switch (these three entries are how glibc implements - * __thread variables). So we have a hypercall specifically for this case. */ -static void lguest_load_tls(struct thread_struct *t, unsigned int cpu) -{ - /* There's one problem which normal hardware doesn't have: the Host - * can't handle us removing entries we're currently using. So we clear - * the GS register here: if it's needed it'll be reloaded anyway. */ - loadsegment(gs, 0); - lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0); -} - -/*G:038 That's enough excitement for now, back to ploughing through each of - * the different pv_ops structures (we're about 1/3 of the way through). - * - * This is the Local Descriptor Table, another weird Intel thingy. Linux only - * uses this for some strange applications like Wine. We don't do anything - * here, so they'll get an informative and friendly Segmentation Fault. */ -static void lguest_set_ldt(const void *addr, unsigned entries) -{ -} - -/* This loads a GDT entry into the "Task Register": that entry points to a - * structure called the Task State Segment. Some comments scattered though the - * kernel code indicate that this used for task switching in ages past, along - * with blood sacrifice and astrology. - * - * Now there's nothing interesting in here that we don't get told elsewhere. - * But the native version uses the "ltr" instruction, which makes the Host - * complain to the Guest about a Segmentation Fault and it'll oops. So we - * override the native version with a do-nothing version. */ -static void lguest_load_tr_desc(void) -{ -} - -/* The "cpuid" instruction is a way of querying both the CPU identity - * (manufacturer, model, etc) and its features. It was introduced before the - * Pentium in 1993 and keeps getting extended by both Intel and AMD. As you - * might imagine, after a decade and a half this treatment, it is now a giant - * ball of hair. Its entry in the current Intel manual runs to 28 pages. - * - * This instruction even it has its own Wikipedia entry. The Wikipedia entry - * has been translated into 4 languages. I am not making this up! - * - * We could get funky here and identify ourselves as "GenuineLguest", but - * instead we just use the real "cpuid" instruction. Then I pretty much turned - * off feature bits until the Guest booted. (Don't say that: you'll damage - * lguest sales!) Shut up, inner voice! (Hey, just pointing out that this is - * hardly future proof.) Noone's listening! They don't like you anyway, - * parenthetic weirdo! - * - * Replacing the cpuid so we can turn features off is great for the kernel, but - * anyone (including userspace) can just use the raw "cpuid" instruction and - * the Host won't even notice since it isn't privileged. So we try not to get - * too worked up about it. */ -static void lguest_cpuid(unsigned int *eax, unsigned int *ebx, - unsigned int *ecx, unsigned int *edx) -{ - int function = *eax; - - native_cpuid(eax, ebx, ecx, edx); - switch (function) { - case 1: /* Basic feature request. */ - /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */ - *ecx &= 0x00002201; - /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, FPU. */ - *edx &= 0x07808101; - /* The Host can do a nice optimization if it knows that the - * kernel mappings (addresses above 0xC0000000 or whatever - * PAGE_OFFSET is set to) haven't changed. But Linux calls - * flush_tlb_user() for both user and kernel mappings unless - * the Page Global Enable (PGE) feature bit is set. */ - *edx |= 0x00002000; - break; - case 0x80000000: - /* Futureproof this a little: if they ask how much extended - * processor information there is, limit it to known fields. */ - if (*eax > 0x80000008) - *eax = 0x80000008; - break; - } -} - -/* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4. - * I assume there's a cr1, but it hasn't bothered us yet, so we'll not bother - * it. The Host needs to know when the Guest wants to change them, so we have - * a whole series of functions like read_cr0() and write_cr0(). - * - * We start with CR0. CR0 allows you to turn on and off all kinds of basic - * features, but Linux only really cares about one: the horrifically-named Task - * Switched (TS) bit at bit 3 (ie. 8) - * - * What does the TS bit do? Well, it causes the CPU to trap (interrupt 7) if - * the floating point unit is used. Which allows us to restore FPU state - * lazily after a task switch, and Linux uses that gratefully, but wouldn't a - * name like "FPUTRAP bit" be a little less cryptic? - * - * We store cr0 (and cr3) locally, because the Host never changes it. The - * Guest sometimes wants to read it and we'd prefer not to bother the Host - * unnecessarily. */ -static unsigned long current_cr0, current_cr3; -static void lguest_write_cr0(unsigned long val) -{ - /* 8 == TS bit. */ - lazy_hcall(LHCALL_TS, val & 8, 0, 0); - current_cr0 = val; -} - -static unsigned long lguest_read_cr0(void) -{ - return current_cr0; -} - -/* Intel provided a special instruction to clear the TS bit for people too cool - * to use write_cr0() to do it. This "clts" instruction is faster, because all - * the vowels have been optimized out. */ -static void lguest_clts(void) -{ - lazy_hcall(LHCALL_TS, 0, 0, 0); - current_cr0 &= ~8U; -} - -/* CR2 is the virtual address of the last page fault, which the Guest only ever - * reads. The Host kindly writes this into our "struct lguest_data", so we - * just read it out of there. */ -static unsigned long lguest_read_cr2(void) -{ - return lguest_data.cr2; -} - -/* CR3 is the current toplevel pagetable page: the principle is the same as - * cr0. Keep a local copy, and tell the Host when it changes. */ -static void lguest_write_cr3(unsigned long cr3) -{ - lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0); - current_cr3 = cr3; -} - -static unsigned long lguest_read_cr3(void) -{ - return current_cr3; -} - -/* CR4 is used to enable and disable PGE, but we don't care. */ -static unsigned long lguest_read_cr4(void) -{ - return 0; -} - -static void lguest_write_cr4(unsigned long val) -{ -} - -/* - * Page Table Handling. - * - * Now would be a good time to take a rest and grab a coffee or similarly - * relaxing stimulant. The easy parts are behind us, and the trek gradually - * winds uphill from here. - * - * Quick refresher: memory is divided into "pages" of 4096 bytes each. The CPU - * maps virtual addresses to physical addresses using "page tables". We could - * use one huge index of 1 million entries: each address is 4 bytes, so that's - * 1024 pages just to hold the page tables. But since most virtual addresses - * are unused, we use a two level index which saves space. The CR3 register - * contains the physical address of the top level "page directory" page, which - * contains physical addresses of up to 1024 second-level pages. Each of these - * second level pages contains up to 1024 physical addresses of actual pages, - * or Page Table Entries (PTEs). - * - * Here's a diagram, where arrows indicate physical addresses: - * - * CR3 ---> +---------+ - * | --------->+---------+ - * | | | PADDR1 | - * Top-level | | PADDR2 | - * (PMD) page | | | - * | | Lower-level | - * | | (PTE) page | - * | | | | - * .... .... - * - * So to convert a virtual address to a physical address, we look up the top - * level, which points us to the second level, which gives us the physical - * address of that page. If the top level entry was not present, or the second - * level entry was not present, then the virtual address is invalid (we - * say "the page was not mapped"). - * - * Put another way, a 32-bit virtual address is divided up like so: - * - * 1 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - * |<---- 10 bits ---->|<---- 10 bits ---->|<------ 12 bits ------>| - * Index into top Index into second Offset within page - * page directory page pagetable page - * - * The kernel spends a lot of time changing both the top-level page directory - * and lower-level pagetable pages. The Guest doesn't know physical addresses, - * so while it maintains these page tables exactly like normal, it also needs - * to keep the Host informed whenever it makes a change: the Host will create - * the real page tables based on the Guests'. - */ - -/* The Guest calls this to set a second-level entry (pte), ie. to map a page - * into a process' address space. We set the entry then tell the Host the - * toplevel and address this corresponds to. The Guest uses one pagetable per - * process, so we need to tell the Host which one we're changing (mm->pgd). */ -static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr, - pte_t *ptep, pte_t pteval) -{ - *ptep = pteval; - lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, pteval.pte_low); -} - -/* The Guest calls this to set a top-level entry. Again, we set the entry then - * tell the Host which top-level page we changed, and the index of the entry we - * changed. */ -static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval) -{ - *pmdp = pmdval; - lazy_hcall(LHCALL_SET_PMD, __pa(pmdp)&PAGE_MASK, - (__pa(pmdp)&(PAGE_SIZE-1))/4, 0); -} - -/* There are a couple of legacy places where the kernel sets a PTE, but we - * don't know the top level any more. This is useless for us, since we don't - * know which pagetable is changing or what address, so we just tell the Host - * to forget all of them. Fortunately, this is very rare. - * - * ... except in early boot when the kernel sets up the initial pagetables, - * which makes booting astonishingly slow. So we don't even tell the Host - * anything changed until we've done the first page table switch. - */ -static void lguest_set_pte(pte_t *ptep, pte_t pteval) -{ - *ptep = pteval; - /* Don't bother with hypercall before initial setup. */ - if (current_cr3) - lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0); -} - -/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on - * native page table operations. On native hardware you can set a new page - * table entry whenever you want, but if you want to remove one you have to do - * a TLB flush (a TLB is a little cache of page table entries kept by the CPU). - * - * So the lguest_set_pte_at() and lguest_set_pmd() functions above are only - * called when a valid entry is written, not when it's removed (ie. marked not - * present). Instead, this is where we come when the Guest wants to remove a - * page table entry: we tell the Host to set that entry to 0 (ie. the present - * bit is zero). */ -static void lguest_flush_tlb_single(unsigned long addr) -{ - /* Simply set it to zero: if it was not, it will fault back in. */ - lazy_hcall(LHCALL_SET_PTE, current_cr3, addr, 0); -} - -/* This is what happens after the Guest has removed a large number of entries. - * This tells the Host that any of the page table entries for userspace might - * have changed, ie. virtual addresses below PAGE_OFFSET. */ -static void lguest_flush_tlb_user(void) -{ - lazy_hcall(LHCALL_FLUSH_TLB, 0, 0, 0); -} - -/* This is called when the kernel page tables have changed. That's not very - * common (unless the Guest is using highmem, which makes the Guest extremely - * slow), so it's worth separating this from the user flushing above. */ -static void lguest_flush_tlb_kernel(void) -{ - lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0); -} - -/* - * The Unadvanced Programmable Interrupt Controller. - * - * This is an attempt to implement the simplest possible interrupt controller. - * I spent some time looking though routines like set_irq_chip_and_handler, - * set_irq_chip_and_handler_name, set_irq_chip_data and set_phasers_to_stun and - * I *think* this is as simple as it gets. - * - * We can tell the Host what interrupts we want blocked ready for using the - * lguest_data.interrupts bitmap, so disabling (aka "masking") them is as - * simple as setting a bit. We don't actually "ack" interrupts as such, we - * just mask and unmask them. I wonder if we should be cleverer? - */ -static void disable_lguest_irq(unsigned int irq) -{ - set_bit(irq, lguest_data.blocked_interrupts); -} - -static void enable_lguest_irq(unsigned int irq) -{ - clear_bit(irq, lguest_data.blocked_interrupts); -} - -/* This structure describes the lguest IRQ controller. */ -static struct irq_chip lguest_irq_controller = { - .name = "lguest", - .mask = disable_lguest_irq, - .mask_ack = disable_lguest_irq, - .unmask = enable_lguest_irq, -}; - -/* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware - * interrupt (except 128, which is used for system calls), and then tells the - * Linux infrastructure that each interrupt is controlled by our level-based - * lguest interrupt controller. */ -static void __init lguest_init_IRQ(void) -{ - unsigned int i; - - for (i = 0; i < LGUEST_IRQS; i++) { - int vector = FIRST_EXTERNAL_VECTOR + i; - if (vector != SYSCALL_VECTOR) { - set_intr_gate(vector, interrupt[i]); - set_irq_chip_and_handler(i, &lguest_irq_controller, - handle_level_irq); - } - } - /* This call is required to set up for 4k stacks, where we have - * separate stacks for hard and soft interrupts. */ - irq_ctx_init(smp_processor_id()); -} - -/* - * Time. - * - * It would be far better for everyone if the Guest had its own clock, but - * until then the Host gives us the time on every interrupt. - */ -static unsigned long lguest_get_wallclock(void) -{ - return lguest_data.time.tv_sec; -} - -static cycle_t lguest_clock_read(void) -{ - unsigned long sec, nsec; - - /* If the Host tells the TSC speed, we can trust that. */ - if (lguest_data.tsc_khz) - return native_read_tsc(); - - /* If we can't use the TSC, we read the time value written by the Host. - * Since it's in two parts (seconds and nanoseconds), we risk reading - * it just as it's changing from 99 & 0.999999999 to 100 and 0, and - * getting 99 and 0. As Linux tends to come apart under the stress of - * time travel, we must be careful: */ - do { - /* First we read the seconds part. */ - sec = lguest_data.time.tv_sec; - /* This read memory barrier tells the compiler and the CPU that - * this can't be reordered: we have to complete the above - * before going on. */ - rmb(); - /* Now we read the nanoseconds part. */ - nsec = lguest_data.time.tv_nsec; - /* Make sure we've done that. */ - rmb(); - /* Now if the seconds part has changed, try again. */ - } while (unlikely(lguest_data.time.tv_sec != sec)); - - /* Our non-TSC clock is in real nanoseconds. */ - return sec*1000000000ULL + nsec; -} - -/* This is what we tell the kernel is our clocksource. */ -static struct clocksource lguest_clock = { - .name = "lguest", - .rating = 400, - .read = lguest_clock_read, - .mask = CLOCKSOURCE_MASK(64), - .mult = 1 << 22, - .shift = 22, -}; - -/* The "scheduler clock" is just our real clock, adjusted to start at zero */ -static unsigned long long lguest_sched_clock(void) -{ - return cyc2ns(&lguest_clock, lguest_clock_read() - clock_base); -} - -/* We also need a "struct clock_event_device": Linux asks us to set it to go - * off some time in the future. Actually, James Morris figured all this out, I - * just applied the patch. */ -static int lguest_clockevent_set_next_event(unsigned long delta, - struct clock_event_device *evt) -{ - if (delta < LG_CLOCK_MIN_DELTA) { - if (printk_ratelimit()) - printk(KERN_DEBUG "%s: small delta %lu ns\n", - __FUNCTION__, delta); - return -ETIME; - } - hcall(LHCALL_SET_CLOCKEVENT, delta, 0, 0); - return 0; -} - -static void lguest_clockevent_set_mode(enum clock_event_mode mode, - struct clock_event_device *evt) -{ - switch (mode) { - case CLOCK_EVT_MODE_UNUSED: - case CLOCK_EVT_MODE_SHUTDOWN: - /* A 0 argument shuts the clock down. */ - hcall(LHCALL_SET_CLOCKEVENT, 0, 0, 0); - break; - case CLOCK_EVT_MODE_ONESHOT: - /* This is what we expect. */ - break; - case CLOCK_EVT_MODE_PERIODIC: - BUG(); - case CLOCK_EVT_MODE_RESUME: - break; - } -} - -/* This describes our primitive timer chip. */ -static struct clock_event_device lguest_clockevent = { - .name = "lguest", - .features = CLOCK_EVT_FEAT_ONESHOT, - .set_next_event = lguest_clockevent_set_next_event, - .set_mode = lguest_clockevent_set_mode, - .rating = INT_MAX, - .mult = 1, - .shift = 0, - .min_delta_ns = LG_CLOCK_MIN_DELTA, - .max_delta_ns = LG_CLOCK_MAX_DELTA, -}; - -/* This is the Guest timer interrupt handler (hardware interrupt 0). We just - * call the clockevent infrastructure and it does whatever needs doing. */ -static void lguest_time_irq(unsigned int irq, struct irq_desc *desc) -{ - unsigned long flags; - - /* Don't interrupt us while this is running. */ - local_irq_save(flags); - lguest_clockevent.event_handler(&lguest_clockevent); - local_irq_restore(flags); -} - -/* At some point in the boot process, we get asked to set up our timing - * infrastructure. The kernel doesn't expect timer interrupts before this, but - * we cleverly initialized the "blocked_interrupts" field of "struct - * lguest_data" so that timer interrupts were blocked until now. */ -static void lguest_time_init(void) -{ - /* Set up the timer interrupt (0) to go to our simple timer routine */ - set_irq_handler(0, lguest_time_irq); - - /* Our clock structure look like arch/i386/kernel/tsc.c if we can use - * the TSC, otherwise it's a dumb nanosecond-resolution clock. Either - * way, the "rating" is initialized so high that it's always chosen - * over any other clocksource. */ - if (lguest_data.tsc_khz) { - lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz, - lguest_clock.shift); - lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS; - } - clock_base = lguest_clock_read(); - clocksource_register(&lguest_clock); - - /* Now we've set up our clock, we can use it as the scheduler clock */ - pv_time_ops.sched_clock = lguest_sched_clock; - - /* We can't set cpumask in the initializer: damn C limitations! Set it - * here and register our timer device. */ - lguest_clockevent.cpumask = cpumask_of_cpu(0); - clockevents_register_device(&lguest_clockevent); - - /* Finally, we unblock the timer interrupt. */ - enable_lguest_irq(0); -} - -/* - * Miscellaneous bits and pieces. - * - * Here is an oddball collection of functions which the Guest needs for things - * to work. They're pretty simple. - */ - -/* The Guest needs to tell the host what stack it expects traps to use. For - * native hardware, this is part of the Task State Segment mentioned above in - * lguest_load_tr_desc(), but to help hypervisors there's this special call. - * - * We tell the Host the segment we want to use (__KERNEL_DS is the kernel data - * segment), the privilege level (we're privilege level 1, the Host is 0 and - * will not tolerate us trying to use that), the stack pointer, and the number - * of pages in the stack. */ -static void lguest_load_esp0(struct tss_struct *tss, - struct thread_struct *thread) -{ - lazy_hcall(LHCALL_SET_STACK, __KERNEL_DS|0x1, thread->esp0, - THREAD_SIZE/PAGE_SIZE); -} - -/* Let's just say, I wouldn't do debugging under a Guest. */ -static void lguest_set_debugreg(int regno, unsigned long value) -{ - /* FIXME: Implement */ -} - -/* There are times when the kernel wants to make sure that no memory writes are - * caught in the cache (that they've all reached real hardware devices). This - * doesn't matter for the Guest which has virtual hardware. - * - * On the Pentium 4 and above, cpuid() indicates that the Cache Line Flush - * (clflush) instruction is available and the kernel uses that. Otherwise, it - * uses the older "Write Back and Invalidate Cache" (wbinvd) instruction. - * Unlike clflush, wbinvd can only be run at privilege level 0. So we can - * ignore clflush, but replace wbinvd. - */ -static void lguest_wbinvd(void) -{ -} - -/* If the Guest expects to have an Advanced Programmable Interrupt Controller, - * we play dumb by ignoring writes and returning 0 for reads. So it's no - * longer Programmable nor Controlling anything, and I don't think 8 lines of - * code qualifies for Advanced. It will also never interrupt anything. It - * does, however, allow us to get through the Linux boot code. */ -#ifdef CONFIG_X86_LOCAL_APIC -static void lguest_apic_write(unsigned long reg, unsigned long v) -{ -} - -static unsigned long lguest_apic_read(unsigned long reg) -{ - return 0; -} -#endif - -/* STOP! Until an interrupt comes in. */ -static void lguest_safe_halt(void) -{ - hcall(LHCALL_HALT, 0, 0, 0); -} - -/* Perhaps CRASH isn't the best name for this hypercall, but we use it to get a - * message out when we're crashing as well as elegant termination like powering - * off. - * - * Note that the Host always prefers that the Guest speak in physical addresses - * rather than virtual addresses, so we use __pa() here. */ -static void lguest_power_off(void) -{ - hcall(LHCALL_CRASH, __pa("Power down"), 0, 0); -} - -/* - * Panicing. - * - * Don't. But if you did, this is what happens. - */ -static int lguest_panic(struct notifier_block *nb, unsigned long l, void *p) -{ - hcall(LHCALL_CRASH, __pa(p), 0, 0); - /* The hcall won't return, but to keep gcc happy, we're "done". */ - return NOTIFY_DONE; -} - -static struct notifier_block paniced = { - .notifier_call = lguest_panic -}; - -/* Setting up memory is fairly easy. */ -static __init char *lguest_memory_setup(void) -{ - /* We do this here and not earlier because lockcheck barfs if we do it - * before start_kernel() */ - atomic_notifier_chain_register(&panic_notifier_list, &paniced); - - /* The Linux bootloader header contains an "e820" memory map: the - * Launcher populated the first entry with our memory limit. */ - add_memory_region(boot_params.e820_map[0].addr, - boot_params.e820_map[0].size, - boot_params.e820_map[0].type); - - /* This string is for the boot messages. */ - return "LGUEST"; -} - -/*G:050 - * Patching (Powerfully Placating Performance Pedants) - * - * We have already seen that pv_ops structures let us replace simple - * native instructions with calls to the appropriate back end all throughout - * the kernel. This allows the same kernel to run as a Guest and as a native - * kernel, but it's slow because of all the indirect branches. - * - * Remember that David Wheeler quote about "Any problem in computer science can - * be solved with another layer of indirection"? The rest of that quote is - * "... But that usually will create another problem." This is the first of - * those problems. - * - * Our current solution is to allow the paravirt back end to optionally patch - * over the indirect calls to replace them with something more efficient. We - * patch the four most commonly called functions: disable interrupts, enable - * interrupts, restore interrupts and save interrupts. We usually have 10 - * bytes to patch into: the Guest versions of these operations are small enough - * that we can fit comfortably. - * - * First we need assembly templates of each of the patchable Guest operations, - * and these are in lguest_asm.S. */ - -/*G:060 We construct a table from the assembler templates: */ -static const struct lguest_insns -{ - const char *start, *end; -} lguest_insns[] = { - [PARAVIRT_PATCH(pv_irq_ops.irq_disable)] = { lgstart_cli, lgend_cli }, - [PARAVIRT_PATCH(pv_irq_ops.irq_enable)] = { lgstart_sti, lgend_sti }, - [PARAVIRT_PATCH(pv_irq_ops.restore_fl)] = { lgstart_popf, lgend_popf }, - [PARAVIRT_PATCH(pv_irq_ops.save_fl)] = { lgstart_pushf, lgend_pushf }, -}; - -/* Now our patch routine is fairly simple (based on the native one in - * paravirt.c). If we have a replacement, we copy it in and return how much of - * the available space we used. */ -static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf, - unsigned long addr, unsigned len) -{ - unsigned int insn_len; - - /* Don't do anything special if we don't have a replacement */ - if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start) - return paravirt_patch_default(type, clobber, ibuf, addr, len); - - insn_len = lguest_insns[type].end - lguest_insns[type].start; - - /* Similarly if we can't fit replacement (shouldn't happen, but let's - * be thorough). */ - if (len < insn_len) - return paravirt_patch_default(type, clobber, ibuf, addr, len); - - /* Copy in our instructions. */ - memcpy(ibuf, lguest_insns[type].start, insn_len); - return insn_len; -} - -/*G:030 Once we get to lguest_init(), we know we're a Guest. The pv_ops - * structures in the kernel provide points for (almost) every routine we have - * to override to avoid privileged instructions. */ -__init void lguest_init(void *boot) -{ - /* Copy boot parameters first: the Launcher put the physical location - * in %esi, and head.S converted that to a virtual address and handed - * it to us. We use "__memcpy" because "memcpy" sometimes tries to do - * tricky things to go faster, and we're not ready for that. */ - __memcpy(&boot_params, boot, PARAM_SIZE); - /* The boot parameters also tell us where the command-line is: save - * that, too. */ - __memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr), - COMMAND_LINE_SIZE); - - /* We're under lguest, paravirt is enabled, and we're running at - * privilege level 1, not 0 as normal. */ - pv_info.name = "lguest"; - pv_info.paravirt_enabled = 1; - pv_info.kernel_rpl = 1; - - /* We set up all the lguest overrides for sensitive operations. These - * are detailed with the operations themselves. */ - - /* interrupt-related operations */ - pv_irq_ops.init_IRQ = lguest_init_IRQ; - pv_irq_ops.save_fl = save_fl; - pv_irq_ops.restore_fl = restore_fl; - pv_irq_ops.irq_disable = irq_disable; - pv_irq_ops.irq_enable = irq_enable; - pv_irq_ops.safe_halt = lguest_safe_halt; - - /* init-time operations */ - pv_init_ops.memory_setup = lguest_memory_setup; - pv_init_ops.patch = lguest_patch; - - /* Intercepts of various cpu instructions */ - pv_cpu_ops.load_gdt = lguest_load_gdt; - pv_cpu_ops.cpuid = lguest_cpuid; - pv_cpu_ops.load_idt = lguest_load_idt; - pv_cpu_ops.iret = lguest_iret; - pv_cpu_ops.load_esp0 = lguest_load_esp0; - pv_cpu_ops.load_tr_desc = lguest_load_tr_desc; - pv_cpu_ops.set_ldt = lguest_set_ldt; - pv_cpu_ops.load_tls = lguest_load_tls; - pv_cpu_ops.set_debugreg = lguest_set_debugreg; - pv_cpu_ops.clts = lguest_clts; - pv_cpu_ops.read_cr0 = lguest_read_cr0; - pv_cpu_ops.write_cr0 = lguest_write_cr0; - pv_cpu_ops.read_cr4 = lguest_read_cr4; - pv_cpu_ops.write_cr4 = lguest_write_cr4; - pv_cpu_ops.write_gdt_entry = lguest_write_gdt_entry; - pv_cpu_ops.write_idt_entry = lguest_write_idt_entry; - pv_cpu_ops.wbinvd = lguest_wbinvd; - pv_cpu_ops.lazy_mode.enter = paravirt_enter_lazy_cpu; - pv_cpu_ops.lazy_mode.leave = lguest_leave_lazy_mode; - - /* pagetable management */ - pv_mmu_ops.write_cr3 = lguest_write_cr3; - pv_mmu_ops.flush_tlb_user = lguest_flush_tlb_user; - pv_mmu_ops.flush_tlb_single = lguest_flush_tlb_single; - pv_mmu_ops.flush_tlb_kernel = lguest_flush_tlb_kernel; - pv_mmu_ops.set_pte = lguest_set_pte; - pv_mmu_ops.set_pte_at = lguest_set_pte_at; - pv_mmu_ops.set_pmd = lguest_set_pmd; - pv_mmu_ops.read_cr2 = lguest_read_cr2; - pv_mmu_ops.read_cr3 = lguest_read_cr3; - pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu; - pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mode; - -#ifdef CONFIG_X86_LOCAL_APIC - /* apic read/write intercepts */ - pv_apic_ops.apic_write = lguest_apic_write; - pv_apic_ops.apic_write_atomic = lguest_apic_write; - pv_apic_ops.apic_read = lguest_apic_read; -#endif - - /* time operations */ - pv_time_ops.get_wallclock = lguest_get_wallclock; - pv_time_ops.time_init = lguest_time_init; - - /* Now is a good time to look at the implementations of these functions - * before returning to the rest of lguest_init(). */ - - /*G:070 Now we've seen all the paravirt_ops, we return to - * lguest_init() where the rest of the fairly chaotic boot setup - * occurs. - * - * The Host expects our first hypercall to tell it where our "struct - * lguest_data" is, so we do that first. */ - hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0); - - /* The native boot code sets up initial page tables immediately after - * the kernel itself, and sets init_pg_tables_end so they're not - * clobbered. The Launcher places our initial pagetables somewhere at - * the top of our physical memory, so we don't need extra space: set - * init_pg_tables_end to the end of the kernel. */ - init_pg_tables_end = __pa(pg0); - - /* Load the %fs segment register (the per-cpu segment register) with - * the normal data segment to get through booting. */ - asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory"); - - /* Clear the part of the kernel data which is expected to be zero. - * Normally it will be anyway, but if we're loading from a bzImage with - * CONFIG_RELOCATALE=y, the relocations will be sitting here. */ - memset(__bss_start, 0, __bss_stop - __bss_start); - - /* The Host uses the top of the Guest's virtual address space for the - * Host<->Guest Switcher, and it tells us how much it needs in - * lguest_data.reserve_mem, set up on the LGUEST_INIT hypercall. */ - reserve_top_address(lguest_data.reserve_mem); - - /* If we don't initialize the lock dependency checker now, it crashes - * paravirt_disable_iospace. */ - lockdep_init(); - - /* The IDE code spends about 3 seconds probing for disks: if we reserve - * all the I/O ports up front it can't get them and so doesn't probe. - * Other device drivers are similar (but less severe). This cuts the - * kernel boot time on my machine from 4.1 seconds to 0.45 seconds. */ - paravirt_disable_iospace(); - - /* This is messy CPU setup stuff which the native boot code does before - * start_kernel, so we have to do, too: */ - cpu_detect(&new_cpu_data); - /* head.S usually sets up the first capability word, so do it here. */ - new_cpu_data.x86_capability[0] = cpuid_edx(1); - - /* Math is always hard! */ - new_cpu_data.hard_math = 1; - -#ifdef CONFIG_X86_MCE - mce_disabled = 1; -#endif -#ifdef CONFIG_ACPI - acpi_disabled = 1; - acpi_ht = 0; -#endif - - /* We set the perferred console to "hvc". This is the "hypervisor - * virtual console" driver written by the PowerPC people, which we also - * adapted for lguest's use. */ - add_preferred_console("hvc", 0, NULL); - - /* Last of all, we set the power management poweroff hook to point to - * the Guest routine to power off. */ - pm_power_off = lguest_power_off; - - /* Now we're set up, call start_kernel() in init/main.c and we proceed - * to boot as normal. It never returns. */ - start_kernel(); -} -/* - * This marks the end of stage II of our journey, The Guest. - * - * It is now time for us to explore the nooks and crannies of the three Guest - * devices and complete our understanding of the Guest in "make Drivers". - */ diff --git a/drivers/lguest/lguest_asm.S b/drivers/lguest/lguest_asm.S deleted file mode 100644 index 1ddcd5cd20f6..000000000000 --- a/drivers/lguest/lguest_asm.S +++ /dev/null @@ -1,93 +0,0 @@ -#include <linux/linkage.h> -#include <linux/lguest.h> -#include <asm/asm-offsets.h> -#include <asm/thread_info.h> -#include <asm/processor-flags.h> - -/*G:020 This is where we begin: we have a magic signature which the launcher - * looks for. The plan is that the Linux boot protocol will be extended with a - * "platform type" field which will guide us here from the normal entry point, - * but for the moment this suffices. The normal boot code uses %esi for the - * boot header, so we do too. We convert it to a virtual address by adding - * PAGE_OFFSET, and hand it to lguest_init() as its argument (ie. %eax). - * - * The .section line puts this code in .init.text so it will be discarded after - * boot. */ -.section .init.text, "ax", @progbits -.ascii "GenuineLguest" - /* Set up initial stack. */ - movl $(init_thread_union+THREAD_SIZE),%esp - movl %esi, %eax - addl $__PAGE_OFFSET, %eax - jmp lguest_init - -/*G:055 We create a macro which puts the assembler code between lgstart_ and - * lgend_ markers. These templates are put in the .text section: they can't be - * discarded after boot as we may need to patch modules, too. */ -.text -#define LGUEST_PATCH(name, insns...) \ - lgstart_##name: insns; lgend_##name:; \ - .globl lgstart_##name; .globl lgend_##name - -LGUEST_PATCH(cli, movl $0, lguest_data+LGUEST_DATA_irq_enabled) -LGUEST_PATCH(sti, movl $X86_EFLAGS_IF, lguest_data+LGUEST_DATA_irq_enabled) -LGUEST_PATCH(popf, movl %eax, lguest_data+LGUEST_DATA_irq_enabled) -LGUEST_PATCH(pushf, movl lguest_data+LGUEST_DATA_irq_enabled, %eax) -/*:*/ - -/* These demark the EIP range where host should never deliver interrupts. */ -.global lguest_noirq_start -.global lguest_noirq_end - -/*M:004 When the Host reflects a trap or injects an interrupt into the Guest, - * it sets the eflags interrupt bit on the stack based on - * lguest_data.irq_enabled, so the Guest iret logic does the right thing when - * restoring it. However, when the Host sets the Guest up for direct traps, - * such as system calls, the processor is the one to push eflags onto the - * stack, and the interrupt bit will be 1 (in reality, interrupts are always - * enabled in the Guest). - * - * This turns out to be harmless: the only trap which should happen under Linux - * with interrupts disabled is Page Fault (due to our lazy mapping of vmalloc - * regions), which has to be reflected through the Host anyway. If another - * trap *does* go off when interrupts are disabled, the Guest will panic, and - * we'll never get to this iret! :*/ - -/*G:045 There is one final paravirt_op that the Guest implements, and glancing - * at it you can see why I left it to last. It's *cool*! It's in *assembler*! - * - * The "iret" instruction is used to return from an interrupt or trap. The - * stack looks like this: - * old address - * old code segment & privilege level - * old processor flags ("eflags") - * - * The "iret" instruction pops those values off the stack and restores them all - * at once. The only problem is that eflags includes the Interrupt Flag which - * the Guest can't change: the CPU will simply ignore it when we do an "iret". - * So we have to copy eflags from the stack to lguest_data.irq_enabled before - * we do the "iret". - * - * There are two problems with this: firstly, we need to use a register to do - * the copy and secondly, the whole thing needs to be atomic. The first - * problem is easy to solve: push %eax on the stack so we can use it, and then - * restore it at the end just before the real "iret". - * - * The second is harder: copying eflags to lguest_data.irq_enabled will turn - * interrupts on before we're finished, so we could be interrupted before we - * return to userspace or wherever. Our solution to this is to surround the - * code with lguest_noirq_start: and lguest_noirq_end: labels. We tell the - * Host that it is *never* to interrupt us there, even if interrupts seem to be - * enabled. */ -ENTRY(lguest_iret) - pushl %eax - movl 12(%esp), %eax -lguest_noirq_start: - /* Note the %ss: segment prefix here. Normal data accesses use the - * "ds" segment, but that will have already been restored for whatever - * we're returning to (such as userspace): we can't trust it. The %ss: - * prefix makes sure we use the stack segment, which is still valid. */ - movl %eax,%ss:lguest_data+LGUEST_DATA_irq_enabled - popl %eax - iret -lguest_noirq_end: diff --git a/drivers/lguest/lguest_bus.c b/drivers/lguest/lguest_bus.c deleted file mode 100644 index 57329788f8a7..000000000000 --- a/drivers/lguest/lguest_bus.c +++ /dev/null @@ -1,218 +0,0 @@ -/*P:050 Lguest guests use a very simple bus for devices. It's a simple array - * of device descriptors contained just above the top of normal memory. The - * lguest bus is 80% tedious boilerplate code. :*/ -#include <linux/init.h> -#include <linux/bootmem.h> -#include <linux/lguest_bus.h> -#include <asm/io.h> -#include <asm/paravirt.h> - -static ssize_t type_show(struct device *_dev, - struct device_attribute *attr, char *buf) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - return sprintf(buf, "%hu", lguest_devices[dev->index].type); -} -static ssize_t features_show(struct device *_dev, - struct device_attribute *attr, char *buf) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - return sprintf(buf, "%hx", lguest_devices[dev->index].features); -} -static ssize_t pfn_show(struct device *_dev, - struct device_attribute *attr, char *buf) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - return sprintf(buf, "%u", lguest_devices[dev->index].pfn); -} -static ssize_t status_show(struct device *_dev, - struct device_attribute *attr, char *buf) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - return sprintf(buf, "%hx", lguest_devices[dev->index].status); -} -static ssize_t status_store(struct device *_dev, struct device_attribute *attr, - const char *buf, size_t count) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - if (sscanf(buf, "%hi", &lguest_devices[dev->index].status) != 1) - return -EINVAL; - return count; -} -static struct device_attribute lguest_dev_attrs[] = { - __ATTR_RO(type), - __ATTR_RO(features), - __ATTR_RO(pfn), - __ATTR(status, 0644, status_show, status_store), - __ATTR_NULL -}; - -/*D:130 The generic bus infrastructure requires a function which says whether a - * device matches a driver. For us, it is simple: "struct lguest_driver" - * contains a "device_type" field which indicates what type of device it can - * handle, so we just cast the args and compare: */ -static int lguest_dev_match(struct device *_dev, struct device_driver *_drv) -{ - struct lguest_device *dev = container_of(_dev,struct lguest_device,dev); - struct lguest_driver *drv = container_of(_drv,struct lguest_driver,drv); - - return (drv->device_type == lguest_devices[dev->index].type); -} -/*:*/ - -struct lguest_bus { - struct bus_type bus; - struct device dev; -}; - -static struct lguest_bus lguest_bus = { - .bus = { - .name = "lguest", - .match = lguest_dev_match, - .dev_attrs = lguest_dev_attrs, - }, - .dev = { - .parent = NULL, - .bus_id = "lguest", - } -}; - -/*D:140 This is the callback which occurs once the bus infrastructure matches - * up a device and driver, ie. in response to add_lguest_device() calling - * device_register(), or register_lguest_driver() calling driver_register(). - * - * At the moment it's always the latter: the devices are added first, since - * scan_devices() is called from a "core_initcall", and the drivers themselves - * called later as a normal "initcall". But it would work the other way too. - * - * So now we have the happy couple, we add the status bit to indicate that we - * found a driver. If the driver truly loves the device, it will return - * happiness from its probe function (ok, perhaps this wasn't my greatest - * analogy), and we set the final "driver ok" bit so the Host sees it's all - * green. */ -static int lguest_dev_probe(struct device *_dev) -{ - int ret; - struct lguest_device*dev = container_of(_dev,struct lguest_device,dev); - struct lguest_driver*drv = container_of(dev->dev.driver, - struct lguest_driver, drv); - - lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER; - ret = drv->probe(dev); - if (ret == 0) - lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER_OK; - return ret; -} - -/* The last part of the bus infrastructure is the function lguest drivers use - * to register themselves. Firstly, we do nothing if there's no lguest bus - * (ie. this is not a Guest), otherwise we fill in the embedded generic "struct - * driver" fields and call the generic driver_register(). */ -int register_lguest_driver(struct lguest_driver *drv) -{ - if (!lguest_devices) - return 0; - - drv->drv.bus = &lguest_bus.bus; - drv->drv.name = drv->name; - drv->drv.owner = drv->owner; - drv->drv.probe = lguest_dev_probe; - - return driver_register(&drv->drv); -} - -/* At the moment we build all the drivers into the kernel because they're so - * simple: 8144 bytes for all three of them as I type this. And as the console - * really needs to be built in, it's actually only 3527 bytes for the network - * and block drivers. - * - * If they get complex it will make sense for them to be modularized, so we - * need to explicitly export the symbol. - * - * I don't think non-GPL modules make sense, so it's a GPL-only export. - */ -EXPORT_SYMBOL_GPL(register_lguest_driver); - -/*D:120 This is the core of the lguest bus: actually adding a new device. - * It's a separate function because it's neater that way, and because an - * earlier version of the code supported hotplug and unplug. They were removed - * early on because they were never used. - * - * As Andrew Tridgell says, "Untested code is buggy code". - * - * It's worth reading this carefully: we start with an index into the array of - * "struct lguest_device_desc"s indicating the device which is new: */ -static void add_lguest_device(unsigned int index) -{ - struct lguest_device *new; - - /* Each "struct lguest_device_desc" has a "status" field, which the - * Guest updates as the device is probed. In the worst case, the Host - * can look at these bits to tell what part of device setup failed, - * even if the console isn't available. */ - lguest_devices[index].status |= LGUEST_DEVICE_S_ACKNOWLEDGE; - new = kmalloc(sizeof(struct lguest_device), GFP_KERNEL); - if (!new) { - printk(KERN_EMERG "Cannot allocate lguest device %u\n", index); - lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED; - return; - } - - /* The "struct lguest_device" setup is pretty straight-forward example - * code. */ - new->index = index; - new->private = NULL; - memset(&new->dev, 0, sizeof(new->dev)); - new->dev.parent = &lguest_bus.dev; - new->dev.bus = &lguest_bus.bus; - sprintf(new->dev.bus_id, "%u", index); - - /* device_register() causes the bus infrastructure to look for a - * matching driver. */ - if (device_register(&new->dev) != 0) { - printk(KERN_EMERG "Cannot register lguest device %u\n", index); - lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED; - kfree(new); - } -} - -/*D:110 scan_devices() simply iterates through the device array. The type 0 - * is reserved to mean "no device", and anything else means we have found a - * device: add it. */ -static void scan_devices(void) -{ - unsigned int i; - - for (i = 0; i < LGUEST_MAX_DEVICES; i++) - if (lguest_devices[i].type) - add_lguest_device(i); -} - -/*D:100 Fairly early in boot, lguest_bus_init() is called to set up the lguest - * bus. We check that we are a Guest by checking paravirt_ops.name: there are - * other ways of checking, but this seems most obvious to me. - * - * So we can access the array of "struct lguest_device_desc"s easily, we map - * that memory and store the pointer in the global "lguest_devices". Then we - * register the bus with the core. Doing two registrations seems clunky to me, - * but it seems to be the correct sysfs incantation. - * - * Finally we call scan_devices() which adds all the devices found in the - * "struct lguest_device_desc" array. */ -static int __init lguest_bus_init(void) -{ - if (strcmp(pv_info.name, "lguest") != 0) - return 0; - - /* Devices are in a single page above top of "normal" mem */ - lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1); - - if (bus_register(&lguest_bus.bus) != 0 - || device_register(&lguest_bus.dev) != 0) - panic("lguest bus registration failed"); - - scan_devices(); - return 0; -} -/* Do this after core stuff, before devices. */ -postcore_initcall(lguest_bus_init); diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c new file mode 100644 index 000000000000..8904f72f97c6 --- /dev/null +++ b/drivers/lguest/lguest_device.c @@ -0,0 +1,376 @@ +/*P:050 Lguest guests use a very simple method to describe devices. It's a + * series of device descriptors contained just above the top of normal + * memory. + * + * We use the standard "virtio" device infrastructure, which provides us with a + * console, a network and a block driver. Each one expects some configuration + * information and a "virtqueue" mechanism to send and receive data. :*/ +#include <linux/init.h> +#include <linux/bootmem.h> +#include <linux/lguest_launcher.h> +#include <linux/virtio.h> +#include <linux/virtio_config.h> +#include <linux/interrupt.h> +#include <linux/virtio_ring.h> +#include <linux/err.h> +#include <asm/io.h> +#include <asm/paravirt.h> +#include <asm/lguest_hcall.h> + +/* The pointer to our (page) of device descriptions. */ +static void *lguest_devices; + +/* Unique numbering for lguest devices. */ +static unsigned int dev_index; + +/* For Guests, device memory can be used as normal memory, so we cast away the + * __iomem to quieten sparse. */ +static inline void *lguest_map(unsigned long phys_addr, unsigned long pages) +{ + return (__force void *)ioremap(phys_addr, PAGE_SIZE*pages); +} + +static inline void lguest_unmap(void *addr) +{ + iounmap((__force void __iomem *)addr); +} + +/*D:100 Each lguest device is just a virtio device plus a pointer to its entry + * in the lguest_devices page. */ +struct lguest_device { + struct virtio_device vdev; + + /* The entry in the lguest_devices page for this device. */ + struct lguest_device_desc *desc; +}; + +/* Since the virtio infrastructure hands us a pointer to the virtio_device all + * the time, it helps to have a curt macro to get a pointer to the struct + * lguest_device it's enclosed in. */ +#define to_lgdev(vdev) container_of(vdev, struct lguest_device, vdev) + +/*D:130 + * Device configurations + * + * The configuration information for a device consists of a series of fields. + * We don't really care what they are: the Launcher set them up, and the driver + * will look at them during setup. + * + * For us these fields come immediately after that device's descriptor in the + * lguest_devices page. + * + * Each field starts with a "type" byte, a "length" byte, then that number of + * bytes of configuration information. The device descriptor tells us the + * total configuration length so we know when we've reached the last field. */ + +/* type + length bytes */ +#define FHDR_LEN 2 + +/* This finds the first field of a given type for a device's configuration. */ +static void *lg_find(struct virtio_device *vdev, u8 type, unsigned int *len) +{ + struct lguest_device_desc *desc = to_lgdev(vdev)->desc; + int i; + + for (i = 0; i < desc->config_len; i += FHDR_LEN + desc->config[i+1]) { + if (desc->config[i] == type) { + /* Mark it used, so Host can know we looked at it, and + * also so we won't find the same one twice. */ + desc->config[i] |= 0x80; + /* Remember, the second byte is the length. */ + *len = desc->config[i+1]; + /* We return a pointer to the field header. */ + return desc->config + i; + } + } + + /* Not found: return NULL for failure. */ + return NULL; +} + +/* Once they've found a field, getting a copy of it is easy. */ +static void lg_get(struct virtio_device *vdev, void *token, + void *buf, unsigned len) +{ + /* Check they didn't ask for more than the length of the field! */ + BUG_ON(len > ((u8 *)token)[1]); + memcpy(buf, token + FHDR_LEN, len); +} + +/* Setting the contents is also trivial. */ +static void lg_set(struct virtio_device *vdev, void *token, + const void *buf, unsigned len) +{ + BUG_ON(len > ((u8 *)token)[1]); + memcpy(token + FHDR_LEN, buf, len); +} + +/* The operations to get and set the status word just access the status field + * of the device descriptor. */ +static u8 lg_get_status(struct virtio_device *vdev) +{ + return to_lgdev(vdev)->desc->status; +} + +static void lg_set_status(struct virtio_device *vdev, u8 status) +{ + to_lgdev(vdev)->desc->status = status; +} + +/* + * Virtqueues + * + * The other piece of infrastructure virtio needs is a "virtqueue": a way of + * the Guest device registering buffers for the other side to read from or + * write into (ie. send and receive buffers). Each device can have multiple + * virtqueues: for example the console driver uses one queue for sending and + * another for receiving. + * + * Fortunately for us, a very fast shared-memory-plus-descriptors virtqueue + * already exists in virtio_ring.c. We just need to connect it up. + * + * We start with the information we need to keep about each virtqueue. + */ + +/*D:140 This is the information we remember about each virtqueue. */ +struct lguest_vq_info +{ + /* A copy of the information contained in the device config. */ + struct lguest_vqconfig config; + + /* The address where we mapped the virtio ring, so we can unmap it. */ + void *pages; +}; + +/* When the virtio_ring code wants to prod the Host, it calls us here and we + * make a hypercall. We hand the page number of the virtqueue so the Host + * knows which virtqueue we're talking about. */ +static void lg_notify(struct virtqueue *vq) +{ + /* We store our virtqueue information in the "priv" pointer of the + * virtqueue structure. */ + struct lguest_vq_info *lvq = vq->priv; + + hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0); +} + +/* This routine finds the first virtqueue described in the configuration of + * this device and sets it up. + * + * This is kind of an ugly duckling. It'd be nicer to have a standard + * representation of a virtqueue in the configuration space, but it seems that + * everyone wants to do it differently. The KVM coders want the Guest to + * allocate its own pages and tell the Host where they are, but for lguest it's + * simpler for the Host to simply tell us where the pages are. + * + * So we provide devices with a "find virtqueue and set it up" function. */ +static struct virtqueue *lg_find_vq(struct virtio_device *vdev, + bool (*callback)(struct virtqueue *vq)) +{ + struct lguest_vq_info *lvq; + struct virtqueue *vq; + unsigned int len; + void *token; + int err; + + /* Look for a field of the correct type to mark a virtqueue. Note that + * if this succeeds, then the type will be changed so it won't be found + * again, and future lg_find_vq() calls will find the next + * virtqueue (if any). */ + token = vdev->config->find(vdev, VIRTIO_CONFIG_F_VIRTQUEUE, &len); + if (!token) + return ERR_PTR(-ENOENT); + + lvq = kmalloc(sizeof(*lvq), GFP_KERNEL); + if (!lvq) + return ERR_PTR(-ENOMEM); + + /* Note: we could use a configuration space inside here, just like we + * do for the device. This would allow expansion in future, because + * our configuration system is designed to be expansible. But this is + * way easier. */ + if (len != sizeof(lvq->config)) { + dev_err(&vdev->dev, "Unexpected virtio config len %u\n", len); + err = -EIO; + goto free_lvq; + } + /* Make a copy of the "struct lguest_vqconfig" field. We need a copy + * because the config space might not be aligned correctly. */ + vdev->config->get(vdev, token, &lvq->config, sizeof(lvq->config)); + + /* Figure out how many pages the ring will take, and map that memory */ + lvq->pages = lguest_map((unsigned long)lvq->config.pfn << PAGE_SHIFT, + DIV_ROUND_UP(vring_size(lvq->config.num), + PAGE_SIZE)); + if (!lvq->pages) { + err = -ENOMEM; + goto free_lvq; + } + + /* OK, tell virtio_ring.c to set up a virtqueue now we know its size + * and we've got a pointer to its pages. */ + vq = vring_new_virtqueue(lvq->config.num, vdev, lvq->pages, + lg_notify, callback); + if (!vq) { + err = -ENOMEM; + goto unmap; + } + + /* Tell the interrupt for this virtqueue to go to the virtio_ring + * interrupt handler. */ + /* FIXME: We used to have a flag for the Host to tell us we could use + * the interrupt as a source of randomness: it'd be nice to have that + * back.. */ + err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED, + vdev->dev.bus_id, vq); + if (err) + goto destroy_vring; + + /* Last of all we hook up our 'struct lguest_vq_info" to the + * virtqueue's priv pointer. */ + vq->priv = lvq; + return vq; + +destroy_vring: + vring_del_virtqueue(vq); +unmap: + lguest_unmap(lvq->pages); +free_lvq: + kfree(lvq); + return ERR_PTR(err); +} +/*:*/ + +/* Cleaning up a virtqueue is easy */ +static void lg_del_vq(struct virtqueue *vq) +{ + struct lguest_vq_info *lvq = vq->priv; + + /* Tell virtio_ring.c to free the virtqueue. */ + vring_del_virtqueue(vq); + /* Unmap the pages containing the ring. */ + lguest_unmap(lvq->pages); + /* Free our own queue information. */ + kfree(lvq); +} + +/* The ops structure which hooks everything together. */ +static struct virtio_config_ops lguest_config_ops = { + .find = lg_find, + .get = lg_get, + .set = lg_set, + .get_status = lg_get_status, + .set_status = lg_set_status, + .find_vq = lg_find_vq, + .del_vq = lg_del_vq, +}; + +/* The root device for the lguest virtio devices. This makes them appear as + * /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */ +static struct device lguest_root = { + .parent = NULL, + .bus_id = "lguest", +}; + +/*D:120 This is the core of the lguest bus: actually adding a new device. + * It's a separate function because it's neater that way, and because an + * earlier version of the code supported hotplug and unplug. They were removed + * early on because they were never used. + * + * As Andrew Tridgell says, "Untested code is buggy code". + * + * It's worth reading this carefully: we start with a pointer to the new device + * descriptor in the "lguest_devices" page. */ +static void add_lguest_device(struct lguest_device_desc *d) +{ + struct lguest_device *ldev; + + /* Start with zeroed memory; Linux's device layer seems to count on + * it. */ + ldev = kzalloc(sizeof(*ldev), GFP_KERNEL); + if (!ldev) { + printk(KERN_EMERG "Cannot allocate lguest dev %u\n", + dev_index++); + return; + } + + /* This devices' parent is the lguest/ dir. */ + ldev->vdev.dev.parent = &lguest_root; + /* We have a unique device index thanks to the dev_index counter. */ + ldev->vdev.index = dev_index++; + /* The device type comes straight from the descriptor. There's also a + * device vendor field in the virtio_device struct, which we leave as + * 0. */ + ldev->vdev.id.device = d->type; + /* We have a simple set of routines for querying the device's + * configuration information and setting its status. */ + ldev->vdev.config = &lguest_config_ops; + /* And we remember the device's descriptor for lguest_config_ops. */ + ldev->desc = d; + + /* register_virtio_device() sets up the generic fields for the struct + * virtio_device and calls device_register(). This makes the bus + * infrastructure look for a matching driver. */ + if (register_virtio_device(&ldev->vdev) != 0) { + printk(KERN_ERR "Failed to register lguest device %u\n", + ldev->vdev.index); + kfree(ldev); + } +} + +/*D:110 scan_devices() simply iterates through the device page. The type 0 is + * reserved to mean "end of devices". */ +static void scan_devices(void) +{ + unsigned int i; + struct lguest_device_desc *d; + + /* We start at the page beginning, and skip over each entry. */ + for (i = 0; i < PAGE_SIZE; i += sizeof(*d) + d->config_len) { + d = lguest_devices + i; + + /* Once we hit a zero, stop. */ + if (d->type == 0) + break; + + add_lguest_device(d); + } +} + +/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the + * lguest device infrastructure. We check that we are a Guest by checking + * pv_info.name: there are other ways of checking, but this seems most + * obvious to me. + * + * So we can access the "struct lguest_device_desc"s easily, we map that memory + * and store the pointer in the global "lguest_devices". Then we register a + * root device from which all our devices will hang (this seems to be the + * correct sysfs incantation). + * + * Finally we call scan_devices() which adds all the devices found in the + * lguest_devices page. */ +static int __init lguest_devices_init(void) +{ + if (strcmp(pv_info.name, "lguest") != 0) + return 0; + + if (device_register(&lguest_root) != 0) + panic("Could not register lguest root"); + + /* Devices are in a single page above top of "normal" mem */ + lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1); + + scan_devices(); + return 0; +} +/* We do this after core stuff, but before the drivers. */ +postcore_initcall(lguest_devices_init); + +/*D:150 At this point in the journey we used to now wade through the lguest + * devices themselves: net, block and console. Since they're all now virtio + * devices rather than lguest-specific, I've decided to ignore them. Mostly, + * they're kind of boring. But this does mean you'll never experience the + * thrill of reading the forbidden love scene buried deep in the block driver. + * + * "make Launcher" beckons, where we answer questions like "Where do Guests + * come from?", and "What do you do when someone asks for optimization?". */ diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index 80d1b58c7698..9d716fa42cad 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -1,83 +1,29 @@ /*P:200 This contains all the /dev/lguest code, whereby the userspace launcher * controls and communicates with the Guest. For example, the first write will - * tell us the memory size, pagetable, entry point and kernel address offset. - * A read will run the Guest until a signal is pending (-EINTR), or the Guest - * does a DMA out to the Launcher. Writes are also used to get a DMA buffer - * registered by the Guest and to send the Guest an interrupt. :*/ + * tell us the Guest's memory layout, pagetable, entry point and kernel address + * offset. A read will run the Guest until something happens, such as a signal + * or the Guest doing a NOTIFY out to the Launcher. :*/ #include <linux/uaccess.h> #include <linux/miscdevice.h> #include <linux/fs.h> #include "lg.h" -/*L:030 setup_regs() doesn't really belong in this file, but it gives us an - * early glimpse deeper into the Host so it's worth having here. - * - * Most of the Guest's registers are left alone: we used get_zeroed_page() to - * allocate the structure, so they will be 0. */ -static void setup_regs(struct lguest_regs *regs, unsigned long start) -{ - /* There are four "segment" registers which the Guest needs to boot: - * The "code segment" register (cs) refers to the kernel code segment - * __KERNEL_CS, and the "data", "extra" and "stack" segment registers - * refer to the kernel data segment __KERNEL_DS. - * - * The privilege level is packed into the lower bits. The Guest runs - * at privilege level 1 (GUEST_PL).*/ - regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; - regs->cs = __KERNEL_CS|GUEST_PL; - - /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002) - * is supposed to always be "1". Bit 9 (0x200) controls whether - * interrupts are enabled. We always leave interrupts enabled while - * running the Guest. */ - regs->eflags = 0x202; - - /* The "Extended Instruction Pointer" register says where the Guest is - * running. */ - regs->eip = start; - - /* %esi points to our boot information, at physical address 0, so don't - * touch it. */ -} - -/*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a - * DMA buffer. This is done by writing LHREQ_GETDMA and the key to - * /dev/lguest. */ -static long user_get_dma(struct lguest *lg, const u32 __user *input) -{ - unsigned long key, udma, irq; - - /* Fetch the key they wrote to us. */ - if (get_user(key, input) != 0) - return -EFAULT; - /* Look for a free Guest DMA buffer bound to that key. */ - udma = get_dma_buffer(lg, key, &irq); - if (!udma) - return -ENOENT; - - /* We need to tell the Launcher what interrupt the Guest expects after - * the buffer is filled. We stash it in udma->used_len. */ - lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq); - - /* The (guest-physical) address of the DMA buffer is returned from - * the write(). */ - return udma; -} - -/*L:315 To force the Guest to stop running and return to the Launcher, the - * Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest. The - * Launcher then writes LHREQ_BREAK and "0" to release the Waker. */ -static int break_guest_out(struct lguest *lg, const u32 __user *input) +/*L:055 When something happens, the Waker process needs a way to stop the + * kernel running the Guest and return to the Launcher. So the Waker writes + * LHREQ_BREAK and the value "1" to /dev/lguest to do this. Once the Launcher + * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release + * the Waker. */ +static int break_guest_out(struct lguest *lg, const unsigned long __user *input) { unsigned long on; - /* Fetch whether they're turning break on or off.. */ + /* Fetch whether they're turning break on or off. */ if (get_user(on, input) != 0) return -EFAULT; if (on) { lg->break_out = 1; - /* Pop it out (may be running on different CPU) */ + /* Pop it out of the Guest (may be running on different CPU) */ wake_up_process(lg->tsk); /* Wait for them to reset it */ return wait_event_interruptible(lg->break_wq, !lg->break_out); @@ -90,9 +36,9 @@ static int break_guest_out(struct lguest *lg, const u32 __user *input) /*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt * number to /dev/lguest. */ -static int user_send_irq(struct lguest *lg, const u32 __user *input) +static int user_send_irq(struct lguest *lg, const unsigned long __user *input) { - u32 irq; + unsigned long irq; if (get_user(irq, input) != 0) return -EFAULT; @@ -114,7 +60,7 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) if (!lg) return -EINVAL; - /* If you're not the task which owns the guest, go away. */ + /* If you're not the task which owns the Guest, go away. */ if (current != lg->tsk) return -EPERM; @@ -133,43 +79,39 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) return len; } - /* If we returned from read() last time because the Guest sent DMA, + /* If we returned from read() last time because the Guest notified, * clear the flag. */ - if (lg->dma_is_pending) - lg->dma_is_pending = 0; + if (lg->pending_notify) + lg->pending_notify = 0; /* Run the Guest until something interesting happens. */ return run_guest(lg, (unsigned long __user *)user); } -/*L:020 The initialization write supplies 4 32-bit values (in addition to the - * 32-bit LHREQ_INITIALIZE value). These are: +/*L:020 The initialization write supplies 4 pointer sized (32 or 64 bit) + * values (in addition to the LHREQ_INITIALIZE value). These are: + * + * base: The start of the Guest-physical memory inside the Launcher memory. * * pfnlimit: The highest (Guest-physical) page number the Guest should be - * allowed to access. The Launcher has to live in Guest memory, so it sets - * this to ensure the Guest can't reach it. + * allowed to access. The Guest memory lives inside the Launcher, so it sets + * this to ensure the Guest can only reach its own memory. * * pgdir: The (Guest-physical) address of the top of the initial Guest * pagetables (which are set up by the Launcher). * * start: The first instruction to execute ("eip" in x86-speak). - * - * page_offset: The PAGE_OFFSET constant in the Guest kernel. We should - * probably wean the code off this, but it's a very useful constant! Any - * address above this is within the Guest kernel, and any kernel address can - * quickly converted from physical to virtual by adding PAGE_OFFSET. It's - * 0xC0000000 (3G) by default, but it's configurable at kernel build time. */ -static int initialize(struct file *file, const u32 __user *input) +static int initialize(struct file *file, const unsigned long __user *input) { /* "struct lguest" contains everything we (the Host) know about a * Guest. */ struct lguest *lg; - int err, i; - u32 args[4]; + int err; + unsigned long args[4]; - /* We grab the Big Lguest lock, which protects the global array - * "lguests" and multiple simultaneous initializations. */ + /* We grab the Big Lguest lock, which protects against multiple + * simultaneous initializations. */ mutex_lock(&lguest_lock); /* You can't initialize twice! Close the device and start again... */ if (file->private_data) { @@ -182,20 +124,15 @@ static int initialize(struct file *file, const u32 __user *input) goto unlock; } - /* Find an unused guest. */ - i = find_free_guest(); - if (i < 0) { - err = -ENOSPC; + lg = kzalloc(sizeof(*lg), GFP_KERNEL); + if (!lg) { + err = -ENOMEM; goto unlock; } - /* OK, we have an index into the "lguest" array: "lg" is a convenient - * pointer. */ - lg = &lguests[i]; /* Populate the easy fields of our "struct lguest" */ - lg->guestid = i; - lg->pfn_limit = args[0]; - lg->page_offset = args[3]; + lg->mem_base = (void __user *)(long)args[0]; + lg->pfn_limit = args[1]; /* We need a complete page for the Guest registers: they are accessible * to the Guest and we can only grant it access to whole pages. */ @@ -210,17 +147,13 @@ static int initialize(struct file *file, const u32 __user *input) /* Initialize the Guest's shadow page tables, using the toplevel * address the Launcher gave us. This allocates memory, so can * fail. */ - err = init_guest_pagetable(lg, args[1]); + err = init_guest_pagetable(lg, args[2]); if (err) goto free_regs; /* Now we initialize the Guest's registers, handing it the start * address. */ - setup_regs(lg->regs, args[2]); - - /* There are a couple of GDT entries the Guest expects when first - * booting. */ - setup_guest_gdt(lg); + lguest_arch_setup_regs(lg, args[3]); /* The timer for lguest's clock needs initialization. */ init_clockdev(lg); @@ -258,20 +191,21 @@ unlock: } /*L:010 The first operation the Launcher does must be a write. All writes - * start with a 32 bit number: for the first write this must be + * start with an unsigned long number: for the first write this must be * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use - * writes of other values to get DMA buffers and send interrupts. */ -static ssize_t write(struct file *file, const char __user *input, + * writes of other values to send interrupts. */ +static ssize_t write(struct file *file, const char __user *in, size_t size, loff_t *off) { /* Once the guest is initialized, we hold the "struct lguest" in the * file private data. */ struct lguest *lg = file->private_data; - u32 req; + const unsigned long __user *input = (const unsigned long __user *)in; + unsigned long req; if (get_user(req, input) != 0) return -EFAULT; - input += sizeof(req); + input++; /* If you haven't initialized, you must do that first. */ if (req != LHREQ_INITIALIZE && !lg) @@ -287,13 +221,11 @@ static ssize_t write(struct file *file, const char __user *input, switch (req) { case LHREQ_INITIALIZE: - return initialize(file, (const u32 __user *)input); - case LHREQ_GETDMA: - return user_get_dma(lg, (const u32 __user *)input); + return initialize(file, input); case LHREQ_IRQ: - return user_send_irq(lg, (const u32 __user *)input); + return user_send_irq(lg, input); case LHREQ_BREAK: - return break_guest_out(lg, (const u32 __user *)input); + return break_guest_out(lg, input); default: return -EINVAL; } @@ -319,8 +251,6 @@ static int close(struct inode *inode, struct file *file) mutex_lock(&lguest_lock); /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ hrtimer_cancel(&lg->hrt); - /* Free any DMA buffers the Guest had bound. */ - release_all_dma(lg); /* Free up the shadow page tables for the Guest. */ free_guest_pagetable(lg); /* Now all the memory cleanups are done, it's safe to release the @@ -347,8 +277,7 @@ static int close(struct inode *inode, struct file *file) * The Launcher is the Host userspace program which sets up, runs and services * the Guest. In fact, many comments in the Drivers which refer to "the Host" * doing things are inaccurate: the Launcher does all the device handling for - * the Guest. The Guest can't tell what's done by the the Launcher and what by - * the Host. + * the Guest, but the Guest can't know that. * * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we * shall see more of that later. diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index b7a924ace684..fffabb327157 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -13,6 +13,7 @@ #include <linux/random.h> #include <linux/percpu.h> #include <asm/tlbflush.h> +#include <asm/uaccess.h> #include "lg.h" /*M:008 We hold reference to pages, which prevents them from being swapped. @@ -25,7 +26,8 @@ * * We use two-level page tables for the Guest. If you're not entirely * comfortable with virtual addresses, physical addresses and page tables then - * I recommend you review lguest.c's "Page Table Handling" (with diagrams!). + * I recommend you review arch/x86/lguest/boot.c's "Page Table Handling" (with + * diagrams!). * * The Guest keeps page tables, but we maintain the actual ones here: these are * called "shadow" page tables. Which is a very Guest-centric name: these are @@ -35,53 +37,40 @@ * * Anyway, this is the most complicated part of the Host code. There are seven * parts to this: - * (i) Setting up a page table entry for the Guest when it faults, - * (ii) Setting up the page table entry for the Guest stack, - * (iii) Setting up a page table entry when the Guest tells us it has changed, + * (i) Looking up a page table entry when the Guest faults, + * (ii) Making sure the Guest stack is mapped, + * (iii) Setting up a page table entry when the Guest tells us one has changed, * (iv) Switching page tables, - * (v) Flushing (thowing away) page tables, + * (v) Flushing (throwing away) page tables, * (vi) Mapping the Switcher when the Guest is about to run, * (vii) Setting up the page tables initially. :*/ -/* Pages a 4k long, and each page table entry is 4 bytes long, giving us 1024 - * (or 2^10) entries per page. */ -#define PTES_PER_PAGE_SHIFT 10 -#define PTES_PER_PAGE (1 << PTES_PER_PAGE_SHIFT) /* 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is * conveniently placed at the top 4MB, so it uses a separate, complete PTE * page. */ -#define SWITCHER_PGD_INDEX (PTES_PER_PAGE - 1) +#define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1) /* We actually need a separate PTE page for each CPU. Remember that after the * Switcher code itself comes two pages for each CPU, and we don't want this * CPU's guest to see the pages of any other CPU. */ -static DEFINE_PER_CPU(spte_t *, switcher_pte_pages); +static DEFINE_PER_CPU(pte_t *, switcher_pte_pages); #define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu) -/*H:320 With our shadow and Guest types established, we need to deal with - * them: the page table code is curly enough to need helper functions to keep - * it clear and clean. +/*H:320 The page table code is curly enough to need helper functions to keep it + * clear and clean. * - * The first helper takes a virtual address, and says which entry in the top - * level page table deals with that address. Since each top level entry deals - * with 4M, this effectively divides by 4M. */ -static unsigned vaddr_to_pgd_index(unsigned long vaddr) -{ - return vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT); -} - -/* There are two functions which return pointers to the shadow (aka "real") + * There are two functions which return pointers to the shadow (aka "real") * page tables. * * spgd_addr() takes the virtual address and returns a pointer to the top-level - * page directory entry for that address. Since we keep track of several page - * tables, the "i" argument tells us which one we're interested in (it's + * page directory entry (PGD) for that address. Since we keep track of several + * page tables, the "i" argument tells us which one we're interested in (it's * usually the current one). */ -static spgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr) +static pgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr) { - unsigned int index = vaddr_to_pgd_index(vaddr); + unsigned int index = pgd_index(vaddr); /* We kill any Guest trying to touch the Switcher addresses. */ if (index >= SWITCHER_PGD_INDEX) { @@ -92,31 +81,31 @@ static spgd_t *spgd_addr(struct lguest *lg, u32 i, unsigned long vaddr) return &lg->pgdirs[i].pgdir[index]; } -/* This routine then takes the PGD entry given above, which contains the - * address of the PTE page. It then returns a pointer to the PTE entry for the - * given address. */ -static spte_t *spte_addr(struct lguest *lg, spgd_t spgd, unsigned long vaddr) +/* This routine then takes the page directory entry returned above, which + * contains the address of the page table entry (PTE) page. It then returns a + * pointer to the PTE entry for the given address. */ +static pte_t *spte_addr(struct lguest *lg, pgd_t spgd, unsigned long vaddr) { - spte_t *page = __va(spgd.pfn << PAGE_SHIFT); + pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT); /* You should never call this if the PGD entry wasn't valid */ - BUG_ON(!(spgd.flags & _PAGE_PRESENT)); - return &page[(vaddr >> PAGE_SHIFT) % PTES_PER_PAGE]; + BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); + return &page[(vaddr >> PAGE_SHIFT) % PTRS_PER_PTE]; } /* These two functions just like the above two, except they access the Guest * page tables. Hence they return a Guest address. */ static unsigned long gpgd_addr(struct lguest *lg, unsigned long vaddr) { - unsigned int index = vaddr >> (PAGE_SHIFT + PTES_PER_PAGE_SHIFT); - return lg->pgdirs[lg->pgdidx].cr3 + index * sizeof(gpgd_t); + unsigned int index = vaddr >> (PGDIR_SHIFT); + return lg->pgdirs[lg->pgdidx].gpgdir + index * sizeof(pgd_t); } static unsigned long gpte_addr(struct lguest *lg, - gpgd_t gpgd, unsigned long vaddr) + pgd_t gpgd, unsigned long vaddr) { - unsigned long gpage = gpgd.pfn << PAGE_SHIFT; - BUG_ON(!(gpgd.flags & _PAGE_PRESENT)); - return gpage + ((vaddr>>PAGE_SHIFT) % PTES_PER_PAGE) * sizeof(gpte_t); + unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; + BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); + return gpage + ((vaddr>>PAGE_SHIFT) % PTRS_PER_PTE) * sizeof(pte_t); } /*H:350 This routine takes a page number given by the Guest and converts it to @@ -149,58 +138,60 @@ static unsigned long get_pfn(unsigned long virtpfn, int write) * entry can be a little tricky. The flags are (almost) the same, but the * Guest PTE contains a virtual page number: the CPU needs the real page * number. */ -static spte_t gpte_to_spte(struct lguest *lg, gpte_t gpte, int write) +static pte_t gpte_to_spte(struct lguest *lg, pte_t gpte, int write) { - spte_t spte; - unsigned long pfn; + unsigned long pfn, base, flags; /* The Guest sets the global flag, because it thinks that it is using * PGE. We only told it to use PGE so it would tell us whether it was * flushing a kernel mapping or a userspace mapping. We don't actually * use the global bit, so throw it away. */ - spte.flags = (gpte.flags & ~_PAGE_GLOBAL); + flags = (pte_flags(gpte) & ~_PAGE_GLOBAL); + + /* The Guest's pages are offset inside the Launcher. */ + base = (unsigned long)lg->mem_base / PAGE_SIZE; /* We need a temporary "unsigned long" variable to hold the answer from * get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't * fit in spte.pfn. get_pfn() finds the real physical number of the * page, given the virtual number. */ - pfn = get_pfn(gpte.pfn, write); + pfn = get_pfn(base + pte_pfn(gpte), write); if (pfn == -1UL) { - kill_guest(lg, "failed to get page %u", gpte.pfn); + kill_guest(lg, "failed to get page %lu", pte_pfn(gpte)); /* When we destroy the Guest, we'll go through the shadow page * tables and release_pte() them. Make sure we don't think * this one is valid! */ - spte.flags = 0; + flags = 0; } - /* Now we assign the page number, and our shadow PTE is complete. */ - spte.pfn = pfn; - return spte; + /* Now we assemble our shadow PTE from the page number and flags. */ + return pfn_pte(pfn, __pgprot(flags)); } /*H:460 And to complete the chain, release_pte() looks like this: */ -static void release_pte(spte_t pte) +static void release_pte(pte_t pte) { /* Remember that get_user_pages() took a reference to the page, in * get_pfn()? We have to put it back now. */ - if (pte.flags & _PAGE_PRESENT) - put_page(pfn_to_page(pte.pfn)); + if (pte_flags(pte) & _PAGE_PRESENT) + put_page(pfn_to_page(pte_pfn(pte))); } /*:*/ -static void check_gpte(struct lguest *lg, gpte_t gpte) +static void check_gpte(struct lguest *lg, pte_t gpte) { - if ((gpte.flags & (_PAGE_PWT|_PAGE_PSE)) || gpte.pfn >= lg->pfn_limit) + if ((pte_flags(gpte) & (_PAGE_PWT|_PAGE_PSE)) + || pte_pfn(gpte) >= lg->pfn_limit) kill_guest(lg, "bad page table entry"); } -static void check_gpgd(struct lguest *lg, gpgd_t gpgd) +static void check_gpgd(struct lguest *lg, pgd_t gpgd) { - if ((gpgd.flags & ~_PAGE_TABLE) || gpgd.pfn >= lg->pfn_limit) + if ((pgd_flags(gpgd) & ~_PAGE_TABLE) || pgd_pfn(gpgd) >= lg->pfn_limit) kill_guest(lg, "bad page directory entry"); } /*H:330 - * (i) Setting up a page table entry for the Guest when it faults + * (i) Looking up a page table entry when the Guest faults. * * We saw this call in run_guest(): when we see a page fault in the Guest, we * come here. That's because we only set up the shadow page tables lazily as @@ -208,24 +199,24 @@ static void check_gpgd(struct lguest *lg, gpgd_t gpgd) * and return to the Guest without it knowing. * * If we fixed up the fault (ie. we mapped the address), this routine returns - * true. */ + * true. Otherwise, it was a real fault and we need to tell the Guest. */ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode) { - gpgd_t gpgd; - spgd_t *spgd; + pgd_t gpgd; + pgd_t *spgd; unsigned long gpte_ptr; - gpte_t gpte; - spte_t *spte; + pte_t gpte; + pte_t *spte; /* First step: get the top-level Guest page table entry. */ - gpgd = mkgpgd(lgread_u32(lg, gpgd_addr(lg, vaddr))); + gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ - if (!(gpgd.flags & _PAGE_PRESENT)) + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) return 0; /* Now look at the matching shadow entry. */ spgd = spgd_addr(lg, lg->pgdidx, vaddr); - if (!(spgd->flags & _PAGE_PRESENT)) { + if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) { /* No shadow entry: allocate a new shadow PTE page. */ unsigned long ptepage = get_zeroed_page(GFP_KERNEL); /* This is not really the Guest's fault, but killing it is @@ -238,34 +229,35 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode) check_gpgd(lg, gpgd); /* And we copy the flags to the shadow PGD entry. The page * number in the shadow PGD is the page we just allocated. */ - spgd->raw.val = (__pa(ptepage) | gpgd.flags); + *spgd = __pgd(__pa(ptepage) | pgd_flags(gpgd)); } /* OK, now we look at the lower level in the Guest page table: keep its * address, because we might update it later. */ gpte_ptr = gpte_addr(lg, gpgd, vaddr); - gpte = mkgpte(lgread_u32(lg, gpte_ptr)); + gpte = lgread(lg, gpte_ptr, pte_t); /* If this page isn't in the Guest page tables, we can't page it in. */ - if (!(gpte.flags & _PAGE_PRESENT)) + if (!(pte_flags(gpte) & _PAGE_PRESENT)) return 0; /* Check they're not trying to write to a page the Guest wants * read-only (bit 2 of errcode == write). */ - if ((errcode & 2) && !(gpte.flags & _PAGE_RW)) + if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW)) return 0; - /* User access to a kernel page? (bit 3 == user access) */ - if ((errcode & 4) && !(gpte.flags & _PAGE_USER)) + /* User access to a kernel-only page? (bit 3 == user access) */ + if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER)) return 0; /* Check that the Guest PTE flags are OK, and the page number is below * the pfn_limit (ie. not mapping the Launcher binary). */ check_gpte(lg, gpte); + /* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */ - gpte.flags |= _PAGE_ACCESSED; + gpte = pte_mkyoung(gpte); if (errcode & 2) - gpte.flags |= _PAGE_DIRTY; + gpte = pte_mkdirty(gpte); /* Get the pointer to the shadow PTE entry we're going to set. */ spte = spte_addr(lg, *spgd, vaddr); @@ -275,47 +267,50 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode) /* If this is a write, we insist that the Guest page is writable (the * final arg to gpte_to_spte()). */ - if (gpte.flags & _PAGE_DIRTY) + if (pte_dirty(gpte)) *spte = gpte_to_spte(lg, gpte, 1); - else { + else /* If this is a read, don't set the "writable" bit in the page * table entry, even if the Guest says it's writable. That way - * we come back here when a write does actually ocur, so we can - * update the Guest's _PAGE_DIRTY flag. */ - gpte_t ro_gpte = gpte; - ro_gpte.flags &= ~_PAGE_RW; - *spte = gpte_to_spte(lg, ro_gpte, 0); - } + * we will come back here when a write does actually occur, so + * we can update the Guest's _PAGE_DIRTY flag. */ + *spte = gpte_to_spte(lg, pte_wrprotect(gpte), 0); /* Finally, we write the Guest PTE entry back: we've set the * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ - lgwrite_u32(lg, gpte_ptr, gpte.raw.val); + lgwrite(lg, gpte_ptr, pte_t, gpte); - /* We succeeded in mapping the page! */ + /* The fault is fixed, the page table is populated, the mapping + * manipulated, the result returned and the code complete. A small + * delay and a trace of alliteration are the only indications the Guest + * has that a page fault occurred at all. */ return 1; } -/*H:360 (ii) Setting up the page table entry for the Guest stack. +/*H:360 + * (ii) Making sure the Guest stack is mapped. * - * Remember pin_stack_pages() which makes sure the stack is mapped? It could - * simply call demand_page(), but as we've seen that logic is quite long, and - * usually the stack pages are already mapped anyway, so it's not required. + * Remember that direct traps into the Guest need a mapped Guest kernel stack. + * pin_stack_pages() calls us here: we could simply call demand_page(), but as + * we've seen that logic is quite long, and usually the stack pages are already + * mapped, so it's overkill. * * This is a quick version which answers the question: is this virtual address * mapped by the shadow page tables, and is it writable? */ static int page_writable(struct lguest *lg, unsigned long vaddr) { - spgd_t *spgd; + pgd_t *spgd; unsigned long flags; - /* Look at the top level entry: is it present? */ + /* Look at the current top level entry: is it present? */ spgd = spgd_addr(lg, lg->pgdidx, vaddr); - if (!(spgd->flags & _PAGE_PRESENT)) + if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) return 0; /* Check the flags on the pte entry itself: it must be present and * writable. */ - flags = spte_addr(lg, *spgd, vaddr)->flags; + flags = pte_flags(*(spte_addr(lg, *spgd, vaddr))); + return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); } @@ -329,39 +324,40 @@ void pin_page(struct lguest *lg, unsigned long vaddr) } /*H:450 If we chase down the release_pgd() code, it looks like this: */ -static void release_pgd(struct lguest *lg, spgd_t *spgd) +static void release_pgd(struct lguest *lg, pgd_t *spgd) { /* If the entry's not present, there's nothing to release. */ - if (spgd->flags & _PAGE_PRESENT) { + if (pgd_flags(*spgd) & _PAGE_PRESENT) { unsigned int i; /* Converting the pfn to find the actual PTE page is easy: turn * the page number into a physical address, then convert to a * virtual address (easy for kernel pages like this one). */ - spte_t *ptepage = __va(spgd->pfn << PAGE_SHIFT); + pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); /* For each entry in the page, we might need to release it. */ - for (i = 0; i < PTES_PER_PAGE; i++) + for (i = 0; i < PTRS_PER_PTE; i++) release_pte(ptepage[i]); /* Now we can free the page of PTEs */ free_page((long)ptepage); - /* And zero out the PGD entry we we never release it twice. */ - spgd->raw.val = 0; + /* And zero out the PGD entry so we never release it twice. */ + *spgd = __pgd(0); } } -/*H:440 (v) Flushing (thowing away) page tables, - * - * We saw flush_user_mappings() called when we re-used a top-level pgdir page. - * It simply releases every PTE page from 0 up to the kernel address. */ +/*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings() + * hypercall and once in new_pgdir() when we re-used a top-level pgdir page. + * It simply releases every PTE page from 0 up to the Guest's kernel address. */ static void flush_user_mappings(struct lguest *lg, int idx) { unsigned int i; /* Release every pgd entry up to the kernel's address. */ - for (i = 0; i < vaddr_to_pgd_index(lg->page_offset); i++) + for (i = 0; i < pgd_index(lg->kernel_address); i++) release_pgd(lg, lg->pgdirs[idx].pgdir + i); } -/* The Guest also has a hypercall to do this manually: it's used when a large - * number of mappings have been changed. */ +/*H:440 (v) Flushing (throwing away) page tables, + * + * The Guest has a hypercall to throw away the page tables: it's used when a + * large number of mappings have been changed. */ void guest_pagetable_flush_user(struct lguest *lg) { /* Drop the userspace part of the current page table. */ @@ -369,6 +365,25 @@ void guest_pagetable_flush_user(struct lguest *lg) } /*:*/ +/* We walk down the guest page tables to get a guest-physical address */ +unsigned long guest_pa(struct lguest *lg, unsigned long vaddr) +{ + pgd_t gpgd; + pte_t gpte; + + /* First step: get the top-level Guest page table entry. */ + gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t); + /* Toplevel not present? We can't map it in. */ + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + gpte = lgread(lg, gpte_addr(lg, gpgd, vaddr), pte_t); + if (!(pte_flags(gpte) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); +} + /* We keep several page tables. This is a simple routine to find the page * table (if any) corresponding to this top-level address the Guest has given * us. */ @@ -376,7 +391,7 @@ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) { unsigned int i; for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - if (lg->pgdirs[i].cr3 == pgtable) + if (lg->pgdirs[i].gpgdir == pgtable) break; return i; } @@ -385,7 +400,7 @@ static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable) * allocate a new one (and so the kernel parts are not there), we set * blank_pgdir. */ static unsigned int new_pgdir(struct lguest *lg, - unsigned long cr3, + unsigned long gpgdir, int *blank_pgdir) { unsigned int next; @@ -395,7 +410,7 @@ static unsigned int new_pgdir(struct lguest *lg, next = random32() % ARRAY_SIZE(lg->pgdirs); /* If it's never been allocated at all before, try now. */ if (!lg->pgdirs[next].pgdir) { - lg->pgdirs[next].pgdir = (spgd_t *)get_zeroed_page(GFP_KERNEL); + lg->pgdirs[next].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); /* If the allocation fails, just keep using the one we have */ if (!lg->pgdirs[next].pgdir) next = lg->pgdidx; @@ -405,7 +420,7 @@ static unsigned int new_pgdir(struct lguest *lg, *blank_pgdir = 1; } /* Record which Guest toplevel this shadows. */ - lg->pgdirs[next].cr3 = cr3; + lg->pgdirs[next].gpgdir = gpgdir; /* Release all the non-kernel mappings. */ flush_user_mappings(lg, next); @@ -414,8 +429,9 @@ static unsigned int new_pgdir(struct lguest *lg, /*H:430 (iv) Switching page tables * - * This is what happens when the Guest changes page tables (ie. changes the - * top-level pgdir). This happens on almost every context switch. */ + * Now we've seen all the page table setting and manipulation, let's see what + * what happens when the Guest changes page tables (ie. changes the top-level + * pgdir). This occurs on almost every context switch. */ void guest_new_pagetable(struct lguest *lg, unsigned long pgtable) { int newpgdir, repin = 0; @@ -434,7 +450,8 @@ void guest_new_pagetable(struct lguest *lg, unsigned long pgtable) } /*H:470 Finally, a routine which throws away everything: all PGD entries in all - * the shadow page tables. This is used when we destroy the Guest. */ + * the shadow page tables, including the Guest's kernel mappings. This is used + * when we destroy the Guest. */ static void release_all_pagetables(struct lguest *lg) { unsigned int i, j; @@ -449,13 +466,22 @@ static void release_all_pagetables(struct lguest *lg) /* We also throw away everything when a Guest tells us it's changed a kernel * mapping. Since kernel mappings are in every page table, it's easiest to - * throw them all away. This is amazingly slow, but thankfully rare. */ + * throw them all away. This traps the Guest in amber for a while as + * everything faults back in, but it's rare. */ void guest_pagetable_clear_all(struct lguest *lg) { release_all_pagetables(lg); /* We need the Guest kernel stack mapped again. */ pin_stack_pages(lg); } +/*:*/ +/*M:009 Since we throw away all mappings when a kernel mapping changes, our + * performance sucks for guests using highmem. In fact, a guest with + * PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is + * usually slower than a Guest with less memory. + * + * This, of course, cannot be fixed. It would take some kind of... well, I + * don't know, but the term "puissant code-fu" comes to mind. :*/ /*H:420 This is the routine which actually sets the page table entry for then * "idx"'th shadow page table. @@ -472,26 +498,28 @@ void guest_pagetable_clear_all(struct lguest *lg) * they set _PAGE_DIRTY then we can put a writable PTE entry in immediately. */ static void do_set_pte(struct lguest *lg, int idx, - unsigned long vaddr, gpte_t gpte) + unsigned long vaddr, pte_t gpte) { - /* Look up the matching shadow page directot entry. */ - spgd_t *spgd = spgd_addr(lg, idx, vaddr); + /* Look up the matching shadow page directory entry. */ + pgd_t *spgd = spgd_addr(lg, idx, vaddr); /* If the top level isn't present, there's no entry to update. */ - if (spgd->flags & _PAGE_PRESENT) { + if (pgd_flags(*spgd) & _PAGE_PRESENT) { /* Otherwise, we start by releasing the existing entry. */ - spte_t *spte = spte_addr(lg, *spgd, vaddr); + pte_t *spte = spte_addr(lg, *spgd, vaddr); release_pte(*spte); /* If they're setting this entry as dirty or accessed, we might * as well put that entry they've given us in now. This shaves * 10% off a copy-on-write micro-benchmark. */ - if (gpte.flags & (_PAGE_DIRTY | _PAGE_ACCESSED)) { + if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { check_gpte(lg, gpte); - *spte = gpte_to_spte(lg, gpte, gpte.flags&_PAGE_DIRTY); + *spte = gpte_to_spte(lg, gpte, + pte_flags(gpte) & _PAGE_DIRTY); } else - /* Otherwise we can demand_page() it in later. */ - spte->raw.val = 0; + /* Otherwise kill it and we can demand_page() it in + * later. */ + *spte = __pte(0); } } @@ -506,18 +534,18 @@ static void do_set_pte(struct lguest *lg, int idx, * The benefit is that when we have to track a new page table, we can copy keep * all the kernel mappings. This speeds up context switch immensely. */ void guest_set_pte(struct lguest *lg, - unsigned long cr3, unsigned long vaddr, gpte_t gpte) + unsigned long gpgdir, unsigned long vaddr, pte_t gpte) { /* Kernel mappings must be changed on all top levels. Slow, but * doesn't happen often. */ - if (vaddr >= lg->page_offset) { + if (vaddr >= lg->kernel_address) { unsigned int i; for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) if (lg->pgdirs[i].pgdir) do_set_pte(lg, i, vaddr, gpte); } else { /* Is this page table one we have a shadow for? */ - int pgdir = find_pgdir(lg, cr3); + int pgdir = find_pgdir(lg, gpgdir); if (pgdir != ARRAY_SIZE(lg->pgdirs)) /* If so, do the update. */ do_set_pte(lg, pgdir, vaddr, gpte); @@ -525,7 +553,7 @@ void guest_set_pte(struct lguest *lg, } /*H:400 - * (iii) Setting up a page table entry when the Guest tells us it has changed. + * (iii) Setting up a page table entry when the Guest tells us one has changed. * * Just like we did in interrupts_and_traps.c, it makes sense for us to deal * with the other side of page tables while we're here: what happens when the @@ -538,7 +566,7 @@ void guest_set_pte(struct lguest *lg, * * So with that in mind here's our code to to update a (top-level) PGD entry: */ -void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 idx) +void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) { int pgdir; @@ -548,7 +576,7 @@ void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 idx) return; /* If they're talking about a page table we have a shadow for... */ - pgdir = find_pgdir(lg, cr3); + pgdir = find_pgdir(lg, gpgdir); if (pgdir < ARRAY_SIZE(lg->pgdirs)) /* ... throw it away. */ release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx); @@ -560,21 +588,34 @@ void guest_set_pmd(struct lguest *lg, unsigned long cr3, u32 idx) * its first page table is. We set some things up here: */ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) { - /* In flush_user_mappings() we loop from 0 to - * "vaddr_to_pgd_index(lg->page_offset)". This assumes it won't hit - * the Switcher mappings, so check that now. */ - if (vaddr_to_pgd_index(lg->page_offset) >= SWITCHER_PGD_INDEX) - return -EINVAL; /* We start on the first shadow page table, and give it a blank PGD * page. */ lg->pgdidx = 0; - lg->pgdirs[lg->pgdidx].cr3 = pgtable; - lg->pgdirs[lg->pgdidx].pgdir = (spgd_t*)get_zeroed_page(GFP_KERNEL); + lg->pgdirs[lg->pgdidx].gpgdir = pgtable; + lg->pgdirs[lg->pgdidx].pgdir = (pgd_t*)get_zeroed_page(GFP_KERNEL); if (!lg->pgdirs[lg->pgdidx].pgdir) return -ENOMEM; return 0; } +/* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ +void page_table_guest_data_init(struct lguest *lg) +{ + /* We get the kernel address: above this is all kernel memory. */ + if (get_user(lg->kernel_address, &lg->lguest_data->kernel_address) + /* We tell the Guest that it can't use the top 4MB of virtual + * addresses used by the Switcher. */ + || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) + || put_user(lg->pgdirs[lg->pgdidx].gpgdir,&lg->lguest_data->pgdir)) + kill_guest(lg, "bad guest page %p", lg->lguest_data); + + /* In flush_user_mappings() we loop from 0 to + * "pgd_index(lg->kernel_address)". This assumes it won't hit the + * Switcher mappings, so check that now. */ + if (pgd_index(lg->kernel_address) >= SWITCHER_PGD_INDEX) + kill_guest(lg, "bad kernel address %#lx", lg->kernel_address); +} + /* When a Guest dies, our cleanup is fairly simple. */ void free_guest_pagetable(struct lguest *lg) { @@ -589,19 +630,20 @@ void free_guest_pagetable(struct lguest *lg) /*H:480 (vi) Mapping the Switcher when the Guest is about to run. * - * The Switcher and the two pages for this CPU need to be available to the + * The Switcher and the two pages for this CPU need to be visible in the * Guest (and not the pages for other CPUs). We have the appropriate PTE pages - * for each CPU already set up, we just need to hook them in. */ + * for each CPU already set up, we just need to hook them in now we know which + * Guest is about to run on this CPU. */ void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages) { - spte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages); - spgd_t switcher_pgd; - spte_t regs_pte; + pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages); + pgd_t switcher_pgd; + pte_t regs_pte; /* Make the last PGD entry for this Guest point to the Switcher's PTE * page for this CPU (with appropriate flags). */ - switcher_pgd.pfn = __pa(switcher_pte_page) >> PAGE_SHIFT; - switcher_pgd.flags = _PAGE_KERNEL; + switcher_pgd = __pgd(__pa(switcher_pte_page) | _PAGE_KERNEL); + lg->pgdirs[lg->pgdidx].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd; /* We also change the Switcher PTE page. When we're running the Guest, @@ -611,10 +653,8 @@ void map_switcher_in_guest(struct lguest *lg, struct lguest_pages *pages) * CPU's "struct lguest_pages": if we make sure the Guest's register * page is already mapped there, we don't have to copy them out * again. */ - regs_pte.pfn = __pa(lg->regs_page) >> PAGE_SHIFT; - regs_pte.flags = _PAGE_KERNEL; - switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTES_PER_PAGE] - = regs_pte; + regs_pte = pfn_pte (__pa(lg->regs_page) >> PAGE_SHIFT, __pgprot(_PAGE_KERNEL)); + switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTRS_PER_PTE] = regs_pte; } /*:*/ @@ -635,26 +675,39 @@ static __init void populate_switcher_pte_page(unsigned int cpu, unsigned int pages) { unsigned int i; - spte_t *pte = switcher_pte_page(cpu); + pte_t *pte = switcher_pte_page(cpu); /* The first entries are easy: they map the Switcher code. */ for (i = 0; i < pages; i++) { - pte[i].pfn = page_to_pfn(switcher_page[i]); - pte[i].flags = _PAGE_PRESENT|_PAGE_ACCESSED; + pte[i] = mk_pte(switcher_page[i], + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); } /* The only other thing we map is this CPU's pair of pages. */ i = pages + cpu*2; /* First page (Guest registers) is writable from the Guest */ - pte[i].pfn = page_to_pfn(switcher_page[i]); - pte[i].flags = _PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW; + pte[i] = pfn_pte(page_to_pfn(switcher_page[i]), + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)); + /* The second page contains the "struct lguest_ro_state", and is * read-only. */ - pte[i+1].pfn = page_to_pfn(switcher_page[i+1]); - pte[i+1].flags = _PAGE_PRESENT|_PAGE_ACCESSED; + pte[i+1] = pfn_pte(page_to_pfn(switcher_page[i+1]), + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); } +/* We've made it through the page table code. Perhaps our tired brains are + * still processing the details, or perhaps we're simply glad it's over. + * + * If nothing else, note that all this complexity in juggling shadow page + * tables in sync with the Guest's page tables is for one reason: for most + * Guests this page table dance determines how bad performance will be. This + * is why Xen uses exotic direct Guest pagetable manipulation, and why both + * Intel and AMD have implemented shadow page table support directly into + * hardware. + * + * There is just one file remaining in the Host. */ + /*H:510 At boot or module load time, init_pagetables() allocates and populates * the Switcher PTE page for each CPU. */ __init int init_pagetables(struct page **switcher_page, unsigned int pages) @@ -662,7 +715,7 @@ __init int init_pagetables(struct page **switcher_page, unsigned int pages) unsigned int i; for_each_possible_cpu(i) { - switcher_pte_page(i) = (spte_t *)get_zeroed_page(GFP_KERNEL); + switcher_pte_page(i) = (pte_t *)get_zeroed_page(GFP_KERNEL); if (!switcher_pte_page(i)) { free_switcher_pte_pages(); return -ENOMEM; diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c index 9b81119f46e9..9e189cbec7dd 100644 --- a/drivers/lguest/segments.c +++ b/drivers/lguest/segments.c @@ -12,8 +12,6 @@ #include "lg.h" /*H:600 - * We've almost completed the Host; there's just one file to go! - * * Segments & The Global Descriptor Table * * (That title sounds like a bad Nerdcore group. Not to suggest that there are @@ -55,7 +53,7 @@ static int ignored_gdt(unsigned int num) || num == GDT_ENTRY_DOUBLEFAULT_TSS); } -/*H:610 Once the GDT has been changed, we fix the new entries up a little. We +/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We * don't care if they're invalid: the worst that can happen is a General * Protection Fault in the Switcher when it restores a Guest segment register * which tries to use that entry. Then we kill the Guest for causing such a @@ -73,63 +71,68 @@ static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end) /* Segment descriptors contain a privilege level: the Guest is * sometimes careless and leaves this as 0, even though it's * running at privilege level 1. If so, we fix it here. */ - if ((lg->gdt[i].b & 0x00006000) == 0) - lg->gdt[i].b |= (GUEST_PL << 13); + if ((lg->arch.gdt[i].b & 0x00006000) == 0) + lg->arch.gdt[i].b |= (GUEST_PL << 13); /* Each descriptor has an "accessed" bit. If we don't set it * now, the CPU will try to set it when the Guest first loads * that entry into a segment register. But the GDT isn't * writable by the Guest, so bad things can happen. */ - lg->gdt[i].b |= 0x00000100; + lg->arch.gdt[i].b |= 0x00000100; } } -/* This routine is called at boot or modprobe time for each CPU to set up the - * "constant" GDT entries for Guests running on that CPU. */ +/*H:610 Like the IDT, we never simply use the GDT the Guest gives us. We keep + * a GDT for each CPU, and copy across the Guest's entries each time we want to + * run the Guest on that CPU. + * + * This routine is called at boot or modprobe time for each CPU to set up the + * constant GDT entries: the ones which are the same no matter what Guest we're + * running. */ void setup_default_gdt_entries(struct lguest_ro_state *state) { struct desc_struct *gdt = state->guest_gdt; unsigned long tss = (unsigned long)&state->guest_tss; - /* The hypervisor segments are full 0-4G segments, privilege level 0 */ + /* The Switcher segments are full 0-4G segments, privilege level 0 */ gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; - /* The TSS segment refers to the TSS entry for this CPU, so we cannot - * copy it from the Guest. Forgive the magic flags */ + /* The TSS segment refers to the TSS entry for this particular CPU. + * Forgive the magic flags: the 0x8900 means the entry is Present, it's + * privilege level 0 Available 386 TSS system segment, and the 0x67 + * means Saturn is eclipsed by Mercury in the twelfth house. */ gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16); gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000) | ((tss >> 16) & 0x000000FF); } -/* This routine is called before the Guest is run for the first time. */ +/* This routine sets up the initial Guest GDT for booting. All entries start + * as 0 (unusable). */ void setup_guest_gdt(struct lguest *lg) { /* Start with full 0-4G segments... */ - lg->gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; - lg->gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; + lg->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; + lg->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; /* ...except the Guest is allowed to use them, so set the privilege * level appropriately in the flags. */ - lg->gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); - lg->gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); + lg->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); + lg->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); } -/* Like the IDT, we never simply use the GDT the Guest gives us. We set up the - * GDTs for each CPU, then we copy across the entries each time we want to run - * a different Guest on that CPU. */ - -/* A partial GDT load, for the three "thead-local storage" entries. Otherwise - * it's just like load_guest_gdt(). So much, in fact, it would probably be - * neater to have a single hypercall to cover both. */ +/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage" + * entries. */ void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt) { unsigned int i; for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++) - gdt[i] = lg->gdt[i]; + gdt[i] = lg->arch.gdt[i]; } -/* This is the full version */ +/*H:640 When the Guest is run on a different CPU, or the GDT entries have + * changed, copy_gdt() is called to copy the Guest's GDT entries across to this + * CPU's GDT. */ void copy_gdt(const struct lguest *lg, struct desc_struct *gdt) { unsigned int i; @@ -138,35 +141,42 @@ void copy_gdt(const struct lguest *lg, struct desc_struct *gdt) * replaced. See ignored_gdt() above. */ for (i = 0; i < GDT_ENTRIES; i++) if (!ignored_gdt(i)) - gdt[i] = lg->gdt[i]; + gdt[i] = lg->arch.gdt[i]; } -/* This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT). */ +/*H:620 This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT). + * We copy it from the Guest and tweak the entries. */ void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num) { /* We assume the Guest has the same number of GDT entries as the * Host, otherwise we'd have to dynamically allocate the Guest GDT. */ - if (num > ARRAY_SIZE(lg->gdt)) + if (num > ARRAY_SIZE(lg->arch.gdt)) kill_guest(lg, "too many gdt entries %i", num); /* We read the whole thing in, then fix it up. */ - lgread(lg, lg->gdt, table, num * sizeof(lg->gdt[0])); - fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->gdt)); + __lgread(lg, lg->arch.gdt, table, num * sizeof(lg->arch.gdt[0])); + fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->arch.gdt)); /* Mark that the GDT changed so the core knows it has to copy it again, * even if the Guest is run on the same CPU. */ lg->changed |= CHANGED_GDT; } +/* This is the fast-track version for just changing the three TLS entries. + * Remember that this happens on every context switch, so it's worth + * optimizing. But wouldn't it be neater to have a single hypercall to cover + * both cases? */ void guest_load_tls(struct lguest *lg, unsigned long gtls) { - struct desc_struct *tls = &lg->gdt[GDT_ENTRY_TLS_MIN]; + struct desc_struct *tls = &lg->arch.gdt[GDT_ENTRY_TLS_MIN]; - lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES); + __lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES); fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1); + /* Note that just the TLS entries have changed. */ lg->changed |= CHANGED_GDT_TLS; } +/*:*/ -/* +/*H:660 * With this, we have finished the Host. * * Five of the seven parts of our task are complete. You have made it through diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c new file mode 100644 index 000000000000..482aec2a9631 --- /dev/null +++ b/drivers/lguest/x86/core.c @@ -0,0 +1,581 @@ +/* + * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation. + * Copyright (C) 2007, Jes Sorensen <jes@sgi.com> SGI. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for more + * details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ +#include <linux/kernel.h> +#include <linux/start_kernel.h> +#include <linux/string.h> +#include <linux/console.h> +#include <linux/screen_info.h> +#include <linux/irq.h> +#include <linux/interrupt.h> +#include <linux/clocksource.h> +#include <linux/clockchips.h> +#include <linux/cpu.h> +#include <linux/lguest.h> +#include <linux/lguest_launcher.h> +#include <asm/paravirt.h> +#include <asm/param.h> +#include <asm/page.h> +#include <asm/pgtable.h> +#include <asm/desc.h> +#include <asm/setup.h> +#include <asm/lguest.h> +#include <asm/uaccess.h> +#include <asm/i387.h> +#include "../lg.h" + +static int cpu_had_pge; + +static struct { + unsigned long offset; + unsigned short segment; +} lguest_entry; + +/* Offset from where switcher.S was compiled to where we've copied it */ +static unsigned long switcher_offset(void) +{ + return SWITCHER_ADDR - (unsigned long)start_switcher_text; +} + +/* This cpu's struct lguest_pages. */ +static struct lguest_pages *lguest_pages(unsigned int cpu) +{ + return &(((struct lguest_pages *) + (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]); +} + +static DEFINE_PER_CPU(struct lguest *, last_guest); + +/*S:010 + * We approach the Switcher. + * + * Remember that each CPU has two pages which are visible to the Guest when it + * runs on that CPU. This has to contain the state for that Guest: we copy the + * state in just before we run the Guest. + * + * Each Guest has "changed" flags which indicate what has changed in the Guest + * since it last ran. We saw this set in interrupts_and_traps.c and + * segments.c. + */ +static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages) +{ + /* Copying all this data can be quite expensive. We usually run the + * same Guest we ran last time (and that Guest hasn't run anywhere else + * meanwhile). If that's not the case, we pretend everything in the + * Guest has changed. */ + if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) { + __get_cpu_var(last_guest) = lg; + lg->last_pages = pages; + lg->changed = CHANGED_ALL; + } + + /* These copies are pretty cheap, so we do them unconditionally: */ + /* Save the current Host top-level page directory. */ + pages->state.host_cr3 = __pa(current->mm->pgd); + /* Set up the Guest's page tables to see this CPU's pages (and no + * other CPU's pages). */ + map_switcher_in_guest(lg, pages); + /* Set up the two "TSS" members which tell the CPU what stack to use + * for traps which do directly into the Guest (ie. traps at privilege + * level 1). */ + pages->state.guest_tss.esp1 = lg->esp1; + pages->state.guest_tss.ss1 = lg->ss1; + + /* Copy direct-to-Guest trap entries. */ + if (lg->changed & CHANGED_IDT) + copy_traps(lg, pages->state.guest_idt, default_idt_entries); + + /* Copy all GDT entries which the Guest can change. */ + if (lg->changed & CHANGED_GDT) + copy_gdt(lg, pages->state.guest_gdt); + /* If only the TLS entries have changed, copy them. */ + else if (lg->changed & CHANGED_GDT_TLS) + copy_gdt_tls(lg, pages->state.guest_gdt); + + /* Mark the Guest as unchanged for next time. */ + lg->changed = 0; +} + +/* Finally: the code to actually call into the Switcher to run the Guest. */ +static void run_guest_once(struct lguest *lg, struct lguest_pages *pages) +{ + /* This is a dummy value we need for GCC's sake. */ + unsigned int clobber; + + /* Copy the guest-specific information into this CPU's "struct + * lguest_pages". */ + copy_in_guest_info(lg, pages); + + /* Set the trap number to 256 (impossible value). If we fault while + * switching to the Guest (bad segment registers or bug), this will + * cause us to abort the Guest. */ + lg->regs->trapnum = 256; + + /* Now: we push the "eflags" register on the stack, then do an "lcall". + * This is how we change from using the kernel code segment to using + * the dedicated lguest code segment, as well as jumping into the + * Switcher. + * + * The lcall also pushes the old code segment (KERNEL_CS) onto the + * stack, then the address of this call. This stack layout happens to + * exactly match the stack layout created by an interrupt... */ + asm volatile("pushf; lcall *lguest_entry" + /* This is how we tell GCC that %eax ("a") and %ebx ("b") + * are changed by this routine. The "=" means output. */ + : "=a"(clobber), "=b"(clobber) + /* %eax contains the pages pointer. ("0" refers to the + * 0-th argument above, ie "a"). %ebx contains the + * physical address of the Guest's top-level page + * directory. */ + : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir)) + /* We tell gcc that all these registers could change, + * which means we don't have to save and restore them in + * the Switcher. */ + : "memory", "%edx", "%ecx", "%edi", "%esi"); +} +/*:*/ + +/*M:002 There are hooks in the scheduler which we can register to tell when we + * get kicked off the CPU (preempt_notifier_register()). This would allow us + * to lazily disable SYSENTER which would regain some performance, and should + * also simplify copy_in_guest_info(). Note that we'd still need to restore + * things when we exit to Launcher userspace, but that's fairly easy. + * + * The hooks were designed for KVM, but we can also put them to good use. :*/ + +/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts + * are disabled: we own the CPU. */ +void lguest_arch_run_guest(struct lguest *lg) +{ + /* Remember the awfully-named TS bit? If the Guest has asked to set it + * we set it now, so we can trap and pass that trap to the Guest if it + * uses the FPU. */ + if (lg->ts) + lguest_set_ts(); + + /* SYSENTER is an optimized way of doing system calls. We can't allow + * it because it always jumps to privilege level 0. A normal Guest + * won't try it because we don't advertise it in CPUID, but a malicious + * Guest (or malicious Guest userspace program) could, so we tell the + * CPU to disable it before running the Guest. */ + if (boot_cpu_has(X86_FEATURE_SEP)) + wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); + + /* Now we actually run the Guest. It will return when something + * interesting happens, and we can examine its registers to see what it + * was doing. */ + run_guest_once(lg, lguest_pages(raw_smp_processor_id())); + + /* Note that the "regs" pointer contains two extra entries which are + * not really registers: a trap number which says what interrupt or + * trap made the switcher code come back, and an error code which some + * traps set. */ + + /* If the Guest page faulted, then the cr2 register will tell us the + * bad virtual address. We have to grab this now, because once we + * re-enable interrupts an interrupt could fault and thus overwrite + * cr2, or we could even move off to a different CPU. */ + if (lg->regs->trapnum == 14) + lg->arch.last_pagefault = read_cr2(); + /* Similarly, if we took a trap because the Guest used the FPU, + * we have to restore the FPU it expects to see. */ + else if (lg->regs->trapnum == 7) + math_state_restore(); + + /* Restore SYSENTER if it's supposed to be on. */ + if (boot_cpu_has(X86_FEATURE_SEP)) + wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); +} + +/*H:130 Now we've examined the hypercall code; our Guest can make requests. + * Our Guest is usually so well behaved; it never tries to do things it isn't + * allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual + * infrastructure isn't quite complete, because it doesn't contain replacements + * for the Intel I/O instructions. As a result, the Guest sometimes fumbles + * across one during the boot process as it probes for various things which are + * usually attached to a PC. + * + * When the Guest uses one of these instructions, we get a trap (General + * Protection Fault) and come here. We see if it's one of those troublesome + * instructions and skip over it. We return true if we did. */ +static int emulate_insn(struct lguest *lg) +{ + u8 insn; + unsigned int insnlen = 0, in = 0, shift = 0; + /* The eip contains the *virtual* address of the Guest's instruction: + * guest_pa just subtracts the Guest's page_offset. */ + unsigned long physaddr = guest_pa(lg, lg->regs->eip); + + /* This must be the Guest kernel trying to do something, not userspace! + * The bottom two bits of the CS segment register are the privilege + * level. */ + if ((lg->regs->cs & 3) != GUEST_PL) + return 0; + + /* Decoding x86 instructions is icky. */ + insn = lgread(lg, physaddr, u8); + + /* 0x66 is an "operand prefix". It means it's using the upper 16 bits + of the eax register. */ + if (insn == 0x66) { + shift = 16; + /* The instruction is 1 byte so far, read the next byte. */ + insnlen = 1; + insn = lgread(lg, physaddr + insnlen, u8); + } + + /* We can ignore the lower bit for the moment and decode the 4 opcodes + * we need to emulate. */ + switch (insn & 0xFE) { + case 0xE4: /* in <next byte>,%al */ + insnlen += 2; + in = 1; + break; + case 0xEC: /* in (%dx),%al */ + insnlen += 1; + in = 1; + break; + case 0xE6: /* out %al,<next byte> */ + insnlen += 2; + break; + case 0xEE: /* out %al,(%dx) */ + insnlen += 1; + break; + default: + /* OK, we don't know what this is, can't emulate. */ + return 0; + } + + /* If it was an "IN" instruction, they expect the result to be read + * into %eax, so we change %eax. We always return all-ones, which + * traditionally means "there's nothing there". */ + if (in) { + /* Lower bit tells is whether it's a 16 or 32 bit access */ + if (insn & 0x1) + lg->regs->eax = 0xFFFFFFFF; + else + lg->regs->eax |= (0xFFFF << shift); + } + /* Finally, we've "done" the instruction, so move past it. */ + lg->regs->eip += insnlen; + /* Success! */ + return 1; +} + +/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */ +void lguest_arch_handle_trap(struct lguest *lg) +{ + switch (lg->regs->trapnum) { + case 13: /* We've intercepted a General Protection Fault. */ + /* Check if this was one of those annoying IN or OUT + * instructions which we need to emulate. If so, we just go + * back into the Guest after we've done it. */ + if (lg->regs->errcode == 0) { + if (emulate_insn(lg)) + return; + } + break; + case 14: /* We've intercepted a Page Fault. */ + /* The Guest accessed a virtual address that wasn't mapped. + * This happens a lot: we don't actually set up most of the + * page tables for the Guest at all when we start: as it runs + * it asks for more and more, and we set them up as + * required. In this case, we don't even tell the Guest that + * the fault happened. + * + * The errcode tells whether this was a read or a write, and + * whether kernel or userspace code. */ + if (demand_page(lg, lg->arch.last_pagefault, lg->regs->errcode)) + return; + + /* OK, it's really not there (or not OK): the Guest needs to + * know. We write out the cr2 value so it knows where the + * fault occurred. + * + * Note that if the Guest were really messed up, this could + * happen before it's done the LHCALL_LGUEST_INIT hypercall, so + * lg->lguest_data could be NULL */ + if (lg->lguest_data && + put_user(lg->arch.last_pagefault, &lg->lguest_data->cr2)) + kill_guest(lg, "Writing cr2"); + break; + case 7: /* We've intercepted a Device Not Available fault. */ + /* If the Guest doesn't want to know, we already restored the + * Floating Point Unit, so we just continue without telling + * it. */ + if (!lg->ts) + return; + break; + case 32 ... 255: + /* These values mean a real interrupt occurred, in which case + * the Host handler has already been run. We just do a + * friendly check if another process should now be run, then + * return to run the Guest again */ + cond_resched(); + return; + case LGUEST_TRAP_ENTRY: + /* Our 'struct hcall_args' maps directly over our regs: we set + * up the pointer now to indicate a hypercall is pending. */ + lg->hcall = (struct hcall_args *)lg->regs; + return; + } + + /* We didn't handle the trap, so it needs to go to the Guest. */ + if (!deliver_trap(lg, lg->regs->trapnum)) + /* If the Guest doesn't have a handler (either it hasn't + * registered any yet, or it's one of the faults we don't let + * it handle), it dies with a cryptic error message. */ + kill_guest(lg, "unhandled trap %li at %#lx (%#lx)", + lg->regs->trapnum, lg->regs->eip, + lg->regs->trapnum == 14 ? lg->arch.last_pagefault + : lg->regs->errcode); +} + +/* Now we can look at each of the routines this calls, in increasing order of + * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(), + * deliver_trap() and demand_page(). After all those, we'll be ready to + * examine the Switcher, and our philosophical understanding of the Host/Guest + * duality will be complete. :*/ +static void adjust_pge(void *on) +{ + if (on) + write_cr4(read_cr4() | X86_CR4_PGE); + else + write_cr4(read_cr4() & ~X86_CR4_PGE); +} + +/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do + * some more i386-specific initialization. */ +void __init lguest_arch_host_init(void) +{ + int i; + + /* Most of the i386/switcher.S doesn't care that it's been moved; on + * Intel, jumps are relative, and it doesn't access any references to + * external code or data. + * + * The only exception is the interrupt handlers in switcher.S: their + * addresses are placed in a table (default_idt_entries), so we need to + * update the table with the new addresses. switcher_offset() is a + * convenience function which returns the distance between the builtin + * switcher code and the high-mapped copy we just made. */ + for (i = 0; i < IDT_ENTRIES; i++) + default_idt_entries[i] += switcher_offset(); + + /* + * Set up the Switcher's per-cpu areas. + * + * Each CPU gets two pages of its own within the high-mapped region + * (aka. "struct lguest_pages"). Much of this can be initialized now, + * but some depends on what Guest we are running (which is set up in + * copy_in_guest_info()). + */ + for_each_possible_cpu(i) { + /* lguest_pages() returns this CPU's two pages. */ + struct lguest_pages *pages = lguest_pages(i); + /* This is a convenience pointer to make the code fit one + * statement to a line. */ + struct lguest_ro_state *state = &pages->state; + + /* The Global Descriptor Table: the Host has a different one + * for each CPU. We keep a descriptor for the GDT which says + * where it is and how big it is (the size is actually the last + * byte, not the size, hence the "-1"). */ + state->host_gdt_desc.size = GDT_SIZE-1; + state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); + + /* All CPUs on the Host use the same Interrupt Descriptor + * Table, so we just use store_idt(), which gets this CPU's IDT + * descriptor. */ + store_idt(&state->host_idt_desc); + + /* The descriptors for the Guest's GDT and IDT can be filled + * out now, too. We copy the GDT & IDT into ->guest_gdt and + * ->guest_idt before actually running the Guest. */ + state->guest_idt_desc.size = sizeof(state->guest_idt)-1; + state->guest_idt_desc.address = (long)&state->guest_idt; + state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; + state->guest_gdt_desc.address = (long)&state->guest_gdt; + + /* We know where we want the stack to be when the Guest enters + * the switcher: in pages->regs. The stack grows upwards, so + * we start it at the end of that structure. */ + state->guest_tss.esp0 = (long)(&pages->regs + 1); + /* And this is the GDT entry to use for the stack: we keep a + * couple of special LGUEST entries. */ + state->guest_tss.ss0 = LGUEST_DS; + + /* x86 can have a finegrained bitmap which indicates what I/O + * ports the process can use. We set it to the end of our + * structure, meaning "none". */ + state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); + + /* Some GDT entries are the same across all Guests, so we can + * set them up now. */ + setup_default_gdt_entries(state); + /* Most IDT entries are the same for all Guests, too.*/ + setup_default_idt_entries(state, default_idt_entries); + + /* The Host needs to be able to use the LGUEST segments on this + * CPU, too, so put them in the Host GDT. */ + get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; + get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; + } + + /* In the Switcher, we want the %cs segment register to use the + * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so + * it will be undisturbed when we switch. To change %cs and jump we + * need this structure to feed to Intel's "lcall" instruction. */ + lguest_entry.offset = (long)switch_to_guest + switcher_offset(); + lguest_entry.segment = LGUEST_CS; + + /* Finally, we need to turn off "Page Global Enable". PGE is an + * optimization where page table entries are specially marked to show + * they never change. The Host kernel marks all the kernel pages this + * way because it's always present, even when userspace is running. + * + * Lguest breaks this: unbeknownst to the rest of the Host kernel, we + * switch to the Guest kernel. If you don't disable this on all CPUs, + * you'll get really weird bugs that you'll chase for two days. + * + * I used to turn PGE off every time we switched to the Guest and back + * on when we return, but that slowed the Switcher down noticibly. */ + + /* We don't need the complexity of CPUs coming and going while we're + * doing this. */ + lock_cpu_hotplug(); + if (cpu_has_pge) { /* We have a broader idea of "global". */ + /* Remember that this was originally set (for cleanup). */ + cpu_had_pge = 1; + /* adjust_pge is a helper function which sets or unsets the PGE + * bit on its CPU, depending on the argument (0 == unset). */ + on_each_cpu(adjust_pge, (void *)0, 0, 1); + /* Turn off the feature in the global feature set. */ + clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); + } + unlock_cpu_hotplug(); +}; +/*:*/ + +void __exit lguest_arch_host_fini(void) +{ + /* If we had PGE before we started, turn it back on now. */ + lock_cpu_hotplug(); + if (cpu_had_pge) { + set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); + /* adjust_pge's argument "1" means set PGE. */ + on_each_cpu(adjust_pge, (void *)1, 0, 1); + } + unlock_cpu_hotplug(); +} + + +/*H:122 The i386-specific hypercalls simply farm out to the right functions. */ +int lguest_arch_do_hcall(struct lguest *lg, struct hcall_args *args) +{ + switch (args->arg0) { + case LHCALL_LOAD_GDT: + load_guest_gdt(lg, args->arg1, args->arg2); + break; + case LHCALL_LOAD_IDT_ENTRY: + load_guest_idt_entry(lg, args->arg1, args->arg2, args->arg3); + break; + case LHCALL_LOAD_TLS: + guest_load_tls(lg, args->arg1); + break; + default: + /* Bad Guest. Bad! */ + return -EIO; + } + return 0; +} + +/*H:126 i386-specific hypercall initialization: */ +int lguest_arch_init_hypercalls(struct lguest *lg) +{ + u32 tsc_speed; + + /* The pointer to the Guest's "struct lguest_data" is the only + * argument. We check that address now. */ + if (!lguest_address_ok(lg, lg->hcall->arg1, sizeof(*lg->lguest_data))) + return -EFAULT; + + /* Having checked it, we simply set lg->lguest_data to point straight + * into the Launcher's memory at the right place and then use + * copy_to_user/from_user from now on, instead of lgread/write. I put + * this in to show that I'm not immune to writing stupid + * optimizations. */ + lg->lguest_data = lg->mem_base + lg->hcall->arg1; + + /* We insist that the Time Stamp Counter exist and doesn't change with + * cpu frequency. Some devious chip manufacturers decided that TSC + * changes could be handled in software. I decided that time going + * backwards might be good for benchmarks, but it's bad for users. + * + * We also insist that the TSC be stable: the kernel detects unreliable + * TSCs for its own purposes, and we use that here. */ + if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable()) + tsc_speed = tsc_khz; + else + tsc_speed = 0; + if (put_user(tsc_speed, &lg->lguest_data->tsc_khz)) + return -EFAULT; + + /* The interrupt code might not like the system call vector. */ + if (!check_syscall_vector(lg)) + kill_guest(lg, "bad syscall vector"); + + return 0; +} + +/*L:030 lguest_arch_setup_regs() + * + * Most of the Guest's registers are left alone: we used get_zeroed_page() to + * allocate the structure, so they will be 0. */ +void lguest_arch_setup_regs(struct lguest *lg, unsigned long start) +{ + struct lguest_regs *regs = lg->regs; + + /* There are four "segment" registers which the Guest needs to boot: + * The "code segment" register (cs) refers to the kernel code segment + * __KERNEL_CS, and the "data", "extra" and "stack" segment registers + * refer to the kernel data segment __KERNEL_DS. + * + * The privilege level is packed into the lower bits. The Guest runs + * at privilege level 1 (GUEST_PL).*/ + regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; + regs->cs = __KERNEL_CS|GUEST_PL; + + /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002) + * is supposed to always be "1". Bit 9 (0x200) controls whether + * interrupts are enabled. We always leave interrupts enabled while + * running the Guest. */ + regs->eflags = X86_EFLAGS_IF | 0x2; + + /* The "Extended Instruction Pointer" register says where the Guest is + * running. */ + regs->eip = start; + + /* %esi points to our boot information, at physical address 0, so don't + * touch it. */ + + /* There are a couple of GDT entries the Guest expects when first + * booting. */ + setup_guest_gdt(lg); +} diff --git a/drivers/lguest/switcher.S b/drivers/lguest/x86/switcher_32.S index 7c9c230cc845..0af8baaa0d4a 100644 --- a/drivers/lguest/switcher.S +++ b/drivers/lguest/x86/switcher_32.S @@ -6,6 +6,37 @@ * are feeling invigorated and refreshed then the next, more challenging stage * can be found in "make Guest". :*/ +/*M:012 Lguest is meant to be simple: my rule of thumb is that 1% more LOC must + * gain at least 1% more performance. Since neither LOC nor performance can be + * measured beforehand, it generally means implementing a feature then deciding + * if it's worth it. And once it's implemented, who can say no? + * + * This is why I haven't implemented this idea myself. I want to, but I + * haven't. You could, though. + * + * The main place where lguest performance sucks is Guest page faulting. When + * a Guest userspace process hits an unmapped page we switch back to the Host, + * walk the page tables, find it's not mapped, switch back to the Guest page + * fault handler, which calls a hypercall to set the page table entry, then + * finally returns to userspace. That's two round-trips. + * + * If we had a small walker in the Switcher, we could quickly check the Guest + * page table and if the page isn't mapped, immediately reflect the fault back + * into the Guest. This means the Switcher would have to know the top of the + * Guest page table and the page fault handler address. + * + * For simplicity, the Guest should only handle the case where the privilege + * level of the fault is 3 and probably only not present or write faults. It + * should also detect recursive faults, and hand the original fault to the + * Host (which is actually really easy). + * + * Two questions remain. Would the performance gain outweigh the complexity? + * And who would write the verse documenting it? :*/ + +/*M:011 Lguest64 handles NMI. This gave me NMI envy (until I looked at their + * code). It's worth doing though, since it would let us use oprofile in the + * Host when a Guest is running. :*/ + /*S:100 * Welcome to the Switcher itself! * @@ -48,7 +79,8 @@ #include <linux/linkage.h> #include <asm/asm-offsets.h> #include <asm/page.h> -#include "lg.h" +#include <asm/segment.h> +#include <asm/lguest.h> // We mark the start of the code to copy // It's placed in .text tho it's never run here @@ -87,7 +119,7 @@ ENTRY(switch_to_guest) // All saved and there's now five steps before us: // Stack, GDT, IDT, TSS - // And last of all the page tables are flipped. + // Then last of all the page tables are flipped. // Yet beware that our stack pointer must be // Always valid lest an NMI hits @@ -102,25 +134,25 @@ ENTRY(switch_to_guest) lgdt LGUEST_PAGES_guest_gdt_desc(%eax) // The Guest's IDT we did partially - // Move to the "struct lguest_pages" as well. + // Copy to "struct lguest_pages" as well. lidt LGUEST_PAGES_guest_idt_desc(%eax) // The TSS entry which controls traps // Must be loaded up with "ltr" now: + // The GDT entry that TSS uses + // Changes type when we load it: damn Intel! // For after we switch over our page tables - // It (as the rest) will be writable no more. - // (The GDT entry TSS needs - // Changes type when we load it: damn Intel!) + // That entry will be read-only: we'd crash. movl $(GDT_ENTRY_TSS*8), %edx ltr %dx // Look back now, before we take this last step! // The Host's TSS entry was also marked used; - // Let's clear it again, ere we return. + // Let's clear it again for our return. // The GDT descriptor of the Host // Points to the table after two "size" bytes movl (LGUEST_PAGES_host_gdt_desc+2)(%eax), %edx - // Clear the type field of "used" (byte 5, bit 2) + // Clear "used" from type field (byte 5, bit 2) andb $0xFD, (GDT_ENTRY_TSS*8 + 5)(%edx) // Once our page table's switched, the Guest is live! @@ -130,8 +162,9 @@ ENTRY(switch_to_guest) // The page table change did one tricky thing: // The Guest's register page has been mapped - // Writable onto our %esp (stack) -- + // Writable under our %esp (stack) -- // We can simply pop off all Guest regs. + popl %eax popl %ebx popl %ecx popl %edx @@ -139,7 +172,6 @@ ENTRY(switch_to_guest) popl %edi popl %ebp popl %gs - popl %eax popl %fs popl %ds popl %es @@ -151,23 +183,21 @@ ENTRY(switch_to_guest) addl $8, %esp // The last five stack slots hold return address - // And everything needed to change privilege - // Into the Guest privilege level of 1, + // And everything needed to switch privilege + // From Switcher's level 0 to Guest's 1, // And the stack where the Guest had last left it. // Interrupts are turned back on: we are Guest. iret -// There are two paths where we switch to the Host +// We treat two paths to switch back to the Host +// Yet both must save Guest state and restore Host // So we put the routine in a macro. -// We are on our way home, back to the Host -// Interrupted out of the Guest, we come here. #define SWITCH_TO_HOST \ /* We save the Guest state: all registers first \ * Laid out just as "struct lguest_regs" defines */ \ pushl %es; \ pushl %ds; \ pushl %fs; \ - pushl %eax; \ pushl %gs; \ pushl %ebp; \ pushl %edi; \ @@ -175,6 +205,7 @@ ENTRY(switch_to_guest) pushl %edx; \ pushl %ecx; \ pushl %ebx; \ + pushl %eax; \ /* Our stack and our code are using segments \ * Set in the TSS and IDT \ * Yet if we were to touch data we'd use \ @@ -193,7 +224,7 @@ ENTRY(switch_to_guest) movl %esp, %eax; \ andl $(~(1 << PAGE_SHIFT - 1)), %eax; \ /* Save our trap number: the switch will obscure it \ - * (The Guest regs are not mapped here in the Host) \ + * (In the Host the Guest regs are not mapped here) \ * %ebx holds it safe for deliver_to_host */ \ movl LGUEST_PAGES_regs_trapnum(%eax), %ebx; \ /* The Host GDT, IDT and stack! \ @@ -209,9 +240,9 @@ ENTRY(switch_to_guest) /* Switch to Host's GDT, IDT. */ \ lgdt LGUEST_PAGES_host_gdt_desc(%eax); \ lidt LGUEST_PAGES_host_idt_desc(%eax); \ - /* Restore the Host's stack where it's saved regs lie */ \ + /* Restore the Host's stack where its saved regs lie */ \ movl LGUEST_PAGES_host_sp(%eax), %esp; \ - /* Last the TSS: our Host is complete */ \ + /* Last the TSS: our Host is returned */ \ movl $(GDT_ENTRY_TSS*8), %edx; \ ltr %dx; \ /* Restore now the regs saved right at the first. */ \ @@ -221,14 +252,15 @@ ENTRY(switch_to_guest) popl %ds; \ popl %es -// Here's where we come when the Guest has just trapped: -// (Which trap we'll see has been pushed on the stack). +// The first path is trod when the Guest has trapped: +// (Which trap it was has been pushed on the stack). // We need only switch back, and the Host will decode // Why we came home, and what needs to be done. return_to_host: SWITCH_TO_HOST iret +// We are lead to the second path like so: // An interrupt, with some cause external // Has ajerked us rudely from the Guest's code // Again we must return home to the Host @@ -237,7 +269,7 @@ deliver_to_host: // But now we must go home via that place // Where that interrupt was supposed to go // Had we not been ensconced, running the Guest. - // Here we see the cleverness of our stack: + // Here we see the trickness of run_guest_once(): // The Host stack is formed like an interrupt // With EIP, CS and EFLAGS layered. // Interrupt handlers end with "iret" @@ -262,7 +294,7 @@ deliver_to_host: xorw %ax, %ax orl %eax, %edx // Now the address of the handler's in %edx - // We call it now: its "iret" takes us home. + // We call it now: its "iret" drops us home. jmp *%edx // Every interrupt can come to us here |