// SPDX-License-Identifier: GPL-2.0 /* * S390 version * Copyright IBM Corp. 1999 * Author(s): Hartmut Penner (hp@de.ibm.com) * Ulrich Weigand (uweigand@de.ibm.com) * * Derived from "arch/i386/mm/fault.c" * Copyright (C) 1995 Linus Torvalds */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "../kernel/entry.h" #define __FAIL_ADDR_MASK -4096L #define __SUBCODE_MASK 0x0600 #define __PF_RES_FIELD 0x8000000000000000ULL #define VM_FAULT_BADCONTEXT 0x010000 #define VM_FAULT_BADMAP 0x020000 #define VM_FAULT_BADACCESS 0x040000 #define VM_FAULT_SIGNAL 0x080000 #define VM_FAULT_PFAULT 0x100000 enum fault_type { KERNEL_FAULT, USER_FAULT, VDSO_FAULT, GMAP_FAULT, }; static unsigned long store_indication __read_mostly; static int __init fault_init(void) { if (test_facility(75)) store_indication = 0xc00; return 0; } early_initcall(fault_init); static inline int notify_page_fault(struct pt_regs *regs) { int ret = 0; /* kprobe_running() needs smp_processor_id() */ if (kprobes_built_in() && !user_mode(regs)) { preempt_disable(); if (kprobe_running() && kprobe_fault_handler(regs, 14)) ret = 1; preempt_enable(); } return ret; } /* * Unlock any spinlocks which will prevent us from getting the * message out. */ void bust_spinlocks(int yes) { if (yes) { oops_in_progress = 1; } else { int loglevel_save = console_loglevel; console_unblank(); oops_in_progress = 0; /* * OK, the message is on the console. Now we call printk() * without oops_in_progress set so that printk will give klogd * a poke. Hold onto your hats... */ console_loglevel = 15; printk(" "); console_loglevel = loglevel_save; } } /* * Find out which address space caused the exception. * Access register mode is impossible, ignore space == 3. */ static inline enum fault_type get_fault_type(struct pt_regs *regs) { unsigned long trans_exc_code; trans_exc_code = regs->int_parm_long & 3; if (likely(trans_exc_code == 0)) { /* primary space exception */ if (IS_ENABLED(CONFIG_PGSTE) && test_pt_regs_flag(regs, PIF_GUEST_FAULT)) return GMAP_FAULT; if (current->thread.mm_segment == USER_DS) return USER_FAULT; return KERNEL_FAULT; } if (trans_exc_code == 2) { /* secondary space exception */ if (current->thread.mm_segment & 1) { if (current->thread.mm_segment == USER_DS_SACF) return USER_FAULT; return KERNEL_FAULT; } return VDSO_FAULT; } /* home space exception -> access via kernel ASCE */ return KERNEL_FAULT; } static int bad_address(void *p) { unsigned long dummy; return probe_kernel_address((unsigned long *)p, dummy); } static void dump_pagetable(unsigned long asce, unsigned long address) { unsigned long *table = __va(asce & _ASCE_ORIGIN); pr_alert("AS:%016lx ", asce); switch (asce & _ASCE_TYPE_MASK) { case _ASCE_TYPE_REGION1: table += (address & _REGION1_INDEX) >> _REGION1_SHIFT; if (bad_address(table)) goto bad; pr_cont("R1:%016lx ", *table); if (*table & _REGION_ENTRY_INVALID) goto out; table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); /* fallthrough */ case _ASCE_TYPE_REGION2: table += (address & _REGION2_INDEX) >> _REGION2_SHIFT; if (bad_address(table)) goto bad; pr_cont("R2:%016lx ", *table); if (*table & _REGION_ENTRY_INVALID) goto out; table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); /* fallthrough */ case _ASCE_TYPE_REGION3: table += (address & _REGION3_INDEX) >> _REGION3_SHIFT; if (bad_address(table)) goto bad; pr_cont("R3:%016lx ", *table); if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE)) goto out; table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN); /* fallthrough */ case _ASCE_TYPE_SEGMENT: table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT; if (bad_address(table)) goto bad; pr_cont("S:%016lx ", *table); if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE)) goto out; table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN); } table += (address & _PAGE_INDEX) >> _PAGE_SHIFT; if (bad_address(table)) goto bad; pr_cont("P:%016lx ", *table); out: pr_cont("\n"); return; bad: pr_cont("BAD\n"); } static void dump_fault_info(struct pt_regs *regs) { unsigned long asce; pr_alert("Failing address: %016lx TEID: %016lx\n", regs->int_parm_long & __FAIL_ADDR_MASK, regs->int_parm_long); pr_alert("Fault in "); switch (regs->int_parm_long & 3) { case 3: pr_cont("home space "); break; case 2: pr_cont("secondary space "); break; case 1: pr_cont("access register "); break; case 0: pr_cont("primary space "); break; } pr_cont("mode while using "); switch (get_fault_type(regs)) { case USER_FAULT: asce = S390_lowcore.user_asce; pr_cont("user "); break; case VDSO_FAULT: asce = S390_lowcore.vdso_asce; pr_cont("vdso "); break; case GMAP_FAULT: asce = ((struct gmap *) S390_lowcore.gmap)->asce; pr_cont("gmap "); break; case KERNEL_FAULT: asce = S390_lowcore.kernel_asce; pr_cont("kernel "); break; } pr_cont("ASCE.\n"); dump_pagetable(asce, regs->int_parm_long & __FAIL_ADDR_MASK); } int show_unhandled_signals = 1; void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault) { if ((task_pid_nr(current) > 1) && !show_unhandled_signals) return; if (!unhandled_signal(current, signr)) return; if (!printk_ratelimit()) return; printk(KERN_ALERT "User process fault: interruption code %04x ilc:%d ", regs->int_code & 0xffff, regs->int_code >> 17); print_vma_addr(KERN_CONT "in ", regs->psw.addr); printk(KERN_CONT "\n"); if (is_mm_fault) dump_fault_info(regs); show_regs(regs); } /* * Send SIGSEGV to task. This is an external routine * to keep the stack usage of do_page_fault small. */ static noinline void do_sigsegv(struct pt_regs *regs, int si_code) { report_user_fault(regs, SIGSEGV, 1); force_sig_fault(SIGSEGV, si_code, (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), current); } static noinline void do_no_context(struct pt_regs *regs) { const struct exception_table_entry *fixup; /* Are we prepared to handle this kernel fault? */ fixup = search_exception_tables(regs->psw.addr); if (fixup) { regs->psw.addr = extable_fixup(fixup); return; } /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice. */ if (get_fault_type(regs) == KERNEL_FAULT) printk(KERN_ALERT "Unable to handle kernel pointer dereference" " in virtual kernel address space\n"); else printk(KERN_ALERT "Unable to handle kernel paging request" " in virtual user address space\n"); dump_fault_info(regs); die(regs, "Oops"); do_exit(SIGKILL); } static noinline void do_low_address(struct pt_regs *regs) { /* Low-address protection hit in kernel mode means NULL pointer write access in kernel mode. */ if (regs->psw.mask & PSW_MASK_PSTATE) { /* Low-address protection hit in user mode 'cannot happen'. */ die (regs, "Low-address protection"); do_exit(SIGKILL); } do_no_context(regs); } static noinline void do_sigbus(struct pt_regs *regs) { /* * Send a sigbus, regardless of whether we were in kernel * or user mode. */ force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)(regs->int_parm_long & __FAIL_ADDR_MASK), current); } static noinline int signal_return(struct pt_regs *regs) { u16 instruction; int rc; rc = __get_user(instruction, (u16 __user *) regs->psw.addr); if (rc) return rc; if (instruction == 0x0a77) { set_pt_regs_flag(regs, PIF_SYSCALL); regs->int_code = 0x00040077; return 0; } else if (instruction == 0x0aad) { set_pt_regs_flag(regs, PIF_SYSCALL); regs->int_code = 0x000400ad; return 0; } return -EACCES; } static noinline void do_fault_error(struct pt_regs *regs, int access, int fault) { int si_code; switch (fault) { case VM_FAULT_BADACCESS: if (access == VM_EXEC && signal_return(regs) == 0) break; case VM_FAULT_BADMAP: /* Bad memory access. Check if it is kernel or user space. */ if (user_mode(regs)) { /* User mode accesses just cause a SIGSEGV */ si_code = (fault == VM_FAULT_BADMAP) ? SEGV_MAPERR : SEGV_ACCERR; do_sigsegv(regs, si_code); break; } case VM_FAULT_BADCONTEXT: case VM_FAULT_PFAULT: do_no_context(regs); break; case VM_FAULT_SIGNAL: if (!user_mode(regs)) do_no_context(regs); break; default: /* fault & VM_FAULT_ERROR */ if (fault & VM_FAULT_OOM) { if (!user_mode(regs)) do_no_context(regs); else pagefault_out_of_memory(); } else if (fault & VM_FAULT_SIGSEGV) { /* Kernel mode? Handle exceptions or die */ if (!user_mode(regs)) do_no_context(regs); else do_sigsegv(regs, SEGV_MAPERR); } else if (fault & VM_FAULT_SIGBUS) { /* Kernel mode? Handle exceptions or die */ if (!user_mode(regs)) do_no_context(regs); else do_sigbus(regs); } else BUG(); break; } } /* * This routine handles page faults. It determines the address, * and the problem, and then passes it off to one of the appropriate * routines. * * interruption code (int_code): * 04 Protection -> Write-Protection (suprression) * 10 Segment translation -> Not present (nullification) * 11 Page translation -> Not present (nullification) * 3b Region third trans. -> Not present (nullification) */ static inline int do_exception(struct pt_regs *regs, int access) { struct gmap *gmap; struct task_struct *tsk; struct mm_struct *mm; struct vm_area_struct *vma; enum fault_type type; unsigned long trans_exc_code; unsigned long address; unsigned int flags; int fault; tsk = current; /* * The instruction that caused the program check has * been nullified. Don't signal single step via SIGTRAP. */ clear_pt_regs_flag(regs, PIF_PER_TRAP); if (notify_page_fault(regs)) return 0; mm = tsk->mm; trans_exc_code = regs->int_parm_long; /* * Verify that the fault happened in user space, that * we are not in an interrupt and that there is a * user context. */ fault = VM_FAULT_BADCONTEXT; type = get_fault_type(regs); switch (type) { case KERNEL_FAULT: goto out; case VDSO_FAULT: fault = VM_FAULT_BADMAP; goto out; case USER_FAULT: case GMAP_FAULT: if (faulthandler_disabled() || !mm) goto out; break; } address = trans_exc_code & __FAIL_ADDR_MASK; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; if (user_mode(regs)) flags |= FAULT_FLAG_USER; if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400) flags |= FAULT_FLAG_WRITE; down_read(&mm->mmap_sem); gmap = NULL; if (IS_ENABLED(CONFIG_PGSTE) && type == GMAP_FAULT) { gmap = (struct gmap *) S390_lowcore.gmap; current->thread.gmap_addr = address; current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE); current->thread.gmap_int_code = regs->int_code & 0xffff; address = __gmap_translate(gmap, address); if (address == -EFAULT) { fault = VM_FAULT_BADMAP; goto out_up; } if (gmap->pfault_enabled) flags |= FAULT_FLAG_RETRY_NOWAIT; } retry: fault = VM_FAULT_BADMAP; vma = find_vma(mm, address); if (!vma) goto out_up; if (unlikely(vma->vm_start > address)) { if (!(vma->vm_flags & VM_GROWSDOWN)) goto out_up; if (expand_stack(vma, address)) goto out_up; } /* * Ok, we have a good vm_area for this memory access, so * we can handle it.. */ fault = VM_FAULT_BADACCESS; if (unlikely(!(vma->vm_flags & access))) goto out_up; if (is_vm_hugetlb_page(vma)) address &= HPAGE_MASK; /* * If for any reason at all we couldn't handle the fault, * make sure we exit gracefully rather than endlessly redo * the fault. */ fault = handle_mm_fault(vma, address, flags); /* No reason to continue if interrupted by SIGKILL. */ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) { fault = VM_FAULT_SIGNAL; if (flags & FAULT_FLAG_RETRY_NOWAIT) goto out_up; goto out; } if (unlikely(fault & VM_FAULT_ERROR)) goto out_up; /* * Major/minor page fault accounting is only done on the * initial attempt. If we go through a retry, it is extremely * likely that the page will be found in page cache at that point. */ if (flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_MAJOR) { tsk->maj_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); } else { tsk->min_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); } if (fault & VM_FAULT_RETRY) { if (IS_ENABLED(CONFIG_PGSTE) && gmap && (flags & FAULT_FLAG_RETRY_NOWAIT)) { /* FAULT_FLAG_RETRY_NOWAIT has been set, * mmap_sem has not been released */ current->thread.gmap_pfault = 1; fault = VM_FAULT_PFAULT; goto out_up; } /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk * of starvation. */ flags &= ~(FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT); flags |= FAULT_FLAG_TRIED; down_read(&mm->mmap_sem); goto retry; } } if (IS_ENABLED(CONFIG_PGSTE) && gmap) { address = __gmap_link(gmap, current->thread.gmap_addr, address); if (address == -EFAULT) { fault = VM_FAULT_BADMAP; goto out_up; } if (address == -ENOMEM) { fault = VM_FAULT_OOM; goto out_up; } } fault = 0; out_up: up_read(&mm->mmap_sem); out: return fault; } void do_protection_exception(struct pt_regs *regs) { unsigned long trans_exc_code; int access, fault; trans_exc_code = regs->int_parm_long; /* * Protection exceptions are suppressing, decrement psw address. * The exception to this rule are aborted transactions, for these * the PSW already points to the correct location. */ if (!(regs->int_code & 0x200)) regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); /* * Check for low-address protection. This needs to be treated * as a special case because the translation exception code * field is not guaranteed to contain valid data in this case. */ if (unlikely(!(trans_exc_code & 4))) { do_low_address(regs); return; } if (unlikely(MACHINE_HAS_NX && (trans_exc_code & 0x80))) { regs->int_parm_long = (trans_exc_code & ~PAGE_MASK) | (regs->psw.addr & PAGE_MASK); access = VM_EXEC; fault = VM_FAULT_BADACCESS; } else { access = VM_WRITE; fault = do_exception(regs, access); } if (unlikely(fault)) do_fault_error(regs, access, fault); } NOKPROBE_SYMBOL(do_protection_exception); void do_dat_exception(struct pt_regs *regs) { int access, fault; access = VM_READ | VM_EXEC | VM_WRITE; fault = do_exception(regs, access); if (unlikely(fault)) do_fault_error(regs, access, fault); } NOKPROBE_SYMBOL(do_dat_exception); #ifdef CONFIG_PFAULT /* * 'pfault' pseudo page faults routines. */ static int pfault_disable; static int __init nopfault(char *str) { pfault_disable = 1; return 1; } __setup("nopfault", nopfault); struct pfault_refbk { u16 refdiagc; u16 reffcode; u16 refdwlen; u16 refversn; u64 refgaddr; u64 refselmk; u64 refcmpmk; u64 reserved; } __attribute__ ((packed, aligned(8))); int pfault_init(void) { struct pfault_refbk refbk = { .refdiagc = 0x258, .reffcode = 0, .refdwlen = 5, .refversn = 2, .refgaddr = __LC_LPP, .refselmk = 1ULL << 48, .refcmpmk = 1ULL << 48, .reserved = __PF_RES_FIELD }; int rc; if (pfault_disable) return -1; diag_stat_inc(DIAG_STAT_X258); asm volatile( " diag %1,%0,0x258\n" "0: j 2f\n" "1: la %0,8\n" "2:\n" EX_TABLE(0b,1b) : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc"); return rc; } void pfault_fini(void) { struct pfault_refbk refbk = { .refdiagc = 0x258, .reffcode = 1, .refdwlen = 5, .refversn = 2, }; if (pfault_disable) return; diag_stat_inc(DIAG_STAT_X258); asm volatile( " diag %0,0,0x258\n" "0: nopr %%r7\n" EX_TABLE(0b,0b) : : "a" (&refbk), "m" (refbk) : "cc"); } static DEFINE_SPINLOCK(pfault_lock); static LIST_HEAD(pfault_list); #define PF_COMPLETE 0x0080 /* * The mechanism of our pfault code: if Linux is running as guest, runs a user * space process and the user space process accesses a page that the host has * paged out we get a pfault interrupt. * * This allows us, within the guest, to schedule a different process. Without * this mechanism the host would have to suspend the whole virtual cpu until * the page has been paged in. * * So when we get such an interrupt then we set the state of the current task * to uninterruptible and also set the need_resched flag. Both happens within * interrupt context(!). If we later on want to return to user space we * recognize the need_resched flag and then call schedule(). It's not very * obvious how this works... * * Of course we have a lot of additional fun with the completion interrupt (-> * host signals that a page of a process has been paged in and the process can * continue to run). This interrupt can arrive on any cpu and, since we have * virtual cpus, actually appear before the interrupt that signals that a page * is missing. */ static void pfault_interrupt(struct ext_code ext_code, unsigned int param32, unsigned long param64) { struct task_struct *tsk; __u16 subcode; pid_t pid; /* * Get the external interruption subcode & pfault initial/completion * signal bit. VM stores this in the 'cpu address' field associated * with the external interrupt. */ subcode = ext_code.subcode; if ((subcode & 0xff00) != __SUBCODE_MASK) return; inc_irq_stat(IRQEXT_PFL); /* Get the token (= pid of the affected task). */ pid = param64 & LPP_PID_MASK; rcu_read_lock(); tsk = find_task_by_pid_ns(pid, &init_pid_ns); if (tsk) get_task_struct(tsk); rcu_read_unlock(); if (!tsk) return; spin_lock(&pfault_lock); if (subcode & PF_COMPLETE) { /* signal bit is set -> a page has been swapped in by VM */ if (tsk->thread.pfault_wait == 1) { /* Initial interrupt was faster than the completion * interrupt. pfault_wait is valid. Set pfault_wait * back to zero and wake up the process. This can * safely be done because the task is still sleeping * and can't produce new pfaults. */ tsk->thread.pfault_wait = 0; list_del(&tsk->thread.list); wake_up_process(tsk); put_task_struct(tsk); } else { /* Completion interrupt was faster than initial * interrupt. Set pfault_wait to -1 so the initial * interrupt doesn't put the task to sleep. * If the task is not running, ignore the completion * interrupt since it must be a leftover of a PFAULT * CANCEL operation which didn't remove all pending * completion interrupts. */ if (tsk->state == TASK_RUNNING) tsk->thread.pfault_wait = -1; } } else { /* signal bit not set -> a real page is missing. */ if (WARN_ON_ONCE(tsk != current)) goto out; if (tsk->thread.pfault_wait == 1) { /* Already on the list with a reference: put to sleep */ goto block; } else if (tsk->thread.pfault_wait == -1) { /* Completion interrupt was faster than the initial * interrupt (pfault_wait == -1). Set pfault_wait * back to zero and exit. */ tsk->thread.pfault_wait = 0; } else { /* Initial interrupt arrived before completion * interrupt. Let the task sleep. * An extra task reference is needed since a different * cpu may set the task state to TASK_RUNNING again * before the scheduler is reached. */ get_task_struct(tsk); tsk->thread.pfault_wait = 1; list_add(&tsk->thread.list, &pfault_list); block: /* Since this must be a userspace fault, there * is no kernel task state to trample. Rely on the * return to userspace schedule() to block. */ __set_current_state(TASK_UNINTERRUPTIBLE); set_tsk_need_resched(tsk); set_preempt_need_resched(); } } out: spin_unlock(&pfault_lock); put_task_struct(tsk); } static int pfault_cpu_dead(unsigned int cpu) { struct thread_struct *thread, *next; struct task_struct *tsk; spin_lock_irq(&pfault_lock); list_for_each_entry_safe(thread, next, &pfault_list, list) { thread->pfault_wait = 0; list_del(&thread->list); tsk = container_of(thread, struct task_struct, thread); wake_up_process(tsk); put_task_struct(tsk); } spin_unlock_irq(&pfault_lock); return 0; } static int __init pfault_irq_init(void) { int rc; rc = register_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); if (rc) goto out_extint; rc = pfault_init() == 0 ? 0 : -EOPNOTSUPP; if (rc) goto out_pfault; irq_subclass_register(IRQ_SUBCLASS_SERVICE_SIGNAL); cpuhp_setup_state_nocalls(CPUHP_S390_PFAULT_DEAD, "s390/pfault:dead", NULL, pfault_cpu_dead); return 0; out_pfault: unregister_external_irq(EXT_IRQ_CP_SERVICE, pfault_interrupt); out_extint: pfault_disable = 1; return rc; } early_initcall(pfault_irq_init); #endif /* CONFIG_PFAULT */