summaryrefslogtreecommitdiff
path: root/arch/x86/lguest/i386_head.S
diff options
context:
space:
mode:
authorRusty Russell <rusty@rustcorp.com.au>2007-10-22 05:03:36 +0400
committerRusty Russell <rusty@rustcorp.com.au>2007-10-23 09:49:54 +0400
commit47436aa4ad054c1c7c8231618e86ebd9305308dc (patch)
treea9ba6e0521f9116442144a86e781a3164ec86094 /arch/x86/lguest/i386_head.S
parentc18acd73ffc209def08003a1927473096f66c5ad (diff)
downloadlinux-47436aa4ad054c1c7c8231618e86ebd9305308dc.tar.xz
Boot with virtual == physical to get closer to native Linux.
1) This allows us to get alot closer to booting bzImages. 2) It means we don't have to know page_offset. 3) The Guest needs to modify the boot pagetables to create the PAGE_OFFSET mapping before jumping to C code. 4) guest_pa() walks the page tables rather than using page_offset. 5) We don't use page_offset to figure out whether to emulate: it was always kinda quesationable, and won't work for instructions done before remapping (bzImage unpacking in particular). 6) We still want the kernel address for tlb flushing: have the initial hypercall give us that, too. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'arch/x86/lguest/i386_head.S')
-rw-r--r--arch/x86/lguest/i386_head.S41
1 files changed, 36 insertions, 5 deletions
diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S
index 6d7a74f07c41..ba4282eba5bf 100644
--- a/arch/x86/lguest/i386_head.S
+++ b/arch/x86/lguest/i386_head.S
@@ -1,5 +1,6 @@
#include <linux/linkage.h>
#include <linux/lguest.h>
+#include <asm/lguest_hcall.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/processor-flags.h>
@@ -8,18 +9,48 @@
* 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).
+ * boot header, so we do too.
+ *
+ * WARNING: be very careful here! We're running at addresses equal to physical
+ * addesses (around 0), not above PAGE_OFFSET as most code expectes
+ * (eg. 0xC0000000). Jumps are relative, so they're OK, but we can't touch any
+ * data.
*
* 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
+ /* Make initial hypercall now, so we can set up the pagetables. */
+ movl $LHCALL_LGUEST_INIT, %eax
+ movl $lguest_data - __PAGE_OFFSET, %edx
+ int $LGUEST_TRAP_ENTRY
+
+ /* Set up boot information pointer to hand to lguest_init(): it wants
+ * a virtual address. */
movl %esi, %eax
addl $__PAGE_OFFSET, %eax
- jmp lguest_init
+
+ /* The Host put the toplevel pagetable in lguest_data.pgdir. The movsl
+ * instruction uses %esi, so we needed to save it above. */
+ movl lguest_data - __PAGE_OFFSET + LGUEST_DATA_pgdir, %esi
+
+ /* Copy first 32 entries of page directory to __PAGE_OFFSET entries.
+ * This means the first 128M of kernel memory will be mapped at
+ * PAGE_OFFSET where the kernel expects to run. This will get it far
+ * enough through boot to switch to its own pagetables. */
+ movl $32, %ecx
+ movl %esi, %edi
+ addl $((__PAGE_OFFSET >> 22) * 4), %edi
+ rep
+ movsl
+
+ /* Set up the initial stack so we can run C code. */
+ movl $(init_thread_union+THREAD_SIZE),%esp
+
+
+ /* Jumps are relative, and we're running __PAGE_OFFSET too low at the
+ * moment. */
+ jmp lguest_init+__PAGE_OFFSET
/*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