Boot with virtual == physical to get closer to native Linux.

[safe/jmp/linux-2.6] / arch / x86 / lguest / i386_head.S

diff --git a/arch/x86/lguest/i386_head.S b/arch/x86/lguest/i386_head.S
index 6d7a74f..ba4282e 100644 (file)
--- 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