From adf58f0350ae4da00f93128ef9598b0eddb3ef7a Mon Sep 17 00:00:00 2001
From: Artur Grabowski <art@cvs.openbsd.org>
Date: Fri, 13 Apr 2007 11:16:09 +0000
Subject: Move the proc0 stack below the proc0 page tables so that in case we
 overflow the stack, we run into the symbol table (not critical) instead of
 overwriting the page tables.

From mickey, ok art@, ok toby@
---
 sys/arch/i386/i386/locore.s | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

(limited to 'sys/arch/i386')

diff --git a/sys/arch/i386/i386/locore.s b/sys/arch/i386/i386/locore.s
index 2a1820fed71..fc08292dc61 100644
--- a/sys/arch/i386/i386/locore.s
+++ b/sys/arch/i386/i386/locore.s
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.s,v 1.107 2007/04/03 10:14:47 art Exp $	*/
+/*	$OpenBSD: locore.s,v 1.108 2007/04/13 11:16:08 art Exp $	*/
 /*	$NetBSD: locore.s,v 1.145 1996/05/03 19:41:19 christos Exp $	*/
 
 /*-
@@ -534,11 +534,11 @@ try586:	/* Use the `cpuid' instruction. */
 /*
  * Virtual address space of kernel:
  *
- * text | data | bss | [syms] | page dir | proc0 kstack | Sysmap
- *			      0          1       2      3
+ * text | data | bss | [syms] | proc0 stack | page dir     | Sysmap
+ *			      0             1       2      3
  */
-#define	PROC0PDIR	((0)		* NBPG)
-#define	PROC0STACK	((1)		* NBPG)
+#define	PROC0STACK	((0)		* NBPG)
+#define	PROC0PDIR	((  UPAGES)	* NBPG)
 #define	SYSMAP		((1+UPAGES)	* NBPG)
 #define	TABLESIZE	((1+UPAGES) * NBPG) /* + _C_LABEL(nkpde) * NBPG */
 
@@ -603,7 +603,7 @@ try586:	/* Use the `cpuid' instruction. */
 	leal	(RELOC(_C_LABEL(etext))+PGOFSET),%edx
 	andl	$~PGOFSET,%edx
 
-	/* Skip over the first 1MB. */
+	/* Skip over the first 2MB. */
 	movl	$RELOC(KERNTEXTOFF),%eax
 	movl	%eax,%ecx
 	shrl	$PGSHIFT,%ecx
@@ -657,10 +657,10 @@ try586:	/* Use the `cpuid' instruction. */
 	movl	%eax,(PROC0PDIR+PDSLOT_PTE*4)(%esi)	# recursive PD slot
 
 	/* Save phys. addr of PTD, for libkvm. */
-	movl	%esi,RELOC(_C_LABEL(PTDpaddr))
+	leal	(PROC0PDIR)(%esi),%eax		# phys address of ptd in proc 0
+	movl	%eax,RELOC(_C_LABEL(PTDpaddr))
 
 	/* Load base of page directory and enable mapping. */
-	movl	%esi,%eax		# phys address of ptd in proc 0
 	movl	%eax,%cr3		# load ptd addr into mmu
 	movl	%cr0,%eax		# get control word
 					# enable paging & NPX emulation
@@ -690,7 +690,8 @@ begin:
 	leal	(PROC0STACK+KERNBASE)(%esi),%eax
 	movl	%eax,_C_LABEL(proc0paddr)
 	leal	(USPACE-FRAMESIZE)(%eax),%esp
-	movl	%esi,PCB_CR3(%eax)	# pcb->pcb_cr3
+	leal	(PROC0PDIR)(%esi),%ebx	# phys address of ptd in proc 0
+	movl	%ebx,PCB_CR3(%eax)	# pcb->pcb_cr3
 	xorl	%ebp,%ebp		# mark end of frames
 
 	movl	_C_LABEL(nkpde),%eax
-- 
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