From 65385d6d793d5e9164cbe9c8d5eb4f4f95d4d46e Mon Sep 17 00:00:00 2001
From: Marcel Moolenaar <marcel@FreeBSD.org>
Date: Sat, 14 May 2011 14:47:19 +0000
Subject: [PATCH] Sharpening the saw: o   Clobber the register that holds the
 restart token immediately after     crossing the restart point. This prevents
 false positives (i.e. a     nested exception that we don't know can happen
 and that is being     treated as one we know by virtue of a lingering restart
 token). o   Now that the bootstrap kernel stack is free, switch onto it and
 call     trap() for nested traps that we don't know about. In trap we panic()
     so that we can analyze the condition.

---
 sys/ia64/ia64/exception.S | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/sys/ia64/ia64/exception.S b/sys/ia64/ia64/exception.S
index 7ff771a460b..729a96c5a18 100644
--- a/sys/ia64/ia64/exception.S
+++ b/sys/ia64/ia64/exception.S
@@ -202,13 +202,13 @@ exception_save_restart:
 {	.mmi
 	st8		[r30]=r19,16		// length
 	st8		[r31]=r0,16		// flags
-	add		r19=16,r19
+	add		r29=16,r19		// Clobber restart token
 	;;
 }
 {	.mmi
 	st8.spill	[r30]=sp,16		// sp
 	st8		[r31]=r20,16		// unat
-	sub		sp=r23,r19
+	sub		sp=r23,r29
 	;;
 }
 {	.mmi
@@ -641,7 +641,7 @@ exception_restore_restart:
 	mov		r30=ar.bspstore
 	;;
 	loadrs					// load user regs
-	nop		0
+	mov		r29=0			// Clobber restart token
 	;;
 }
 {	.mmi
@@ -1094,22 +1094,26 @@ IVT_ENTRY(Data_Nested_TLB, 0x1400)
 }
 {	.mlx
 	mov		r26=ar.bsp
-	movl		r27=kstack
+	movl		r29=kstack
 	;;
 }
-{	.mmi
+{	.mlx
 	mov		r28=sp
-	nop		0
-	addl		r27=KSTACK_PAGES*PAGE_SIZE-16,r0
+	movl		r27=kstack_top
 	;;
 }
 {	.mmi
-	mov		sp=r27
+	add		sp=-16,r27
 	;;
 	mov		r27=ar.bspstore
 	nop		0
 	;;
 }
+	mov		ar.rsc=0
+	dep		r29=r27,r29,0,9
+	;;
+	mov		ar.bspstore=r29
+	;;
 	CALL(trap, 5, r30)
 IVT_END(Data_Nested_TLB)