[patch] i386-PDA, lockdep: fix %gs restore

Ingo Molnar
2006-09-11T05:33:09Z

Jeremy,

could you back out Andi's patch and try the patch below, does it fix the
crash too?

Ingo

--------------->
Subject: [patch] i386-PDA, lockdep: fix %gs restore
From: Ingo Molnar <mingo@elte.hu>

in the syscall exit path the %gs selector has to be restored _after_ the
last kernel function has been called. If lockdep is enabled then this
kernel function is TRACE_IRQS_ON.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
arch/i386/kernel/entry.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux/arch/i386/kernel/entry.S
===================================================================
--- linux.orig/arch/i386/kernel/entry.S
+++ linux/arch/i386/kernel/entry.S
@@ -326,11 +326,12 @@ sysenter_past_esp:
testw $_TIF_ALLWORK_MASK, %cx
jne syscall_exit_work
/* if something modifies registers it must also disable sysexit */
-1: mov PT_GS(%esp), %gs
+1:
+ TRACE_IRQS_ON
+ mov PT_GS(%esp), %gs
movl PT_EIP(%esp), %edx
movl PT_OLDESP(%esp), %ecx
xorl %ebp,%ebp
- TRACE_IRQS_ON
ENABLE_INTERRUPTS_SYSEXIT
CFI_ENDPROC
.pushsection .fixup,"ax"; \