[PATCH] x86_64: fix page fault from show_trace()

The introduction of call_softirq switching to the interrupt stack several
releases earlier resulted in a problem with the code in show_trace, which
assumes that it can pick the previous stack pointer from the end of the
interrupt stack.

Cc: Andi Kleen <ak@muc.de>
Cc: Arjan van de Ven <arjanv@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 7 deletions

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 28b3c8e6b044..45e0ab8a1fca 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -1045,17 +1045,15 @@ ENTRY(call_debug)
 ENTRY(call_softirq)
         CFI_STARTPROC
         movq %gs:pda_irqstackptr,%rax
-        pushq %r15
-        CFI_ADJUST_CFA_OFFSET 8
-        movq %rsp,%r15
-        CFI_DEF_CFA_REGISTER    r15
+        movq %rsp,%rdx
+        CFI_DEF_CFA_REGISTER    rdx
         incl %gs:pda_irqcount
         cmove %rax,%rsp
+        pushq %rdx
+        /*todo CFI_DEF_CFA_EXPRESSION ...*/
         call __do_softirq
-        movq %r15,%rsp
+        popq %rsp
         CFI_DEF_CFA_REGISTER    rsp
         decl %gs:pda_irqcount
-        popq %r15
-        CFI_ADJUST_CFA_OFFSET -8
         ret
         CFI_ENDPROC