[PATCH] x86_64: Fix backtracing for interrupt stacks
Re-add backlink for old style unwinder to stack switching. Add proper
stack frame and CFI annotations to call_softirq
This prevents a oops when backtracing with fallback through the
interrupt stack top.
Suggested by Jan Beulich and Herbert Xu wanted it in 2.6.18.
Cc: jbeulich@novell.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index d464dde..6f81042 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -513,6 +513,7 @@
swapgs
1: incl %gs:pda_irqcount # RED-PEN should check preempt count
cmoveq %gs:pda_irqstackptr,%rsp
+ push %rbp # backlink for old unwinder
/*
* We entered an interrupt context - irqs are off:
*/
@@ -1139,18 +1140,21 @@
END(machine_check)
#endif
+/* Call softirq on interrupt stack. Interrupts are off. */
ENTRY(call_softirq)
CFI_STARTPROC
- movq %gs:pda_irqstackptr,%rax
- movq %rsp,%rdx
- CFI_DEF_CFA_REGISTER rdx
+ push %rbp
+ CFI_ADJUST_CFA_OFFSET 8
+ CFI_REL_OFFSET rbp,0
+ mov %rsp,%rbp
+ CFI_DEF_CFA_REGISTER rbp
incl %gs:pda_irqcount
- cmove %rax,%rsp
- pushq %rdx
- /*todo CFI_DEF_CFA_EXPRESSION ...*/
+ cmove %gs:pda_irqstackptr,%rsp
+ push %rbp # backlink for old unwinder
call __do_softirq
- popq %rsp
+ leaveq
CFI_DEF_CFA_REGISTER rsp
+ CFI_ADJUST_CFA_OFFSET -8
decl %gs:pda_irqcount
ret
CFI_ENDPROC