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Commit 2699500b authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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[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: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ae74c3b6

arch/x86_64/kernel/entry.S

+11 −7
Original line number Diff line number Diff line
@@ -513,6 +513,7 @@ END(stub_rt_sigreturn) 
	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 @@ ENTRY(machine_check) 
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