[PATCH] x86_64: Fix backtracing for interrupt stacks (2699500b) · Commits · 戴 / test

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>

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

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