| From | Josh Poimboeuf <> | Subject | [PATCH v3 14/51] x86/asm/head: put real return address on idle task stack | Date | Fri, 12 Aug 2016 09:28:33 -0500 |
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The frame at the end of each idle task stack has a zeroed return address. This is inconsistent with real task stacks, which have a real return address at that spot. This inconsistency can be confusing for stack unwinders.
Make it a real address by using the side effect of a call instruction to push the instruction pointer on the stack.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- arch/x86/kernel/head_64.S | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 3621ad2..c90f481 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -298,8 +298,9 @@ ENTRY(start_cpu) * REX.W + FF /5 JMP m16:64 Jump far, absolute indirect, * address given in m16:64. */ - movq initial_code(%rip),%rax - pushq $0 # fake return address to stop unwinder + call 1f # put return address on stack for unwinder +1: xorq %rbp, %rbp # clear frame pointer + movq initial_code(%rip), %rax pushq $__KERNEL_CS # set correct cs pushq %rax # target address in negative space lretq -- 2.7.4
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