Commit-ID: 595c1e645d9fd8561104b5680931f68a429aaa1c Gitweb: http://git.kernel.org/tip/595c1e645d9fd8561104b5680931f68a429aaa1c Author: Josh Poimboeuf <[email protected]> AuthorDate: Wed, 21 Sep 2016 16:04:05 -0500 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 20 Oct 2016 09:15:23 +0200
x86/boot/64: Put a real return address on the idle task stack 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. It also hides useful information about what asm code was involved in calling into C. 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 <[email protected]> Reviewed-by: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Nilay Vaish <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/f59593ae7b15d5126f872b0a23143173d28aa32d.1474480779.git.jpoim...@redhat.com Signed-off-by: Ingo Molnar <[email protected]> --- 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 3631777..1c5e5db 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -299,8 +299,9 @@ 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
