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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 <jpoimboe@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f59593ae7b15d5126f872b0a23143173d28aa32d.1474480779.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
zero-colors
Josh Poimboeuf 2016-09-21 16:04:05 -05:00 committed by Ingo Molnar
parent a9468df5ad
commit 595c1e645d
1 changed files with 3 additions and 2 deletions
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5
arch/x86/kernel/head_64.S
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@ -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