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SubjectRe: [PATCH] x86_64,entry: Fix RCX for traced syscalls
> show RCX == RIP even under strace.

If you think it's really worth the extra instruction?

It's not wrong, but it's not clear if it's useful.

-Andi

>
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
> arch/x86/kernel/entry_64.S | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index b25ca96..6624e18 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -143,7 +143,8 @@ ENDPROC(native_usergs_sysret64)
> movq \tmp,RSP+\offset(%rsp)
> movq $__USER_DS,SS+\offset(%rsp)
> movq $__USER_CS,CS+\offset(%rsp)
> - movq $-1,RCX+\offset(%rsp)
> + movq RIP+\offset(%rsp),\tmp /* get rip */
> + movq \tmp,RCX+\offset(%rsp) /* copy it to rcx as sysret would do */
> movq R11+\offset(%rsp),\tmp /* get eflags */
> movq \tmp,EFLAGS+\offset(%rsp)
> .endm
> --
> 1.9.3
>

--
ak@linux.intel.com -- Speaking for myself only.


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