[PATCH] x86_64: Use TESTB instead of TESTL in CHECK_INVALID_LONGJMP

[H.J. Lu]

On Mon, Aug 18, 2025 at 2:19 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> There is no need to use TESTL when checking the least-significant bit
> with a TEST instruction. Use TESTB, which is three bytes shorter:
>
>    f6 44 24 f0 01          testb  $0x1,-0x10(%rsp)
>
> vs:
>
>    f7 44 24 f0 01 00 00    testl  $0x1,-0x10(%rsp)
>    00
>
> for the same effect.
>
> No functional changes intended.
>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: H.J.Lu <hjl.tools@gmail.com>
> Cc: Carlos O'Donell <carlos@redhat.com>
> ---
>  sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S b/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
> index b73a18bdb8..3bcdd6a87c 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
> +++ b/sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S
> @@ -44,7 +44,7 @@ longjmp_msg:
>         /* Without working sigaltstack we cannot perform the test.  */  \
>         testl   %eax, %eax;                                             \
>         jne     .Lok2;                                                  \
> -       testl   $1, (-sizeSS + oSS_FLAGS)(%rsp);                        \
> +       testb   $1, (-sizeSS + oSS_FLAGS)(%rsp);                        \
>         jz      .Lfail;                                                 \
>         mov     (-sizeSS + oSS_SP)(%rsp), %RAX_LP;                      \
>         add     (-sizeSS + oSS_SIZE)(%rsp), %RAX_LP;                    \
> --
> 2.50.1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.