Re: [PATCH] x86-64/entry: add instruction suffix to SYSRET

[Andy Lutomirski]

> On Dec 10, 2019, at 2:48 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> 
> ïOmitting suffixes from instructions in AT&T mode is bad practice when
> operand size cannot be determined by the assembler from register
> operands, and is likely going to be warned about by upstream gas in the
> future. Add the missing suffix here.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -1728,7 +1728,7 @@ END(nmi)
> SYM_CODE_START(ignore_sysret)
>    UNWIND_HINT_EMPTY
>    mov    $-ENOSYS, %eax
> -    sysret
> +    sysretl

Isnât the default sysretq?  sysretl looks more correct, but that suggests that your changelog is wrong.

Is this code even reachable?

> SYM_CODE_END(ignore_sysret)
> #endif
>