Re: [PATCH 1/1] x86: fix text_poke

[H. Peter Anvin]

Mathieu Desnoyers wrote:
> This epilogue should then be used on both branches of the condition,
> like this :
>
> if (unlikely(imv_cond(var))) {
>   imv_cond_end();
>   ...
> } else {
>   imv_cond_end();
>    ...
> }
>
> Where imv_cond_end() would look like this :
>
> +/*
> + * Puts a test and branch make sure the %al register and ZF are not live
> + * anymore.
> + * All asm statements clobbers the flags, but add "cc" clobber just to be sure.
> + * Clobbers %al.
> + */
> +#define imv_cond_end()                                                 \
> +       do {                                                            \
> +               asm (".section __imv_cond_end,\"a\",@progbits\n\t"      \
> +                               _ASM_PTR "1f\n\t"                       \
> +                               ".previous\n\t"                         \
> +                               "1:\n\t"                                \
> +                               : : : "a", "cc");                       \
> +       } while (0)
> +

As far as this is concerned, all you accomplish here is that gcc, if it 
wants to re-use the %al value, will copy it into another register before 
doing your imv_conv_end().

	-hpa
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