Re: [PATCH] x86, boot: fix word-size assumptions in has_eflag()inline asm

[Kees Cook]

On Wed, Jan 29, 2014 at 4:01 AM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote:
> Commit dd78b97367bd575918204cc89107c1479d3fc1a7 ("x86, boot: Move CPU
> flags out of cpucheck") introduced ambiguous inline asm in the
> has_eflag() function. We want the instruction to be 'pushfl', but we
> just say 'pushf' and hope the compiler does what we wanted.
>
> When building with 'clang -m16', it won't, because clang doesn't use
> the horrid '.code16gcc' hack that even 'gcc -m16' uses internally.
>
> Say what we mean and don't make the compiler make assumptions.
>
> Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>

Yes, excellent point. Thanks!

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

-- 
Kees Cook
Chrome OS Security
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