* tip-bot for David Woodhouse <tipbot@xxxxxxxxx> wrote:
> Commit-ID: 9b3614ccfa5492f57f743f3856253f285b10a702
> Gitweb: http://git.kernel.org/tip/9b3614ccfa5492f57f743f3856253f285b10a702
> Author: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
> AuthorDate: Wed, 29 Jan 2014 12:01:37 +0000
> Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> CommitDate: Wed, 29 Jan 2014 09:09:40 -0800
>
> x86, boot: Fix word-size assumptions in has_eflag() inline asm
>
> 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.
>
> [ hpa: we use plain "pushf" in the equivalent code elsewhere which may
> be compiled as either 32- or 64-bit code. In those cases we want
> the assembler to pick the appropriate size for us. However, this is
> *16-bit* code and we still need these to be 32-bit operations. ]
>
> Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
> Link: http://lkml.kernel.org/r/1390996897.20153.123.camel@xxxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> ---
> arch/x86/boot/cpuflags.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
> index a9fcb7c..168dd25 100644
> --- a/arch/x86/boot/cpuflags.c
> +++ b/arch/x86/boot/cpuflags.c
> @@ -32,16 +32,16 @@ int has_eflag(unsigned long mask)
> {
> unsigned long f0, f1;
>
> - asm volatile("pushf \n\t"
> - "pushf \n\t"
> + asm volatile("pushfl \n\t"
> + "pushfl \n\t"
> "pop %0 \n\t"
> "mov %0,%1 \n\t"
> "xor %2,%1 \n\t"
> "push %1 \n\t"
> - "popf \n\t"
> - "pushf \n\t"
> + "popfl \n\t"
> + "pushfl \n\t"
> "pop %1 \n\t"
> - "popf"
> + "popfl"
> : "=&r" (f0), "=&r" (f1)
> : "ri" (mask));
This broke the build though:
arch/x86/boot/compressed/../cpuflags.c: Assembler messages:
arch/x86/boot/compressed/../cpuflags.c:35: Error: invalid instruction suffix for `pushf'
Thanks,
Ingo
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