linux-kernel - Re: [PATCH] x86: add missed clobber for 32-bit memmove

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Message-ID: <48F8B574.7070401@goop.org>
Date:	Fri, 17 Oct 2008 08:55:32 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jike Song <albcamus@...il.com>
CC:	hpa@...or.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: add missed clobber for 32-bit memmove

Jike Song wrote:
> memmove() is implemented by inline assembly. It calls std at first
> and cld at last, but EFLAGS still should be clobbered.
>   

I think x86 gcc assumes "cc" is always clobbered by asms.  Otherwise 
there'll need to be a lot more "cc" clobbers than this...

    J

> Signed-off-by: Jike Song <albcamus@...il.com>
> ---
>  arch/x86/lib/memcpy_32.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c
> index 5415a9d..99a8240 100644
> --- a/arch/x86/lib/memcpy_32.c
> +++ b/arch/x86/lib/memcpy_32.c
> @@ -36,7 +36,7 @@ void *memmove(void *dest, const void *src, size_t n)
>  			:"0" (n),
>  			 "1" (n-1+src),
>  			 "2" (n-1+dest)
> -			:"memory");
> +			:"cc", "memory");
>  	}
>  	return dest;
>  }
>   

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