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

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Message-ID: <df9815e70810192344v3a80f70awfc8f621e155bda6@mail.gmail.com>
Date:	Mon, 20 Oct 2008 14:44:04 +0800
From:	"Jike Song" <albcamus@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: add missed clobber for 32-bit memmove

On Sat, Oct 18, 2008 at 12:35 AM, H. Peter Anvin <hpa@...or.com> wrote:
> Jike Song wrote:
>>
>> memmove() is implemented by inline assembly. It calls std at first
>> and cld at last, but EFLAGS still should be clobbered.
>
> gcc always treats EFLAGS as clobbered on x86.  The "cc" clobber is needed on
> some platforms, but is a noop on x86.

No wonder there are inline asms that clobbered eflags/rflags but
without declaring them as clobbered. Thanks for your information.

It turns out that I need to read through the gcc x86 back-end as long
as I want to be a Linux/x86 developer, right? That sounds
discouraging:)

-- 
Thanks,
Jike
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