From: Linus Torvalds <torvalds@linux-foundation.org>
To: Brian Gerst <brgerst@gmail.com>
Cc: nai.xia@gmail.com, Andi Kleen <ak@linux.intel.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Question about missing "cld" in x86 string assembly code
Date: Sat, 17 Dec 2011 10:39:03 -0800 [thread overview]
Message-ID: <CA+55aFzyEgDUSaNVQ1Nw5SBNd36Cvb-KrVdc1MYj+oRJt8xWgg@mail.gmail.com> (raw)
In-Reply-To: <CAMzpN2inHxaSnaYaYXZ4Ya3rK+MWXqR6dN5NVNZy3=OvP04uQA@mail.gmail.com>
On Sat, Dec 17, 2011 at 9:08 AM, Brian Gerst <brgerst@gmail.com> wrote:
>
> The i386 ELF ABI states "The direction flag must be set to the
> ‘‘forward’’ (that is, zero) direction before entry and upon exit from
> a function." Therefore it can be assumed to be clear, unless
> explicitly set.
The exception, of course, being bootup, fault and interrupt handlers,
and after we've called out to foreign code (ie BIOS).
So there *are* a few cld's sprinkled around, they are just fairly rare.
Linus
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next prev parent reply other threads:[~2011-12-17 18:39 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-17 14:58 Nai Xia
2011-12-17 17:08 ` Brian Gerst
2011-12-17 18:39 ` Linus Torvalds [this message]
2011-12-22 15:52 ` nai.xia
2011-12-22 15:34 ` nai.xia
-- strict thread matches above, loose matches on Subject: below --
2011-12-17 14:52 Nai Xia
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