From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx168.postini.com [74.125.245.168]) by kanga.kvack.org (Postfix) with SMTP id 3CFB76B004F for ; Sat, 17 Dec 2011 13:39:26 -0500 (EST) Received: by wgbds13 with SMTP id ds13so6912179wgb.26 for ; Sat, 17 Dec 2011 10:39:24 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <201112172258.24221.nai.xia@gmail.com> From: Linus Torvalds Date: Sat, 17 Dec 2011 10:39:03 -0800 Message-ID: Subject: Re: Question about missing "cld" in x86 string assembly code Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Brian Gerst Cc: nai.xia@gmail.com, Andi Kleen , Linux-MM , LKML On Sat, Dec 17, 2011 at 9:08 AM, Brian Gerst wrote: > > The i386 ELF ABI states "The direction flag must be set to the > =91=91forward=92=92 (that is, zero) direction before entry and upon exit = from > a function." =A0Therefore 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org