From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262081AbVF0XKl (ORCPT ); Mon, 27 Jun 2005 19:10:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262100AbVF0XIj (ORCPT ); Mon, 27 Jun 2005 19:08:39 -0400 Received: from smtp.osdl.org ([65.172.181.4]:62904 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S262093AbVF0XCb (ORCPT ); Mon, 27 Jun 2005 19:02:31 -0400 Date: Mon, 27 Jun 2005 16:01:44 -0700 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: akpm@osdl.org, "Theodore Ts'o" , Zwane Mwaikambo , Justin Forbes , Randy Dunlap , torvalds@osdl.org, Chuck Wolber , alan@lxorguk.ukuu.org.uk, jgarzik@pobox.com Subject: [05/07] Add "memory" clobbers to the x86 inline asm of strncmp and friends Message-ID: <20050627230144.GN9046@shell0.pdx.osdl.net> References: <20050627224651.GI9046@shell0.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050627224651.GI9046@shell0.pdx.osdl.net> User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org -stable review patch. If anyone has any objections, please let us know. ------------------ From: Linus Torvalds Add "memory" clobbers to the x86 inline asm of strncmp and friends They don't actually clobber memory, but gcc doesn't even know they _read_ memory, so can apparently re-order memory accesses around them. Which obviously does the wrong thing if the memory access happens to change the memory that the compare function is accessing.. Verified to fix a strange boot problem by Jens Axboe. Signed-off-by: Chris Wright --- include/asm-i386/string.h | 32 ++++++++++++++++++++++---------- 1 files changed, 22 insertions(+), 10 deletions(-) diff --git a/include/asm-i386/string.h b/include/asm-i386/string.h --- a/include/asm-i386/string.h +++ b/include/asm-i386/string.h @@ -116,7 +116,8 @@ __asm__ __volatile__( "orb $1,%%al\n" "3:" :"=a" (__res), "=&S" (d0), "=&D" (d1) - :"1" (cs),"2" (ct)); + :"1" (cs),"2" (ct) + :"memory"); return __res; } @@ -138,8 +139,9 @@ __asm__ __volatile__( "3:\tsbbl %%eax,%%eax\n\t" "orb $1,%%al\n" "4:" - :"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2) - :"1" (cs),"2" (ct),"3" (count)); + :"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2) + :"1" (cs),"2" (ct),"3" (count) + :"memory"); return __res; } @@ -158,7 +160,9 @@ __asm__ __volatile__( "movl $1,%1\n" "2:\tmovl %1,%0\n\t" "decl %0" - :"=a" (__res), "=&S" (d0) : "1" (s),"0" (c)); + :"=a" (__res), "=&S" (d0) + :"1" (s),"0" (c) + :"memory"); return __res; } @@ -175,7 +179,9 @@ __asm__ __volatile__( "leal -1(%%esi),%0\n" "2:\ttestb %%al,%%al\n\t" "jne 1b" - :"=g" (__res), "=&S" (d0), "=&a" (d1) :"0" (0),"1" (s),"2" (c)); + :"=g" (__res), "=&S" (d0), "=&a" (d1) + :"0" (0),"1" (s),"2" (c) + :"memory"); return __res; } @@ -189,7 +195,9 @@ __asm__ __volatile__( "scasb\n\t" "notl %0\n\t" "decl %0" - :"=c" (__res), "=&D" (d0) :"1" (s),"a" (0), "0" (0xffffffffu)); + :"=c" (__res), "=&D" (d0) + :"1" (s),"a" (0), "0" (0xffffffffu) + :"memory"); return __res; } @@ -333,7 +341,9 @@ __asm__ __volatile__( "je 1f\n\t" "movl $1,%0\n" "1:\tdecl %0" - :"=D" (__res), "=&c" (d0) : "a" (c),"0" (cs),"1" (count)); + :"=D" (__res), "=&c" (d0) + :"a" (c),"0" (cs),"1" (count) + :"memory"); return __res; } @@ -369,7 +379,7 @@ __asm__ __volatile__( "je 2f\n\t" "stosb\n" "2:" - : "=&c" (d0), "=&D" (d1) + :"=&c" (d0), "=&D" (d1) :"a" (c), "q" (count), "0" (count/4), "1" ((long) s) :"memory"); return (s); @@ -392,7 +402,8 @@ __asm__ __volatile__( "jne 1b\n" "3:\tsubl %2,%0" :"=a" (__res), "=&d" (d0) - :"c" (s),"1" (count)); + :"c" (s),"1" (count) + :"memory"); return __res; } /* end of additional stuff */ @@ -473,7 +484,8 @@ static inline void * memscan(void * addr "dec %%edi\n" "1:" : "=D" (addr), "=c" (size) - : "0" (addr), "1" (size), "a" (c)); + : "0" (addr), "1" (size), "a" (c) + : "memory"); return addr; }