Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752515Ab0BSRdk (ORCPT ); Fri, 19 Feb 2010 12:33:40 -0500 Received: from mail-fx0-f219.google.com ([209.85.220.219]:41923 "EHLO mail-fx0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754193Ab0BSRdi (ORCPT ); Fri, 19 Feb 2010 12:33:38 -0500 X-Greylist: delayed 386 seconds by postgrey-1.27 at vger.kernel.org; Fri, 19 Feb 2010 12:33:37 EST DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references; b=tNQfItnhzIpZsIxdfGlEp8nIYhqH4A9XSFMqyz8Ksmyf3FW8dq1lWM2lYPi/baDVlO rq6XrJ3qZYex1XCd12doPouA5YXANBN5RoobxzL84a+0Z2iNGk9uyEfyEcyt3EWHhXgD FAd3l83/9xMAqYuO5TB7DfUfAW4nqOcvj+yR4= From: Luca Barbieri To: mingo@elte.hu Cc: hpa@zytor.com, a.p.zijlstra@chello.nl, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Luca Barbieri Subject: [PATCH 2/5] x86: add support for lock prefix in alternatives (v2) Date: Fri, 19 Feb 2010 18:26:41 +0100 Message-Id: <1266600404-16402-3-git-send-email-luca@luca-barbieri.com> X-Mailer: git-send-email 1.6.6.1.476.g01ddb In-Reply-To: <1266600404-16402-1-git-send-email-luca@luca-barbieri.com> References: <1266600404-16402-1-git-send-email-luca@luca-barbieri.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2667 Lines: 81 Changes in v2: - Naming change - Change label to not conflict with alternatives The current lock prefix UP/SMP alternative code doesn't allow LOCK_PREFIX to be used in alternatives code. This patch solves the problem by adding a new LOCK_PREFIX_ALTERNATIVE_PATCH macro that only records the lock prefix location but does not emit the prefix. The user of this macro can then start any alternative sequence with "lock" and have it UP/SMP patched. To make this work, the UP/SMP alternative code is changed to do the lock/DS prefix switching only if the byte actually contains a lock or DS prefix. Thus, if an alternative without the "lock" is selected, it will now do nothing instead of clobbering the code. Signed-off-by: Luca Barbieri --- arch/x86/include/asm/alternative.h | 8 +++++--- arch/x86/kernel/alternative.c | 6 ++++-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 77f78e2..2ed9784 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -28,12 +28,14 @@ */ #ifdef CONFIG_SMP -#define LOCK_PREFIX \ +#define LOCK_PREFIX_HERE \ ".section .smp_locks,\"a\"\n" \ _ASM_ALIGN "\n" \ - _ASM_PTR "661f\n" /* address */ \ + _ASM_PTR "671f\n" /* address */ \ ".previous\n" \ - "661:\n\tlock; " + "671:" + +#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " #else /* ! CONFIG_SMP */ #define LOCK_PREFIX "" diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 77eba91..57a672c 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -258,7 +258,8 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) if (*ptr > text_end) continue; /* turn DS segment override prefix into lock prefix */ - text_poke(*ptr, ((unsigned char []){0xf0}), 1); + if (**ptr == 0x3e) + text_poke(*ptr, ((unsigned char []){0xf0}), 1); }; mutex_unlock(&text_mutex); } @@ -277,7 +278,8 @@ static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end if (*ptr > text_end) continue; /* turn lock prefix into DS segment override prefix */ - text_poke(*ptr, ((unsigned char []){0x3E}), 1); + if (**ptr == 0xf0) + text_poke(*ptr, ((unsigned char []){0x3E}), 1); }; mutex_unlock(&text_mutex); } -- 1.6.6.1.476.g01ddb -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/