Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756229Ab0BXJyf (ORCPT ); Wed, 24 Feb 2010 04:54:35 -0500 Received: from mail-fx0-f219.google.com ([209.85.220.219]:65005 "EHLO mail-fx0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756195Ab0BXJyb (ORCPT ); Wed, 24 Feb 2010 04:54:31 -0500 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=eh0N5K4NVczmprOHdQ+vkfhFx395js9KLOdySJkrD9p9BYiJG9oxnvSd+WtBArvLv+ RQ3YGOskqoZcYxbjgBtH2WqAqwG/Cj43TeAYiNmJrHU95VTam9KJ5GY3aTPgiX+V5OYL Hv9nwQwnZ5xiuKzSJzvDHNKPZIC67L0C1mGjM= From: Luca Barbieri To: hpa@zytor.com Cc: mingo@elte.hu, a.p.zijlstra@chello.nl, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Luca Barbieri Subject: [PATCH 1/4] x86: add support for lock prefix in alternatives (v2) Date: Wed, 24 Feb 2010 10:54:22 +0100 Message-Id: <1267005265-27958-2-git-send-email-luca@luca-barbieri.com> X-Mailer: git-send-email 1.6.6.1.476.g01ddb In-Reply-To: <1267005265-27958-1-git-send-email-luca@luca-barbieri.com> References: <1267005265-27958-1-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 3b5b828..55fee12 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 2589ea4..80b222e 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -244,7 +244,8 @@ 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); } @@ -263,7 +264,8 @@ 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/