From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754694AbYCJQqs (ORCPT ); Mon, 10 Mar 2008 12:46:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751104AbYCJQqk (ORCPT ); Mon, 10 Mar 2008 12:46:40 -0400 Received: from smtp-out01.alice-dsl.net ([88.44.60.11]:14433 "EHLO smtp-out01.alice-dsl.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751085AbYCJQqk (ORCPT ); Mon, 10 Mar 2008 12:46:40 -0400 To: Stephan Diestelhorst Cc: Ingo Molnar , davej@codemonkey.org.uk, cpufreq@lists.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX References: <200803051559.09962.langer_mann@web.de> <200803060951.12002.langer_mann@web.de> <20080306105603.GL13391@elte.hu> <200803101605.42251.langer_mann@web.de> From: Andi Kleen Date: 10 Mar 2008 17:46:37 +0100 In-Reply-To: <200803101605.42251.langer_mann@web.de> Message-ID: <87iqzu8r2q.fsf@basil.nowhere.org> User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 10 Mar 2008 16:40:06.0345 (UTC) FILETIME=[65891B90:01C882CD] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Stephan Diestelhorst writes: > > New attempt with full clobbers, note that I deliberatly did not change > the order of the output registers. Real output operands still preceede > outputs used for potential clobbering. > > I'm not too sure about the EBP push/pop frame, but as folks pointed > out already, we should not trust the SMI code too much. Be careful -- older gcc versions tend to abort for inline asm that clobbers too many registers. Especially when the register is already used (like ebp in a frame pointer enabled kernel) Make sure it at least works on the oldest supported gcc version (gcc 3.2) and with frame pointer on. For asms with so many clobbers explicit push/pop is usually safer. -Andi