From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763628AbYESVRS (ORCPT ); Mon, 19 May 2008 17:17:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758227AbYESVRH (ORCPT ); Mon, 19 May 2008 17:17:07 -0400 Received: from one.firstfloor.org ([213.235.205.2]:33201 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759889AbYESVRG (ORCPT ); Mon, 19 May 2008 17:17:06 -0400 Message-ID: <4831EE48.5050908@firstfloor.org> Date: Mon, 19 May 2008 23:16:56 +0200 From: Andi Kleen User-Agent: Thunderbird 1.5.0.12 (X11/20060911) MIME-Version: 1.0 To: Vegard Nossum CC: Ingo Molnar , Arjan van de Ven , Pekka Enberg , linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH] x86: don't destroy %rbp on kernel-mode faults References: <20080519200230.GA12210@damson.getinternet.no> In-Reply-To: <20080519200230.GA12210@damson.getinternet.no> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vegard Nossum wrote: > Hi, > > The RFC part of this patch is: Does anybody see why touching %rcx would > be bad? It certainly looks like %ecx is free. This fixes the stacktrace > problem I was seeing, and Pekka tested a bootup to userspace. (Pekka also > did half of the debugging. When will git allow multiple authors for a > patch? :-)) The patch is ok, but I'm sure there's lots of other assembler code that destroys %rbp when it was saved elsewhere. When I wrote all the assembler the assumption was always that a real unwinder would be used for backtraces, not frame pointer. -Andi