From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756305AbXFSIle (ORCPT ); Tue, 19 Jun 2007 04:41:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753297AbXFSIl0 (ORCPT ); Tue, 19 Jun 2007 04:41:26 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:46080 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752712AbXFSIlZ (ORCPT ); Tue, 19 Jun 2007 04:41:25 -0400 X-Greylist: delayed 156636 seconds by postgrey-1.27 at vger.kernel.org; Tue, 19 Jun 2007 04:41:24 EDT Date: Tue, 19 Jun 2007 10:41:16 +0200 From: Ingo Molnar To: Steven Rostedt Cc: Thomas Gleixner , LKML , RT Subject: Re: [PATCH RT] Don't call mcount from vsyscall_fn's Message-ID: <20070619084116.GA1663@elte.hu> References: <1182220869.15228.10.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1182220869.15228.10.camel@localhost.localdomain> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt wrote: > This bit me in the butt. > > I couldn't understand why my init app was segfaulting, with a kernel > address, but a user RIP and RSP. Well, the RIP I think was bogus, but > the kernel address was always the start of "mcount". Looking deeper, > I printed out what was in the RSP (even though it was a user stack). > It ended up showing me that the calling address was from the VDSO > area. Looking even further, I found the offending culprit, which was > vread_hpet. > > Looking at the assembly dump, I saw the vread_hpet was calling mcount, > but I could not see it in the code. Nor could I see it in hpet.i (-E > option of compiling). > > Well, I guess Ingo is a magician when it comes to compiler tricks, and > has the mcount being called by "every!!" function, unless you add the > "notrace" option. > > This patch adds the notrace to vsyscall_fn, so that we don't have user > land apps calling mcount and crashing! doh - applied. Thanks! Ingo