From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH RT] Don't call mcount from vsyscall_fn's Date: Tue, 19 Jun 2007 10:41:16 +0200 Message-ID: <20070619084116.GA1663@elte.hu> References: <1182220869.15228.10.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Thomas Gleixner , LKML , RT To: Steven Rostedt Return-path: 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 Content-Disposition: inline In-Reply-To: <1182220869.15228.10.camel@localhost.localdomain> Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.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