From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758182AbaAJUMs (ORCPT ); Fri, 10 Jan 2014 15:12:48 -0500 Received: from merlin.infradead.org ([205.233.59.134]:40423 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751483AbaAJUMp (ORCPT ); Fri, 10 Jan 2014 15:12:45 -0500 Date: Fri, 10 Jan 2014 21:12:34 +0100 From: Peter Zijlstra To: Andy Lutomirski Cc: Waiman Long , Ingo Molnar , Arnaldo Carvalho de Melo , Linux Kernel Mailing List , Aswin Chandramouleeswaran , Scott J Norton , Linus Torvalds Subject: Re: SIGSEGV when using "perf record -g" with 3.13-rc* kernel Message-ID: <20140110201234.GL7572@laptop.programming.kicks-ass.net> References: <52D011C9.7000209@hp.com> <20140110165822.GI7572@laptop.programming.kicks-ass.net> <20140110170223.GD8224@laptop.programming.kicks-ass.net> <20140110174141.GE8224@laptop.programming.kicks-ass.net> <52D04D6D.9010504@hp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 10, 2014 at 11:56:07AM -0800, Andy Lutomirski wrote: > - The perf callchain code tries to read from a bad userspace pointer > (not sure why -- the ip value in the vsyscall page *is* readable). > That traps (as expected), but the trap handler injects SIGSEGV due to > sig_on_uaccess_fault==1. So the perf thing tries to walk the entire stack in order to obtain a callchain. Its fairly common to hit crap when attempting this :-)