From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750979AbaBWFQU (ORCPT ); Sun, 23 Feb 2014 00:16:20 -0500 Received: from mail-qa0-f51.google.com ([209.85.216.51]:62294 "EHLO mail-qa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbaBWFQT (ORCPT ); Sun, 23 Feb 2014 00:16:19 -0500 Date: Sun, 23 Feb 2014 00:18:17 -0500 (EST) From: Vince Weaver To: "H. Peter Anvin" cc: Vince Weaver , Linux Kernel , Peter Zijlstra , Ingo Molnar , "H.J. Lu" Subject: Re: perf_fuzzer compiled for x32 causes reboot In-Reply-To: <53084317.4090304@zytor.com> Message-ID: References: <53084317.4090304@zytor.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 21 Feb 2014, H. Peter Anvin wrote: > Error 6 reflects a write in userspace to a not-present page. > > Since your previous trace indicates that the value of the register in question > is a different one, I'm guessing that what we have here is PEBS getting > activated. 0x120 is 2*0x90, and 0x90 is the size of a 64-bit PEBS record. I'm having problems generating a replayable syscall trace that exhibits the problem. It turns out that the segfault address listed (the multiple of 0x120) happens to be the value in the RBP register at the time of the segfault. That's odd, as the instruction is movdqa %xmm0,(%rdi) and rdi is the valid mmap address of the perf ring buffer rdi 0xf7768000 4151738368 so I'm not sure why RBP is involved at all. In all of the cases I've investigated the precise_ip value has been set for the problem event... but none of the events have been hardware events (software and breakpoint so far). So probably not PEBS related? Vince