Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752510AbeAKFZl (ORCPT + 1 other); Thu, 11 Jan 2018 00:25:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbeAKFZk (ORCPT ); Thu, 11 Jan 2018 00:25:40 -0500 Date: Wed, 10 Jan 2018 23:25:38 -0600 From: Josh Poimboeuf To: Peter Zijlstra Cc: Vince Weaver , Ingo Molnar , linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner , Andy Lutomirski Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7 Message-ID: <20180111052538.2qhj6oxnc24xumhk@treble> References: <20180109102507.GG6176@hirez.programming.kicks-ass.net> <20180109132602.GA2369@hirez.programming.kicks-ass.net> <20180109151253.GK6176@hirez.programming.kicks-ass.net> <20180109153341.GL6176@hirez.programming.kicks-ass.net> <20180109160551.GK3040@hirez.programming.kicks-ass.net> <20180109170716.bqmexpmywwr4bwuv@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180109170716.bqmexpmywwr4bwuv@treble> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 11 Jan 2018 05:25:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Tue, Jan 09, 2018 at 11:07:16AM -0600, Josh Poimboeuf wrote: > On Tue, Jan 09, 2018 at 05:05:51PM +0100, Peter Zijlstra wrote: > > On Tue, Jan 09, 2018 at 10:56:52AM -0500, Vince Weaver wrote: > > > On Tue, 9 Jan 2018, Peter Zijlstra wrote: > > > > > > > So CONFIG_PAGE_TABLE_ISOLATION=y and booting with "pti=off" makes it > > > > 'work', right? > > > > > > yes. Previously I was changing CONFIG_PAGE_TABLE_ISOLATION and > > > recompiling, but just now I booted with it set to yes and pti=off and the > > > fuzzer has been running fine for a half hour (usually it crashes in under > > > 5 minutes). For the crash, you might try enabling CONFIG_DEBUG_ENTRY and seeing if that gives you any output. > > > I did see these in the logs which I don't think I've seen before. > > > > > > WARNING: stack recursion on stack type 2 > > > WARNING: can't dereference iret registers at 000000000783fea8 for ip paranoid_entry+0x2e/0x90 > > > WARNING: can't dereference registers at 00000000f0698d17 for ip paranoid_entry+0x4c/0x90 > > > WARNING: stack going in the wrong direction? ip=native_sched_clock+0x9/0x90 This all looks very weird. The stack pointers -- 000000000783fea8 and 00000000f0698d17 -- are obviously very wrong. I will try to recreate locally. -- Josh