From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935499Ab1JEWls (ORCPT ); Wed, 5 Oct 2011 18:41:48 -0400 Received: from mail-vx0-f174.google.com ([209.85.220.174]:48625 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935480Ab1JEWlq convert rfc822-to-8bit (ORCPT ); Wed, 5 Oct 2011 18:41:46 -0400 MIME-Version: 1.0 In-Reply-To: <20111005223055.GG14406@localhost.pp.htv.fi> References: <20111003090846.GA25136@localhost.pp.htv.fi> <20111003173359.GA3072@localhost.pp.htv.fi> <20111005223055.GG14406@localhost.pp.htv.fi> Date: Thu, 6 Oct 2011 00:41:45 +0200 Message-ID: Subject: Re: [3.1 patch] x86: default to vsyscall=native From: richard -rw- weinberger To: Adrian Bunk Cc: Andrew Lutomirski , "H. Peter Anvin" , Linus Torvalds , Thomas Gleixner , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 6, 2011 at 12:30 AM, Adrian Bunk wrote: > On Thu, Oct 06, 2011 at 12:22:34AM +0200, richard -rw- weinberger wrote: >> On Thu, Oct 6, 2011 at 12:13 AM, Andrew Lutomirski wrote: >> > On Mon, Oct 3, 2011 at 10:33 AM, Adrian Bunk wrote: >> >> On Mon, Oct 03, 2011 at 06:04:53AM -0700, Andrew Lutomirski wrote: >> >>> On Mon, Oct 3, 2011 at 2:08 AM, Adrian Bunk wrote: >> >>> > After upgrading a kernel the existing userspace should just work >> >>> > (assuming it did work before ;-) ), but when I upgraded my kernel >> >>> > from 3.0.4 to 3.1.0-rc8 a UML instance didn't come up properly. >> >>> > >> >>> > dmesg said: >> >>> >  linux-2.6.30.1[3800] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb9c498 ax:ffffffffff600000 si:0 di:606790 >> >>> >  linux-2.6.30.1[3856] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb13168 ax:ffffffffff600000 si:0 di:606790 >> >>> > >> >>> > Looking throught the changelog I ended up at commit 3ae36655 >> >>> > ("x86-64: Rework vsyscall emulation and add vsyscall= parameter"). >> >>> > >> >>> > Linus suggested in https://lkml.org/lkml/2011/8/9/376 to default to >> >>> > vsyscall=native. >> >>> > >> >>> > That sounds reasonable to me, and fixes the problem for me. >> >>> >> >>> At this point in the -rc cycle, this sounds fine. >> >>> >> >>> That being said, I'd like to fix it for real for 3.2.  This particular >> >>> failure is suspicious -- the "vsyscall fault" message means that >> >>> sys_gettimeofday returned EFAULT, which means that the old (3.0 and >> >>> before) vgettimeofday should *also* have segfaulted. >> >> >> >> This 2.6.30.1 UML kernel binary from 2009 worked for me for all host >> >> kernels from 2.6.30 to 3.0, and with 3.1.0-rc8 and vsyscall=native >> >> it also seems to run nicely. >> >> >> >> Looking deeper into "a UML instance didn't come up properly", >> >> the problem is that it comes up in a strange (readonly) state. >> >> >> >> There are "Using makefile-style concurrent boot in runlevel S." >> >> and "Using makefile-style concurrent boot in runlevel 2." in the >> >> logs with a Debian userspace, but no output from the init scripts >> >> in these broken bootups (normal messages are in non-broken bootups). >> >> >> >> Perhaps the two the messages I see in dmesg on the host are from the >> >> processes running rcS and rc2 failing early? >> >> >> >> In a working startup with a Debian userspace, I'm getting during rcS >> >>  Setting the system clock. >> >>  Cannot access the Hardware Clock via any known method. >> >>  Use the --debug option to see the details of our search for an access method. >> >>  Unable to set System Clock to: Mon Oct 3 17:01:35 UTC 2011 ... (warning). >> >> >> >>> We do have a bit >> >>> of a bug in that the new code doesn't report si_addr properly, but >> >>> that sounds unlikely as a culprit.  Did you try with the offending >> >>> commit reverted (i.e. fce8dc0)?  I bet that it also fails there. >> >> >> >> fce8dc0 is "x86-64: Wire up getcpu syscall", is that really the one you >> >> want me to revert? >> >> >> >>> What's the .config for your UML binary?  I'd like to see if I can >> >>> reproduce this. >> >> >> >> It's attached. >> >> >> > >> > I can't reproduce it.  What distro is running inside the UML instance? >> >> Same here. >> Adrian, is the UML kernel crashing before executing init? > > As I wrote: >  Looking deeper into "a UML instance didn't come up properly", >  the problem is that it comes up in a strange (readonly) state. > > The UML kernel is running happily without crashing, and as I wrote my > guess about my problems is: >  Perhaps the two the messages I see in dmesg on the host are from the >  processes running rcS and rc2 failing early? > >> We definitely need more information... > > I gave the information that was requested. plus my observations. > Whoops, the mail containing that information did not make it into my head, sorry. Now I know where to look for... BTW: Can you please test 3.1-rcX as UML kernel? It contains vDSO/vsyscall fixes... -- Thanks, //richard