From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935478Ab1JEWbE (ORCPT ); Wed, 5 Oct 2011 18:31:04 -0400 Received: from filtteri1.pp.htv.fi ([213.243.153.184]:36076 "EHLO filtteri1.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932231Ab1JEWbC (ORCPT ); Wed, 5 Oct 2011 18:31:02 -0400 Date: Thu, 6 Oct 2011 01:30:57 +0300 From: Adrian Bunk To: richard -rw- weinberger Cc: Andrew Lutomirski , "H. Peter Anvin" , Linus Torvalds , Thomas Gleixner , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [3.1 patch] x86: default to vsyscall=native Message-ID: <20111005223055.GG14406@localhost.pp.htv.fi> References: <20111003090846.GA25136@localhost.pp.htv.fi> <20111003173359.GA3072@localhost.pp.htv.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. What more information exactly do you need from me? > Thanks, > //richard cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed