Messages in this thread | | | Date | Thu, 6 Oct 2011 01:30:57 +0300 | From | Adrian Bunk <> | Subject | Re: [3.1 patch] x86: default to vsyscall=native |
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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 <luto@mit.edu> wrote: > > On Mon, Oct 3, 2011 at 10:33 AM, Adrian Bunk <bunk@stusta.de> 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 <bunk@stusta.de> 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
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