[Crash-utility] Problem on getting kernel backtrace with a `virsh dump' dumped kvm dumpfile

[Dave Anderson]

----- hutao at cn.fujitsu.com wrote:

> Hi Dave,
> 
> On Fri, Aug 27, 2010 at 08:40:17AM -0400, Dave Anderson wrote:
> > 
> > ----- hutao at cn.fujitsu.com wrote:
> > 
> > > Hi,
> > > 
> > > I encountered a problem on getting backtrace with a `virsh dump' dumped
> > > kvm dumpfile, the bt command did not get kernel backtrace properly.
> > > 
> > > guest kernel: 2.6.32
> > > crash: 5.0.6 patched with qemu_ram_version_4.patch(attached)
> > > 
> > > steps to get dumpfile:
> > > 
> > >   1. virsh start vm
> > >   2. connect to vm, say by vnc
> > >   3. On guest, build and run the code:
> > > 
> > > int main(void)
> > > {
> > > 	while (1);
> > > 
> > > 	return 0;
> > > }
> > > 
> > >   4. On host, run `virsh dump vm
> > > /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop'
> > > 
> > > Then run crash:
> > > 
> > >   crash /mnt/data/kernel/linux-2.6.32/System.map
> > > /mnt/data/kernel/linux-2.6.32/vmlinux
> > > /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop
> > > 
> > > got the result:
> > > 
> > > crash 5.0.6
> > > Copyright (C) 2002-2010  Red Hat, Inc.
> > > Copyright (C) 2004, 2005, 2006  IBM Corporation
> > > Copyright (C) 1999-2006  Hewlett-Packard Co
> > > Copyright (C) 2005, 2006  Fujitsu Limited
> > > Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
> > > Copyright (C) 2005  NEC Corporation
> > > Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
> > > Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux,
> Inc.
> > > This program is free software, covered by the GNU General Public License,
> > > and you are welcome to change it and/or distribute copies of it under
> > > certain conditions.  Enter "help copying" to see the conditions.
> > > This program has absolutely no warranty.  Enter "help warranty" for
> > > details.
> > >  
> > > GNU gdb (GDB) 7.0                               
> > > Copyright (C) 2009 Free Software Foundation, Inc.
> > > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> > > This is free software: you are free to change and redistribute it.
> > > There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> > > and "show warranty" for details.
> > > This GDB was configured as "x86_64-unknown-linux-gnu"...
> > > 
> > >   SYSTEM MAP: /mnt/data/kernel/linux-2.6.32/System.map 
> > > DEBUG KERNEL: /mnt/data/kernel/linux-2.6.32/vmlinux (2.6.32)
> > >     DUMPFILE: /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop
> > >         CPUS: 1
> > >         DATE: Fri Aug 27 05:18:12 2010
> > >       UPTIME: 00:00:51
> > > LOAD AVERAGE: 0.44, 0.11, 0.03
> > >        TASKS: 67
> > >     NODENAME: localhost.localdomain
> > >      RELEASE: 2.6.32
> > >      VERSION: #2 SMP PREEMPT Wed Aug 25 15:26:48 CST 2010
> > >      MACHINE: x86_64  (2925 Mhz)
> > >       MEMORY: 511.6 MB
> > >        PANIC: "Oops: 0003 [#1] PREEMPT SMP " (check log for details)
> > >          PID: 0
> > >      COMMAND: "swapper"
> > >         TASK: ffffffff8158df70  [THREAD_INFO: ffffffff8154e000]
> > >          CPU: 0
> > >        STATE: TASK_RUNNING 
> > >      WARNING: panic task not found
> > > 
> > > crash> bt
> > > PID: 0      TASK: ffffffff8158df70  CPU: 0   COMMAND: "swapper"
> > >  #0 [ffffffff8154fe28] schedule at ffffffff8138baa3
> > > bt: invalid kernel virtual address: 41  type: "call byte"
> > > bt: invalid kernel virtual address: 44e6835ad  type: "call byte"
> > > bt: load_memfile_offset: read: Success
> > > bt: read error: kernel virtual address: fffffffffffffffc  type: "call byte"
> > > bt: invalid kernel virtual address: e7ab  type: "call byte"
> > > bt: invalid kernel virtual address: e273  type: "call byte"
> > > bt: invalid kernel virtual address: 13a7b  type: "call byte"
> > > bt: invalid kernel virtual address: 935cb  type: "call byte"
> > > bt: load_memfile_offset: read: Success
> > > bt: read error: kernel virtual address: fffffffffffffffb  type: "call byte"
> > > bt: invalid kernel virtual address: 935cb  type: "call byte" 
> > >  #1 [ffffffff8154fef0] cpu_idle at ffffffff8100ad1e
> > > crash> 
> > > 
> > > 
> > > Note the output of `bt' command. Without running that endless-loop
> > > code then`bt' got:
> > > 
> > > 
> > > crash> bt
> > > PID: 0      TASK: ffffffff8158df70  CPU: 0   COMMAND: "swapper"
> > >  #0 [ffffffff8154fe28] schedule at ffffffff8138baa3
> > >  #1 [ffffffff8154fe48] apic_timer_interrupt at ffffffff8100c65e
> > >  #2 [ffffffff8154fed0] need_resched at ffffffff810125a8
> > >  #3 [ffffffff8154fee0] default_idle at ffffffff81012e03
> > >  #4 [ffffffff8154fef0] cpu_idle at ffffffff8100acd6
> > > crash> 
> > > 
> > > 
> > > Any suggestions on how to solve the problem?
> > 
> > Not really.
> > 
> > If there's no kernel crash, then the selection of the current
> > context defaults to the cpu 0 swapper task.  I don't know
> > what was happening to the "swapper" task at the time that the
> > guest was paused.
> 
> Without using System.map, `bt' indeed got
> 
> crash> bt
> PID: 0      TASK: ffffffff8158df70  CPU: 0   COMMAND: "swapper"
>  #0 [ffffffff8154fe28] schedule at ffffffff8138baa3
>  #1 [ffffffff8154fef0] cpu_idle at ffffffff8100ad1e
> crash>
> > 
> > If you want to make the vmlinux/dumpfile available for me
> > to download, I can take a look.  (I don't know why you're
> > using a System.map).
> 
> Do you still need vmlinux/dumpfile? If yes I will make them
> available for you.

Is the "non-System.map" bt output above from the dumpfile containing
the user-space endless-loop, or is it from the second one you tried?

If the backtrace above occurs with the user-space-endless-loop
dumpfile, then it's not necessary to send them to me.  But if the
bt errors still occur with the dumpfile containing the user-space
endless-loop (and with no System.map), then yes, I would like to
see the vmlinux/dumpfile pair.  (You can send the download details
off-list...)

Thanks,
  Dave

 
> Thank you, Dave.
> 
> > 
> > Dave
> >  
> > > 
> > > Regards,
> > > Hu Tao