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

[Dave Anderson]

----- 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.
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> 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.

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).

Dave
 
> 
> Regards,
> Hu Tao