----- hutao@xxxxxxxxxxxxxx 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.
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
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