kdump with /proc/oldproc

Maxim Uvarov muvarov at gmail.com
Wed May 18 03:00:39 EDT 2011

2011/5/17 WANG Cong <xiyou.wangcong at gmail.com>:
> On Tue, 17 May 2011 12:30:58 -0500, Nathan D Miller wrote:
>> Hello-
>> Has anyone tried reconstituting a portion of the old kernel's /proc
>> while in the capture kernel?
>> I had the idea while digging through the kexec/kdump code and it seemed
>> intriguing.
>> It might be a means by which user-space dump applications running under
>> the capture kernel could interrogate the old system, and identify bad
>> processes that instigated the panic.  In particular, I'm thinking of Out
>> Of Memory scenarios.   We've modified our kernel to panic instead of
>> invoking the kernel's OOM killer, but we still have the problem of
>> identifying the "bad" process while running in the capture kernel.
>> Perhaps everything could be accomplished using some sort of FUSE
>> file-system around /proc/oldmem and /proc/vmcore.  Not all the
>> proc/<pid>/ files would need to be implemented, of course.  In addition,
>> each old process could have its own 'vmcore' file for getting a core
>> dump of the original process.
> Well, actually you don't need to bother the old /proc
> to find which process is the killer. The old dmesg contains
> the PID/comm of the killer process, and we have a tool named
> vmcore-dmesg to read out the dmesg from the vmcore.
> With the utility 'crash', you can query any info of any process
> in the old kernel, so why do you need a per-process vmcore anyway?

If you use one of the latest kernel and gdb you can do it with gdb
without  crash or vmcore-dmesg.

> Thanks.
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Best regards,
Maxim Uvarov

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