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Date: Wed, 23 Jan 2013 09:49:15 +0100
From: Bouchard Louis <louis.bouchard@canonical.com>
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Subject: Re: makedumpfile --dump-dmesg option broken on 3.5 kernels and later
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To: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: kexec@lists.infradead.org

Hi Kumagai-san,

Le 23/01/2013 02:19, Atsushi Kumagai a =E9crit :
> Hello Louis,
> =

> On Tue, 22 Jan 2013 14:52:09 +0100
> Bouchard Louis <louis.bouchard@canonical.com> wrote:
> =

>> Hello Kumagai-san,
>>
>> Following a suggestion from Dave Anderson, I have tested the
>> makedumpfile --dump-dmesg option. After some research, I realized that
>> the option was no longer working on 3.5 kernel and later. Here is an
>> example of the result (on Ubuntu Quantal) :
>>
>> # makedumpfile --dump-dmesg /proc/vmcore /tmp/dmesg
>> dump_dmesg: Can't find some symbols for log_buf.
>>
>> makedumpfile Failed.
>>
>> On 3.5 kernel and later, the log_end symbol no longer exists.
>>
>> This is caused by the change from byte-buffer structure to
>> variable-length record buffer of the kernel log buffer introduced by
>> this commit :
>> 	http://goo.gl/NCgLI
>>
>> I am curious to know if you were aware of this change and if you had
>> done some work on modifying dump_dmesg() accordingly ? Just so I don't
>> go off and try to work on something that you have already solved.
> =

> Thanks for your report.
> I haven't been aware of this, so could I ask you to help me ?
> =


I will be happy to do so. Dave Anderson has already fixed in for crash,
so I have an example to follow. I've already started work on a patch for
the post 3.5 kernels.

I might need to come back to you for some details about the code though.

Kind regards,

...Louis


-- =

Louis Bouchard
Backline Support Analyst
Canonical Ltd
Ubuntu support: http://landscape.canonical.com

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