linux-kernel - Re: Query about kdump_msg hook into crash

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Message-ID: <20110201073853.GB21239@cr0.nay.redhat.com>
Date:	Tue, 1 Feb 2011 15:38:53 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	kosaki.motohiro@...fujitsu.com,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Jarod Wilson <jwilson@...hat.com>
Subject: Re: Query about kdump_msg hook into crash_kexec()

On Mon, Jan 31, 2011 at 11:33:15PM -0800, Eric W. Biederman wrote:
>Américo Wang <xiyou.wangcong@...il.com> writes:
>
>> On Mon, Jan 31, 2011 at 05:59:39PM -0500, Vivek Goyal wrote:
>>>
>>>Anyway, if an image is loaded and we have setup to capture dump also
>>>why do we need to save kmsg with the help of an helper. I am assuming
>>>this is more of a debugging aid if we have no other way to capture the
>>>kernel log buffer. So if somebody has setup kdump to capture the
>>>vmcore, why to call another handler which tries to save part of the
>>>vmcore (kmsg) separately.
>>>
>>
>> Well, kmsg dumper is not only for panic/oops, it can also save kernel
>> messages when the system is reboot/halt.
>>
>> Yeah, it is true that vmcore contains log_buf, but I think the users
>> of ramoops/mtdoops are mainly those who don't have kdump configured
>> in their kernels, they are cheaper than kdump, but less powerful
>
>The issue is the inane call inside crash_kexec.
>
>It requires both a kexec kernel to be loaded and it requires you to be
>crashing.  Given that when I audited the kmsg_dump handlers they really
>weren't safe in a crash dump scenario we should just remove it.
>

Probably, I think we need to get rid of KMSG_DUMP_KEXEC.

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