linux-kernel - Re: [Patch] kexec: remove KMSG_DUMP_KEXEC (was Re: Query about kdump_msg hook into crash

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Message-ID: <20110203020703.GB21603@redhat.com>
Date:	Wed, 2 Feb 2011 21:07:03 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Americo Wang <xiyou.wangcong@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Jarod Wilson <jwilson@...hat.com>, akpm@...ux-foundation.org
Subject: Re: [Patch] kexec: remove KMSG_DUMP_KEXEC (was Re: Query about
 kdump_msg hook into crash_kexec())

On Thu, Feb 03, 2011 at 09:59:04AM +0900, KOSAKI Motohiro wrote:
> > On Tue, Feb 01, 2011 at 03:38:53PM +0800, Américo Wang wrote:
> > >On Mon, Jan 31, 2011 at 11:33:15PM -0800, Eric W. Biederman wrote:
> > >>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.
> > >
> > 
> > Here we go.
> > 
> > --------->
> > 
> > KMSG_DUMP_KEXEC is useless because we already save kernel messages
> > inside /proc/vmcore, and it is unsafe to allow modules to do
> > other stuffs in a crash dump scenario.
> > 
> > Reported-by: Vivek Goyal <vgoyal@...hat.com>
> > Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> > Signed-off-by: WANG Cong <xiyou.wangcong@...il.com>
> 
> I wrote why this is no good idea by another mail. Please see it.
> Anyway you have a right to don't use this feature.
> 

But you have not explained that why do you need to hook into crash_kexec()
and you have also not explained why do you need to send out kdump_msg()
notification if kdump is configured.

Some detailed explanation here would help.

Thanks
Vivek

> Nack.
> 
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