linux-kernel - Re: [Patch 1/4][kernel][slimdump] Add new elf-note of type NT

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Date:	Wed, 5 Oct 2011 18:16:26 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Valdis.Kletnieks@...edu
Cc:	Vivek Goyal <vgoyal@...hat.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Borislav Petkov <bp@...en8.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, crash-utility@...hat.com,
	kexec@...ts.infradead.org, Andi Kleen <andi@...stfloor.org>,
	"Luck, Tony" <tony.luck@...el.com>, anderson@...hat.com,
	tachibana@....nes.nec.co.jp, oomichi@....nes.nec.co.jp
Subject: Re: [Patch 1/4][kernel][slimdump] Add new elf-note of type
 NT_NOCOREDUMP to capture slimdump

On Wed, Oct 05, 2011 at 12:00:38PM -0400, Valdis.Kletnieks@...edu wrote:
> On Wed, 05 Oct 2011 11:52:17 EDT, Vivek Goyal said:
> 
> > I am assuming that basic MCE error messages are available in kernel log. 
> 
> They're not in the kernel log if it's an MCE that causes the kernel to declare
> a panic. There's some MCE's that you can retry the operation and continue, and
> some that you can get away with poisoning a page, killing the process, and rest
> of the system is OK.  But some you really need to roll over and die because you
> can't guarantee kernel integrity anymore.
> 
> And at that point, those messages are never gonna make it to syslogd and onto
> disk.

AFAICT, and for the sake of getting the MCE info, arguably one could
look for log_buf in the vmcore of the old kernel and try to find the
last lines in the kernel log ringbuffer. They should be the MCE error
information from the do_machine_check MCE handler.

This all assuming of course we've managed to dump vmcore successfully by
sidestepping the landmines :-).

-- 
Regards/Gruss,
Boris.
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