linux-kernel - Re: [RFC Patch 1/2][slimdump] Append CRASH

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Date:	Mon, 28 Nov 2011 09:26:52 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc:	Dave Anderson <anderson@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Tony Luck <tony.luck@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	tachibana@....nes.nec.co.jp, oomichi@....nes.nec.co.jp,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Nick Bowler <nbowler@...iptictech.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC Patch 1/2][slimdump] Append CRASH_REASON to VMCOREINFO
 elf-note

On Wed, Nov 23, 2011 at 11:09:31PM +0530, K.Prasad wrote:
> On Mon, Nov 21, 2011 at 10:19:31AM -0500, Dave Anderson wrote:
> > 
> > 
> > ----- Original Message -----
> > > Allow various crash paths to append the reason of crash into the
> > > VMCOREINFO elf-note through the field CRASH_REASON. We also make the
> > > fatal machine check exceptions append "PANIC_MCE" as the crash
> > > reason.  This string will be recognised by upstream tools like makedumpfile and
> > > crash to generate slimdump.
> > 
> > I don't understand -- how could "various paths" append a reason?
> > The patch below seems to return "PANIC_MCE" for every x86 crash.
> > What am I missing?
> > 
> > Dave
> > 
> 
> Yes, presently it can only be "PANIC_MCE" for MCE crashes in x86 (not
> for every crash though).
> 
> With increased usage, we should move this code to a generic location and
> let each of these crash paths return a string to be appended. In fact it
> doesn't have to be a string for CRASH_REASON but just an encoding of the
> various crash types into numbers. User-space tools could then do a lookup
> for getting the right crash string.

Probably string is a better idea? Where do we do lookup to find out what
maps to what? This would require kernel exporting this info in a header
and then comes the issue of having same kernel version info. Or the issue
of analyzing kernel dumps on the same machine.

Storing a string will atleast help that one does not have to worry about
mapping error code. makedumpfile shall have to grep for exact same string
though.

Thanks
Vivek
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