linux-kernel - Re: Determine version of kernel that produced vmcore

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Date:	Tue, 10 Jul 2007 23:36:45 +0300
From:	Dan Aloni <da-x@...atomic.org>
To:	Neil Horman <nhorman@...hat.com>
Cc:	Vivek Goyal <vgoyal@...ibm.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Bernhard Walle <bwalle@...e.de>
Subject: Re: Determine version of kernel that produced vmcore

On Tue, Jul 10, 2007 at 03:00:09PM -0400, Neil Horman wrote:
> On Tue, Jul 10, 2007 at 08:35:41PM +0300, Dan Aloni wrote:
>[...]
> > 
> > Isn't there some sort of a circular dependency going on here? As I 
> > understand it the vmlinux binary already contains the initramfs as 
> > built-in data (at least that's what I use here for initramfs). It 
> You're misunderstood.  The vmlinux binary and the initramfs are stored in the
> same protected memory area when you execute a kexec -l, but they are separate
> and distinct files.
> 
> > makes more sense if you guys are creating an _initrd_ image (that's 
> > what mkinitrd originally did AFAIK) and supply it to the boot-loader.
> initrd is old, initramfs is the new way to go, but they effecitvley do the same
> thing, and while the initramfs _can_ be built into the kernel, it can also be
> separately managed (which is what most distros tend to do, AFAICS).
> Neil

Yes, I was under the impression that the external initramfs was the 
'special case' and I seem to forget about it, I guess that's what most  
kernel distribution still do (I haven't been using a distribution-supplied 
kernel for quite a while...).

Anyway, the patches I contributed in one the previous mail (didn't reach 
the kexec list due to moderation but available on LKML) can help with 
what Bernhard is aiming for. I took quite a dive into makedumpfile's code 
to figure out what's the best way to integrate it. What I was thinking 
was something in the lines of:

 * early on, detect if /proc/vmcore has a LINUX elf note 
   * if it has, then don't require '-x' or '-i' on the command line,
     extract it to a temporary file and treat it as a CONFIGFILE for 
     the rest of the code flow.
   * otherwise, continue with the regular flow.

For just extracting OSRELEASE, it is possible to write a simple program or 
script that searches for it at the first few kilobytes of the file.

-- 
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il
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