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

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Date:	Tue, 10 Jul 2007 11:14:14 +0300
From:	Dan Aloni <da-x@...atomic.org>
To:	Vivek Goyal <vgoyal@...ibm.com>
Cc:	Neil Horman <nhorman@...hat.com>,
	Ken'ichi Ohmichi <oomichi@....nes.nec.co.jp>,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: Determine version of kernel that produced vmcore

On Tue, Jul 10, 2007 at 12:18:17PM +0530, Vivek Goyal wrote:
> On Fri, Jul 06, 2007 at 05:58:04PM +0300, Dan Aloni wrote:
> > 
>[..]
> > It contains enough information in order to make a compact kernel
> > dump (makedumpinfo needs to go over the struct page arrays). As
> > you see, it also contains the kernel version.
> > 
> 
> But this will not solve Bernhard's problem where looking at a vmcore
> he wants to know which vmlinux (kernel version with time stamp) has
> generated this vmcore. So adding a ELF NOTE should help.

That, or pass it in *runtime* by other means.
 
> > However, this file needs to be passed somehow to the rootfs
> > of the kdump kernel. This poses a chicken-and-egg problem on 
> > my setup where the initramfs of the first kernel contains 
> > a staticlu linked version of the kexec executable along with a
> > kdump kernel to be loaded before mount rootfs and running 
> > init. 
> > 
> 
> Why are you loading kdump kernel from first kernel's initramfs?
> I guess to enable the dump capture as soon as possible so if some
> driver panics() you can capture the dump?

Yes, that's one of the reasons.
 
> Can't we modify the initramfs generation process (mkinitrd) to take
> care of this situation?. By the way, how is second kernel's initramfs
> is generated currently? The moment we start packing a file which contains
> the debuginfo for first kernel, initramfs of second kernel becomes dependent
> on first kernel and to me its not a good approach.

That's not what I'm aiming for, they are actually independent (my 
initramfs is a build-time constant). I have described it in another
mail.
 
> A dump kernel and its initrd should be independent of the crashing kernel.

I agree.

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