[PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon panic

Ahmed S. Darwish darwish.07 at gmail.com
Wed Jan 26 22:33:47 EST 2011

(Very timely! was just exploring kexec-tools and friends)

On Wed, Jan 26, 2011 at 09:13:38PM -0500, Vivek Goyal wrote:
> On Wed, Jan 26, 2011 at 02:49:54PM +0200, Ahmed S. Darwish wrote:
> > 
> >   If not, can kexec be modified to do so? That possibly needs the help
> >   of a a bootloader extension.
> - Generally kdump uses same kernel as first one. So if first kernel panics
>   then kdump kernel will also panic. Though one can keep a known good kdump
>   kernel.

I was thinking of a 'special' kdump kernel: the older kernel will just pass
the physical RAM address of its ring buffer to the newer kernel. The newer
kernel will be __so specialized__ that it will just:

 - display the log in a friendly manner
 - write it to the swap partition
 - .. and halt

This way, I completely toss the BIOS while accomplishing similar goals.

> - Currently kexec-tools take care of loading the kdump kernel, and then
>   preparing memory map for second kernel and pass to it and also pass
>   along some information about vmcore in ELF headers to second kernel. 
> There is so much to it that I really don't think that modifying bootloaders to
> do all that might not trivial and more importantly I think it probably is not
> worth the effort.

IMHO if done in a user-friendly and stable manner, it can really be worth
the effort. But quite honestly, since I did not read all the setup work
done by kexec-tools yet, I might be too optimistic.

> Thanks
> Vivek



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