[Crash-utility] Identity of a Xen Dom0 vmcore file

[Louis Bouchard]

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Hello and a very happy new year to everyone !

I'm still at work on crashdc and making good progress. I have a working
version for the standard i386 kernels of RHEL5, SLES10 and SLES11 working.

I'm currently working on making sure that all type of kernels delivered
by the distros will work fine with crashdc and I'm hitting a snag with
Xen on RHEL5 (for Dom0). No big deal, but when there is more than 4 Gb
of memory, kdump loads the PAE kernel even if a Xen kernel was
previously running. So I cannot use 'uname' to identify the kernel
context to use the appropriate debuginfo kernel.

So if I want to be able to choose the adequate vmcore from the debuginfo
package, I must rely on the vmcore file produced to identify which one
(i.e. PAE, XEN or std) to use.

It looks like the first few bytes of the xen vmcore file might hold the
information I'm looking for. Doing the following 'od' on a vmcore file
created from a Xen kernel gives me this :

 od -N2000 -S3 vmcore.xen | more
 0000544 CORE
 0001010 Xen
 0001050 Xen
 0001140 VMCOREINFO_XEN

Same on a PAE or standard vmcore brings back this :
 od -N2000 -S3 vmcore.pae | more
 0000544 CORE
 0001010 VMCOREINFO

I might search the web for a description of the vmcore file format, but
I'm sure that many of you here can point me to the right direction and,
maybe, tell me if I'm making the right assumption in thinking that those
values can safely identify a Xen kernel.

I've looked at xendump.[c|h] from the crash utility sources and it looks
like there is a Xen specific signature but I might be interpreting this
in the wrong way.

Maybe someone care to comment ?

TIA and Kind Regards,

- --
Louis Bouchard, Linux Support Engineer
Team lead, EMEA Linux Competency Center,
Linux Ambassador, HP

HP Services                       1 Ave du Canada
HP France                         Z.A. de Courtaboeuf
louis.bouchard at hp.com             91 947 Les Ulis
http://www.hp.com/go/linux        France
http://www.hp.com/fr
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