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

[Louis Bouchard]

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Hi, it's me again,

I hate when I do that. If I had searched 5 more minutes, I would have
found this thread on the ML that talks about VMCOREINFO_XEN and how to
read it with 'readelf':

http://www.redhat.com/archives/crash-utility/2008-September/msg00006.html

Sorry for the noise ;-)

Kind Regards,

...Louis
Bouchard, Louis a écrit :
> 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,
> 

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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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