[Crash-utility] help debug number of CPU detect failure

[Dave Anderson]

----- Original Message -----
> 
> 
> ----- Original Message -----
> 
> ...
> 
> > Hi Dave,
> > 
> > I did some more experiments and found that it is nothing to do with numa.
> >
> > I also found that the issue gets resolved when I insert "SYMBOL(_stext)="
> > into vmcoreinfo.
> > Meaning sometime crash needs _stext value along with kaslr & phys_base.
> >
> > Thanks,
> > Santosh
> 
> There is this comment in kaslr_init():
> 
>  *  Setting RELOC_AUTO will ensure that derive_kaslr_offset() is
>  *  called after the sorting operation has captured the vmlinux
>  *  file's "_stext" symbol value -- which it will compare to the
>  *  relocated "_stext" value found in either a dumpfile's vmcoreinfo
>  *  or in /proc/kallsyms on a live system.
> 
> You should report that back to the vm2core developers to fix that
> half-baked ELF header.
> 
> For example, when the KVM "virsh dump" feature is used by a KVM
> host to create a dumpfile of a guest VM, they have a mechanism in
> place that transfers the vmcoreinfo data from the guest back to
> the host, resulting in a vmcore that is identical to a bare-metal
> vmcore.

By the way, I note on the vm2core github site, they suggest using
the guest's System.map file on the command line (in addition to 
--kaslr and --machdep phys_base=xxxx).  Doing that would supply
the _stext value.  

Dave