[Crash-utility] [PATCH] arm64: Fix segfault by "bt" command with offline cpus

[HAGIO KAZUHITO(萩尾 一仁)]

-----Original Message-----
> 
> You can add
> Tested-by: Dave Wysochanski <dwysocha at redhat.com>
> 
> Before this patch I had a vmcore that would segfault with 'bt -a',
> with backtrace as in
> https://github.com/crash-utility/crash/issues/105#issuecomment-1017176451
> After this patch the segfault is gone.

Thank you Dave, for testing.

Lianbo, please add the tag when you merge this.

> 
> FWIW, I saw was some new warnings with the vmcore but may be expected:
> 
> WARNING: cannot determine starting stack frame for task ffff809920692100
> 
> WARNING: cannot determine starting stack frame for task ffff80992068ee00
> 
> WARNING: cannot determine starting stack frame for task ffff80992069ed00
> WARNING: cpu 4: cannot find NT_PRSTATUS note
> WARNING: cpu 5: cannot find NT_PRSTATUS note
> WARNING: cpu 6: cannot find NT_PRSTATUS note
> WARNING: cpu 7: cannot find NT_PRSTATUS note
> WARNING: cpu 8: cannot find NT_PRSTATUS note
> WARNING: cpu 9: cannot find NT_PRSTATUS note
> WARNING: cpu 10: cannot find NT_PRSTATUS note
> WARNING: cpu 11: cannot find NT_PRSTATUS note

I cannot try the patch, but if those warnings are for offline cpus,
they are expected.

Thanks,
Kazu