[Crash-utility] [PATCH] debuginfo does not pick user_regs_struct on x86_64

[Dave Anderson]

----- Original Message -----
> >
> > Right -- over the years it has been "found" in some kernel
> > version's debuginfo data, but certainly not in all kernel
> > versions. (mostly not)
> >
> > But anyway, its potential non-existence has been worked
> > around such that the offset_table entries are not required.
> >
> > I did test it out on ~150 sample dumpfiles, and while it doesn't
> > break anything, it doesn't help either -- the "bt -a" output is
> > identical with or without the patch.
> 
> The command "bt -a" can work fine without the patch now, because we
> have checked it in get_netdump_regs_x86_64().
> 
> We have a new hardware to do dump, and use makedumpfile to generate
> vmcore. Our hardware can work when the OS is out of controll(for
> example: dead loop). When we use crash to analyze the vmcore, bt can
> not work, because there is no panic task.
> 
> We have provide the value of register in the vmcore(the format is elf_prstatus,
> it is same with normal kdump's vmcore). So I write the code to use the register
> from notes in the vmcore when we do not find panic task. So we should know
> these offsets. We can check it where we use, but I think it's better to check
> and init it in x86_64_init().

Interesting -- so you essentially have an alternative dumping method
whose format simulates a kdump.

> >
> > Did you actually have a situation where a backtrace failed
> > without it -- but then worked OK with your patch?
> >
> > And was there a reason you used "unsigned long long" declarations?
> > I understand they are the same, but the kernel uses "unsigned long".
> > Why the difference?
> 
> Does this case exist: we build crash on x86 box and use it to analyze the
> vmcore which is generate in x86_64 box? If it does not exist, I think
> we should use "unsigend long", the same with the kernel.

No, that cannot be done.  You can build an x86 binary on an x86_64 machine
with "make target=X86", but not the other way around.

I'll revert them to "unsigned long" declarations, and queue the patch
for crash-5.1.3.

Thanks,
  Dave