Re: [Crash-utility] Why are there two ways of getting register values for active tasks?
----- "Dave Anderson" <anderson(a)redhat.com> wrote:
----- "Daisuke HATAYAMA" <d.hatayama(a)jp.fujitsu.com>
wrote:
> Hi, all.
>
> I have a question on the implementation of
get_netdump_regs_x86_64().
>
> Currently, in order to get register values for active tasks, only
> panic task makes use of note information. On the other hand, other
> active tasks search stack frame for registers saved at nmi
> switch. However, crash dump contains the note information for every
> CPUs, so I think it uncessary to search stack frame.
Originally it was done that way because the code was written for
netdump-generated dumpfiles, which only generated note information
for the panic task. But if I'm not mistaken, given that recent
kernels do not store debuginfo data for the user_regs_struct, it
almost always falls through into x86_64_get_stack_frame().
I take that back -- when it's not in the debuginfo, it hardwires
the user_regs_struct data structure information.
That being the case, I don't remember why it is restricted to the
panic task, but it had to have been put in place based upon actual
dumpfiles where it didn't work correctly for a non-panic task.
If I get the time, I'll remove the restriction and run it on
my set of stashed dumpfile examples to see if I can be more
specific.
Anyway, good question -- sorry for such a weak answer...
Dave