Re: How to backtrace an separate stack?

Stefan Hajnoczi <[email protected]> Tue, 8 Mar 2022 08:43:27 +0000

Newsgroups	gmane.comp.emulators.qemu,gmane.comp.gdb.devel
Message-ID	<[email protected]>

On Mon, Mar 07, 2022 at 05:18:12PM +0000, Pedro Alves wrote:
> On 2022-03-07 16:58, Tom Tromey wrote:
> >>>>>> "Stefan" == Stefan Hajnoczi <[email protected]> writes:
> > 
> > Stefan> I hoped that "select-frame address ADDRESS" could be used instead so
> > Stefan> this would work on coredumps too. Unfortunately "select-frame" only
> > Stefan> searches stack frames that GDB is already aware of, so it cannot be used
> > Stefan> to backtrace coroutine stacks.
> > 
> > I wonder if "select-frame view" is closer to what you want.
> > 
> > I can't attest to how well it works or doesn't work.  I've never tried
> > it.
> 
> A backtrace after "select-frame view" will still start at the
> current (machine register's) frame.  Maybe it's sufficient to emulate it with
> a sequence of "up" + "frame", though.  Keep in mind that you'll lose the view
> with "info threads" or any command that flushes the frame cache internally,
> as I mentioned in that ancient discussion.

I tried the following with gdb (11.2-1.fc35):

  select-frame view STACK_ADDR PC
  frame <-- this displays the top coroutine stack frame
  up
  frame <-- this displays the secondmost main stack frame

Unfortunately "up" returns to the main stack instead of unwinding the
coroutine stack.

"i r" and "i lo" still show values from the main stack frame after
"select-frame view". This makes sense since "select-frame view" only
sets the stack and PC addresses, not the register contents.

Alas, "select-frame view" isn't quite enough from what I can tell.

Stefan

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