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Re: [Qemu-devel] [PATCH] scripts/qemugdb: support coroutine backtrace in
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] scripts/qemugdb: support coroutine backtrace in coredumps |
Date: |
Mon, 23 Apr 2018 10:33:34 +0100 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
On Sun, Apr 22, 2018 at 09:37:52PM -0400, Simon Marchi wrote:
> On 2018-04-09 10:08 PM, Stefan Hajnoczi wrote:
> > I wonder what the point of select-frame is then...
> >
> > I have CCed the GDB mailing list. Maybe someone can help us. Context:
> >
> > QEMU implements coroutines using jmpbuf. We'd like to print coroutine
> > call stacks in GDB and have a script that works when a process is being
> > debugged (it sets the registers).
> >
> > Now we'd like to extend the script to work on core dumps where it's not
> > possible to set registers (since there is no process being debugged).
> >
> > Is there a way to backtrace an arbitrary call stack in a core dump?
>
> Not that I know of. The "frame <stack-addr> <pc-addr>" form of the frame
> command sounds like it should be usable to achieve that, but it doesn't
> seem to work in that way. I really wonder if it's working as it was
> intended initially. I guess using that form of the frame command should
> override/mask the real current values of $sp and $pc?
Yes, that is what I was expecting.
Vladimir has a script to copy the coredump file and manipulate the
registers on disk, but it would be nicer to do stack-switching inside
the GDB session without needing to create another coredump file.
Vladimir: Would you like to write a GDB patch? If GDB is fixed then
workaround won't be necessary.
Stefan
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