[Qemu-devel] [PATCH] scripts/qemugdb: support coroutine backtrace in coredumps

Pedro Alves palves@redhat.com
Mon Apr 23 13:45:00 GMT 2018


On 04/23/2018 02:37 AM, 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?

Yeah, "frame <args>" has a lot of problems.

This series was working toward sorting out the "frame" command:

  https://sourceware.org/ml/gdb-patches/2015-09/msg00248.html

Follow the urls there for more background.

To me, the important questions to answer are here:
 https://sourceware.org/ml/gdb-patches/2015-09/msg00658.html

Unfortunately, I don't think the series moved past that point.

Thanks,
Pedro Alves



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