Re: [PATCH] gdbstub: Permit reverse step/break to provide stop response

[Peter Maydell]

On Fri, 23 Jun 2023 at 13:19, Matheus Tavares Bernardino
<quic_mathbern@quicinc.com> wrote:
>
> > Nicholas Piggin <npiggin@gmail.com> wrote:
> >
> > The final part of the reverse step and break handling is to bring
> > the machine back to a debug stop state. gdb expects a response.
> >
> > A gdb 'rsi' command hangs forever because the gdbstub filters out
> > the response (also observable with reverse_debugging.py avocado
> > tests).
> >
> > Fix by setting allow_stop_reply for the gdb backward packets.
>
> Ah, it's interesting that [1] doesn't include 'bc' and 'bs' in the list
> of cmds that may respond with a stop-reply packet:
>
>     "The 'C', 'c', 'S', 's', 'vCont', 'vAttach', 'vRun', 'vStopped', and
>     '?' packets can receive any of the below as a reply."
>
> But their definitions at [2] do say the following:
>
>     'bc' (and 'bc')
>     [...]
>     Reply: See Stop Reply Packets, for the reply specifications.
>
> So I guess the list from [1] is not exhaustive. Anyway, thanks for the
> fix!

That looks like it's probably a gdb docs bug (forgetting to
update that list when the bc/bs packets were added); we
should probably report that to upstream gdb.

thanks
-- PMM