Re: [PULL 29/38] gdbstub: Permit reverse step/break to provide stop response

[Michael Tokarev]

03.07.2023 16:44, Alex Bennée wrote:
> From: Nicholas Piggin <npiggin@gmail.com>
>
> 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.
>
> Fixes: 758370052fb ("gdbstub: only send stop-reply packets when allowed to")
> Cc: qemu-stable@nongnu.org

Hi!

Are you guys sure this needs to be in -stable?

To me it looks a sort of "partial revert" of a previous commit:

commit 758370052fb602f9f23c3b8ae26a6133373c78e6
Author: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Date:   Thu May 4 12:37:31 2023 -0300
Subject: gdbstub: only send stop-reply packets when allowed to

which introduced `allow_stop_reply' field in GdbCmdParseEntry.
This change ("gdbstub: Permit..") does not work in 8.0 without
the above mentioned "gdbstub: only send" commit, and I guess
it is *not* supposed to be in stable. Or is it?

I'm not applying this one to stable for now.

Thanks,

/mjt

> Cc: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: Taylor Simpson <tsimpson@quicinc.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> Acked-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
> Message-Id: <20230623035304.279833-1-npiggin@gmail.com>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Message-Id: <20230630180423.558337-30-alex.bennee@linaro.org>
>
> diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
> index be18568d0a..9496d7b175 100644
> --- a/gdbstub/gdbstub.c
> +++ b/gdbstub/gdbstub.c
> @@ -1814,6 +1814,7 @@ static int gdb_handle_packet(const char *line_buf)
>                   .handler = handle_backward,
>                   .cmd = "b",
>                   .cmd_startswith = 1,
> +                .allow_stop_reply = true,
>                   .schema = "o0"
>               };
>               cmd_parser = &backward_cmd_desc;