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gdbstub: only send stop-reply packets when allowed to

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GDB's remote serial protocol allows stop-reply messages to be sent by
the stub either as a notification packet or as a reply to a GDB command
(provided that the cmd accepts such a response). QEMU currently does not
implement notification packets, so it should only send stop-replies
synchronously and when requested. Nevertheless, it still issues
unsolicited stop messages through gdb_vm_state_change().

Although this behavior doesn't seem to cause problems with GDB itself
(the messages are just ignored), it can impact other debuggers that
implement the GDB remote serial protocol, like hexagon-lldb. Let's
change the gdbstub to send stop messages only as a response to a
previous GDB command that accepts such a reply.

Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <a49c0897fc22a6a7827c8dfc32aef2e1d933ec6b.1683214375.git.quic_mathbern@quicinc.com>
This commit is contained in:
Matheus Tavares Bernardino 2023-05-04 12:37:31 -03:00 • committed by Taylor Simpson
parent 9e6d4938d1
commit 758370052f
4 changed files with 60 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

13
gdbstub/softmmu.c
View file

@ -43,6 +43,7 @@ static void reset_gdbserver_state(void)
g_free(gdbserver_state.processes);
gdbserver_state.processes = NULL;
gdbserver_state.process_num = 0;
gdbserver_state.allow_stop_reply = false;
}
/*
@ -139,6 +140,10 @@ static void gdb_vm_state_change(void *opaque, bool running, RunState state)
return;
}
if (!gdbserver_state.allow_stop_reply) {
return;
}
gdb_append_thread_id(cpu, tid);
switch (state) {
@ -205,6 +210,7 @@ static void gdb_vm_state_change(void *opaque, bool running, RunState state)
send_packet:
gdb_put_packet(buf->str);
gdbserver_state.allow_stop_reply = false;
/* disable single step if it was enabled */
cpu_single_step(cpu, 0);
@ -422,8 +428,11 @@ void gdb_exit(int code)
trace_gdbstub_op_exiting((uint8_t)code);
snprintf(buf, sizeof(buf), "W%02x", (uint8_t)code);
gdb_put_packet(buf);
if (gdbserver_state.allow_stop_reply) {
snprintf(buf, sizeof(buf), "W%02x", (uint8_t)code);
gdb_put_packet(buf);
gdbserver_state.allow_stop_reply = false;
}
qemu_chr_fe_deinit(&gdbserver_system_state.chr, true);
}