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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
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24
gdbstub/user.c
View file

@ -108,8 +108,11 @@ 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;
}
}
int gdb_handlesig(CPUState *cpu, int sig)
@ -127,11 +130,14 @@ int gdb_handlesig(CPUState *cpu, int sig)
if (sig != 0) {
gdb_set_stop_cpu(cpu);
g_string_printf(gdbserver_state.str_buf,
"T%02xthread:", gdb_target_signal_to_gdb(sig));
gdb_append_thread_id(cpu, gdbserver_state.str_buf);
g_string_append_c(gdbserver_state.str_buf, ';');
gdb_put_strbuf();
if (gdbserver_state.allow_stop_reply) {
g_string_printf(gdbserver_state.str_buf,
"T%02xthread:", gdb_target_signal_to_gdb(sig));
gdb_append_thread_id(cpu, gdbserver_state.str_buf);
g_string_append_c(gdbserver_state.str_buf, ';');
gdb_put_strbuf();
gdbserver_state.allow_stop_reply = false;
}
}
/*
* gdb_put_packet() might have detected that the peer terminated the
@ -174,12 +180,14 @@ void gdb_signalled(CPUArchState *env, int sig)
{
char buf[4];
if (!gdbserver_state.init || gdbserver_user_state.fd < 0) {
if (!gdbserver_state.init || gdbserver_user_state.fd < 0 ||
!gdbserver_state.allow_stop_reply) {
return;
}
snprintf(buf, sizeof(buf), "X%02x", gdb_target_signal_to_gdb(sig));
gdb_put_packet(buf);
gdbserver_state.allow_stop_reply = false;
}
static void gdb_accept_init(int fd)