When starting a remote connection GDB sends an '+':

  /* Ack any packet which the remote side has already sent.  */
  remote_serial_write ("+", 1);

which gets flagged as a garbage character in the gdbstub state
machine. As gdb does send it out lets be permissive about the handling
so we can better see real issues.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: gdb-patches@sourceware.org
---
 gdbstub/gdbstub.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
index 20b6fe03fb..5f28d5cf57 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -2074,6 +2074,11 @@ void gdb_read_byte(uint8_t ch)
                 gdbserver_state.line_buf_index = 0;
                 gdbserver_state.line_sum = 0;
                 gdbserver_state.state = RS_GETLINE;
+            } else if (ch == '+') {
+                /*
+                 * do nothing, gdb may preemptively send out ACKs on
+                 * initial connection
+                 */
             } else {
                 trace_gdbstub_err_garbage(ch);
             }
-- 
2.39.2

On 10/8/23 17:36, Alex Bennée wrote:
> When starting a remote connection GDB sends an '+':
> 
>    /* Ack any packet which the remote side has already sent.  */
>    remote_serial_write ("+", 1);
> 
> which gets flagged as a garbage character in the gdbstub state
> machine. As gdb does send it out lets be permissive about the handling
> so we can better see real issues.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Cc: gdb-patches@sourceware.org
> ---
>   gdbstub/gdbstub.c | 5 +++++
>   1 file changed, 5 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>