#449 GDB Server Should Return an Empty Response for Undefined GDB Packets

[patryk sondej]

Hi.
Not all undefined GDB packets return an empty response.
This is issue when debugging using LLDB. Since the openocd does not immediately return an empty response, each nexti command becomes very slow due to LLDB waiting for a receive timeout.

Eg:

(gdb) maintenance packet jThreadsInfo
sending: jThreadsInfo
Ignoring packet error, continuing...
error while fetching packet from remote target

(gdb) maintenance packet xxx
sending: xxx
received: ""

(gdb) maintenance packet jxxx
sending: jxxx
Ignoring packet error, continuing...
error while fetching packet from remote target

I found out, a lot of gdb packets in openocd has missing else with empty response.

[patryk sondej]

int gdb_read_smp_packet(struct connection *connection,
        char const *packet, int packet_size)
{
    struct target *target = get_target_from_connection(connection);
    int retval = ERROR_OK;

    LOG_WARNING(DEPRECATED_MSG);

    if (target->smp) {
        if (strncmp(packet, "jc", 2) == 0) {
            const uint32_t len = sizeof(target->gdb_service->core[0]);
            char hex_buffer[len * 2 + 1];
            uint8_t buffer[len];
            buf_set_u32(buffer, 0, len * 8, target->gdb_service->core[0]);
            size_t pkt_len = hexify(hex_buffer, buffer, sizeof(buffer),
                sizeof(hex_buffer));

            retval = gdb_put_packet(connection, hex_buffer, pkt_len);
        }
        // BUG: <-- MISSING ELSE HERE
    } else
        retval = gdb_put_packet(connection, "E01", 3);
    return retval;
}

should have else with:

gdb_put_packet(connection, "", 0);

[Tomas Vanek]

Thanks for the report.
Could you please submit a patch to https://review.openocd.org ?
You may find details in https://openocd.org/doc/doxygen/html/patchguide.html