openocd: fix SPDX tag format for files .c
[fw/openocd] / src / server / gdb_server.c
index 857cffd9c428b12d3326e40e7b1fd5a40bc93955..d8dbc2c8b75df536e7d63396d8b7507ab332962a 100644 (file)
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 /***************************************************************************
  *   Copyright (C) 2005 by Dominic Rath                                    *
  *   Dominic.Rath@gmx.de                                                   *
  *                                                                         *
  *   Copyright (C) 2013 Franck Jullien                                     *
  *   elec4fun@gmail.com                                                    *
- *                                                                         *
- *   This program is free software; you can redistribute it and/or modify  *
- *   it under the terms of the GNU General Public License as published by  *
- *   the Free Software Foundation; either version 2 of the License, or     *
- *   (at your option) any later version.                                   *
- *                                                                         *
- *   This program is distributed in the hope that it will be useful,       *
- *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
- *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
- *   GNU General Public License for more details.                          *
- *                                                                         *
- *   You should have received a copy of the GNU General Public License     *
- *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  ***************************************************************************/
 
 #ifdef HAVE_CONFIG_H
  * found in most modern embedded processors.
  */
 
+enum gdb_output_flag {
+       /* GDB doesn't accept 'O' packets */
+       GDB_OUTPUT_NO,
+       /* GDB accepts 'O' packets */
+       GDB_OUTPUT_ALL,
+};
+
 struct target_desc_format {
        char *tdesc;
        uint32_t tdesc_length;
@@ -68,7 +64,7 @@ struct target_desc_format {
 
 /* private connection data for GDB */
 struct gdb_connection {
-       char buffer[GDB_BUFFER_SIZE + 1]; /* Extra byte for nul-termination */
+       char buffer[GDB_BUFFER_SIZE + 1]; /* Extra byte for null-termination */
        char *buf_p;
        int buf_cnt;
        bool ctrl_c;
@@ -97,6 +93,8 @@ struct gdb_connection {
        struct target_desc_format target_desc;
        /* temporarily used for thread list support */
        char *thread_list;
+       /* flag to mask the output from gdb_log_callback() */
+       enum gdb_output_flag output_flag;
 };
 
 #if 0
@@ -177,7 +175,7 @@ static int check_pending(struct connection *connection,
        fd_set read_fds;
        struct gdb_connection *gdb_con = connection->priv;
        int t;
-       if (got_data == NULL)
+       if (!got_data)
                got_data = &t;
        *got_data = 0;
 
@@ -227,6 +225,7 @@ static int gdb_get_char_inner(struct connection *connection, int *next_char)
                if (gdb_con->buf_cnt > 0)
                        break;
                if (gdb_con->buf_cnt == 0) {
+                       LOG_DEBUG("GDB connection closed by the remote client");
                        gdb_con->closed = true;
                        return ERROR_SERVER_REMOTE_CLOSED;
                }
@@ -277,9 +276,9 @@ static int gdb_get_char_inner(struct connection *connection, int *next_char)
        gdb_con->buf_cnt--;
        *next_char = *(gdb_con->buf_p++);
        if (gdb_con->buf_cnt > 0)
-               connection->input_pending = 1;
+               connection->input_pending = true;
        else
-               connection->input_pending = 0;
+               connection->input_pending = false;
 #ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
 #endif
@@ -302,9 +301,9 @@ static inline int gdb_get_char_fast(struct connection *connection,
                *next_char = **buf_p;
                (*buf_p)++;
                if (*buf_cnt > 0)
-                       connection->input_pending = 1;
+                       connection->input_pending = true;
                else
-                       connection->input_pending = 0;
+                       connection->input_pending = false;
 
 #ifdef _DEBUG_GDB_IO_
                LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
@@ -348,23 +347,71 @@ static int gdb_putback_char(struct connection *connection, int last_char)
 static int gdb_write(struct connection *connection, void *data, int len)
 {
        struct gdb_connection *gdb_con = connection->priv;
-       if (gdb_con->closed)
+       if (gdb_con->closed) {
+               LOG_DEBUG("GDB socket marked as closed, cannot write to it.");
                return ERROR_SERVER_REMOTE_CLOSED;
+       }
 
        if (connection_write(connection, data, len) == len)
                return ERROR_OK;
+
+       LOG_WARNING("Error writing to GDB socket. Dropping the connection.");
        gdb_con->closed = true;
        return ERROR_SERVER_REMOTE_CLOSED;
 }
 
+static void gdb_log_incoming_packet(struct connection *connection, char *packet)
+{
+       if (!LOG_LEVEL_IS(LOG_LVL_DEBUG))
+               return;
+
+       struct target *target = get_target_from_connection(connection);
+
+       /* Avoid dumping non-printable characters to the terminal */
+       const unsigned packet_len = strlen(packet);
+       const char *nonprint = find_nonprint_char(packet, packet_len);
+       if (nonprint) {
+               /* Does packet at least have a prefix that is printable?
+                * Look within the first 50 chars of the packet. */
+               const char *colon = memchr(packet, ':', MIN(50, packet_len));
+               const bool packet_has_prefix = (colon);
+               const bool packet_prefix_printable = (packet_has_prefix && nonprint > colon);
+
+               if (packet_prefix_printable) {
+                       const unsigned int prefix_len = colon - packet + 1;  /* + 1 to include the ':' */
+                       const unsigned int payload_len = packet_len - prefix_len;
+                       LOG_TARGET_DEBUG(target, "received packet: %.*s<binary-data-%u-bytes>", prefix_len,
+                               packet, payload_len);
+               } else {
+                       LOG_TARGET_DEBUG(target, "received packet: <binary-data-%u-bytes>", packet_len);
+               }
+       } else {
+               /* All chars printable, dump the packet as is */
+               LOG_TARGET_DEBUG(target, "received packet: %s", packet);
+       }
+}
+
+static void gdb_log_outgoing_packet(struct connection *connection, char *packet_buf,
+       unsigned int packet_len, unsigned char checksum)
+{
+       if (!LOG_LEVEL_IS(LOG_LVL_DEBUG))
+               return;
+
+       struct target *target = get_target_from_connection(connection);
+
+       if (find_nonprint_char(packet_buf, packet_len))
+               LOG_TARGET_DEBUG(target, "sending packet: $<binary-data-%u-bytes>#%2.2x",
+                       packet_len, checksum);
+       else
+               LOG_TARGET_DEBUG(target, "sending packet: $%.*s#%2.2x", packet_len, packet_buf,
+                       checksum);
+}
+
 static int gdb_put_packet_inner(struct connection *connection,
                char *buffer, int len)
 {
        int i;
        unsigned char my_checksum = 0;
-#ifdef _DEBUG_GDB_IO_
-       char *debug_buffer;
-#endif
        int reply;
        int retval;
        struct gdb_connection *gdb_con = connection->priv;
@@ -400,11 +447,7 @@ static int gdb_put_packet_inner(struct connection *connection,
 #endif
 
        while (1) {
-#ifdef _DEBUG_GDB_IO_
-               debug_buffer = strndup(buffer, len);
-               LOG_DEBUG("sending packet '$%s#%2.2x'", debug_buffer, my_checksum);
-               free(debug_buffer);
-#endif
+               gdb_log_outgoing_packet(connection, buffer, len, my_checksum);
 
                char local_buffer[1024];
                local_buffer[0] = '$';
@@ -437,22 +480,27 @@ static int gdb_put_packet_inner(struct connection *connection,
                if (retval != ERROR_OK)
                        return retval;
 
-               if (reply == '+')
+               if (reply == '+') {
+                       gdb_log_incoming_packet(connection, "+");
                        break;
-               else if (reply == '-') {
+               else if (reply == '-') {
                        /* Stop sending output packets for now */
-                       log_remove_callback(gdb_log_callback, connection);
+                       gdb_con->output_flag = GDB_OUTPUT_NO;
+                       gdb_log_incoming_packet(connection, "-");
                        LOG_WARNING("negative reply, retrying");
                } else if (reply == 0x3) {
                        gdb_con->ctrl_c = true;
+                       gdb_log_incoming_packet(connection, "<Ctrl-C>");
                        retval = gdb_get_char(connection, &reply);
                        if (retval != ERROR_OK)
                                return retval;
-                       if (reply == '+')
+                       if (reply == '+') {
+                               gdb_log_incoming_packet(connection, "+");
                                break;
-                       else if (reply == '-') {
+                       else if (reply == '-') {
                                /* Stop sending output packets for now */
-                               log_remove_callback(gdb_log_callback, connection);
+                               gdb_con->output_flag = GDB_OUTPUT_NO;
+                               gdb_log_incoming_packet(connection, "-");
                                LOG_WARNING("negative reply, retrying");
                        } else if (reply == '$') {
                                LOG_ERROR("GDB missing ack(1) - assumed good");
@@ -629,6 +677,7 @@ static int gdb_get_packet_inner(struct connection *connection,
                                case '$':
                                        break;
                                case '+':
+                                       gdb_log_incoming_packet(connection, "+");
                                        /* According to the GDB documentation
                                         * (https://sourceware.org/gdb/onlinedocs/gdb/Packet-Acknowledgment.html):
                                         * "gdb sends a final `+` acknowledgment of the stub's `OK`
@@ -646,9 +695,11 @@ static int gdb_get_packet_inner(struct connection *connection,
                                        }
                                        break;
                                case '-':
+                                       gdb_log_incoming_packet(connection, "-");
                                        LOG_WARNING("negative acknowledgment, but no packet pending");
                                        break;
                                case 0x3:
+                                       gdb_log_incoming_packet(connection, "<Ctrl-C>");
                                        gdb_con->ctrl_c = true;
                                        *len = 0;
                                        return ERROR_OK;
@@ -705,7 +756,7 @@ static int gdb_output_con(struct connection *connection, const char *line)
        bin_size = strlen(line);
 
        hex_buffer = malloc(bin_size * 2 + 2);
-       if (hex_buffer == NULL)
+       if (!hex_buffer)
                return ERROR_GDB_BUFFER_TOO_SMALL;
 
        hex_buffer[0] = 'O';
@@ -728,7 +779,7 @@ static void gdb_signal_reply(struct target *target, struct connection *connectio
 {
        struct gdb_connection *gdb_connection = connection->priv;
        char sig_reply[65];
-       char stop_reason[20];
+       char stop_reason[32];
        char current_thread[25];
        int sig_reply_len;
        int signal_var;
@@ -739,7 +790,7 @@ static void gdb_signal_reply(struct target *target, struct connection *connectio
                sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "W00");
        } else {
                struct target *ct;
-               if (target->rtos != NULL) {
+               if (target->rtos) {
                        target->rtos->current_threadid = target->rtos->current_thread;
                        target->rtos->gdb_target_for_threadid(connection, target->rtos->current_threadid, &ct);
                } else {
@@ -778,7 +829,7 @@ static void gdb_signal_reply(struct target *target, struct connection *connectio
                }
 
                current_thread[0] = '\0';
-               if (target->rtos != NULL)
+               if (target->rtos)
                        snprintf(current_thread, sizeof(current_thread), "thread:%" PRIx64 ";",
                                        target->rtos->current_thread);
 
@@ -895,7 +946,7 @@ static void gdb_frontend_halted(struct target *target, struct connection *connec
         */
        if (gdb_connection->frontend_state == TARGET_RUNNING) {
                /* stop forwarding log packets! */
-               log_remove_callback(gdb_log_callback, connection);
+               gdb_connection->output_flag = GDB_OUTPUT_NO;
 
                /* check fileio first */
                if (target_get_gdb_fileio_info(target, target->fileio_info) == ERROR_OK)
@@ -955,6 +1006,7 @@ static int gdb_new_connection(struct connection *connection)
        gdb_connection->target_desc.tdesc = NULL;
        gdb_connection->target_desc.tdesc_length = 0;
        gdb_connection->thread_list = NULL;
+       gdb_connection->output_flag = GDB_OUTPUT_NO;
 
        /* send ACK to GDB for debug request */
        gdb_write(connection, "+", 1);
@@ -969,6 +1021,21 @@ static int gdb_new_connection(struct connection *connection)
        breakpoint_clear_target(target);
        watchpoint_clear_target(target);
 
+       /* Since version 3.95 (gdb-19990504), with the exclusion of 6.5~6.8, GDB
+        * sends an ACK at connection with the following comment in its source code:
+        * "Ack any packet which the remote side has already sent."
+        * LLDB does the same since the first gdb-remote implementation.
+        * Remove the initial ACK from the incoming buffer.
+        */
+       retval = gdb_get_char(connection, &initial_ack);
+       if (retval != ERROR_OK)
+               return retval;
+
+       if (initial_ack != '+')
+               gdb_putback_char(connection, initial_ack);
+
+       target_call_event_callbacks(target, TARGET_EVENT_GDB_ATTACH);
+
        if (target->rtos) {
                /* clean previous rtos session if supported*/
                if (target->rtos->type->clean)
@@ -978,33 +1045,20 @@ static int gdb_new_connection(struct connection *connection)
                rtos_update_threads(target);
        }
 
-       /* remove the initial ACK from the incoming buffer */
-       retval = gdb_get_char(connection, &initial_ack);
-       if (retval != ERROR_OK)
-               return retval;
-
-       /* FIX!!!??? would we actually ever receive a + here???
-        * Not observed.
-        */
-       if (initial_ack != '+')
-               gdb_putback_char(connection, initial_ack);
-       target_call_event_callbacks(target, TARGET_EVENT_GDB_ATTACH);
-
        if (gdb_use_memory_map) {
                /* Connect must fail if the memory map can't be set up correctly.
                 *
                 * This will cause an auto_probe to be invoked, which is either
                 * a no-op or it will fail when the target isn't ready(e.g. not halted).
                 */
-               int i;
-               for (i = 0; i < flash_get_bank_count(); i++) {
+               for (unsigned int i = 0; i < flash_get_bank_count(); i++) {
                        struct flash_bank *p;
                        p = get_flash_bank_by_num_noprobe(i);
                        if (p->target != target)
                                continue;
                        retval = get_flash_bank_by_num(i, &p);
                        if (retval != ERROR_OK) {
-                               LOG_ERROR("Connect failed. Consider setting up a gdb-attach event for the target " \
+                               LOG_ERROR("Connect failed. Consider setting up a gdb-attach event for the target "
                                                "to prepare target for GDB connect, or use 'gdb_memory_map disable'.");
                                return retval;
                        }
@@ -1012,13 +1066,24 @@ static int gdb_new_connection(struct connection *connection)
        }
 
        gdb_actual_connections++;
-       log_printf_lf(all_targets->next != NULL ? LOG_LVL_INFO : LOG_LVL_DEBUG,
+       log_printf_lf(all_targets->next ? LOG_LVL_INFO : LOG_LVL_DEBUG,
                        __FILE__, __LINE__, __func__,
                        "New GDB Connection: %d, Target %s, state: %s",
                        gdb_actual_connections,
                        target_name(target),
                        target_state_name(target));
 
+       if (!target_was_examined(target)) {
+               LOG_ERROR("Target %s not examined yet, refuse gdb connection %d!",
+                                 target_name(target), gdb_actual_connections);
+               gdb_actual_connections--;
+               return ERROR_TARGET_NOT_EXAMINED;
+       }
+
+       if (target->state != TARGET_HALTED)
+               LOG_WARNING("GDB connection %d on target %s not halted",
+                                       gdb_actual_connections, target_name(target));
+
        /* DANGER! If we fail subsequently, we must remove this handler,
         * otherwise we occasionally see crashes as the timer can invoke the
         * callback fn.
@@ -1026,6 +1091,8 @@ static int gdb_new_connection(struct connection *connection)
         * register callback to be informed about target events */
        target_register_event_callback(gdb_target_callback_event_handler, connection);
 
+       log_add_callback(gdb_log_callback, connection);
+
        return ERROR_OK;
 }
 
@@ -1057,11 +1124,8 @@ static int gdb_connection_closed(struct connection *connection)
        /* if this connection registered a debug-message receiver delete it */
        delete_debug_msg_receiver(connection->cmd_ctx, target);
 
-       if (connection->priv) {
-               free(connection->priv);
-               connection->priv = NULL;
-       } else
-               LOG_ERROR("BUG: connection->priv == NULL");
+       free(connection->priv);
+       connection->priv = NULL;
 
        target_unregister_event_callback(gdb_target_callback_event_handler, connection);
 
@@ -1173,7 +1237,7 @@ static int gdb_get_registers_packet(struct connection *connection,
        LOG_DEBUG("-");
 #endif
 
-       if ((target->rtos != NULL) && (ERROR_OK == rtos_get_gdb_reg_list(connection)))
+       if ((target->rtos) && (rtos_get_gdb_reg_list(connection) == ERROR_OK))
                return ERROR_OK;
 
        retval = target_get_gdb_reg_list(target, &reg_list, &reg_list_size,
@@ -1182,7 +1246,7 @@ static int gdb_get_registers_packet(struct connection *connection,
                return gdb_error(connection, retval);
 
        for (i = 0; i < reg_list_size; i++) {
-               if (reg_list[i] == NULL || reg_list[i]->exist == false)
+               if (!reg_list[i] || reg_list[i]->exist == false || reg_list[i]->hidden)
                        continue;
                reg_packet_size += DIV_ROUND_UP(reg_list[i]->size, 8) * 2;
        }
@@ -1190,13 +1254,13 @@ static int gdb_get_registers_packet(struct connection *connection,
        assert(reg_packet_size > 0);
 
        reg_packet = malloc(reg_packet_size + 1); /* plus one for string termination null */
-       if (reg_packet == NULL)
+       if (!reg_packet)
                return ERROR_FAIL;
 
        reg_packet_p = reg_packet;
 
        for (i = 0; i < reg_list_size; i++) {
-               if (reg_list[i] == NULL || reg_list[i]->exist == false)
+               if (!reg_list[i] || reg_list[i]->exist == false || reg_list[i]->hidden)
                        continue;
                if (!reg_list[i]->valid) {
                        retval = reg_list[i]->type->get(reg_list[i]);
@@ -1259,6 +1323,8 @@ static int gdb_set_registers_packet(struct connection *connection,
        packet_p = packet;
        for (i = 0; i < reg_list_size; i++) {
                uint8_t *bin_buf;
+               if (!reg_list[i] || !reg_list[i]->exist || reg_list[i]->hidden)
+                       continue;
                int chars = (DIV_ROUND_UP(reg_list[i]->size, 8) * 2);
 
                if (packet_p + chars > packet + packet_size)
@@ -1303,7 +1369,7 @@ static int gdb_get_register_packet(struct connection *connection,
        LOG_DEBUG("-");
 #endif
 
-       if ((target->rtos != NULL) && (ERROR_OK == rtos_get_gdb_reg(connection, reg_num)))
+       if ((target->rtos) && (rtos_get_gdb_reg(connection, reg_num) == ERROR_OK))
                return ERROR_OK;
 
        retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
@@ -1311,8 +1377,9 @@ static int gdb_get_register_packet(struct connection *connection,
        if (retval != ERROR_OK)
                return gdb_error(connection, retval);
 
-       if (reg_list_size <= reg_num) {
-               LOG_ERROR("gdb requested a non-existing register");
+       if ((reg_list_size <= reg_num) || !reg_list[reg_num] ||
+               !reg_list[reg_num]->exist || reg_list[reg_num]->hidden) {
+               LOG_ERROR("gdb requested a non-existing register (reg_num=%d)", reg_num);
                return ERROR_SERVER_REMOTE_CLOSED;
        }
 
@@ -1325,7 +1392,7 @@ static int gdb_get_register_packet(struct connection *connection,
                }
        }
 
-       reg_packet = malloc(DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2 + 1); /* plus one for string termination null */
+       reg_packet = calloc(DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2 + 1, 1); /* plus one for string termination null */
 
        gdb_str_to_target(target, reg_packet, reg_list[reg_num]);
 
@@ -1359,8 +1426,8 @@ static int gdb_set_register_packet(struct connection *connection,
        uint8_t *bin_buf = malloc(chars / 2);
        gdb_target_to_reg(target, separator + 1, chars, bin_buf);
 
-       if ((target->rtos != NULL) &&
-                       (ERROR_OK == rtos_set_reg(connection, reg_num, bin_buf))) {
+       if ((target->rtos) &&
+                       (rtos_set_reg(connection, reg_num, bin_buf) == ERROR_OK)) {
                free(bin_buf);
                gdb_put_packet(connection, "OK", 2);
                return ERROR_OK;
@@ -1373,16 +1440,17 @@ static int gdb_set_register_packet(struct connection *connection,
                return gdb_error(connection, retval);
        }
 
-       if (reg_list_size <= reg_num) {
-               LOG_ERROR("gdb requested a non-existing register");
+       if ((reg_list_size <= reg_num) || !reg_list[reg_num] ||
+               !reg_list[reg_num]->exist || reg_list[reg_num]->hidden) {
+               LOG_ERROR("gdb requested a non-existing register (reg_num=%d)", reg_num);
                free(bin_buf);
                free(reg_list);
                return ERROR_SERVER_REMOTE_CLOSED;
        }
 
        if (chars != (DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2)) {
-               LOG_ERROR("gdb sent %d bits for a %d-bit register (%s)",
-                               (int) chars * 4, reg_list[reg_num]->size, reg_list[reg_num]->name);
+               LOG_ERROR("gdb sent %zu bits for a %" PRIu32 "-bit register (%s)",
+                               chars * 4, reg_list[reg_num]->size, reg_list[reg_num]->name);
                free(bin_buf);
                free(reg_list);
                return ERROR_SERVER_REMOTE_CLOSED;
@@ -1455,7 +1523,11 @@ static int gdb_read_memory_packet(struct connection *connection,
 
        LOG_DEBUG("addr: 0x%16.16" PRIx64 ", len: 0x%8.8" PRIx32 "", addr, len);
 
-       retval = target_read_buffer(target, addr, len, buffer);
+       retval = ERROR_NOT_IMPLEMENTED;
+       if (target->rtos)
+               retval = rtos_read_buffer(target, addr, len, buffer);
+       if (retval == ERROR_NOT_IMPLEMENTED)
+               retval = target_read_buffer(target, addr, len, buffer);
 
        if ((retval != ERROR_OK) && !gdb_report_data_abort) {
                /* TODO : Here we have to lie and send back all zero's lest stack traces won't work.
@@ -1526,7 +1598,11 @@ static int gdb_write_memory_packet(struct connection *connection,
        if (unhexify(buffer, separator, len) != len)
                LOG_ERROR("unable to decode memory packet");
 
-       retval = target_write_buffer(target, addr, len, buffer);
+       retval = ERROR_NOT_IMPLEMENTED;
+       if (target->rtos)
+               retval = rtos_write_buffer(target, addr, len, buffer);
+       if (retval == ERROR_NOT_IMPLEMENTED)
+               retval = target_write_buffer(target, addr, len, buffer);
 
        if (retval == ERROR_OK)
                gdb_put_packet(connection, "OK", 2);
@@ -1595,7 +1671,12 @@ static int gdb_write_memory_binary_packet(struct connection *connection,
        if (len) {
                LOG_DEBUG("addr: 0x%" PRIx64 ", len: 0x%8.8" PRIx32 "", addr, len);
 
-               retval = target_write_buffer(target, addr, len, (uint8_t *)separator);
+               retval = ERROR_NOT_IMPLEMENTED;
+               if (target->rtos)
+                       retval = rtos_write_buffer(target, addr, len, (uint8_t *)separator);
+               if (retval == ERROR_NOT_IMPLEMENTED)
+                       retval = target_write_buffer(target, addr, len, (uint8_t *)separator);
+
                if (retval != ERROR_OK)
                        gdb_connection->mem_write_error = true;
        }
@@ -1693,7 +1774,10 @@ static int gdb_breakpoint_watchpoint_packet(struct connection *connection,
                case 1:
                        if (packet[0] == 'Z') {
                                retval = breakpoint_add(target, address, size, bp_type);
-                               if (retval != ERROR_OK) {
+                               if (retval == ERROR_NOT_IMPLEMENTED) {
+                                       /* Send empty reply to report that breakpoints of this type are not supported */
+                                       gdb_put_packet(connection, "", 0);
+                               } else if (retval != ERROR_OK) {
                                        retval = gdb_error(connection, retval);
                                        if (retval != ERROR_OK)
                                                return retval;
@@ -1710,7 +1794,10 @@ static int gdb_breakpoint_watchpoint_packet(struct connection *connection,
                {
                        if (packet[0] == 'Z') {
                                retval = watchpoint_add(target, address, size, wp_type, 0, 0xffffffffu);
-                               if (retval != ERROR_OK) {
+                               if (retval == ERROR_NOT_IMPLEMENTED) {
+                                       /* Send empty reply to report that watchpoints of this type are not supported */
+                                       gdb_put_packet(connection, "", 0);
+                               } else if (retval != ERROR_OK) {
                                        retval = gdb_error(connection, retval);
                                        if (retval != ERROR_OK)
                                                return retval;
@@ -1740,16 +1827,15 @@ static __attribute__ ((format (PRINTF_ATTRIBUTE_FORMAT, 5, 6))) void xml_printf(
        int first = 1;
 
        for (;; ) {
-               if ((*xml == NULL) || (!first)) {
+               if ((!*xml) || (!first)) {
                        /* start by 0 to exercise all the code paths.
                         * Need minimum 2 bytes to fit 1 char and 0 terminator. */
 
                        *size = *size * 2 + 2;
                        char *t = *xml;
                        *xml = realloc(*xml, *size);
-                       if (*xml == NULL) {
-                               if (t)
-                                       free(t);
+                       if (!*xml) {
+                               free(t);
                                *retval = ERROR_SERVER_REMOTE_CLOSED;
                                return;
                        }
@@ -1773,7 +1859,7 @@ static int decode_xfer_read(char const *buf, char **annex, int *ofs, unsigned in
 {
        /* Locate the annex. */
        const char *annex_end = strchr(buf, ':');
-       if (annex_end == NULL)
+       if (!annex_end)
                return ERROR_FAIL;
 
        /* After the read marker and annex, qXfer looks like a
@@ -1787,9 +1873,9 @@ static int decode_xfer_read(char const *buf, char **annex, int *ofs, unsigned in
        *len = strtoul(separator + 1, NULL, 16);
 
        /* Extract the annex if needed */
-       if (annex != NULL) {
+       if (annex) {
                *annex = strndup(buf, annex_end - buf);
-               if (*annex == NULL)
+               if (!*annex)
                        return ERROR_FAIL;
        }
 
@@ -1831,8 +1917,7 @@ static int gdb_memory_map(struct connection *connection,
        int length;
        char *separator;
        target_addr_t ram_start = 0;
-       int i;
-       int target_flash_banks = 0;
+       unsigned int target_flash_banks = 0;
 
        /* skip command character */
        packet += 23;
@@ -1848,7 +1933,7 @@ static int gdb_memory_map(struct connection *connection,
         */
        banks = malloc(sizeof(struct flash_bank *)*flash_get_bank_count());
 
-       for (i = 0; i < flash_get_bank_count(); i++) {
+       for (unsigned int i = 0; i < flash_get_bank_count(); i++) {
                p = get_flash_bank_by_num_noprobe(i);
                if (p->target != target)
                        continue;
@@ -1864,8 +1949,7 @@ static int gdb_memory_map(struct connection *connection,
        qsort(banks, target_flash_banks, sizeof(struct flash_bank *),
                compare_bank);
 
-       for (i = 0; i < target_flash_banks; i++) {
-               int j;
+       for (unsigned int i = 0; i < target_flash_banks; i++) {
                unsigned sector_size = 0;
                unsigned group_len = 0;
 
@@ -1883,7 +1967,7 @@ static int gdb_memory_map(struct connection *connection,
                 * smaller ones at the end (maybe 32KB).  STR7 will have
                 * regions with 8KB, 32KB, and 64KB sectors; etc.
                 */
-               for (j = 0; j < p->num_sectors; j++) {
+               for (unsigned int j = 0; j < p->num_sectors; j++) {
 
                        /* Maybe start a new group of sectors. */
                        if (sector_size == 0) {
@@ -2010,7 +2094,7 @@ static int lookup_add_arch_defined_types(char const **arch_defined_types_list[],
 {
        int tbl_sz = *num_arch_defined_types;
 
-       if (type_id != NULL && (strcmp(type_id, ""))) {
+       if (type_id && (strcmp(type_id, ""))) {
                for (int j = 0; j < (tbl_sz + 1); j++) {
                        if (!((*arch_defined_types_list)[j])) {
                                (*arch_defined_types_list)[tbl_sz++] = type_id;
@@ -2046,14 +2130,14 @@ static int gdb_generate_reg_type_description(struct target *target,
                }
                /* <vector id="id" type="type" count="count"/> */
                xml_printf(&retval, tdesc, pos, size,
-                               "<vector id=\"%s\" type=\"%s\" count=\"%d\"/>\n",
+                               "<vector id=\"%s\" type=\"%s\" count=\"%" PRIu32 "\"/>\n",
                                type->id, type->reg_type_vector->type->id,
                                type->reg_type_vector->count);
 
        } else if (type->type_class == REG_TYPE_CLASS_UNION) {
                struct reg_data_type_union_field *field;
                field = type->reg_type_union->fields;
-               while (field != NULL) {
+               while (field) {
                        struct reg_data_type *data_type = field->type;
                        if (data_type->type == REG_TYPE_ARCH_DEFINED) {
                                if (lookup_add_arch_defined_types(arch_defined_types_list, data_type->id,
@@ -2073,7 +2157,7 @@ static int gdb_generate_reg_type_description(struct target *target,
                                type->id);
 
                field = type->reg_type_union->fields;
-               while (field != NULL) {
+               while (field) {
                        xml_printf(&retval, tdesc, pos, size,
                                        "<field name=\"%s\" type=\"%s\"/>\n",
                                        field->name, field->type->id);
@@ -2093,18 +2177,18 @@ static int gdb_generate_reg_type_description(struct target *target,
                         *  <field name="name" start="start" end="end"/> ...
                         * </struct> */
                        xml_printf(&retval, tdesc, pos, size,
-                                       "<struct id=\"%s\" size=\"%d\">\n",
+                                       "<struct id=\"%s\" size=\"%" PRIu32 "\">\n",
                                        type->id, type->reg_type_struct->size);
-                       while (field != NULL) {
+                       while (field) {
                                xml_printf(&retval, tdesc, pos, size,
-                                               "<field name=\"%s\" start=\"%d\" end=\"%d\" type=\"%s\" />\n",
+                                               "<field name=\"%s\" start=\"%" PRIu32 "\" end=\"%" PRIu32 "\" type=\"%s\" />\n",
                                                field->name, field->bitfield->start, field->bitfield->end,
                                                gdb_get_reg_type_name(field->bitfield->type));
 
                                field = field->next;
                        }
                } else {
-                       while (field != NULL) {
+                       while (field) {
                                struct reg_data_type *data_type = field->type;
                                if (data_type->type == REG_TYPE_ARCH_DEFINED) {
                                        if (lookup_add_arch_defined_types(arch_defined_types_list, data_type->id,
@@ -2121,7 +2205,7 @@ static int gdb_generate_reg_type_description(struct target *target,
                        xml_printf(&retval, tdesc, pos, size,
                                        "<struct id=\"%s\">\n",
                                        type->id);
-                       while (field != NULL) {
+                       while (field) {
                                xml_printf(&retval, tdesc, pos, size,
                                                "<field name=\"%s\" type=\"%s\"/>\n",
                                                field->name, field->type->id);
@@ -2138,14 +2222,14 @@ static int gdb_generate_reg_type_description(struct target *target,
                 *  <field name="name" start="start" end="end"/> ...
                 * </flags> */
                xml_printf(&retval, tdesc, pos, size,
-                               "<flags id=\"%s\" size=\"%d\">\n",
+                               "<flags id=\"%s\" size=\"%" PRIu32 "\">\n",
                                type->id, type->reg_type_flags->size);
 
                struct reg_data_type_flags_field *field;
                field = type->reg_type_flags->fields;
-               while (field != NULL) {
+               while (field) {
                        xml_printf(&retval, tdesc, pos, size,
-                                       "<field name=\"%s\" start=\"%d\" end=\"%d\" type=\"%s\" />\n",
+                                       "<field name=\"%s\" start=\"%" PRIu32 "\" end=\"%" PRIu32 "\" type=\"%s\" />\n",
                                        field->name, field->bitfield->start, field->bitfield->end,
                                        gdb_get_reg_type_name(field->bitfield->type));
 
@@ -2172,11 +2256,11 @@ static int get_reg_features_list(struct target *target, char const **feature_lis
        *feature_list = calloc(1, sizeof(char *));
 
        for (int i = 0; i < reg_list_size; i++) {
-               if (reg_list[i]->exist == false)
+               if (reg_list[i]->exist == false || reg_list[i]->hidden)
                        continue;
 
-               if (reg_list[i]->feature != NULL
-                       && reg_list[i]->feature->name != NULL
+               if (reg_list[i]->feature
+                       && reg_list[i]->feature->name
                        && (strcmp(reg_list[i]->feature->name, ""))) {
                        /* We found a feature, check if the feature is already in the
                         * table. If not, allocate a new entry for the table and
@@ -2202,6 +2286,122 @@ static int get_reg_features_list(struct target *target, char const **feature_lis
        return ERROR_OK;
 }
 
+/* Create a register list that's the union of all the registers of the SMP
+ * group this target is in. If the target is not part of an SMP group, this
+ * returns the same as target_get_gdb_reg_list_noread().
+ */
+static int smp_reg_list_noread(struct target *target,
+               struct reg **combined_list[], int *combined_list_size,
+               enum target_register_class reg_class)
+{
+       if (!target->smp)
+               return target_get_gdb_reg_list_noread(target, combined_list,
+                               combined_list_size, REG_CLASS_ALL);
+
+       unsigned int combined_allocated = 256;
+       struct reg **local_list = malloc(combined_allocated * sizeof(struct reg *));
+       if (!local_list) {
+               LOG_ERROR("malloc(%zu) failed", combined_allocated * sizeof(struct reg *));
+               return ERROR_FAIL;
+       }
+       unsigned int local_list_size = 0;
+
+       struct target_list *head;
+       foreach_smp_target(head, target->smp_targets) {
+               if (!target_was_examined(head->target))
+                       continue;
+
+               struct reg **reg_list = NULL;
+               int reg_list_size;
+               int result = target_get_gdb_reg_list_noread(head->target, &reg_list,
+                               &reg_list_size, reg_class);
+               if (result != ERROR_OK) {
+                       free(local_list);
+                       return result;
+               }
+               for (int i = 0; i < reg_list_size; i++) {
+                       bool found = false;
+                       struct reg *a = reg_list[i];
+                       if (a->exist) {
+                               /* Nested loop makes this O(n^2), but this entire function with
+                                * 5 RISC-V targets takes just 2ms on my computer. Fast enough
+                                * for me. */
+                               for (unsigned int j = 0; j < local_list_size; j++) {
+                                       struct reg *b = local_list[j];
+                                       if (!strcmp(a->name, b->name)) {
+                                               found = true;
+                                               if (a->size != b->size) {
+                                                       LOG_ERROR("SMP register %s is %d bits on one "
+                                                                       "target, but %d bits on another target.",
+                                                                       a->name, a->size, b->size);
+                                                       free(reg_list);
+                                                       free(local_list);
+                                                       return ERROR_FAIL;
+                                               }
+                                               break;
+                                       }
+                               }
+                               if (!found) {
+                                       LOG_DEBUG("[%s] %s not found in combined list", target_name(target), a->name);
+                                       if (local_list_size >= combined_allocated) {
+                                               combined_allocated *= 2;
+                                               local_list = realloc(local_list, combined_allocated * sizeof(struct reg *));
+                                               if (!local_list) {
+                                                       LOG_ERROR("realloc(%zu) failed", combined_allocated * sizeof(struct reg *));
+                                                       return ERROR_FAIL;
+                                               }
+                                       }
+                                       local_list[local_list_size] = a;
+                                       local_list_size++;
+                               }
+                       }
+               }
+               free(reg_list);
+       }
+
+       if (local_list_size == 0) {
+               LOG_ERROR("Unable to get register list");
+               free(local_list);
+               return ERROR_FAIL;
+       }
+
+       /* Now warn the user about any registers that weren't found in every target. */
+       foreach_smp_target(head, target->smp_targets) {
+               if (!target_was_examined(head->target))
+                       continue;
+
+               struct reg **reg_list = NULL;
+               int reg_list_size;
+               int result = target_get_gdb_reg_list_noread(head->target, &reg_list,
+                               &reg_list_size, reg_class);
+               if (result != ERROR_OK) {
+                       free(local_list);
+                       return result;
+               }
+               for (unsigned int i = 0; i < local_list_size; i++) {
+                       bool found = false;
+                       struct reg *a = local_list[i];
+                       for (int j = 0; j < reg_list_size; j++) {
+                               struct reg *b = reg_list[j];
+                               if (b->exist && !strcmp(a->name, b->name)) {
+                                       found = true;
+                                       break;
+                               }
+                       }
+                       if (!found) {
+                               LOG_WARNING("Register %s does not exist in %s, which is part of an SMP group where "
+                                           "this register does exist.",
+                                           a->name, target_name(head->target));
+                       }
+               }
+               free(reg_list);
+       }
+
+       *combined_list = local_list;
+       *combined_list_size = local_list_size;
+       return ERROR_OK;
+}
+
 static int gdb_generate_target_description(struct target *target, char **tdesc_out)
 {
        int retval = ERROR_OK;
@@ -2215,8 +2415,8 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
        int size = 0;
 
 
-       retval = target_get_gdb_reg_list_noread(target, &reg_list,
-                       &reg_list_size, REG_CLASS_ALL);
+       retval = smp_reg_list_noread(target, &reg_list, &reg_list_size,
+                       REG_CLASS_ALL);
 
        if (retval != ERROR_OK) {
                LOG_ERROR("get register list failed");
@@ -2248,12 +2448,12 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
 
        /* generate architecture element if supported by target */
        architecture = target_get_gdb_arch(target);
-       if (architecture != NULL)
+       if (architecture)
                xml_printf(&retval, &tdesc, &pos, &size,
                                "<architecture>%s</architecture>\n", architecture);
 
        /* generate target description according to register list */
-       if (features != NULL) {
+       if (features) {
                while (features[current_feature]) {
                        char const **arch_defined_types = NULL;
                        int num_arch_defined_types = 0;
@@ -2266,14 +2466,14 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
                        int i;
                        for (i = 0; i < reg_list_size; i++) {
 
-                               if (reg_list[i]->exist == false)
+                               if (reg_list[i]->exist == false || reg_list[i]->hidden)
                                        continue;
 
                                if (strcmp(reg_list[i]->feature->name, features[current_feature]))
                                        continue;
 
                                const char *type_str;
-                               if (reg_list[i]->reg_data_type != NULL) {
+                               if (reg_list[i]->reg_data_type) {
                                        if (reg_list[i]->reg_data_type->type == REG_TYPE_ARCH_DEFINED) {
                                                /* generate <type... first, if there are architecture-defined types. */
                                                if (lookup_add_arch_defined_types(&arch_defined_types,
@@ -2298,9 +2498,9 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
                                xml_printf(&retval, &tdesc, &pos, &size,
                                                "<reg name=\"%s\"", reg_list[i]->name);
                                xml_printf(&retval, &tdesc, &pos, &size,
-                                               " bitsize=\"%d\"", reg_list[i]->size);
+                                               " bitsize=\"%" PRIu32 "\"", reg_list[i]->size);
                                xml_printf(&retval, &tdesc, &pos, &size,
-                                               " regnum=\"%d\"", reg_list[i]->number);
+                                               " regnum=\"%" PRIu32 "\"", reg_list[i]->number);
                                if (reg_list[i]->caller_save)
                                        xml_printf(&retval, &tdesc, &pos, &size,
                                                        " save-restore=\"yes\"");
@@ -2311,7 +2511,7 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
                                xml_printf(&retval, &tdesc, &pos, &size,
                                                " type=\"%s\"", type_str);
 
-                               if (reg_list[i]->group != NULL)
+                               if (reg_list[i]->group)
                                        xml_printf(&retval, &tdesc, &pos, &size,
                                                        " group=\"%s\"", reg_list[i]->group);
 
@@ -2345,7 +2545,7 @@ error:
 static int gdb_get_target_description_chunk(struct target *target, struct target_desc_format *target_desc,
                char **chunk, int32_t offset, uint32_t length)
 {
-       if (target_desc == NULL) {
+       if (!target_desc) {
                LOG_ERROR("Unable to Generate Target Description");
                return ERROR_FAIL;
        }
@@ -2353,7 +2553,7 @@ static int gdb_get_target_description_chunk(struct target *target, struct target
        char *tdesc = target_desc->tdesc;
        uint32_t tdesc_length = target_desc->tdesc_length;
 
-       if (tdesc == NULL) {
+       if (!tdesc) {
                int retval = gdb_generate_target_description(target, &tdesc);
                if (retval != ERROR_OK) {
                        LOG_ERROR("Unable to Generate Target Description");
@@ -2371,7 +2571,7 @@ static int gdb_get_target_description_chunk(struct target *target, struct target
                transfer_type = 'l';
 
        *chunk = malloc(length + 2);
-       if (*chunk == NULL) {
+       if (!*chunk) {
                LOG_ERROR("Unable to allocate memory");
                return ERROR_FAIL;
        }
@@ -2453,22 +2653,28 @@ static int gdb_generate_thread_list(struct target *target, char **thread_list_ou
                   "<?xml version=\"1.0\"?>\n"
                   "<threads>\n");
 
-       if (rtos != NULL) {
+       if (rtos) {
                for (int i = 0; i < rtos->thread_count; i++) {
                        struct thread_detail *thread_detail = &rtos->thread_details[i];
 
                        if (!thread_detail->exists)
                                continue;
 
-                       xml_printf(&retval, &thread_list, &pos, &size,
-                                  "<thread id=\"%" PRIx64 "\">", thread_detail->threadid);
+                       if (thread_detail->thread_name_str)
+                               xml_printf(&retval, &thread_list, &pos, &size,
+                                          "<thread id=\"%" PRIx64 "\" name=\"%s\">",
+                                          thread_detail->threadid,
+                                          thread_detail->thread_name_str);
+                       else
+                               xml_printf(&retval, &thread_list, &pos, &size,
+                                          "<thread id=\"%" PRIx64 "\">", thread_detail->threadid);
 
-                       if (thread_detail->thread_name_str != NULL)
+                       if (thread_detail->thread_name_str)
                                xml_printf(&retval, &thread_list, &pos, &size,
                                           "Name: %s", thread_detail->thread_name_str);
 
-                       if (thread_detail->extra_info_str != NULL) {
-                               if (thread_detail->thread_name_str != NULL)
+                       if (thread_detail->extra_info_str) {
+                               if (thread_detail->thread_name_str)
                                        xml_printf(&retval, &thread_list, &pos, &size,
                                                   ", ");
                                xml_printf(&retval, &thread_list, &pos, &size,
@@ -2494,7 +2700,7 @@ static int gdb_generate_thread_list(struct target *target, char **thread_list_ou
 static int gdb_get_thread_list_chunk(struct target *target, char **thread_list,
                char **chunk, int32_t offset, uint32_t length)
 {
-       if (*thread_list == NULL) {
+       if (!*thread_list) {
                int retval = gdb_generate_thread_list(target, thread_list);
                if (retval != ERROR_OK) {
                        LOG_ERROR("Unable to Generate Thread List");
@@ -2512,11 +2718,11 @@ static int gdb_get_thread_list_chunk(struct target *target, char **thread_list,
                transfer_type = 'l';
 
        *chunk = malloc(length + 2 + 3);
-    /* Allocating extra 3 bytes prevents false positive valgrind report
+       /* Allocating extra 3 bytes prevents false positive valgrind report
         * of strlen(chunk) word access:
         * Invalid read of size 4
         * Address 0x4479934 is 44 bytes inside a block of size 45 alloc'd */
-       if (*chunk == NULL) {
+       if (!*chunk) {
                LOG_ERROR("Unable to allocate memory");
                return ERROR_FAIL;
        }
@@ -2543,22 +2749,75 @@ static int gdb_query_packet(struct connection *connection,
 
        if (strncmp(packet, "qRcmd,", 6) == 0) {
                if (packet_size > 6) {
+                       Jim_Interp *interp = cmd_ctx->interp;
                        char *cmd;
                        cmd = malloc((packet_size - 6) / 2 + 1);
                        size_t len = unhexify((uint8_t *)cmd, packet + 6, (packet_size - 6) / 2);
                        cmd[len] = 0;
 
                        /* We want to print all debug output to GDB connection */
-                       log_add_callback(gdb_log_callback, connection);
+                       gdb_connection->output_flag = GDB_OUTPUT_ALL;
                        target_call_timer_callbacks_now();
                        /* some commands need to know the GDB connection, make note of current
                         * GDB connection. */
                        current_gdb_connection = gdb_connection;
-                       command_run_line(cmd_ctx, cmd);
+
+                       struct target *saved_target_override = cmd_ctx->current_target_override;
+                       cmd_ctx->current_target_override = NULL;
+
+                       struct command_context *old_context = Jim_GetAssocData(interp, "context");
+                       Jim_DeleteAssocData(interp, "context");
+                       int retval = Jim_SetAssocData(interp, "context", NULL, cmd_ctx);
+                       if (retval == JIM_OK) {
+                               retval = Jim_EvalObj(interp, Jim_NewStringObj(interp, cmd, -1));
+                               Jim_DeleteAssocData(interp, "context");
+                       }
+                       int inner_retval = Jim_SetAssocData(interp, "context", NULL, old_context);
+                       if (retval == JIM_OK)
+                               retval = inner_retval;
+
+                       cmd_ctx->current_target_override = saved_target_override;
+
                        current_gdb_connection = NULL;
                        target_call_timer_callbacks_now();
-                       log_remove_callback(gdb_log_callback, connection);
+                       gdb_connection->output_flag = GDB_OUTPUT_NO;
                        free(cmd);
+                       if (retval == JIM_RETURN)
+                               retval = interp->returnCode;
+                       int lenmsg;
+                       const char *cretmsg = Jim_GetString(Jim_GetResult(interp), &lenmsg);
+                       char *retmsg;
+                       if (lenmsg && cretmsg[lenmsg - 1] != '\n') {
+                               retmsg = alloc_printf("%s\n", cretmsg);
+                               lenmsg++;
+                       } else {
+                               retmsg = strdup(cretmsg);
+                       }
+                       if (!retmsg)
+                               return ERROR_GDB_BUFFER_TOO_SMALL;
+
+                       if (retval == JIM_OK) {
+                               if (lenmsg) {
+                                       char *hex_buffer = malloc(lenmsg * 2 + 1);
+                                       if (!hex_buffer) {
+                                               free(retmsg);
+                                               return ERROR_GDB_BUFFER_TOO_SMALL;
+                                       }
+
+                                       size_t pkt_len = hexify(hex_buffer, (const uint8_t *)retmsg, lenmsg,
+                                                                                       lenmsg * 2 + 1);
+                                       gdb_put_packet(connection, hex_buffer, pkt_len);
+                                       free(hex_buffer);
+                               } else {
+                                       gdb_put_packet(connection, "OK", 2);
+                               }
+                       } else {
+                               if (lenmsg)
+                                       gdb_output_con(connection, retmsg);
+                               gdb_send_error(connection, retval);
+                       }
+                       free(retmsg);
+                       return ERROR_OK;
                }
                gdb_put_packet(connection, "OK", 2);
                return ERROR_OK;
@@ -2706,6 +2965,11 @@ static int gdb_query_packet(struct connection *connection,
                gdb_connection->noack_mode = 1;
                gdb_put_packet(connection, "OK", 2);
                return ERROR_OK;
+       } else if (target->type->gdb_query_custom) {
+               char *buffer = NULL;
+               int ret = target->type->gdb_query_custom(target, packet, &buffer);
+               gdb_put_packet(connection, buffer, strlen(buffer));
+               return ret;
        }
 
        gdb_put_packet(connection, "", 0);
@@ -2721,7 +2985,7 @@ static bool gdb_handle_vcont_packet(struct connection *connection, const char *p
 
        /* query for vCont supported */
        if (parse[0] == '?') {
-               if (target->type->step != NULL) {
+               if (target->type->step) {
                        /* gdb doesn't accept c without C and s without S */
                        gdb_put_packet(connection, "vCont;c;C;s;S", 13);
                        return true;
@@ -2738,7 +3002,7 @@ static bool gdb_handle_vcont_packet(struct connection *connection, const char *p
        if (parse[0] == 'c') {
                gdb_running_type = 'c';
                LOG_DEBUG("target %s continue", target_name(target));
-               log_add_callback(gdb_log_callback, connection);
+               gdb_connection->output_flag = GDB_OUTPUT_ALL;
                retval = target_resume(target, 1, 0, 0, 0);
                if (retval == ERROR_TARGET_NOT_HALTED)
                        LOG_INFO("target %s was not halted when resume was requested", target_name(target));
@@ -2766,128 +3030,127 @@ static bool gdb_handle_vcont_packet(struct connection *connection, const char *p
                gdb_running_type = 's';
                bool fake_step = false;
 
-               if (strncmp(parse, "s:", 2) == 0) {
-                       struct target *ct = target;
-                       int current_pc = 1;
-                       int64_t thread_id;
+               struct target *ct = target;
+               int current_pc = 1;
+               int64_t thread_id;
+               parse++;
+               packet_size--;
+               if (parse[0] == ':') {
                        char *endp;
-
-                       parse += 2;
-                       packet_size -= 2;
-
+                       parse++;
+                       packet_size--;
                        thread_id = strtoll(parse, &endp, 16);
-                       if (endp != NULL) {
+                       if (endp) {
                                packet_size -= endp - parse;
                                parse = endp;
                        }
+               } else {
+                       thread_id = 0;
+               }
 
-                       if (target->rtos != NULL) {
-                               /* FIXME: why is this necessary? rtos state should be up-to-date here already! */
-                               rtos_update_threads(target);
+               if (target->rtos) {
+                       /* FIXME: why is this necessary? rtos state should be up-to-date here already! */
+                       rtos_update_threads(target);
 
-                               target->rtos->gdb_target_for_threadid(connection, thread_id, &ct);
+                       target->rtos->gdb_target_for_threadid(connection, thread_id, &ct);
 
-                               /*
-                                * check if the thread to be stepped is the current rtos thread
-                                * if not, we must fake the step
-                                */
-                               if (target->rtos->current_thread != thread_id)
-                                       fake_step = true;
-                       }
+                       /*
+                        * check if the thread to be stepped is the current rtos thread
+                        * if not, we must fake the step
+                        */
+                       if (target->rtos->current_thread != thread_id)
+                               fake_step = true;
+               }
 
-                       if (parse[0] == ';') {
-                               ++parse;
-                               --packet_size;
+               if (parse[0] == ';') {
+                       ++parse;
+                       --packet_size;
 
-                               if (parse[0] == 'c') {
+                       if (parse[0] == 'c') {
+                               parse += 1;
+
+                               /* check if thread-id follows */
+                               if (parse[0] == ':') {
+                                       int64_t tid;
                                        parse += 1;
 
-                                       /* check if thread-id follows */
-                                       if (parse[0] == ':') {
-                                               int64_t tid;
-                                               parse += 1;
-
-                                               tid = strtoll(parse, &endp, 16);
-                                               if (tid == thread_id) {
-                                                       /*
-                                                        * Special case: only step a single thread (core),
-                                                        * keep the other threads halted. Currently, only
-                                                        * aarch64 target understands it. Other target types don't
-                                                        * care (nobody checks the actual value of 'current')
-                                                        * and it doesn't really matter. This deserves
-                                                        * a symbolic constant and a formal interface documentation
-                                                        * at a later time.
-                                                        */
-                                                       LOG_DEBUG("request to step current core only");
-                                                       /* uncomment after checking that indeed other targets are safe */
-                                                       /*current_pc = 2;*/
-                                               }
+                                       tid = strtoll(parse, NULL, 16);
+                                       if (tid == thread_id) {
+                                               /*
+                                                * Special case: only step a single thread (core),
+                                                * keep the other threads halted. Currently, only
+                                                * aarch64 target understands it. Other target types don't
+                                                * care (nobody checks the actual value of 'current')
+                                                * and it doesn't really matter. This deserves
+                                                * a symbolic constant and a formal interface documentation
+                                                * at a later time.
+                                                */
+                                               LOG_DEBUG("request to step current core only");
+                                               /* uncomment after checking that indeed other targets are safe */
+                                               /*current_pc = 2;*/
                                        }
                                }
                        }
+               }
 
-                       LOG_DEBUG("target %s single-step thread %"PRIx64, target_name(ct), thread_id);
-                       log_add_callback(gdb_log_callback, connection);
-                       target_call_event_callbacks(ct, TARGET_EVENT_GDB_START);
-
-                       /*
-                        * work around an annoying gdb behaviour: when the current thread
-                        * is changed in gdb, it assumes that the target can follow and also
-                        * make the thread current. This is an assumption that cannot hold
-                        * for a real target running a multi-threading OS. We just fake
-                        * the step to not trigger an internal error in gdb. See
-                        * https://sourceware.org/bugzilla/show_bug.cgi?id=22925 for details
-                        */
-                       if (fake_step) {
-                               int sig_reply_len;
-                               char sig_reply[128];
-
-                               LOG_DEBUG("fake step thread %"PRIx64, thread_id);
+               LOG_DEBUG("target %s single-step thread %"PRIx64, target_name(ct), thread_id);
+               gdb_connection->output_flag = GDB_OUTPUT_ALL;
+               target_call_event_callbacks(ct, TARGET_EVENT_GDB_START);
 
-                               sig_reply_len = snprintf(sig_reply, sizeof(sig_reply),
-                                                                                "T05thread:%016"PRIx64";", thread_id);
+               /*
+                * work around an annoying gdb behaviour: when the current thread
+                * is changed in gdb, it assumes that the target can follow and also
+                * make the thread current. This is an assumption that cannot hold
+                * for a real target running a multi-threading OS. We just fake
+                * the step to not trigger an internal error in gdb. See
+                * https://sourceware.org/bugzilla/show_bug.cgi?id=22925 for details
+                */
+               if (fake_step) {
+                       int sig_reply_len;
+                       char sig_reply[128];
 
-                               gdb_put_packet(connection, sig_reply, sig_reply_len);
-                               log_remove_callback(gdb_log_callback, connection);
+                       LOG_DEBUG("fake step thread %"PRIx64, thread_id);
 
-                               return true;
-                       }
+                       sig_reply_len = snprintf(sig_reply, sizeof(sig_reply),
+                                                                       "T05thread:%016"PRIx64";", thread_id);
 
-                       /* support for gdb_sync command */
-                       if (gdb_connection->sync) {
-                               gdb_connection->sync = false;
-                               if (ct->state == TARGET_HALTED) {
-                                       LOG_DEBUG("stepi ignored. GDB will now fetch the register state " \
-                                                                       "from the target.");
-                                       gdb_sig_halted(connection);
-                                       log_remove_callback(gdb_log_callback, connection);
-                               } else
-                                       gdb_connection->frontend_state = TARGET_RUNNING;
-                               return true;
-                       }
+                       gdb_put_packet(connection, sig_reply, sig_reply_len);
+                       gdb_connection->output_flag = GDB_OUTPUT_NO;
 
-                       retval = target_step(ct, current_pc, 0, 0);
-                       if (retval == ERROR_TARGET_NOT_HALTED)
-                               LOG_INFO("target %s was not halted when step was requested", target_name(ct));
+                       return true;
+               }
 
-                       /* if step was successful send a reply back to gdb */
-                       if (retval == ERROR_OK) {
-                               retval = target_poll(ct);
-                               if (retval != ERROR_OK)
-                                       LOG_DEBUG("error polling target %s after successful step", target_name(ct));
-                               /* send back signal information */
-                               gdb_signal_reply(ct, connection);
-                               /* stop forwarding log packets! */
-                               log_remove_callback(gdb_log_callback, connection);
+               /* support for gdb_sync command */
+               if (gdb_connection->sync) {
+                       gdb_connection->sync = false;
+                       if (ct->state == TARGET_HALTED) {
+                               LOG_DEBUG("stepi ignored. GDB will now fetch the register state "
+                                                               "from the target.");
+                               gdb_sig_halted(connection);
+                               gdb_connection->output_flag = GDB_OUTPUT_NO;
                        } else
                                gdb_connection->frontend_state = TARGET_RUNNING;
-               } else {
-                       LOG_ERROR("Unknown vCont packet");
-                       return false;
+                       return true;
                }
+
+               retval = target_step(ct, current_pc, 0, 0);
+               if (retval == ERROR_TARGET_NOT_HALTED)
+                       LOG_INFO("target %s was not halted when step was requested", target_name(ct));
+
+               /* if step was successful send a reply back to gdb */
+               if (retval == ERROR_OK) {
+                       retval = target_poll(ct);
+                       if (retval != ERROR_OK)
+                               LOG_DEBUG("error polling target %s after successful step", target_name(ct));
+                       /* send back signal information */
+                       gdb_signal_reply(ct, connection);
+                       /* stop forwarding log packets! */
+                       gdb_connection->output_flag = GDB_OUTPUT_NO;
+               } else
+                       gdb_connection->frontend_state = TARGET_RUNNING;
                return true;
        }
-
+       LOG_ERROR("Unknown vCont packet");
        return false;
 }
 
@@ -2899,7 +3162,7 @@ static char *next_hex_encoded_field(const char **str, char sep)
                return NULL;
 
        const char *end = strchr(hex, sep);
-       if (end == NULL)
+       if (!end)
                hexlen = strlen(hex);
        else
                hexlen = end - hex;
@@ -2912,7 +3175,7 @@ static char *next_hex_encoded_field(const char **str, char sep)
 
        size_t count = hexlen / 2;
        char *decoded = malloc(count + 1);
-       if (decoded == NULL)
+       if (!decoded)
                return NULL;
 
        size_t converted = unhexify((void *)decoded, hex, count);
@@ -2957,16 +3220,18 @@ static bool gdb_handle_vrun_packet(struct connection *connection, const char *pa
        free(next_hex_encoded_field(&parse, ';'));
 
        char *cmdline = next_hex_encoded_field(&parse, ';');
-       char *arg;
-       while (cmdline != NULL && (arg = next_hex_encoded_field(&parse, ';')) != NULL) {
+       while (cmdline) {
+               char *arg = next_hex_encoded_field(&parse, ';');
+               if (!arg)
+                       break;
                char *new_cmdline = alloc_printf("%s %s", cmdline, arg);
                free(cmdline);
                free(arg);
                cmdline = new_cmdline;
        }
 
-       if (cmdline != NULL) {
-               if (target->semihosting != NULL) {
+       if (cmdline) {
+               if (target->semihosting) {
                        LOG_INFO("GDB set inferior command line to '%s'", cmdline);
                        free(target->semihosting->cmdline);
                        target->semihosting->cmdline = cmdline;
@@ -3093,7 +3358,7 @@ static int gdb_v_packet(struct connection *connection,
                length = packet_size - (parse - packet);
 
                /* create a new image if there isn't already one */
-               if (gdb_connection->vflash_image == NULL) {
+               if (!gdb_connection->vflash_image) {
                        gdb_connection->vflash_image = malloc(sizeof(struct image));
                        image_open(gdb_connection->vflash_image, "", "build");
                }
@@ -3117,7 +3382,7 @@ static int gdb_v_packet(struct connection *connection,
                target_call_event_callbacks(target,
                                TARGET_EVENT_GDB_FLASH_WRITE_START);
                result = flash_write(target, gdb_connection->vflash_image,
-                       &written, 0);
+                       &written, false);
                target_call_event_callbacks(target,
                        TARGET_EVENT_GDB_FLASH_WRITE_END);
                if (result != ERROR_OK) {
@@ -3206,6 +3471,10 @@ static void gdb_log_callback(void *priv, const char *file, unsigned line,
        struct connection *connection = priv;
        struct gdb_connection *gdb_con = connection->priv;
 
+       if (gdb_con->output_flag == GDB_OUTPUT_NO)
+               /* No out allowed */
+               return;
+
        if (gdb_con->busy) {
                /* do not reply this using the O packet */
                return;
@@ -3224,13 +3493,14 @@ static void gdb_sig_halted(struct connection *connection)
 static int gdb_input_inner(struct connection *connection)
 {
        /* Do not allocate this on the stack */
-       static char gdb_packet_buffer[GDB_BUFFER_SIZE + 1]; /* Extra byte for nul-termination */
+       static char gdb_packet_buffer[GDB_BUFFER_SIZE + 1]; /* Extra byte for null-termination */
 
        struct target *target;
        char const *packet = gdb_packet_buffer;
        int packet_size;
        int retval;
        struct gdb_connection *gdb_con = connection->priv;
+       static bool warn_use_ext;
 
        target = get_target_from_connection(connection);
 
@@ -3254,20 +3524,10 @@ static int gdb_input_inner(struct connection *connection)
                /* terminate with zero */
                gdb_packet_buffer[packet_size] = '\0';
 
-               if (LOG_LEVEL_IS(LOG_LVL_DEBUG)) {
-                       if (packet[0] == 'X') {
-                               /* binary packets spew junk into the debug log stream */
-                               char buf[50];
-                               int x;
-                               for (x = 0; (x < 49) && (packet[x] != ':'); x++)
-                                       buf[x] = packet[x];
-                               buf[x] = 0;
-                               LOG_DEBUG("received packet: '%s:<binary-data>'", buf);
-                       } else
-                               LOG_DEBUG("received packet: '%s'", packet);
-               }
-
                if (packet_size > 0) {
+
+                       gdb_log_incoming_packet(connection, gdb_packet_buffer);
+
                        retval = ERROR_OK;
                        switch (packet[0]) {
                                case 'T':       /* Is thread alive? */
@@ -3307,12 +3567,18 @@ static int gdb_input_inner(struct connection *connection)
                                        break;
                                case '?':
                                        gdb_last_signal_packet(connection, packet, packet_size);
+                                       /* '?' is sent after the eventual '!' */
+                                       if (!warn_use_ext && !gdb_con->extended_protocol) {
+                                               warn_use_ext = true;
+                                               LOG_WARNING("Prefer GDB command \"target extended-remote :%s\" instead of \"target remote :%s\"",
+                                                                       connection->service->port, connection->service->port);
+                                       }
                                        break;
                                case 'c':
                                case 's':
                                {
                                        gdb_thread_packet(connection, packet, packet_size);
-                                       log_add_callback(gdb_log_callback, connection);
+                                       gdb_con->output_flag = GDB_OUTPUT_ALL;
 
                                        if (gdb_con->mem_write_error) {
                                                LOG_ERROR("Memory write failure!");
@@ -3330,7 +3596,7 @@ static int gdb_input_inner(struct connection *connection)
                                                                "Waiting for target to halt.");
                                                already_running = true;
                                        } else if (target->state != TARGET_HALTED) {
-                                               LOG_WARNING("The target is not in the halted nor running stated, " \
+                                               LOG_WARNING("The target is not in the halted nor running stated, "
                                                                "stepi/continue ignored.");
                                                nostep = true;
                                        } else if ((packet[0] == 's') && gdb_con->sync) {
@@ -3339,7 +3605,7 @@ static int gdb_input_inner(struct connection *connection)
                                                 * make only the single stepping have the sync feature...
                                                 */
                                                nostep = true;
-                                               LOG_DEBUG("stepi ignored. GDB will now fetch the register state " \
+                                               LOG_DEBUG("stepi ignored. GDB will now fetch the register state "
                                                                "from the target.");
                                        }
                                        gdb_con->sync = false;
@@ -3355,7 +3621,7 @@ static int gdb_input_inner(struct connection *connection)
                                                gdb_sig_halted(connection);
 
                                                /* stop forwarding log packets! */
-                                               log_remove_callback(gdb_log_callback, connection);
+                                               gdb_con->output_flag = GDB_OUTPUT_NO;
                                        } else {
                                                /* We're running/stepping, in which case we can
                                                 * forward log output until the target is halted
@@ -3406,12 +3672,14 @@ static int gdb_input_inner(struct connection *connection)
                                        break;
 
                                case 'j':
+                                       /* DEPRECATED */
                                        /* packet supported only by smp target i.e cortex_a.c*/
                                        /* handle smp packet replying coreid played to gbd */
                                        gdb_read_smp_packet(connection, packet, packet_size);
                                        break;
 
                                case 'J':
+                                       /* DEPRECATED */
                                        /* packet supported only by smp target i.e cortex_a.c */
                                        /* handle smp packet setting coreid to be played at next
                                         * resume to gdb */
@@ -3427,7 +3695,7 @@ static int gdb_input_inner(struct connection *connection)
                                         * Fretcode,errno,Ctrl-C flag;call-specific attachment
                                         */
                                        gdb_con->frontend_state = TARGET_RUNNING;
-                                       log_add_callback(gdb_log_callback, connection);
+                                       gdb_con->output_flag = GDB_OUTPUT_ALL;
                                        gdb_fileio_response_packet(connection, packet, packet_size);
                                        break;
 
@@ -3480,13 +3748,44 @@ static int gdb_input(struct connection *connection)
        return ERROR_OK;
 }
 
+static void gdb_keep_client_alive(struct connection *connection)
+{
+       struct gdb_connection *gdb_con = connection->priv;
+
+       if (gdb_con->busy) {
+               /* do not send packets, retry asap */
+               return;
+       }
+
+       switch (gdb_con->output_flag) {
+       case GDB_OUTPUT_NO:
+               /* no need for keep-alive */
+               break;
+       case GDB_OUTPUT_ALL:
+               /* send an empty O packet */
+               gdb_output_con(connection, "");
+               break;
+       default:
+               break;
+       }
+}
+
+static const struct service_driver gdb_service_driver = {
+       .name = "gdb",
+       .new_connection_during_keep_alive_handler = NULL,
+       .new_connection_handler = gdb_new_connection,
+       .input_handler = gdb_input,
+       .connection_closed_handler = gdb_connection_closed,
+       .keep_client_alive_handler = gdb_keep_client_alive,
+};
+
 static int gdb_target_start(struct target *target, const char *port)
 {
        struct gdb_service *gdb_service;
        int ret;
        gdb_service = malloc(sizeof(struct gdb_service));
 
-       if (NULL == gdb_service)
+       if (!gdb_service)
                return -ENOMEM;
 
        LOG_INFO("starting gdb server for %s on %s", target_name(target), port);
@@ -3496,19 +3795,14 @@ static int gdb_target_start(struct target *target, const char *port)
        gdb_service->core[1] = -1;
        target->gdb_service = gdb_service;
 
-       ret = add_service("gdb",
-                       port, 1, &gdb_new_connection, &gdb_input,
-                       &gdb_connection_closed, gdb_service);
-       /* initialialize all targets gdb service with the same pointer */
+       ret = add_service(&gdb_service_driver, port, target->gdb_max_connections, gdb_service);
+       /* initialize all targets gdb service with the same pointer */
        {
                struct target_list *head;
-               struct target *curr;
-               head = target->head;
-               while (head != (struct target_list *)NULL) {
-                       curr = head->target;
+               foreach_smp_target(head, target->smp_targets) {
+                       struct target *curr = head->target;
                        if (curr != target)
                                curr->gdb_service = gdb_service;
-                       head = head->next;
                }
        }
        return ret;
@@ -3570,14 +3864,14 @@ static int gdb_target_add_one(struct target *target)
 
 int gdb_target_add_all(struct target *target)
 {
-       if (NULL == target) {
+       if (!target) {
                LOG_WARNING("gdb services need one or more targets defined");
                return ERROR_OK;
        }
 
-       while (NULL != target) {
+       while (target) {
                int retval = gdb_target_add_one(target);
-               if (ERROR_OK != retval)
+               if (retval != ERROR_OK)
                        return retval;
 
                target = target->next;
@@ -3591,7 +3885,7 @@ COMMAND_HANDLER(handle_gdb_sync_command)
        if (CMD_ARGC != 0)
                return ERROR_COMMAND_SYNTAX_ERROR;
 
-       if (current_gdb_connection == NULL) {
+       if (!current_gdb_connection) {
                command_print(CMD,
                        "gdb_sync command can only be run from within gdb using \"monitor gdb_sync\"");
                return ERROR_FAIL;
@@ -3606,7 +3900,7 @@ COMMAND_HANDLER(handle_gdb_sync_command)
 COMMAND_HANDLER(handle_gdb_port_command)
 {
        int retval = CALL_COMMAND_HANDLER(server_pipe_command, &gdb_port);
-       if (ERROR_OK == retval) {
+       if (retval == ERROR_OK) {
                free(gdb_port_next);
                gdb_port_next = strdup(gdb_port);
        }
@@ -3700,7 +3994,7 @@ COMMAND_HANDLER(handle_gdb_save_tdesc_command)
        size_t size_written;
 
        char *tdesc_filename = alloc_printf("%s.xml", target_type_name(target));
-       if (tdesc_filename == NULL) {
+       if (!tdesc_filename) {
                retval = ERROR_FAIL;
                goto out;
        }
@@ -3739,7 +4033,7 @@ static const struct command_registration gdb_command_handlers[] = {
        {
                .name = "gdb_port",
                .handler = handle_gdb_port_command,
-               .mode = COMMAND_ANY,
+               .mode = COMMAND_CONFIG,
                .help = "Normally gdb listens to a TCP/IP port. Each subsequent GDB "
                        "server listens for the next port number after the "
                        "base port number specified. "