gdb_server: add debug signal reason prints

[openocd.git] / src / server / gdb_server.c

// SPDX-License-Identifier: GPL-2.0-or-later

/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   Copyright (C) 2007-2010 Øyvind Harboe                                 *
 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
 *   Copyright (C) 2008 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 *                                                                         *
 *   Copyright (C) 2011 by Broadcom Corporation                            *
 *   Evan Hunter - ehunter@broadcom.com                                    *
 *                                                                         *
 *   Copyright (C) ST-Ericsson SA 2011                                     *
 *   michel.jaouen@stericsson.com : smp minimum support                    *
 *                                                                         *
 *   Copyright (C) 2013 Andes Technology                                   *
 *   Hsiangkai Wang <hkwang@andestech.com>                                 *
 *                                                                         *
 *   Copyright (C) 2013 Franck Jullien                                     *
 *   elec4fun@gmail.com                                                    *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <target/breakpoints.h>
#include <target/target_request.h>
#include <target/register.h>
#include <target/target.h>
#include <target/target_type.h>
#include <target/semihosting_common.h>
#include "server.h"
#include <flash/nor/core.h>
#include "gdb_server.h"
#include <target/image.h>
#include <jtag/jtag.h>
#include "rtos/rtos.h"
#include "target/smp.h"

/**
 * @file
 * GDB server implementation.
 *
 * This implements the GDB Remote Serial Protocol, over TCP connections,
 * giving GDB access to the JTAG or other hardware debugging facilities
 * 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;
};

/* private connection data for GDB */
struct gdb_connection {
        char buffer[GDB_BUFFER_SIZE + 1]; /* Extra byte for null-termination */
        char *buf_p;
        int buf_cnt;
        bool ctrl_c;
        enum target_state frontend_state;
        struct image *vflash_image;
        bool closed;
        bool busy;
        int noack_mode;
        /* set flag to true if you want the next stepi to return immediately.
         * allowing GDB to pick up a fresh set of register values from the target
         * without modifying the target state. */
        bool sync;
        /* We delay reporting memory write errors until next step/continue or memory
         * write. This improves performance of gdb load significantly as the GDB packet
         * can be replied immediately and a new GDB packet will be ready without delay
         * (ca. 10% or so...). */
        bool mem_write_error;
        /* with extended-remote it seems we need to better emulate attach/detach.
         * what this means is we reply with a W stop reply after a kill packet,
         * normally we reply with a S reply via gdb_last_signal_packet.
         * as a side note this behaviour only effects gdb > 6.8 */
        bool attached;
        /* set when extended protocol is used */
        bool extended_protocol;
        /* temporarily used for target description support */
        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
#define _DEBUG_GDB_IO_
#endif

static struct gdb_connection *current_gdb_connection;

static int gdb_breakpoint_override;
static enum breakpoint_type gdb_breakpoint_override_type;

static int gdb_error(struct connection *connection, int retval);
static char *gdb_port;
static char *gdb_port_next;

static void gdb_log_callback(void *priv, const char *file, unsigned line,
                const char *function, const char *string);

static void gdb_sig_halted(struct connection *connection);

/* number of gdb connections, mainly to suppress gdb related debugging spam
 * in helper/log.c when no gdb connections are actually active */
static int gdb_actual_connections;

/* set if we are sending a memory map to gdb
 * via qXfer:memory-map:read packet */
/* enabled by default*/
static int gdb_use_memory_map = 1;
/* enabled by default*/
static int gdb_flash_program = 1;

/* if set, data aborts cause an error to be reported in memory read packets
 * see the code in gdb_read_memory_packet() for further explanations.
 * Disabled by default.
 */
static int gdb_report_data_abort;
/* If set, errors when accessing registers are reported to gdb. Disabled by
 * default. */
static int gdb_report_register_access_error;

/* set if we are sending target descriptions to gdb
 * via qXfer:features:read packet */
/* enabled by default */
static int gdb_use_target_description = 1;

/* current processing free-run type, used by file-I/O */
static char gdb_running_type;

static int gdb_last_signal(struct target *target)
{
        LOG_TARGET_DEBUG(target, "Debug reason is: %s",
                        target_debug_reason_str(target->debug_reason));

        switch (target->debug_reason) {
                case DBG_REASON_DBGRQ:
                        return 0x2;             /* SIGINT */
                case DBG_REASON_BREAKPOINT:
                case DBG_REASON_WATCHPOINT:
                case DBG_REASON_WPTANDBKPT:
                        return 0x05;    /* SIGTRAP */
                case DBG_REASON_SINGLESTEP:
                        return 0x05;    /* SIGTRAP */
                case DBG_REASON_EXC_CATCH:
                        return 0x05;
                case DBG_REASON_NOTHALTED:
                        return 0x0;             /* no signal... shouldn't happen */
                default:
                        LOG_USER("undefined debug reason %d (%s) - target needs reset",
                                        target->debug_reason,
                                        target_debug_reason_str(target->debug_reason));
                        return 0x0;
        }
}

static int check_pending(struct connection *connection,
                int timeout_s, int *got_data)
{
        /* a non-blocking socket will block if there is 0 bytes available on the socket,
         * but return with as many bytes as are available immediately
         */
        struct timeval tv;
        fd_set read_fds;
        struct gdb_connection *gdb_con = connection->priv;
        int t;
        if (!got_data)
                got_data = &t;
        *got_data = 0;

        if (gdb_con->buf_cnt > 0) {
                *got_data = 1;
                return ERROR_OK;
        }

        FD_ZERO(&read_fds);
        FD_SET(connection->fd, &read_fds);

        tv.tv_sec = timeout_s;
        tv.tv_usec = 0;
        if (socket_select(connection->fd + 1, &read_fds, NULL, NULL, &tv) == 0) {
                /* This can typically be because a "monitor" command took too long
                 * before printing any progress messages
                 */
                if (timeout_s > 0)
                        return ERROR_GDB_TIMEOUT;
                else
                        return ERROR_OK;
        }
        *got_data = FD_ISSET(connection->fd, &read_fds) != 0;
        return ERROR_OK;
}

static int gdb_get_char_inner(struct connection *connection, int *next_char)
{
        struct gdb_connection *gdb_con = connection->priv;
        int retval = ERROR_OK;

#ifdef _DEBUG_GDB_IO_
        char *debug_buffer;
#endif
        for (;; ) {
                if (connection->service->type != CONNECTION_TCP)
                        gdb_con->buf_cnt = read(connection->fd, gdb_con->buffer, GDB_BUFFER_SIZE);
                else {
                        retval = check_pending(connection, 1, NULL);
                        if (retval != ERROR_OK)
                                return retval;
                        gdb_con->buf_cnt = read_socket(connection->fd,
                                        gdb_con->buffer,
                                        GDB_BUFFER_SIZE);
                }

                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;
                }

#ifdef _WIN32
                errno = WSAGetLastError();

                switch (errno) {
                        case WSAEWOULDBLOCK:
                                usleep(1000);
                                break;
                        case WSAECONNABORTED:
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                        case WSAECONNRESET:
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                        default:
                                LOG_ERROR("read: %d", errno);
                                exit(-1);
                }
#else
                switch (errno) {
                        case EAGAIN:
                                usleep(1000);
                                break;
                        case ECONNABORTED:
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                        case ECONNRESET:
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                        default:
                                LOG_ERROR("read: %s", strerror(errno));
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                }
#endif
        }

#ifdef _DEBUG_GDB_IO_
        debug_buffer = strndup(gdb_con->buffer, gdb_con->buf_cnt);
        LOG_DEBUG("received '%s'", debug_buffer);
        free(debug_buffer);
#endif

        gdb_con->buf_p = gdb_con->buffer;
        gdb_con->buf_cnt--;
        *next_char = *(gdb_con->buf_p++);
        if (gdb_con->buf_cnt > 0)
                connection->input_pending = true;
        else
                connection->input_pending = false;
#ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
#endif

        return retval;
}

/**
 * The cool thing about this fn is that it allows buf_p and buf_cnt to be
 * held in registers in the inner loop.
 *
 * For small caches and embedded systems this is important!
 */
static inline int gdb_get_char_fast(struct connection *connection,
                int *next_char, char **buf_p, int *buf_cnt)
{
        int retval = ERROR_OK;

        if ((*buf_cnt)-- > 0) {
                *next_char = **buf_p;
                (*buf_p)++;
                if (*buf_cnt > 0)
                        connection->input_pending = true;
                else
                        connection->input_pending = false;

#ifdef _DEBUG_GDB_IO_
                LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
#endif

                return ERROR_OK;
        }

        struct gdb_connection *gdb_con = connection->priv;
        gdb_con->buf_p = *buf_p;
        gdb_con->buf_cnt = *buf_cnt;
        retval = gdb_get_char_inner(connection, next_char);
        *buf_p = gdb_con->buf_p;
        *buf_cnt = gdb_con->buf_cnt;

        return retval;
}

static int gdb_get_char(struct connection *connection, int *next_char)
{
        struct gdb_connection *gdb_con = connection->priv;
        return gdb_get_char_fast(connection, next_char, &gdb_con->buf_p, &gdb_con->buf_cnt);
}

static int gdb_putback_char(struct connection *connection, int last_char)
{
        struct gdb_connection *gdb_con = connection->priv;

        if (gdb_con->buf_p > gdb_con->buffer) {
                *(--gdb_con->buf_p) = last_char;
                gdb_con->buf_cnt++;
        } else
                LOG_ERROR("BUG: couldn't put character back");

        return ERROR_OK;
}

/* The only way we can detect that the socket is closed is the first time
 * we write to it, we will fail. Subsequent write operations will
 * succeed. Shudder! */
static int gdb_write(struct connection *connection, void *data, int len)
{
        struct gdb_connection *gdb_con = connection->priv;
        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;
        int reply;
        int retval;
        struct gdb_connection *gdb_con = connection->priv;

        for (i = 0; i < len; i++)
                my_checksum += buffer[i];

#ifdef _DEBUG_GDB_IO_
        /*
         * At this point we should have nothing in the input queue from GDB,
         * however sometimes '-' is sent even though we've already received
         * an ACK (+) for everything we've sent off.
         */
        int gotdata;
        for (;; ) {
                retval = check_pending(connection, 0, &gotdata);
                if (retval != ERROR_OK)
                        return retval;
                if (!gotdata)
                        break;
                retval = gdb_get_char(connection, &reply);
                if (retval != ERROR_OK)
                        return retval;
                if (reply == '$') {
                        /* fix a problem with some IAR tools */
                        gdb_putback_char(connection, reply);
                        LOG_DEBUG("Unexpected start of new packet");
                        break;
                }

                LOG_WARNING("Discard unexpected char %c", reply);
        }
#endif

        while (1) {
                gdb_log_outgoing_packet(connection, buffer, len, my_checksum);

                char local_buffer[1024];
                local_buffer[0] = '$';
                if ((size_t)len + 4 <= sizeof(local_buffer)) {
                        /* performance gain on smaller packets by only a single call to gdb_write() */
                        memcpy(local_buffer + 1, buffer, len++);
                        len += snprintf(local_buffer + len, sizeof(local_buffer) - len, "#%02x", my_checksum);
                        retval = gdb_write(connection, local_buffer, len);
                        if (retval != ERROR_OK)
                                return retval;
                } else {
                        /* larger packets are transmitted directly from caller supplied buffer
                         * by several calls to gdb_write() to avoid dynamic allocation */
                        snprintf(local_buffer + 1, sizeof(local_buffer) - 1, "#%02x", my_checksum);
                        retval = gdb_write(connection, local_buffer, 1);
                        if (retval != ERROR_OK)
                                return retval;
                        retval = gdb_write(connection, buffer, len);
                        if (retval != ERROR_OK)
                                return retval;
                        retval = gdb_write(connection, local_buffer + 1, 3);
                        if (retval != ERROR_OK)
                                return retval;
                }

                if (gdb_con->noack_mode)
                        break;

                retval = gdb_get_char(connection, &reply);
                if (retval != ERROR_OK)
                        return retval;

                if (reply == '+') {
                        gdb_log_incoming_packet(connection, "+");
                        break;
                } else if (reply == '-') {
                        /* Stop sending output packets for now */
                        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 == '+') {
                                gdb_log_incoming_packet(connection, "+");
                                break;
                        } else if (reply == '-') {
                                /* Stop sending output packets for now */
                                gdb_con->output_flag = GDB_OUTPUT_NO;
                                gdb_log_incoming_packet(connection, "-");
                                LOG_WARNING("negative reply, retrying");
                        } else if (reply == '$') {
                                LOG_ERROR("GDB missing ack(1) - assumed good");
                                gdb_putback_char(connection, reply);
                                return ERROR_OK;
                        } else {
                                LOG_ERROR("unknown character(1) 0x%2.2x in reply, dropping connection", reply);
                                gdb_con->closed = true;
                                return ERROR_SERVER_REMOTE_CLOSED;
                        }
                } else if (reply == '$') {
                        LOG_ERROR("GDB missing ack(2) - assumed good");
                        gdb_putback_char(connection, reply);
                        return ERROR_OK;
                } else {
                        LOG_ERROR("unknown character(2) 0x%2.2x in reply, dropping connection",
                                reply);
                        gdb_con->closed = true;
                        return ERROR_SERVER_REMOTE_CLOSED;
                }
        }
        if (gdb_con->closed)
                return ERROR_SERVER_REMOTE_CLOSED;

        return ERROR_OK;
}

int gdb_put_packet(struct connection *connection, char *buffer, int len)
{
        struct gdb_connection *gdb_con = connection->priv;
        gdb_con->busy = true;
        int retval = gdb_put_packet_inner(connection, buffer, len);
        gdb_con->busy = false;

        /* we sent some data, reset timer for keep alive messages */
        kept_alive();

        return retval;
}

static inline int fetch_packet(struct connection *connection,
                int *checksum_ok, int noack, int *len, char *buffer)
{
        unsigned char my_checksum = 0;
        char checksum[3];
        int character;
        int retval = ERROR_OK;

        struct gdb_connection *gdb_con = connection->priv;
        my_checksum = 0;
        int count = 0;
        count = 0;

        /* move this over into local variables to use registers and give the
         * more freedom to optimize */
        char *buf_p = gdb_con->buf_p;
        int buf_cnt = gdb_con->buf_cnt;

        for (;; ) {
                /* The common case is that we have an entire packet with no escape chars.
                 * We need to leave at least 2 bytes in the buffer to have
                 * gdb_get_char() update various bits and bobs correctly.
                 */
                if ((buf_cnt > 2) && ((buf_cnt + count) < *len)) {
                        /* The compiler will struggle a bit with constant propagation and
                         * aliasing, so we help it by showing that these values do not
                         * change inside the loop
                         */
                        int i;
                        char *buf = buf_p;
                        int run = buf_cnt - 2;
                        i = 0;
                        int done = 0;
                        while (i < run) {
                                character = *buf++;
                                i++;
                                if (character == '#') {
                                        /* Danger! character can be '#' when esc is
                                         * used so we need an explicit boolean for done here. */
                                        done = 1;
                                        break;
                                }

                                if (character == '}') {
                                        /* data transmitted in binary mode (X packet)
                                         * uses 0x7d as escape character */
                                        my_checksum += character & 0xff;
                                        character = *buf++;
                                        i++;
                                        my_checksum += character & 0xff;
                                        buffer[count++] = (character ^ 0x20) & 0xff;
                                } else {
                                        my_checksum += character & 0xff;
                                        buffer[count++] = character & 0xff;
                                }
                        }
                        buf_p += i;
                        buf_cnt -= i;
                        if (done)
                                break;
                }
                if (count > *len) {
                        LOG_ERROR("packet buffer too small");
                        retval = ERROR_GDB_BUFFER_TOO_SMALL;
                        break;
                }

                retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
                if (retval != ERROR_OK)
                        break;

                if (character == '#')
                        break;

                if (character == '}') {
                        /* data transmitted in binary mode (X packet)
                         * uses 0x7d as escape character */
                        my_checksum += character & 0xff;

                        retval = gdb_get_char_fast(connection, &character, &buf_p, &buf_cnt);
                        if (retval != ERROR_OK)
                                break;

                        my_checksum += character & 0xff;
                        buffer[count++] = (character ^ 0x20) & 0xff;
                } else {
                        my_checksum += character & 0xff;
                        buffer[count++] = character & 0xff;
                }
        }

        gdb_con->buf_p = buf_p;
        gdb_con->buf_cnt = buf_cnt;

        if (retval != ERROR_OK)
                return retval;

        *len = count;

        retval = gdb_get_char(connection, &character);
        if (retval != ERROR_OK)
                return retval;
        checksum[0] = character;
        retval = gdb_get_char(connection, &character);
        if (retval != ERROR_OK)
                return retval;
        checksum[1] = character;
        checksum[2] = 0;

        if (!noack)
                *checksum_ok = (my_checksum == strtoul(checksum, NULL, 16));

        return ERROR_OK;
}

static int gdb_get_packet_inner(struct connection *connection,
                char *buffer, int *len)
{
        int character;
        int retval;
        struct gdb_connection *gdb_con = connection->priv;

        while (1) {
                do {
                        retval = gdb_get_char(connection, &character);
                        if (retval != ERROR_OK)
                                return retval;

#ifdef _DEBUG_GDB_IO_
                        LOG_DEBUG("character: '%c'", character);
#endif

                        switch (character) {
                                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`
                                         * response, which can be safely ignored by the stub."
                                         * However OpenOCD server already is in noack mode at this
                                         * point and instead of ignoring this it was emitting a
                                         * warning. This code makes server ignore the first ACK
                                         * that will be received after going into noack mode,
                                         * warning only about subsequent ACK's. */
                                        if (gdb_con->noack_mode > 1) {
                                                LOG_WARNING("acknowledgment received, but no packet pending");
                                        } else if (gdb_con->noack_mode) {
                                                LOG_DEBUG("Received first acknowledgment after entering noack mode. Ignoring it.");
                                                gdb_con->noack_mode = 2;
                                        }
                                        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;
                                default:
                                        LOG_WARNING("ignoring character 0x%x", character);
                                        break;
                        }
                } while (character != '$');

                int checksum_ok = 0;
                /* explicit code expansion here to get faster inlined code in -O3 by not
                 * calculating checksum */
                if (gdb_con->noack_mode) {
                        retval = fetch_packet(connection, &checksum_ok, 1, len, buffer);
                        if (retval != ERROR_OK)
                                return retval;
                } else {
                        retval = fetch_packet(connection, &checksum_ok, 0, len, buffer);
                        if (retval != ERROR_OK)
                                return retval;
                }

                if (gdb_con->noack_mode) {
                        /* checksum is not checked in noack mode */
                        break;
                }
                if (checksum_ok) {
                        retval = gdb_write(connection, "+", 1);
                        if (retval != ERROR_OK)
                                return retval;
                        break;
                }
        }
        if (gdb_con->closed)
                return ERROR_SERVER_REMOTE_CLOSED;

        return ERROR_OK;
}

static int gdb_get_packet(struct connection *connection, char *buffer, int *len)
{
        struct gdb_connection *gdb_con = connection->priv;
        gdb_con->busy = true;
        int retval = gdb_get_packet_inner(connection, buffer, len);
        gdb_con->busy = false;
        return retval;
}

static int gdb_output_con(struct connection *connection, const char *line)
{
        char *hex_buffer;
        int bin_size;

        bin_size = strlen(line);

        hex_buffer = malloc(bin_size * 2 + 2);
        if (!hex_buffer)
                return ERROR_GDB_BUFFER_TOO_SMALL;

        hex_buffer[0] = 'O';
        size_t pkt_len = hexify(hex_buffer + 1, (const uint8_t *)line, bin_size,
                bin_size * 2 + 1);
        int retval = gdb_put_packet(connection, hex_buffer, pkt_len + 1);

        free(hex_buffer);
        return retval;
}

static int gdb_output(struct command_context *context, const char *line)
{
        /* this will be dumped to the log and also sent as an O packet if possible */
        LOG_USER_N("%s", line);
        return ERROR_OK;
}

static void gdb_signal_reply(struct target *target, struct connection *connection)
{
        struct gdb_connection *gdb_connection = connection->priv;
        char sig_reply[65];
        char stop_reason[32];
        char current_thread[25];
        int sig_reply_len;
        int signal_var;

        rtos_update_threads(target);

        if (target->debug_reason == DBG_REASON_EXIT) {
                sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "W00");
        } else {
                struct target *ct;
                if (target->rtos) {
                        target->rtos->current_threadid = target->rtos->current_thread;
                        target->rtos->gdb_target_for_threadid(connection, target->rtos->current_threadid, &ct);
                } else {
                        ct = target;
                }

                if (gdb_connection->ctrl_c) {
                        LOG_TARGET_DEBUG(target, "Responding with signal 2 (SIGINT) to debugger due to Ctrl-C");
                        signal_var = 0x2;
                } else
                        signal_var = gdb_last_signal(ct);

                stop_reason[0] = '\0';
                if (ct->debug_reason == DBG_REASON_WATCHPOINT) {
                        enum watchpoint_rw hit_wp_type;
                        target_addr_t hit_wp_address;

                        if (watchpoint_hit(ct, &hit_wp_type, &hit_wp_address) == ERROR_OK) {

                                switch (hit_wp_type) {
                                        case WPT_WRITE:
                                                snprintf(stop_reason, sizeof(stop_reason),
                                                                "watch:%08" TARGET_PRIxADDR ";", hit_wp_address);
                                                break;
                                        case WPT_READ:
                                                snprintf(stop_reason, sizeof(stop_reason),
                                                                "rwatch:%08" TARGET_PRIxADDR ";", hit_wp_address);
                                                break;
                                        case WPT_ACCESS:
                                                snprintf(stop_reason, sizeof(stop_reason),
                                                                "awatch:%08" TARGET_PRIxADDR ";", hit_wp_address);
                                                break;
                                        default:
                                                break;
                                }
                        }
                }

                current_thread[0] = '\0';
                if (target->rtos)
                        snprintf(current_thread, sizeof(current_thread), "thread:%" PRIx64 ";",
                                        target->rtos->current_thread);

                sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "T%2.2x%s%s",
                                signal_var, stop_reason, current_thread);

                gdb_connection->ctrl_c = false;
        }

        gdb_put_packet(connection, sig_reply, sig_reply_len);
        gdb_connection->frontend_state = TARGET_HALTED;
}

static void gdb_fileio_reply(struct target *target, struct connection *connection)
{
        struct gdb_connection *gdb_connection = connection->priv;
        char fileio_command[256];
        int command_len;
        bool program_exited = false;

        if (strcmp(target->fileio_info->identifier, "open") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2 + 1,       /* len + trailing zero */
                                target->fileio_info->param_3,
                                target->fileio_info->param_4);
        else if (strcmp(target->fileio_info->identifier, "close") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1);
        else if (strcmp(target->fileio_info->identifier, "read") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2,
                                target->fileio_info->param_3);
        else if (strcmp(target->fileio_info->identifier, "write") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2,
                                target->fileio_info->param_3);
        else if (strcmp(target->fileio_info->identifier, "lseek") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2,
                                target->fileio_info->param_3);
        else if (strcmp(target->fileio_info->identifier, "rename") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2 + 1,       /* len + trailing zero */
                                target->fileio_info->param_3,
                                target->fileio_info->param_4 + 1);      /* len + trailing zero */
        else if (strcmp(target->fileio_info->identifier, "unlink") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2 + 1);      /* len + trailing zero */
        else if (strcmp(target->fileio_info->identifier, "stat") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2,
                                target->fileio_info->param_3);
        else if (strcmp(target->fileio_info->identifier, "fstat") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2);
        else if (strcmp(target->fileio_info->identifier, "gettimeofday") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 ",%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2);
        else if (strcmp(target->fileio_info->identifier, "isatty") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1);
        else if (strcmp(target->fileio_info->identifier, "system") == 0)
                sprintf(fileio_command, "F%s,%" PRIx64 "/%" PRIx64, target->fileio_info->identifier,
                                target->fileio_info->param_1,
                                target->fileio_info->param_2 + 1);      /* len + trailing zero */
        else if (strcmp(target->fileio_info->identifier, "exit") == 0) {
                /* If target hits exit syscall, report to GDB the program is terminated.
                 * In addition, let target run its own exit syscall handler. */
                program_exited = true;
                sprintf(fileio_command, "W%02" PRIx64, target->fileio_info->param_1);
        } else {
                LOG_DEBUG("Unknown syscall: %s", target->fileio_info->identifier);

                /* encounter unknown syscall, continue */
                gdb_connection->frontend_state = TARGET_RUNNING;
                target_resume(target, 1, 0x0, 0, 0);
                return;
        }

        command_len = strlen(fileio_command);
        gdb_put_packet(connection, fileio_command, command_len);

        if (program_exited) {
                /* Use target_resume() to let target run its own exit syscall handler. */
                gdb_connection->frontend_state = TARGET_RUNNING;
                target_resume(target, 1, 0x0, 0, 0);
        } else {
                gdb_connection->frontend_state = TARGET_HALTED;
                rtos_update_threads(target);
        }
}

static void gdb_frontend_halted(struct target *target, struct connection *connection)
{
        struct gdb_connection *gdb_connection = connection->priv;

        /* In the GDB protocol when we are stepping or continuing execution,
         * we have a lingering reply. Upon receiving a halted event
         * when we have that lingering packet, we reply to the original
         * step or continue packet.
         *
         * Executing monitor commands can bring the target in and
         * out of the running state so we'll see lots of TARGET_EVENT_XXX
         * that are to be ignored.
         */
        if (gdb_connection->frontend_state == TARGET_RUNNING) {
                /* stop forwarding log packets! */
                gdb_connection->output_flag = GDB_OUTPUT_NO;

                /* check fileio first */
                if (target_get_gdb_fileio_info(target, target->fileio_info) == ERROR_OK)
                        gdb_fileio_reply(target, connection);
                else
                        gdb_signal_reply(target, connection);
        }
}

static int gdb_target_callback_event_handler(struct target *target,
                enum target_event event, void *priv)
{
        struct connection *connection = priv;
        struct gdb_service *gdb_service = connection->service->priv;

        if (gdb_service->target != target)
                return ERROR_OK;

        switch (event) {
                case TARGET_EVENT_GDB_HALT:
                        gdb_frontend_halted(target, connection);
                        break;
                case TARGET_EVENT_HALTED:
                        target_call_event_callbacks(target, TARGET_EVENT_GDB_END);
                        break;
                default:
                        break;
        }

        return ERROR_OK;
}

static int gdb_new_connection(struct connection *connection)
{
        struct gdb_connection *gdb_connection = malloc(sizeof(struct gdb_connection));
        struct target *target;
        int retval;
        int initial_ack;

        target = get_target_from_connection(connection);
        connection->priv = gdb_connection;
        connection->cmd_ctx->current_target = target;

        /* initialize gdb connection information */
        gdb_connection->buf_p = gdb_connection->buffer;
        gdb_connection->buf_cnt = 0;
        gdb_connection->ctrl_c = false;
        gdb_connection->frontend_state = TARGET_HALTED;
        gdb_connection->vflash_image = NULL;
        gdb_connection->closed = false;
        gdb_connection->busy = false;
        gdb_connection->noack_mode = 0;
        gdb_connection->sync = false;
        gdb_connection->mem_write_error = false;
        gdb_connection->attached = true;
        gdb_connection->extended_protocol = false;
        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);

        /* output goes through gdb connection */
        command_set_output_handler(connection->cmd_ctx, gdb_output, connection);

        /* we must remove all breakpoints registered to the target as a previous
         * GDB session could leave dangling breakpoints if e.g. communication
         * timed out.
         */
        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)
                        target->rtos->type->clean(target);

                /* update threads */
                rtos_update_threads(target);
        }

        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).
                 */
                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 "
                                                "to prepare target for GDB connect, or use 'gdb_memory_map disable'.");
                                return retval;
                        }
                }
        }

        gdb_actual_connections++;
        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.
         *
         * 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;
}

static int gdb_connection_closed(struct connection *connection)
{
        struct target *target;
        struct gdb_connection *gdb_connection = connection->priv;

        target = get_target_from_connection(connection);

        /* we're done forwarding messages. Tear down callback before
         * cleaning up connection.
         */
        log_remove_callback(gdb_log_callback, connection);

        gdb_actual_connections--;
        LOG_DEBUG("GDB Close, Target: %s, state: %s, gdb_actual_connections=%d",
                target_name(target),
                target_state_name(target),
                gdb_actual_connections);

        /* see if an image built with vFlash commands is left */
        if (gdb_connection->vflash_image) {
                image_close(gdb_connection->vflash_image);
                free(gdb_connection->vflash_image);
                gdb_connection->vflash_image = NULL;
        }

        /* if this connection registered a debug-message receiver delete it */
        delete_debug_msg_receiver(connection->cmd_ctx, target);

        free(connection->priv);
        connection->priv = NULL;

        target_unregister_event_callback(gdb_target_callback_event_handler, connection);

        target_call_event_callbacks(target, TARGET_EVENT_GDB_END);

        target_call_event_callbacks(target, TARGET_EVENT_GDB_DETACH);

        return ERROR_OK;
}

static void gdb_send_error(struct connection *connection, uint8_t the_error)
{
        char err[4];
        snprintf(err, 4, "E%2.2X", the_error);
        gdb_put_packet(connection, err, 3);
}

static int gdb_last_signal_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        struct gdb_connection *gdb_con = connection->priv;
        char sig_reply[4];
        int signal_var;

        if (!gdb_con->attached) {
                /* if we are here we have received a kill packet
                 * reply W stop reply otherwise gdb gets very unhappy */
                gdb_put_packet(connection, "W00", 3);
                return ERROR_OK;
        }

        signal_var = gdb_last_signal(target);

        snprintf(sig_reply, 4, "S%2.2x", signal_var);
        gdb_put_packet(connection, sig_reply, 3);

        return ERROR_OK;
}

static inline int gdb_reg_pos(struct target *target, int pos, int len)
{
        if (target->endianness == TARGET_LITTLE_ENDIAN)
                return pos;
        else
                return len - 1 - pos;
}

/* Convert register to string of bytes. NB! The # of bits in the
 * register might be non-divisible by 8(a byte), in which
 * case an entire byte is shown.
 *
 * NB! the format on the wire is the target endianness
 *
 * The format of reg->value is little endian
 *
 */
static void gdb_str_to_target(struct target *target,
                char *tstr, struct reg *reg)
{
        int i;

        uint8_t *buf;
        int buf_len;
        buf = reg->value;
        buf_len = DIV_ROUND_UP(reg->size, 8);

        for (i = 0; i < buf_len; i++) {
                int j = gdb_reg_pos(target, i, buf_len);
                tstr += sprintf(tstr, "%02x", buf[j]);
        }
}

/* copy over in register buffer */
static void gdb_target_to_reg(struct target *target,
                char const *tstr, int str_len, uint8_t *bin)
{
        if (str_len % 2) {
                LOG_ERROR("BUG: gdb value with uneven number of characters encountered");
                exit(-1);
        }

        int i;
        for (i = 0; i < str_len; i += 2) {
                unsigned t;
                if (sscanf(tstr + i, "%02x", &t) != 1) {
                        LOG_ERROR("BUG: unable to convert register value");
                        exit(-1);
                }

                int j = gdb_reg_pos(target, i/2, str_len/2);
                bin[j] = t;
        }
}

static int gdb_get_registers_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        struct reg **reg_list;
        int reg_list_size;
        int retval;
        int reg_packet_size = 0;
        char *reg_packet;
        char *reg_packet_p;
        int i;

#ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("-");
#endif

        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,
                        REG_CLASS_GENERAL);
        if (retval != ERROR_OK)
                return gdb_error(connection, retval);

        for (i = 0; i < reg_list_size; i++) {
                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;
        }

        assert(reg_packet_size > 0);

        reg_packet = malloc(reg_packet_size + 1); /* plus one for string termination null */
        if (!reg_packet)
                return ERROR_FAIL;

        reg_packet_p = reg_packet;

        for (i = 0; i < reg_list_size; i++) {
                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]);
                        if (retval != ERROR_OK && gdb_report_register_access_error) {
                                LOG_DEBUG("Couldn't get register %s.", reg_list[i]->name);
                                free(reg_packet);
                                free(reg_list);
                                return gdb_error(connection, retval);
                        }
                }
                gdb_str_to_target(target, reg_packet_p, reg_list[i]);
                reg_packet_p += DIV_ROUND_UP(reg_list[i]->size, 8) * 2;
        }

#ifdef _DEBUG_GDB_IO_
        {
                char *reg_packet_p_debug;
                reg_packet_p_debug = strndup(reg_packet, reg_packet_size);
                LOG_DEBUG("reg_packet: %s", reg_packet_p_debug);
                free(reg_packet_p_debug);
        }
#endif

        gdb_put_packet(connection, reg_packet, reg_packet_size);
        free(reg_packet);

        free(reg_list);

        return ERROR_OK;
}

static int gdb_set_registers_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        int i;
        struct reg **reg_list;
        int reg_list_size;
        int retval;
        char const *packet_p;

#ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("-");
#endif

        /* skip command character */
        packet++;
        packet_size--;

        if (packet_size % 2) {
                LOG_WARNING("GDB set_registers packet with uneven characters received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        retval = target_get_gdb_reg_list(target, &reg_list, &reg_list_size,
                        REG_CLASS_GENERAL);
        if (retval != ERROR_OK)
                return gdb_error(connection, retval);

        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)
                        LOG_ERROR("BUG: register packet is too small for registers");

                bin_buf = malloc(DIV_ROUND_UP(reg_list[i]->size, 8));
                gdb_target_to_reg(target, packet_p, chars, bin_buf);

                retval = reg_list[i]->type->set(reg_list[i], bin_buf);
                if (retval != ERROR_OK && gdb_report_register_access_error) {
                        LOG_DEBUG("Couldn't set register %s.", reg_list[i]->name);
                        free(reg_list);
                        free(bin_buf);
                        return gdb_error(connection, retval);
                }

                /* advance packet pointer */
                packet_p += chars;

                free(bin_buf);
        }

        /* free struct reg *reg_list[] array allocated by get_gdb_reg_list */
        free(reg_list);

        gdb_put_packet(connection, "OK", 2);

        return ERROR_OK;
}

static int gdb_get_register_packet(struct connection *connection,
        char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *reg_packet;
        int reg_num = strtoul(packet + 1, NULL, 16);
        struct reg **reg_list;
        int reg_list_size;
        int retval;

#ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("-");
#endif

        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,
                        REG_CLASS_ALL);
        if (retval != ERROR_OK)
                return gdb_error(connection, retval);

        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;
        }

        if (!reg_list[reg_num]->valid) {
                retval = reg_list[reg_num]->type->get(reg_list[reg_num]);
                if (retval != ERROR_OK && gdb_report_register_access_error) {
                        LOG_DEBUG("Couldn't get register %s.", reg_list[reg_num]->name);
                        free(reg_list);
                        return gdb_error(connection, retval);
                }
        }

        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]);

        gdb_put_packet(connection, reg_packet, DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2);

        free(reg_list);
        free(reg_packet);

        return ERROR_OK;
}

static int gdb_set_register_packet(struct connection *connection,
        char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *separator;
        int reg_num = strtoul(packet + 1, &separator, 16);
        struct reg **reg_list;
        int reg_list_size;
        int retval;

#ifdef _DEBUG_GDB_IO_
        LOG_DEBUG("-");
#endif

        if (*separator != '=') {
                LOG_ERROR("GDB 'set register packet', but no '=' following the register number");
                return ERROR_SERVER_REMOTE_CLOSED;
        }
        size_t chars = strlen(separator + 1);
        uint8_t *bin_buf = malloc(chars / 2);
        gdb_target_to_reg(target, separator + 1, chars, 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;
        }

        retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
                        REG_CLASS_ALL);
        if (retval != ERROR_OK) {
                free(bin_buf);
                return gdb_error(connection, retval);
        }

        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 %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;
        }

        gdb_target_to_reg(target, separator + 1, chars, bin_buf);

        retval = reg_list[reg_num]->type->set(reg_list[reg_num], bin_buf);
        if (retval != ERROR_OK && gdb_report_register_access_error) {
                LOG_DEBUG("Couldn't set register %s.", reg_list[reg_num]->name);
                free(bin_buf);
                free(reg_list);
                return gdb_error(connection, retval);
        }

        gdb_put_packet(connection, "OK", 2);

        free(bin_buf);
        free(reg_list);

        return ERROR_OK;
}

/* No attempt is made to translate the "retval" to
 * GDB speak. This has to be done at the calling
 * site as no mapping really exists.
 */
static int gdb_error(struct connection *connection, int retval)
{
        LOG_DEBUG("Reporting %i to GDB as generic error", retval);
        gdb_send_error(connection, EFAULT);
        return ERROR_OK;
}

/* We don't have to worry about the default 2 second timeout for GDB packets,
 * because GDB breaks up large memory reads into smaller reads.
 */
static int gdb_read_memory_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *separator;
        uint64_t addr = 0;
        uint32_t len = 0;

        uint8_t *buffer;
        char *hex_buffer;

        int retval = ERROR_OK;

        /* skip command character */
        packet++;

        addr = strtoull(packet, &separator, 16);

        if (*separator != ',') {
                LOG_ERROR("incomplete read memory packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        len = strtoul(separator + 1, NULL, 16);

        if (!len) {
                LOG_WARNING("invalid read memory packet received (len == 0)");
                gdb_put_packet(connection, "", 0);
                return ERROR_OK;
        }

        buffer = malloc(len);

        LOG_DEBUG("addr: 0x%16.16" PRIx64 ", len: 0x%8.8" PRIx32 "", addr, len);

        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.
                 * At some point this might be fixed in GDB, in which case this code can be removed.
                 *
                 * OpenOCD developers are acutely aware of this problem, but there is nothing
                 * gained by involving the user in this problem that hopefully will get resolved
                 * eventually
                 *
                 * http://sourceware.org/cgi-bin/gnatsweb.pl? \
                 * cmd = view%20audit-trail&database = gdb&pr = 2395
                 *
                 * For now, the default is to fix up things to make current GDB versions work.
                 * This can be overwritten using the gdb_report_data_abort <'enable'|'disable'> command.
                 */
                memset(buffer, 0, len);
                retval = ERROR_OK;
        }

        if (retval == ERROR_OK) {
                hex_buffer = malloc(len * 2 + 1);

                size_t pkt_len = hexify(hex_buffer, buffer, len, len * 2 + 1);

                gdb_put_packet(connection, hex_buffer, pkt_len);

                free(hex_buffer);
        } else
                retval = gdb_error(connection, retval);

        free(buffer);

        return retval;
}

static int gdb_write_memory_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *separator;
        uint64_t addr = 0;
        uint32_t len = 0;

        uint8_t *buffer;
        int retval;

        /* skip command character */
        packet++;

        addr = strtoull(packet, &separator, 16);

        if (*separator != ',') {
                LOG_ERROR("incomplete write memory packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        len = strtoul(separator + 1, &separator, 16);

        if (*(separator++) != ':') {
                LOG_ERROR("incomplete write memory packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        buffer = malloc(len);

        LOG_DEBUG("addr: 0x%" PRIx64 ", len: 0x%8.8" PRIx32 "", addr, len);

        if (unhexify(buffer, separator, len) != len)
                LOG_ERROR("unable to decode memory packet");

        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);
        else
                retval = gdb_error(connection, retval);

        free(buffer);

        return retval;
}

static int gdb_write_memory_binary_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *separator;
        uint64_t addr = 0;
        uint32_t len = 0;

        int retval = ERROR_OK;
        /* Packets larger than fast_limit bytes will be acknowledged instantly on
         * the assumption that we're in a download and it's important to go as fast
         * as possible. */
        uint32_t fast_limit = 8;

        /* skip command character */
        packet++;

        addr = strtoull(packet, &separator, 16);

        if (*separator != ',') {
                LOG_ERROR("incomplete write memory binary packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        len = strtoul(separator + 1, &separator, 16);

        if (*(separator++) != ':') {
                LOG_ERROR("incomplete write memory binary packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        struct gdb_connection *gdb_connection = connection->priv;

        if (gdb_connection->mem_write_error)
                retval = ERROR_FAIL;

        if (retval == ERROR_OK) {
                if (len >= fast_limit) {
                        /* By replying the packet *immediately* GDB will send us a new packet
                         * while we write the last one to the target.
                         * We only do this for larger writes, so that users who do something like:
                         * p *((int*)0xdeadbeef)=8675309
                         * will get immediate feedback that that write failed.
                         */
                        gdb_put_packet(connection, "OK", 2);
                }
        } else {
                retval = gdb_error(connection, retval);
                /* now that we have reported the memory write error, we can clear the condition */
                gdb_connection->mem_write_error = false;
                if (retval != ERROR_OK)
                        return retval;
        }

        if (len) {
                LOG_DEBUG("addr: 0x%" PRIx64 ", len: 0x%8.8" PRIx32 "", addr, len);

                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;
        }

        if (len < fast_limit) {
                if (retval != ERROR_OK) {
                        gdb_error(connection, retval);
                        gdb_connection->mem_write_error = false;
                } else {
                        gdb_put_packet(connection, "OK", 2);
                }
        }

        return ERROR_OK;
}

static int gdb_step_continue_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        int current = 0;
        uint64_t address = 0x0;
        int retval = ERROR_OK;

        LOG_DEBUG("-");

        if (packet_size > 1)
                address = strtoull(packet + 1, NULL, 16);
        else
                current = 1;

        gdb_running_type = packet[0];
        if (packet[0] == 'c') {
                LOG_DEBUG("continue");
                /* resume at current address, don't handle breakpoints, not debugging */
                retval = target_resume(target, current, address, 0, 0);
        } else if (packet[0] == 's') {
                LOG_DEBUG("step");
                /* step at current or address, don't handle breakpoints */
                retval = target_step(target, current, address, 0);
        }
        return retval;
}

static int gdb_breakpoint_watchpoint_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        int type;
        enum breakpoint_type bp_type = BKPT_SOFT /* dummy init to avoid warning */;
        enum watchpoint_rw wp_type = WPT_READ /* dummy init to avoid warning */;
        uint64_t address;
        uint32_t size;
        char *separator;
        int retval;

        LOG_DEBUG("[%s]", target_name(target));

        type = strtoul(packet + 1, &separator, 16);

        if (type == 0)  /* memory breakpoint */
                bp_type = BKPT_SOFT;
        else if (type == 1)     /* hardware breakpoint */
                bp_type = BKPT_HARD;
        else if (type == 2)     /* write watchpoint */
                wp_type = WPT_WRITE;
        else if (type == 3)     /* read watchpoint */
                wp_type = WPT_READ;
        else if (type == 4)     /* access watchpoint */
                wp_type = WPT_ACCESS;
        else {
                LOG_ERROR("invalid gdb watch/breakpoint type(%d), dropping connection", type);
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        if (gdb_breakpoint_override && ((bp_type == BKPT_SOFT) || (bp_type == BKPT_HARD)))
                bp_type = gdb_breakpoint_override_type;

        if (*separator != ',') {
                LOG_ERROR("incomplete breakpoint/watchpoint packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        address = strtoull(separator + 1, &separator, 16);

        if (*separator != ',') {
                LOG_ERROR("incomplete breakpoint/watchpoint packet received, dropping connection");
                return ERROR_SERVER_REMOTE_CLOSED;
        }

        size = strtoul(separator + 1, &separator, 16);

        switch (type) {
                case 0:
                case 1:
                        if (packet[0] == 'Z') {
                                retval = breakpoint_add(target, address, size, bp_type);
                                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;
                                } else
                                        gdb_put_packet(connection, "OK", 2);
                        } else {
                                breakpoint_remove(target, address);
                                gdb_put_packet(connection, "OK", 2);
                        }
                        break;
                case 2:
                case 3:
                case 4:
                {
                        if (packet[0] == 'Z') {
                                retval = watchpoint_add(target, address, size, wp_type, 0, 0xffffffffu);
                                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;
                                } else
                                        gdb_put_packet(connection, "OK", 2);
                        } else {
                                watchpoint_remove(target, address);
                                gdb_put_packet(connection, "OK", 2);
                        }
                        break;
                }
                default:
                        break;
        }

        return ERROR_OK;
}

/* print out a string and allocate more space as needed,
 * mainly used for XML at this point
 */
static __attribute__ ((format (PRINTF_ATTRIBUTE_FORMAT, 5, 6))) void xml_printf(int *retval,
                char **xml, int *pos, int *size, const char *fmt, ...)
{
        if (*retval != ERROR_OK)
                return;
        int first = 1;

        for (;; ) {
                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) {
                                free(t);
                                *retval = ERROR_SERVER_REMOTE_CLOSED;
                                return;
                        }
                }

                va_list ap;
                int ret;
                va_start(ap, fmt);
                ret = vsnprintf(*xml + *pos, *size - *pos, fmt, ap);
                va_end(ap);
                if ((ret > 0) && ((ret + 1) < *size - *pos)) {
                        *pos += ret;
                        return;
                }
                /* there was just enough or not enough space, allocate more. */
                first = 0;
        }
}

static int decode_xfer_read(char const *buf, char **annex, int *ofs, unsigned int *len)
{
        /* Locate the annex. */
        const char *annex_end = strchr(buf, ':');
        if (!annex_end)
                return ERROR_FAIL;

        /* After the read marker and annex, qXfer looks like a
         * traditional 'm' packet. */
        char *separator;
        *ofs = strtoul(annex_end + 1, &separator, 16);

        if (*separator != ',')
                return ERROR_FAIL;

        *len = strtoul(separator + 1, NULL, 16);

        /* Extract the annex if needed */
        if (annex) {
                *annex = strndup(buf, annex_end - buf);
                if (!*annex)
                        return ERROR_FAIL;
        }

        return ERROR_OK;
}

static int compare_bank(const void *a, const void *b)
{
        struct flash_bank *b1, *b2;
        b1 = *((struct flash_bank **)a);
        b2 = *((struct flash_bank **)b);

        if (b1->base == b2->base)
                return 0;
        else if (b1->base > b2->base)
                return 1;
        else
                return -1;
}

static int gdb_memory_map(struct connection *connection,
                char const *packet, int packet_size)
{
        /* We get away with only specifying flash here. Regions that are not
         * specified are treated as if we provided no memory map(if not we
         * could detect the holes and mark them as RAM).
         * Normally we only execute this code once, but no big deal if we
         * have to regenerate it a couple of times.
         */

        struct target *target = get_target_from_connection(connection);
        struct flash_bank *p;
        char *xml = NULL;
        int size = 0;
        int pos = 0;
        int retval = ERROR_OK;
        struct flash_bank **banks;
        int offset;
        int length;
        char *separator;
        target_addr_t ram_start = 0;
        unsigned int target_flash_banks = 0;

        /* skip command character */
        packet += 23;

        offset = strtoul(packet, &separator, 16);
        length = strtoul(separator + 1, &separator, 16);

        xml_printf(&retval, &xml, &pos, &size, "<memory-map>\n");

        /* Sort banks in ascending order.  We need to report non-flash
         * memory as ram (or rather read/write) by default for GDB, since
         * it has no concept of non-cacheable read/write memory (i/o etc).
         */
        banks = malloc(sizeof(struct flash_bank *)*flash_get_bank_count());

        for (unsigned int i = 0; i < flash_get_bank_count(); i++) {
                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) {
                        free(banks);
                        gdb_error(connection, retval);
                        return retval;
                }
                banks[target_flash_banks++] = p;
        }

        qsort(banks, target_flash_banks, sizeof(struct flash_bank *),
                compare_bank);

        for (unsigned int i = 0; i < target_flash_banks; i++) {
                unsigned sector_size = 0;
                unsigned group_len = 0;

                p = banks[i];

                if (ram_start < p->base)
                        xml_printf(&retval, &xml, &pos, &size,
                                "<memory type=\"ram\" start=\"" TARGET_ADDR_FMT "\" "
                                "length=\"" TARGET_ADDR_FMT "\"/>\n",
                                ram_start, p->base - ram_start);

                /* Report adjacent groups of same-size sectors.  So for
                 * example top boot CFI flash will list an initial region
                 * with several large sectors (maybe 128KB) and several
                 * smaller ones at the end (maybe 32KB).  STR7 will have
                 * regions with 8KB, 32KB, and 64KB sectors; etc.
                 */
                for (unsigned int j = 0; j < p->num_sectors; j++) {

                        /* Maybe start a new group of sectors. */
                        if (sector_size == 0) {
                                if (p->sectors[j].offset + p->sectors[j].size > p->size) {
                                        LOG_WARNING("The flash sector at offset 0x%08" PRIx32
                                                " overflows the end of %s bank.",
                                                p->sectors[j].offset, p->name);
                                        LOG_WARNING("The rest of bank will not show in gdb memory map.");
                                        break;
                                }
                                target_addr_t start;
                                start = p->base + p->sectors[j].offset;
                                xml_printf(&retval, &xml, &pos, &size,
                                        "<memory type=\"flash\" "
                                        "start=\"" TARGET_ADDR_FMT "\" ",
                                        start);
                                sector_size = p->sectors[j].size;
                                group_len = sector_size;
                        } else {
                                group_len += sector_size; /* equal to p->sectors[j].size */
                        }

                        /* Does this finish a group of sectors?
                         * If not, continue an already-started group.
                         */
                        if (j < p->num_sectors - 1
                                        && p->sectors[j + 1].size == sector_size
                                        && p->sectors[j + 1].offset == p->sectors[j].offset + sector_size
                                        && p->sectors[j + 1].offset + p->sectors[j + 1].size <= p->size)
                                continue;

                        xml_printf(&retval, &xml, &pos, &size,
                                "length=\"0x%x\">\n"
                                "<property name=\"blocksize\">"
                                "0x%x</property>\n"
                                "</memory>\n",
                                group_len,
                                sector_size);
                        sector_size = 0;
                }

                ram_start = p->base + p->size;
        }

        if (ram_start != 0)
                xml_printf(&retval, &xml, &pos, &size,
                        "<memory type=\"ram\" start=\"" TARGET_ADDR_FMT "\" "
                        "length=\"" TARGET_ADDR_FMT "\"/>\n",
                        ram_start, target_address_max(target) - ram_start + 1);
        /* ELSE a flash chip could be at the very end of the address space, in
         * which case ram_start will be precisely 0 */

        free(banks);

        xml_printf(&retval, &xml, &pos, &size, "</memory-map>\n");

        if (retval != ERROR_OK) {
                free(xml);
                gdb_error(connection, retval);
                return retval;
        }

        if (offset + length > pos)
                length = pos - offset;

        char *t = malloc(length + 1);
        t[0] = 'l';
        memcpy(t + 1, xml + offset, length);
        gdb_put_packet(connection, t, length + 1);

        free(t);
        free(xml);
        return ERROR_OK;
}

static const char *gdb_get_reg_type_name(enum reg_type type)
{
        switch (type) {
                case REG_TYPE_BOOL:
                        return "bool";
                case REG_TYPE_INT:
                        return "int";
                case REG_TYPE_INT8:
                        return "int8";
                case REG_TYPE_INT16:
                        return "int16";
                case REG_TYPE_INT32:
                        return "int32";
                case REG_TYPE_INT64:
                        return "int64";
                case REG_TYPE_INT128:
                        return "int128";
                case REG_TYPE_UINT:
                        return "uint";
                case REG_TYPE_UINT8:
                        return "uint8";
                case REG_TYPE_UINT16:
                        return "uint16";
                case REG_TYPE_UINT32:
                        return "uint32";
                case REG_TYPE_UINT64:
                        return "uint64";
                case REG_TYPE_UINT128:
                        return "uint128";
                case REG_TYPE_CODE_PTR:
                        return "code_ptr";
                case REG_TYPE_DATA_PTR:
                        return "data_ptr";
                case REG_TYPE_FLOAT:
                        return "float";
                case REG_TYPE_IEEE_SINGLE:
                        return "ieee_single";
                case REG_TYPE_IEEE_DOUBLE:
                        return "ieee_double";
                case REG_TYPE_ARCH_DEFINED:
                        return "int"; /* return arbitrary string to avoid compile warning. */
        }

        return "int"; /* "int" as default value */
}

static int lookup_add_arch_defined_types(char const **arch_defined_types_list[], const char *type_id,
                                        int *num_arch_defined_types)
{
        int tbl_sz = *num_arch_defined_types;

        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;
                                *arch_defined_types_list = realloc(*arch_defined_types_list,
                                                                sizeof(char *) * (tbl_sz + 1));
                                (*arch_defined_types_list)[tbl_sz] = NULL;
                                *num_arch_defined_types = tbl_sz;
                                return 1;
                        } else {
                                if (!strcmp((*arch_defined_types_list)[j], type_id))
                                        return 0;
                        }
                }
        }

        return -1;
}

static int gdb_generate_reg_type_description(struct target *target,
                char **tdesc, int *pos, int *size, struct reg_data_type *type,
                char const **arch_defined_types_list[], int *num_arch_defined_types)
{
        int retval = ERROR_OK;

        if (type->type_class == REG_TYPE_CLASS_VECTOR) {
                struct reg_data_type *data_type = type->reg_type_vector->type;
                if (data_type->type == REG_TYPE_ARCH_DEFINED) {
                        if (lookup_add_arch_defined_types(arch_defined_types_list, data_type->id,
                                                        num_arch_defined_types))
                                gdb_generate_reg_type_description(target, tdesc, pos, size, data_type,
                                                                arch_defined_types_list,
                                                                num_arch_defined_types);
                }
                /* <vector id="id" type="type" count="count"/> */
                xml_printf(&retval, tdesc, pos, size,
                                "<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) {
                        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,
                                                                num_arch_defined_types))
                                        gdb_generate_reg_type_description(target, tdesc, pos, size, data_type,
                                                                        arch_defined_types_list,
                                                                        num_arch_defined_types);
                        }

                        field = field->next;
                }
                /* <union id="id">
                 *  <field name="name" type="type"/> ...
                 * </union> */
                xml_printf(&retval, tdesc, pos, size,
                                "<union id=\"%s\">\n",
                                type->id);

                field = type->reg_type_union->fields;
                while (field) {
                        xml_printf(&retval, tdesc, pos, size,
                                        "<field name=\"%s\" type=\"%s\"/>\n",
                                        field->name, field->type->id);

                        field = field->next;
                }

                xml_printf(&retval, tdesc, pos, size,
                                "</union>\n");

        } else if (type->type_class == REG_TYPE_CLASS_STRUCT) {
                struct reg_data_type_struct_field *field;
                field = type->reg_type_struct->fields;

                if (field->use_bitfields) {
                        /* <struct id="id" size="size">
                         *  <field name="name" start="start" end="end"/> ...
                         * </struct> */
                        xml_printf(&retval, tdesc, pos, size,
                                        "<struct id=\"%s\" size=\"%" PRIu32 "\">\n",
                                        type->id, type->reg_type_struct->size);
                        while (field) {
                                xml_printf(&retval, tdesc, pos, size,
                                                "<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) {
                                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,
                                                                        num_arch_defined_types))
                                                gdb_generate_reg_type_description(target, tdesc, pos, size, data_type,
                                                                                arch_defined_types_list,
                                                                                num_arch_defined_types);
                                }
                        }

                        /* <struct id="id">
                         *  <field name="name" type="type"/> ...
                         * </struct> */
                        xml_printf(&retval, tdesc, pos, size,
                                        "<struct id=\"%s\">\n",
                                        type->id);
                        while (field) {
                                xml_printf(&retval, tdesc, pos, size,
                                                "<field name=\"%s\" type=\"%s\"/>\n",
                                                field->name, field->type->id);

                                field = field->next;
                        }
                }

                xml_printf(&retval, tdesc, pos, size,
                                "</struct>\n");

        } else if (type->type_class == REG_TYPE_CLASS_FLAGS) {
                /* <flags id="id" size="size">
                 *  <field name="name" start="start" end="end"/> ...
                 * </flags> */
                xml_printf(&retval, tdesc, pos, size,
                                "<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) {
                        xml_printf(&retval, tdesc, pos, size,
                                        "<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;
                }

                xml_printf(&retval, tdesc, pos, size,
                                "</flags>\n");

        }

        return ERROR_OK;
}

/* Get a list of available target registers features. feature_list must
 * be freed by caller.
 */
static int get_reg_features_list(struct target *target, char const **feature_list[], int *feature_list_size,
                struct reg **reg_list, int reg_list_size)
{
        int tbl_sz = 0;

        /* Start with only one element */
        *feature_list = calloc(1, sizeof(char *));

        for (int i = 0; i < reg_list_size; i++) {
                if (reg_list[i]->exist == false || reg_list[i]->hidden)
                        continue;

                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
                         * put the new feature in it.
                         */
                        for (int j = 0; j < (tbl_sz + 1); j++) {
                                if (!((*feature_list)[j])) {
                                        (*feature_list)[tbl_sz++] = reg_list[i]->feature->name;
                                        *feature_list = realloc(*feature_list, sizeof(char *) * (tbl_sz + 1));
                                        (*feature_list)[tbl_sz] = NULL;
                                        break;
                                } else {
                                        if (!strcmp((*feature_list)[j], reg_list[i]->feature->name))
                                                break;
                                }
                        }
                }
        }

        if (feature_list_size)
                *feature_list_size = tbl_sz;

        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 *));
                                                        free(reg_list);
                                                        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;
        struct reg **reg_list = NULL;
        int reg_list_size;
        char const *architecture;
        char const **features = NULL;
        int feature_list_size = 0;
        char *tdesc = NULL;
        int pos = 0;
        int size = 0;


        retval = smp_reg_list_noread(target, &reg_list, &reg_list_size,
                        REG_CLASS_ALL);

        if (retval != ERROR_OK) {
                LOG_ERROR("get register list failed");
                retval = ERROR_FAIL;
                goto error;
        }

        if (reg_list_size <= 0) {
                LOG_ERROR("get register list failed");
                retval = ERROR_FAIL;
                goto error;
        }

        /* Get a list of available target registers features */
        retval = get_reg_features_list(target, &features, &feature_list_size, reg_list, reg_list_size);
        if (retval != ERROR_OK) {
                LOG_ERROR("Can't get the registers feature list");
                retval = ERROR_FAIL;
                goto error;
        }

        /* If we found some features associated with registers, create sections */
        int current_feature = 0;

        xml_printf(&retval, &tdesc, &pos, &size,
                        "<?xml version=\"1.0\"?>\n"
                        "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">\n"
                        "<target version=\"1.0\">\n");

        /* generate architecture element if supported by target */
        architecture = target_get_gdb_arch(target);
        if (architecture)
                xml_printf(&retval, &tdesc, &pos, &size,
                                "<architecture>%s</architecture>\n", architecture);

        /* generate target description according to register list */
        if (features) {
                while (features[current_feature]) {
                        char const **arch_defined_types = NULL;
                        int num_arch_defined_types = 0;

                        arch_defined_types = calloc(1, sizeof(char *));
                        xml_printf(&retval, &tdesc, &pos, &size,
                                        "<feature name=\"%s\">\n",
                                        features[current_feature]);

                        int i;
                        for (i = 0; i < reg_list_size; i++) {

                                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) {
                                        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,
                                                                                reg_list[i]->reg_data_type->id,
                                                                                &num_arch_defined_types))
                                                        gdb_generate_reg_type_description(target, &tdesc, &pos, &size,
                                                                                        reg_list[i]->reg_data_type,
                                                                                        &arch_defined_types,
                                                                                        &num_arch_defined_types);

                                                type_str = reg_list[i]->reg_data_type->id;
                                        } else {
                                                /* predefined type */
                                                type_str = gdb_get_reg_type_name(
                                                                reg_list[i]->reg_data_type->type);
                                        }
                                } else {
                                        /* Default type is "int" */
                                        type_str = "int";
                                }

                                xml_printf(&retval, &tdesc, &pos, &size,
                                                "<reg name=\"%s\"", reg_list[i]->name);
                                xml_printf(&retval, &tdesc, &pos, &size,
                                                " bitsize=\"%" PRIu32 "\"", reg_list[i]->size);
                                xml_printf(&retval, &tdesc, &pos, &size,
                                                " regnum=\"%" PRIu32 "\"", reg_list[i]->number);
                                if (reg_list[i]->caller_save)
                                        xml_printf(&retval, &tdesc, &pos, &size,
                                                        " save-restore=\"yes\"");
                                else
                                        xml_printf(&retval, &tdesc, &pos, &size,
                                                        " save-restore=\"no\"");

                                xml_printf(&retval, &tdesc, &pos, &size,
                                                " type=\"%s\"", type_str);

                                if (reg_list[i]->group)
                                        xml_printf(&retval, &tdesc, &pos, &size,
                                                        " group=\"%s\"", reg_list[i]->group);

                                xml_printf(&retval, &tdesc, &pos, &size,
                                                "/>\n");
                        }

                        xml_printf(&retval, &tdesc, &pos, &size,
                                        "</feature>\n");

                        current_feature++;
                        free(arch_defined_types);
                }
        }

        xml_printf(&retval, &tdesc, &pos, &size,
                        "</target>\n");

error:
        free(features);
        free(reg_list);

        if (retval == ERROR_OK)
                *tdesc_out = tdesc;
        else
                free(tdesc);

        return retval;
}

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) {
                LOG_ERROR("Unable to Generate Target Description");
                return ERROR_FAIL;
        }

        char *tdesc = target_desc->tdesc;
        uint32_t tdesc_length = target_desc->tdesc_length;

        if (!tdesc) {
                int retval = gdb_generate_target_description(target, &tdesc);
                if (retval != ERROR_OK) {
                        LOG_ERROR("Unable to Generate Target Description");
                        return ERROR_FAIL;
                }

                tdesc_length = strlen(tdesc);
        }

        char transfer_type;

        if (length < (tdesc_length - offset))
                transfer_type = 'm';
        else
                transfer_type = 'l';

        *chunk = malloc(length + 2);
        if (!*chunk) {
                LOG_ERROR("Unable to allocate memory");
                return ERROR_FAIL;
        }

        (*chunk)[0] = transfer_type;
        if (transfer_type == 'm') {
                strncpy((*chunk) + 1, tdesc + offset, length);
                (*chunk)[1 + length] = '\0';
        } else {
                strncpy((*chunk) + 1, tdesc + offset, tdesc_length - offset);
                (*chunk)[1 + (tdesc_length - offset)] = '\0';

                /* After gdb-server sends out last chunk, invalidate tdesc. */
                free(tdesc);
                tdesc = NULL;
                tdesc_length = 0;
        }

        target_desc->tdesc = tdesc;
        target_desc->tdesc_length = tdesc_length;

        return ERROR_OK;
}

static int gdb_target_description_supported(struct target *target, int *supported)
{
        int retval = ERROR_OK;
        struct reg **reg_list = NULL;
        int reg_list_size = 0;
        char const **features = NULL;
        int feature_list_size = 0;

        char const *architecture = target_get_gdb_arch(target);

        retval = target_get_gdb_reg_list_noread(target, &reg_list,
                        &reg_list_size, REG_CLASS_ALL);
        if (retval != ERROR_OK) {
                LOG_ERROR("get register list failed");
                goto error;
        }

        if (reg_list_size <= 0) {
                LOG_ERROR("get register list failed");
                retval = ERROR_FAIL;
                goto error;
        }

        /* Get a list of available target registers features */
        retval = get_reg_features_list(target, &features, &feature_list_size, reg_list, reg_list_size);
        if (retval != ERROR_OK) {
                LOG_ERROR("Can't get the registers feature list");
                goto error;
        }

        if (supported) {
                if (architecture || feature_list_size)
                        *supported = 1;
                else
                        *supported = 0;
        }

error:
        free(features);

        free(reg_list);

        return retval;
}

static int gdb_generate_thread_list(struct target *target, char **thread_list_out)
{
        struct rtos *rtos = target->rtos;
        int retval = ERROR_OK;
        char *thread_list = NULL;
        int pos = 0;
        int size = 0;

        xml_printf(&retval, &thread_list, &pos, &size,
                   "<?xml version=\"1.0\"?>\n"
                   "<threads>\n");

        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;

                        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)
                                xml_printf(&retval, &thread_list, &pos, &size,
                                           "Name: %s", thread_detail->thread_name_str);

                        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,
                                           "%s", thread_detail->extra_info_str);
                        }

                        xml_printf(&retval, &thread_list, &pos, &size,
                                   "</thread>\n");
                }
        }

        xml_printf(&retval, &thread_list, &pos, &size,
                   "</threads>\n");

        if (retval == ERROR_OK)
                *thread_list_out = thread_list;
        else
                free(thread_list);

        return retval;
}

static int gdb_get_thread_list_chunk(struct target *target, char **thread_list,
                char **chunk, int32_t offset, uint32_t length)
{
        if (!*thread_list) {
                int retval = gdb_generate_thread_list(target, thread_list);
                if (retval != ERROR_OK) {
                        LOG_ERROR("Unable to Generate Thread List");
                        return ERROR_FAIL;
                }
        }

        size_t thread_list_length = strlen(*thread_list);
        char transfer_type;

        length = MIN(length, thread_list_length - offset);
        if (length < (thread_list_length - offset))
                transfer_type = 'm';
        else
                transfer_type = 'l';

        *chunk = malloc(length + 2 + 3);
        /* 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) {
                LOG_ERROR("Unable to allocate memory");
                return ERROR_FAIL;
        }

        (*chunk)[0] = transfer_type;
        strncpy((*chunk) + 1, (*thread_list) + offset, length);
        (*chunk)[1 + length] = '\0';

        /* After gdb-server sends out last chunk, invalidate thread list. */
        if (transfer_type == 'l') {
                free(*thread_list);
                *thread_list = NULL;
        }

        return ERROR_OK;
}

static int gdb_query_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct command_context *cmd_ctx = connection->cmd_ctx;
        struct gdb_connection *gdb_connection = connection->priv;
        struct target *target = get_target_from_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 */
                        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;

                        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();
                        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;
        } else if (strncmp(packet, "qCRC:", 5) == 0) {
                if (packet_size > 5) {
                        int retval;
                        char gdb_reply[10];
                        char *separator;
                        uint32_t checksum;
                        target_addr_t addr = 0;
                        uint32_t len = 0;

                        /* skip command character */
                        packet += 5;

                        addr = strtoull(packet, &separator, 16);

                        if (*separator != ',') {
                                LOG_ERROR("incomplete read memory packet received, dropping connection");
                                return ERROR_SERVER_REMOTE_CLOSED;
                        }

                        len = strtoul(separator + 1, NULL, 16);

                        retval = target_checksum_memory(target, addr, len, &checksum);

                        if (retval == ERROR_OK) {
                                snprintf(gdb_reply, 10, "C%8.8" PRIx32 "", checksum);
                                gdb_put_packet(connection, gdb_reply, 9);
                        } else {
                                retval = gdb_error(connection, retval);
                                if (retval != ERROR_OK)
                                        return retval;
                        }

                        return ERROR_OK;
                }
        } else if (strncmp(packet, "qSupported", 10) == 0) {
                /* we currently support packet size and qXfer:memory-map:read (if enabled)
                 * qXfer:features:read is supported for some targets */
                int retval = ERROR_OK;
                char *buffer = NULL;
                int pos = 0;
                int size = 0;
                int gdb_target_desc_supported = 0;

                /* we need to test that the target supports target descriptions */
                retval = gdb_target_description_supported(target, &gdb_target_desc_supported);
                if (retval != ERROR_OK) {
                        LOG_INFO("Failed detecting Target Description Support, disabling");
                        gdb_target_desc_supported = 0;
                }

                /* support may be disabled globally */
                if (gdb_use_target_description == 0) {
                        if (gdb_target_desc_supported)
                                LOG_WARNING("Target Descriptions Supported, but disabled");
                        gdb_target_desc_supported = 0;
                }

                xml_printf(&retval,
                        &buffer,
                        &pos,
                        &size,
                        "PacketSize=%x;qXfer:memory-map:read%c;qXfer:features:read%c;qXfer:threads:read+;QStartNoAckMode+;vContSupported+",
                        GDB_BUFFER_SIZE,
                        ((gdb_use_memory_map == 1) && (flash_get_bank_count() > 0)) ? '+' : '-',
                        (gdb_target_desc_supported == 1) ? '+' : '-');

                if (retval != ERROR_OK) {
                        gdb_send_error(connection, 01);
                        return ERROR_OK;
                }

                gdb_put_packet(connection, buffer, strlen(buffer));
                free(buffer);

                return ERROR_OK;
        } else if ((strncmp(packet, "qXfer:memory-map:read::", 23) == 0)
                   && (flash_get_bank_count() > 0))
                return gdb_memory_map(connection, packet, packet_size);
        else if (strncmp(packet, "qXfer:features:read:", 20) == 0) {
                char *xml = NULL;
                int retval = ERROR_OK;

                int offset;
                unsigned int length;

                /* skip command character */
                packet += 20;

                if (decode_xfer_read(packet, NULL, &offset, &length) < 0) {
                        gdb_send_error(connection, 01);
                        return ERROR_OK;
                }

                /* Target should prepare correct target description for annex.
                 * The first character of returned xml is 'm' or 'l'. 'm' for
                 * there are *more* chunks to transfer. 'l' for it is the *last*
                 * chunk of target description.
                 */
                retval = gdb_get_target_description_chunk(target, &gdb_connection->target_desc,
                                &xml, offset, length);
                if (retval != ERROR_OK) {
                        gdb_error(connection, retval);
                        return retval;
                }

                gdb_put_packet(connection, xml, strlen(xml));

                free(xml);
                return ERROR_OK;
        } else if (strncmp(packet, "qXfer:threads:read:", 19) == 0) {
                char *xml = NULL;
                int retval = ERROR_OK;

                int offset;
                unsigned int length;

                /* skip command character */
                packet += 19;

                if (decode_xfer_read(packet, NULL, &offset, &length) < 0) {
                        gdb_send_error(connection, 01);
                        return ERROR_OK;
                }

                /* Target should prepare correct thread list for annex.
                 * The first character of returned xml is 'm' or 'l'. 'm' for
                 * there are *more* chunks to transfer. 'l' for it is the *last*
                 * chunk of target description.
                 */
                retval = gdb_get_thread_list_chunk(target, &gdb_connection->thread_list,
                                                   &xml, offset, length);
                if (retval != ERROR_OK) {
                        gdb_error(connection, retval);
                        return retval;
                }

                gdb_put_packet(connection, xml, strlen(xml));

                free(xml);
                return ERROR_OK;
        } else if (strncmp(packet, "QStartNoAckMode", 15) == 0) {
                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);
        return ERROR_OK;
}

static bool gdb_handle_vcont_packet(struct connection *connection, const char *packet,
        __attribute__((unused)) int packet_size)
{
        struct gdb_connection *gdb_connection = connection->priv;
        struct target *target = get_target_from_connection(connection);
        const char *parse = packet;
        int retval;

        /* query for vCont supported */
        if (parse[0] == '?') {
                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;
                }
                return false;
        }

        if (parse[0] == ';') {
                ++parse;
        }

        /* simple case, a continue packet */
        if (parse[0] == 'c') {
                gdb_running_type = 'c';
                LOG_DEBUG("target %s continue", target_name(target));
                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));

                /* poll target in an attempt to make its internal state consistent */
                if (retval != ERROR_OK) {
                        retval = target_poll(target);
                        if (retval != ERROR_OK)
                                LOG_DEBUG("error polling target %s after failed resume", target_name(target));
                }

                /*
                 * We don't report errors to gdb here, move frontend_state to
                 * TARGET_RUNNING to stay in sync with gdb's expectation of the
                 * target state
                 */
                gdb_connection->frontend_state = TARGET_RUNNING;
                target_call_event_callbacks(target, TARGET_EVENT_GDB_START);

                return true;
        }

        /* single-step or step-over-breakpoint */
        if (parse[0] == 's') {
                gdb_running_type = 's';
                bool fake_step = false;

                struct target *ct = target;
                int current_pc = 1;
                int64_t thread_id;
                parse++;
                if (parse[0] == ':') {
                        char *endp;
                        parse++;
                        thread_id = strtoll(parse, &endp, 16);
                        if (endp) {
                                parse = endp;
                        }
                } else {
                        thread_id = 0;
                }

                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);

                        /*
                         * 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;

                        if (parse[0] == 'c') {
                                parse += 1;

                                /* check if thread-id follows */
                                if (parse[0] == ':') {
                                        int64_t tid;
                                        parse += 1;

                                        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);
                gdb_connection->output_flag = GDB_OUTPUT_ALL;
                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);

                        sig_reply_len = snprintf(sig_reply, sizeof(sig_reply),
                                                                        "T05thread:%016"PRIx64";", thread_id);

                        gdb_put_packet(connection, sig_reply, sig_reply_len);
                        gdb_connection->output_flag = GDB_OUTPUT_NO;

                        return true;
                }

                /* 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;
                        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;
}

static char *next_hex_encoded_field(const char **str, char sep)
{
        size_t hexlen;
        const char *hex = *str;
        if (hex[0] == '\0')
                return NULL;

        const char *end = strchr(hex, sep);
        if (!end)
                hexlen = strlen(hex);
        else
                hexlen = end - hex;
        *str = hex + hexlen + 1;

        if (hexlen % 2 != 0) {
                /* Malformed hex data */
                return NULL;
        }

        size_t count = hexlen / 2;
        char *decoded = malloc(count + 1);
        if (!decoded)
                return NULL;

        size_t converted = unhexify((void *)decoded, hex, count);
        if (converted != count) {
                free(decoded);
                return NULL;
        }

        decoded[count] = '\0';
        return decoded;
}

/* handle extended restart packet */
static void gdb_restart_inferior(struct connection *connection, const char *packet, int packet_size)
{
        struct gdb_connection *gdb_con = connection->priv;
        struct target *target = get_target_from_connection(connection);

        breakpoint_clear_target(target);
        watchpoint_clear_target(target);
        command_run_linef(connection->cmd_ctx, "ocd_gdb_restart %s",
                        target_name(target));
        /* set connection as attached after reset */
        gdb_con->attached = true;
        /*  info rtos parts */
        gdb_thread_packet(connection, packet, packet_size);
}

static bool gdb_handle_vrun_packet(struct connection *connection, const char *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        const char *parse = packet;

        /* Skip "vRun" */
        parse += 4;

        if (parse[0] != ';')
                return false;
        parse++;

        /* Skip first field "filename"; don't know what to do with it. */
        free(next_hex_encoded_field(&parse, ';'));

        char *cmdline = next_hex_encoded_field(&parse, ';');
        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) {
                if (target->semihosting) {
                        LOG_INFO("GDB set inferior command line to '%s'", cmdline);
                        free(target->semihosting->cmdline);
                        target->semihosting->cmdline = cmdline;
                } else {
                        LOG_INFO("GDB set inferior command line to '%s' but semihosting is unavailable", cmdline);
                        free(cmdline);
                }
        }

        gdb_restart_inferior(connection, packet, packet_size);
        gdb_put_packet(connection, "S00", 3);
        return true;
}

static int gdb_v_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct gdb_connection *gdb_connection = connection->priv;
        int result;

        struct target *target = get_target_from_connection(connection);

        if (strncmp(packet, "vCont", 5) == 0) {
                bool handled;

                packet += 5;
                packet_size -= 5;

                handled = gdb_handle_vcont_packet(connection, packet, packet_size);
                if (!handled)
                        gdb_put_packet(connection, "", 0);

                return ERROR_OK;
        }

        if (strncmp(packet, "vRun", 4) == 0) {
                bool handled;

                handled = gdb_handle_vrun_packet(connection, packet, packet_size);
                if (!handled)
                        gdb_put_packet(connection, "", 0);

                return ERROR_OK;
        }

        /* if flash programming disabled - send a empty reply */

        if (gdb_flash_program == 0) {
                gdb_put_packet(connection, "", 0);
                return ERROR_OK;
        }

        if (strncmp(packet, "vFlashErase:", 12) == 0) {
                unsigned long addr;
                unsigned long length;

                char const *parse = packet + 12;
                if (*parse == '\0') {
                        LOG_ERROR("incomplete vFlashErase packet received, dropping connection");
                        return ERROR_SERVER_REMOTE_CLOSED;
                }

                addr = strtoul(parse, (char **)&parse, 16);

                if (*(parse++) != ',' || *parse == '\0') {
                        LOG_ERROR("incomplete vFlashErase packet received, dropping connection");
                        return ERROR_SERVER_REMOTE_CLOSED;
                }

                length = strtoul(parse, (char **)&parse, 16);

                if (*parse != '\0') {
                        LOG_ERROR("incomplete vFlashErase packet received, dropping connection");
                        return ERROR_SERVER_REMOTE_CLOSED;
                }

                /* assume all sectors need erasing - stops any problems
                 * when flash_write is called multiple times */
                flash_set_dirty();

                /* perform any target specific operations before the erase */
                target_call_event_callbacks(target,
                        TARGET_EVENT_GDB_FLASH_ERASE_START);

                /* vFlashErase:addr,length messages require region start and
                 * end to be "block" aligned ... if padding is ever needed,
                 * GDB will have become dangerously confused.
                 */
                result = flash_erase_address_range(target, false, addr,
                        length);

                /* perform any target specific operations after the erase */
                target_call_event_callbacks(target,
                        TARGET_EVENT_GDB_FLASH_ERASE_END);

                /* perform erase */
                if (result != ERROR_OK) {
                        /* GDB doesn't evaluate the actual error number returned,
                         * treat a failed erase as an I/O error
                         */
                        gdb_send_error(connection, EIO);
                        LOG_ERROR("flash_erase returned %i", result);
                } else
                        gdb_put_packet(connection, "OK", 2);

                return ERROR_OK;
        }

        if (strncmp(packet, "vFlashWrite:", 12) == 0) {
                int retval;
                unsigned long addr;
                unsigned long length;
                char const *parse = packet + 12;

                if (*parse == '\0') {
                        LOG_ERROR("incomplete vFlashErase packet received, dropping connection");
                        return ERROR_SERVER_REMOTE_CLOSED;
                }
                addr = strtoul(parse, (char **)&parse, 16);
                if (*(parse++) != ':') {
                        LOG_ERROR("incomplete vFlashErase packet received, dropping connection");
                        return ERROR_SERVER_REMOTE_CLOSED;
                }
                length = packet_size - (parse - packet);

                /* create a new image if there isn't already one */
                if (!gdb_connection->vflash_image) {
                        gdb_connection->vflash_image = malloc(sizeof(struct image));
                        image_open(gdb_connection->vflash_image, "", "build");
                }

                /* create new section with content from packet buffer */
                retval = image_add_section(gdb_connection->vflash_image,
                                addr, length, 0x0, (uint8_t const *)parse);
                if (retval != ERROR_OK)
                        return retval;

                gdb_put_packet(connection, "OK", 2);

                return ERROR_OK;
        }

        if (strncmp(packet, "vFlashDone", 10) == 0) {
                uint32_t written;

                /* process the flashing buffer. No need to erase as GDB
                 * always issues a vFlashErase first. */
                target_call_event_callbacks(target,
                                TARGET_EVENT_GDB_FLASH_WRITE_START);
                result = flash_write(target, gdb_connection->vflash_image,
                        &written, false);
                target_call_event_callbacks(target,
                        TARGET_EVENT_GDB_FLASH_WRITE_END);
                if (result != ERROR_OK) {
                        if (result == ERROR_FLASH_DST_OUT_OF_BANK)
                                gdb_put_packet(connection, "E.memtype", 9);
                        else
                                gdb_send_error(connection, EIO);
                } else {
                        LOG_DEBUG("wrote %u bytes from vFlash image to flash", (unsigned)written);
                        gdb_put_packet(connection, "OK", 2);
                }

                image_close(gdb_connection->vflash_image);
                free(gdb_connection->vflash_image);
                gdb_connection->vflash_image = NULL;

                return ERROR_OK;
        }

        gdb_put_packet(connection, "", 0);
        return ERROR_OK;
}

static int gdb_detach(struct connection *connection)
{
        /*
         * Only reply "OK" to GDB
         * it will close the connection and this will trigger a call to
         * gdb_connection_closed() that will in turn trigger the event
         * TARGET_EVENT_GDB_DETACH
         */
        return gdb_put_packet(connection, "OK", 2);
}

/* The format of 'F' response packet is
 * Fretcode,errno,Ctrl-C flag;call-specific attachment
 */
static int gdb_fileio_response_packet(struct connection *connection,
                char const *packet, int packet_size)
{
        struct target *target = get_target_from_connection(connection);
        char *separator;
        char *parsing_point;
        int fileio_retcode = strtoul(packet + 1, &separator, 16);
        int fileio_errno = 0;
        bool fileio_ctrl_c = false;
        int retval;

        LOG_DEBUG("-");

        if (*separator == ',') {
                parsing_point = separator + 1;
                fileio_errno = strtoul(parsing_point, &separator, 16);
                if (*separator == ',') {
                        if (*(separator + 1) == 'C') {
                                /* TODO: process ctrl-c */
                                fileio_ctrl_c = true;
                        }
                }
        }

        LOG_DEBUG("File-I/O response, retcode: 0x%x, errno: 0x%x, ctrl-c: %s",
                        fileio_retcode, fileio_errno, fileio_ctrl_c ? "true" : "false");

        retval = target_gdb_fileio_end(target, fileio_retcode, fileio_errno, fileio_ctrl_c);
        if (retval != ERROR_OK)
                return ERROR_FAIL;

        /* After File-I/O ends, keep continue or step */
        if (gdb_running_type == 'c')
                retval = target_resume(target, 1, 0x0, 0, 0);
        else if (gdb_running_type == 's')
                retval = target_step(target, 1, 0x0, 0);
        else
                retval = ERROR_FAIL;

        if (retval != ERROR_OK)
                return ERROR_FAIL;

        return ERROR_OK;
}

static void gdb_log_callback(void *priv, const char *file, unsigned line,
                const char *function, const char *string)
{
        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;
        }

        gdb_output_con(connection, string);
}

static void gdb_sig_halted(struct connection *connection)
{
        char sig_reply[4];
        snprintf(sig_reply, 4, "T%2.2x", 2);
        gdb_put_packet(connection, sig_reply, 3);
}

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 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);

        /* drain input buffer. If one of the packets fail, then an error
         * packet is replied, if applicable.
         *
         * This loop will terminate and the error code is returned.
         *
         * The calling fn will check if this error is something that
         * can be recovered from, or if the connection must be closed.
         *
         * If the error is recoverable, this fn is called again to
         * drain the rest of the buffer.
         */
        do {
                packet_size = GDB_BUFFER_SIZE;
                retval = gdb_get_packet(connection, gdb_packet_buffer, &packet_size);
                if (retval != ERROR_OK)
                        return retval;

                /* terminate with zero */
                gdb_packet_buffer[packet_size] = '\0';

                if (packet_size > 0) {

                        gdb_log_incoming_packet(connection, gdb_packet_buffer);

                        retval = ERROR_OK;
                        switch (packet[0]) {
                                case 'T':       /* Is thread alive? */
                                        gdb_thread_packet(connection, packet, packet_size);
                                        break;
                                case 'H':       /* Set current thread ( 'c' for step and continue,
                                                         * 'g' for all other operations ) */
                                        gdb_thread_packet(connection, packet, packet_size);
                                        break;
                                case 'q':
                                case 'Q':
                                        retval = gdb_thread_packet(connection, packet, packet_size);
                                        if (retval == GDB_THREAD_PACKET_NOT_CONSUMED)
                                                retval = gdb_query_packet(connection, packet, packet_size);
                                        break;
                                case 'g':
                                        retval = gdb_get_registers_packet(connection, packet, packet_size);
                                        break;
                                case 'G':
                                        retval = gdb_set_registers_packet(connection, packet, packet_size);
                                        break;
                                case 'p':
                                        retval = gdb_get_register_packet(connection, packet, packet_size);
                                        break;
                                case 'P':
                                        retval = gdb_set_register_packet(connection, packet, packet_size);
                                        break;
                                case 'm':
                                        retval = gdb_read_memory_packet(connection, packet, packet_size);
                                        break;
                                case 'M':
                                        retval = gdb_write_memory_packet(connection, packet, packet_size);
                                        break;
                                case 'z':
                                case 'Z':
                                        retval = gdb_breakpoint_watchpoint_packet(connection, packet, packet_size);
                                        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);
                                        gdb_con->output_flag = GDB_OUTPUT_ALL;

                                        if (gdb_con->mem_write_error) {
                                                LOG_ERROR("Memory write failure!");

                                                /* now that we have reported the memory write error,
                                                 * we can clear the condition */
                                                gdb_con->mem_write_error = false;
                                        }

                                        bool nostep = false;
                                        bool already_running = false;
                                        if (target->state == TARGET_RUNNING) {
                                                LOG_WARNING("WARNING! The target is already running. "
                                                                "All changes GDB did to registers will be discarded! "
                                                                "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, "
                                                                "stepi/continue ignored.");
                                                nostep = true;
                                        } else if ((packet[0] == 's') && gdb_con->sync) {
                                                /* Hmm..... when you issue a continue in GDB, then a "stepi" is
                                                 * sent by GDB first to OpenOCD, thus defeating the check to
                                                 * make only the single stepping have the sync feature...
                                                 */
                                                nostep = true;
                                                LOG_DEBUG("stepi ignored. GDB will now fetch the register state "
                                                                "from the target.");
                                        }
                                        gdb_con->sync = false;

                                        if (!already_running && nostep) {
                                                /* Either the target isn't in the halted state, then we can't
                                                 * step/continue. This might be early setup, etc.
                                                 *
                                                 * Or we want to allow GDB to pick up a fresh set of
                                                 * register values without modifying the target state.
                                                 *
                                                 */
                                                gdb_sig_halted(connection);

                                                /* stop forwarding log packets! */
                                                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
                                                 */
                                                gdb_con->frontend_state = TARGET_RUNNING;
                                                target_call_event_callbacks(target, TARGET_EVENT_GDB_START);

                                                if (!already_running) {
                                                        /* Here we don't want packet processing to stop even if this fails,
                                                         * so we use a local variable instead of retval. */
                                                        retval = gdb_step_continue_packet(connection, packet, packet_size);
                                                        if (retval != ERROR_OK) {
                                                                /* we'll never receive a halted
                                                                 * condition... issue a false one..
                                                                 */
                                                                gdb_frontend_halted(target, connection);
                                                        }
                                                }
                                        }
                                }
                                break;
                                case 'v':
                                        retval = gdb_v_packet(connection, packet, packet_size);
                                        break;
                                case 'D':
                                        retval = gdb_detach(connection);
                                        break;
                                case 'X':
                                        retval = gdb_write_memory_binary_packet(connection, packet, packet_size);
                                        if (retval != ERROR_OK)
                                                return retval;
                                        break;
                                case 'k':
                                        if (gdb_con->extended_protocol) {
                                                gdb_con->attached = false;
                                                break;
                                        }
                                        gdb_put_packet(connection, "OK", 2);
                                        return ERROR_SERVER_REMOTE_CLOSED;
                                case '!':
                                        /* handle extended remote protocol */
                                        gdb_con->extended_protocol = true;
                                        gdb_put_packet(connection, "OK", 2);
                                        break;
                                case 'R':
                                        /* handle extended restart packet */
                                        gdb_restart_inferior(connection, packet, packet_size);
                                        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 */
                                        gdb_write_smp_packet(connection, packet, packet_size);
                                        break;

                                case 'F':
                                        /* File-I/O extension */
                                        /* After gdb uses host-side syscall to complete target file
                                         * I/O, gdb sends host-side syscall return value to target
                                         * by 'F' packet.
                                         * The format of 'F' response packet is
                                         * Fretcode,errno,Ctrl-C flag;call-specific attachment
                                         */
                                        gdb_con->frontend_state = TARGET_RUNNING;
                                        gdb_con->output_flag = GDB_OUTPUT_ALL;
                                        gdb_fileio_response_packet(connection, packet, packet_size);
                                        break;

                                default:
                                        /* ignore unknown packets */
                                        LOG_DEBUG("ignoring 0x%2.2x packet", packet[0]);
                                        gdb_put_packet(connection, "", 0);
                                        break;
                        }

                        /* if a packet handler returned an error, exit input loop */
                        if (retval != ERROR_OK)
                                return retval;
                }

                if (gdb_con->ctrl_c) {
                        if (target->state == TARGET_RUNNING) {
                                struct target *t = target;
                                if (target->rtos)
                                        target->rtos->gdb_target_for_threadid(connection, target->rtos->current_threadid, &t);
                                retval = target_halt(t);
                                if (retval == ERROR_OK)
                                        retval = target_poll(t);
                                if (retval != ERROR_OK)
                                        target_call_event_callbacks(target, TARGET_EVENT_GDB_HALT);
                                gdb_con->ctrl_c = false;
                        } else {
                                LOG_INFO("The target is not running when halt was requested, stopping GDB.");
                                target_call_event_callbacks(target, TARGET_EVENT_GDB_HALT);
                        }
                }

        } while (gdb_con->buf_cnt > 0);

        return ERROR_OK;
}

static int gdb_input(struct connection *connection)
{
        int retval = gdb_input_inner(connection);
        struct gdb_connection *gdb_con = connection->priv;
        if (retval == ERROR_SERVER_REMOTE_CLOSED)
                return retval;

        /* logging does not propagate the error, yet can set the gdb_con->closed flag */
        if (gdb_con->closed)
                return ERROR_SERVER_REMOTE_CLOSED;

        /* we'll recover from any other errors(e.g. temporary timeouts, etc.) */
        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 (!gdb_service)
                return -ENOMEM;

        LOG_INFO("starting gdb server for %s on %s", target_name(target), port);

        gdb_service->target = target;
        gdb_service->core[0] = -1;
        gdb_service->core[1] = -1;
        target->gdb_service = gdb_service;

        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;
                foreach_smp_target(head, target->smp_targets) {
                        struct target *curr = head->target;
                        if (curr != target)
                                curr->gdb_service = gdb_service;
                }
        }
        return ret;
}

static int gdb_target_add_one(struct target *target)
{
        /*  one gdb instance per smp list */
        if ((target->smp) && (target->gdb_service))
                return ERROR_OK;

        /* skip targets that cannot handle a gdb connections (e.g. mem_ap) */
        if (!target_supports_gdb_connection(target)) {
                LOG_DEBUG("skip gdb server for target %s", target_name(target));
                return ERROR_OK;
        }

        if (target->gdb_port_override) {
                if (strcmp(target->gdb_port_override, "disabled") == 0) {
                        LOG_INFO("gdb port disabled");
                        return ERROR_OK;
                }
                return gdb_target_start(target, target->gdb_port_override);
        }

        if (strcmp(gdb_port, "disabled") == 0) {
                LOG_INFO("gdb port disabled");
                return ERROR_OK;
        }

        int retval = gdb_target_start(target, gdb_port_next);
        if (retval == ERROR_OK) {
                /* save the port number so can be queried with
                 * $target_name cget -gdb-port
                 */
                target->gdb_port_override = strdup(gdb_port_next);

                long portnumber;
                /* If we can parse the port number
                 * then we increment the port number for the next target.
                 */
                char *end;
                portnumber = strtol(gdb_port_next, &end, 0);
                if (!*end) {
                        if (parse_long(gdb_port_next, &portnumber) == ERROR_OK) {
                                free(gdb_port_next);
                                if (portnumber) {
                                        gdb_port_next = alloc_printf("%ld", portnumber+1);
                                } else {
                                        /* Don't increment if gdb_port is 0, since we're just
                                         * trying to allocate an unused port. */
                                        gdb_port_next = strdup("0");
                                }
                        }
                }
        }
        return retval;
}

int gdb_target_add_all(struct target *target)
{
        if (!target) {
                LOG_WARNING("gdb services need one or more targets defined");
                return ERROR_OK;
        }

        while (target) {
                int retval = gdb_target_add_one(target);
                if (retval != ERROR_OK)
                        return retval;

                target = target->next;
        }

        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_sync_command)
{
        if (CMD_ARGC != 0)
                return ERROR_COMMAND_SYNTAX_ERROR;

        if (!current_gdb_connection) {
                command_print(CMD,
                        "gdb_sync command can only be run from within gdb using \"monitor gdb_sync\"");
                return ERROR_FAIL;
        }

        current_gdb_connection->sync = true;

        return ERROR_OK;
}

/* daemon configuration command gdb_port */
COMMAND_HANDLER(handle_gdb_port_command)
{
        int retval = CALL_COMMAND_HANDLER(server_pipe_command, &gdb_port);
        if (retval == ERROR_OK) {
                free(gdb_port_next);
                gdb_port_next = strdup(gdb_port);
        }
        return retval;
}

COMMAND_HANDLER(handle_gdb_memory_map_command)
{
        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_ENABLE(CMD_ARGV[0], gdb_use_memory_map);
        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_flash_program_command)
{
        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_ENABLE(CMD_ARGV[0], gdb_flash_program);
        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_report_data_abort_command)
{
        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_ENABLE(CMD_ARGV[0], gdb_report_data_abort);
        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_report_register_access_error)
{
        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_ENABLE(CMD_ARGV[0], gdb_report_register_access_error);
        return ERROR_OK;
}

/* gdb_breakpoint_override */
COMMAND_HANDLER(handle_gdb_breakpoint_override_command)
{
        if (CMD_ARGC == 0) {
                /* nothing */
        } else if (CMD_ARGC == 1) {
                gdb_breakpoint_override = 1;
                if (strcmp(CMD_ARGV[0], "hard") == 0)
                        gdb_breakpoint_override_type = BKPT_HARD;
                else if (strcmp(CMD_ARGV[0], "soft") == 0)
                        gdb_breakpoint_override_type = BKPT_SOFT;
                else if (strcmp(CMD_ARGV[0], "disable") == 0)
                        gdb_breakpoint_override = 0;
        } else
                return ERROR_COMMAND_SYNTAX_ERROR;
        if (gdb_breakpoint_override)
                LOG_USER("force %s breakpoints",
                        (gdb_breakpoint_override_type == BKPT_HARD) ? "hard" : "soft");
        else
                LOG_USER("breakpoint type is not overridden");

        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_target_description_command)
{
        if (CMD_ARGC != 1)
                return ERROR_COMMAND_SYNTAX_ERROR;

        COMMAND_PARSE_ENABLE(CMD_ARGV[0], gdb_use_target_description);
        return ERROR_OK;
}

COMMAND_HANDLER(handle_gdb_save_tdesc_command)
{
        char *tdesc;
        uint32_t tdesc_length;
        struct target *target = get_current_target(CMD_CTX);

        int retval = gdb_generate_target_description(target, &tdesc);
        if (retval != ERROR_OK) {
                LOG_ERROR("Unable to Generate Target Description");
                return ERROR_FAIL;
        }

        tdesc_length = strlen(tdesc);

        struct fileio *fileio;
        size_t size_written;

        char *tdesc_filename = alloc_printf("%s.xml", target_type_name(target));
        if (!tdesc_filename) {
                retval = ERROR_FAIL;
                goto out;
        }

        retval = fileio_open(&fileio, tdesc_filename, FILEIO_WRITE, FILEIO_TEXT);

        if (retval != ERROR_OK) {
                LOG_ERROR("Can't open %s for writing", tdesc_filename);
                goto out;
        }

        retval = fileio_write(fileio, tdesc_length, tdesc, &size_written);

        fileio_close(fileio);

        if (retval != ERROR_OK)
                LOG_ERROR("Error while writing the tdesc file");

out:
        free(tdesc_filename);
        free(tdesc);

        return retval;
}

static const struct command_registration gdb_command_handlers[] = {
        {
                .name = "gdb_sync",
                .handler = handle_gdb_sync_command,
                .mode = COMMAND_ANY,
                .help = "next stepi will return immediately allowing "
                        "GDB to fetch register state without affecting "
                        "target state",
                .usage = ""
        },
        {
                .name = "gdb_port",
                .handler = handle_gdb_port_command,
                .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. "
                        "No arguments reports GDB port. \"pipe\" means listen to stdin "
                        "output to stdout, an integer is base port number, \"disabled\" disables "
                        "port. Any other string is are interpreted as named pipe to listen to. "
                        "Output pipe is the same name as input pipe, but with 'o' appended.",
                .usage = "[port_num]",
        },
        {
                .name = "gdb_memory_map",
                .handler = handle_gdb_memory_map_command,
                .mode = COMMAND_CONFIG,
                .help = "enable or disable memory map",
                .usage = "('enable'|'disable')"
        },
        {
                .name = "gdb_flash_program",
                .handler = handle_gdb_flash_program_command,
                .mode = COMMAND_CONFIG,
                .help = "enable or disable flash program",
                .usage = "('enable'|'disable')"
        },
        {
                .name = "gdb_report_data_abort",
                .handler = handle_gdb_report_data_abort_command,
                .mode = COMMAND_CONFIG,
                .help = "enable or disable reporting data aborts",
                .usage = "('enable'|'disable')"
        },
        {
                .name = "gdb_report_register_access_error",
                .handler = handle_gdb_report_register_access_error,
                .mode = COMMAND_CONFIG,
                .help = "enable or disable reporting register access errors",
                .usage = "('enable'|'disable')"
        },
        {
                .name = "gdb_breakpoint_override",
                .handler = handle_gdb_breakpoint_override_command,
                .mode = COMMAND_ANY,
                .help = "Display or specify type of breakpoint "
                        "to be used by gdb 'break' commands.",
                .usage = "('hard'|'soft'|'disable')"
        },
        {
                .name = "gdb_target_description",
                .handler = handle_gdb_target_description_command,
                .mode = COMMAND_CONFIG,
                .help = "enable or disable target description",
                .usage = "('enable'|'disable')"
        },
        {
                .name = "gdb_save_tdesc",
                .handler = handle_gdb_save_tdesc_command,
                .mode = COMMAND_EXEC,
                .help = "Save the target description file",
                .usage = "",
        },
        COMMAND_REGISTRATION_DONE
};

int gdb_register_commands(struct command_context *cmd_ctx)
{
        gdb_port = strdup("3333");
        gdb_port_next = strdup("3333");
        return register_commands(cmd_ctx, NULL, gdb_command_handlers);
}

void gdb_service_free(void)
{
        free(gdb_port);
        free(gdb_port_next);
}

int gdb_get_actual_connections(void)
{
        return gdb_actual_connections;
}