gdb_server.c 55.2 KB
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/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
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 *   Copyright (C) 2007,2008 yvind Harboe                                 *
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 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
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 *   Copyright (C) 2008 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 *                                                                         *
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 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "replacements.h"

#include "gdb_server.h"

#include "server.h"
#include "log.h"
#include "binarybuffer.h"
#include "jtag.h"
#include "breakpoints.h"
#include "flash.h"
#include "target_request.h"
#include "configuration.h"

#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

#if 0
#define _DEBUG_GDB_IO_
#endif

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static int gdb_breakpoint_override;
static enum breakpoint_type gdb_breakpoint_override_type;

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extern int gdb_error(connection_t *connection, int retval);
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static unsigned short gdb_port;
static const char *DIGITS = "0123456789abcdef";

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static void gdb_log_callback(void *priv, const char *file, int line,
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		const char *function, const char *string);
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enum gdb_detach_mode
{
	GDB_DETACH_RESUME,
	GDB_DETACH_RESET,
	GDB_DETACH_HALT,
	GDB_DETACH_NOTHING
};

/* target behaviour on gdb detach */
enum gdb_detach_mode detach_mode = GDB_DETACH_RESUME;

/* set if we are sending a memory map to gdb
 * via qXfer:memory-map:read packet */
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/* enabled by default*/
int gdb_use_memory_map = 1;
/* enabled by default*/
int gdb_flash_program = 1;
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/* 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 */
int gdb_report_data_abort = 0;

int gdb_last_signal(target_t *target)
{
	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_NOTHALTED:
			return 0x0; /* no signal... shouldn't happen */
		default:
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			LOG_USER("undefined debug reason %d - target needs reset", target->debug_reason);
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			return 0x0;
	}
}

int check_pending(connection_t *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;
	gdb_connection_t *gdb_con = connection->priv;
	int t;
	if (got_data==NULL)
		got_data=&t;
	*got_data=0;

	if (gdb_con->buf_cnt>0)
	{
		*got_data = 1;
		return ERROR_OK;
	}
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	FD_ZERO(&read_fds);
	FD_SET(connection->fd, &read_fds);
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	tv.tv_sec = timeout_s;
	tv.tv_usec = 0;
	if (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;
		}
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	}
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	*got_data=FD_ISSET(connection->fd, &read_fds)!=0;
	return ERROR_OK;
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}

int gdb_get_char(connection_t *connection, int* next_char)
{
	gdb_connection_t *gdb_con = connection->priv;
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	int retval=ERROR_OK;
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#ifdef _DEBUG_GDB_IO_
	char *debug_buffer;
#endif

	if (gdb_con->buf_cnt-- > 0)
	{
		*next_char = *(gdb_con->buf_p++);
		if (gdb_con->buf_cnt > 0)
			connection->input_pending = 1;
		else
			connection->input_pending = 0;

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

		return ERROR_OK;
	}

	for (;;)
	{
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		retval=check_pending(connection, 1, NULL);
		if (retval!=ERROR_OK)
			return retval;
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		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)
		{
			gdb_con->closed = 1;
			return ERROR_SERVER_REMOTE_CLOSED;
		}

#ifdef _WIN32
		errno = WSAGetLastError();

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

#ifdef _DEBUG_GDB_IO_
	debug_buffer = malloc(gdb_con->buf_cnt + 1);
	memcpy(debug_buffer, gdb_con->buffer, gdb_con->buf_cnt);
	debug_buffer[gdb_con->buf_cnt] = 0;
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	LOG_DEBUG("received '%s'", debug_buffer);
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	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 = 1;
	else
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		connection->input_pending = 0;
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#ifdef _DEBUG_GDB_IO_
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	LOG_DEBUG("returned char '%c' (0x%2.2x)", *next_char, *next_char);
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#endif

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	return retval;
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}

int gdb_putback_char(connection_t *connection, int last_char)
{
	gdb_connection_t *gdb_con = connection->priv;

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

	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! */
int gdb_write(connection_t *connection, void *data, int len)
{
	gdb_connection_t *gdb_con = connection->priv;
	if (gdb_con->closed)
		return ERROR_SERVER_REMOTE_CLOSED;

	if (write_socket(connection->fd, data, len) == len)
	{
		return ERROR_OK;
	}
	gdb_con->closed = 1;
	return ERROR_SERVER_REMOTE_CLOSED;
}

int gdb_put_packet_inner(connection_t *connection, char *buffer, int len)
{
	int i;
	unsigned char my_checksum = 0;
#ifdef _DEBUG_GDB_IO_
	char *debug_buffer;
#endif
	int reply;
	int retval;
	gdb_connection_t *gdb_con = connection->priv;

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

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#ifdef _DEBUG_GDB_IO_
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	/*
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	 * 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 (;;)
	{
		if ((retval=check_pending(connection, 0, &gotdata))!=ERROR_OK)
			return retval;
		if (!gotdata)
			break;
		if ((retval = gdb_get_char(connection, &reply)) != ERROR_OK)
			return retval;
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        if( reply == '$' ){
			// fix a problem with some IAR tools
			gdb_putback_char( connection, reply );
			LOG_DEBUG("Unexpected start of new packet");
			break;
		}

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

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	while (1)
	{
#ifdef _DEBUG_GDB_IO_
		debug_buffer = malloc(len + 1);
		memcpy(debug_buffer, buffer, len);
		debug_buffer[len] = 0;
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		LOG_DEBUG("sending packet '$%s#%2.2x'", debug_buffer, my_checksum);
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		free(debug_buffer);
#endif
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		char local_buffer[1024];
		local_buffer[0] = '$';
		if (len+4 <= sizeof(local_buffer))
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		{
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			/* performance gain on smaller packets by only a single call to gdb_write() */
			memcpy(local_buffer+1, buffer, len++);
			local_buffer[len++] = '#';
			local_buffer[len++] = DIGITS[(my_checksum >> 4) & 0xf];
			local_buffer[len++] = DIGITS[my_checksum & 0xf];
			gdb_write(connection, local_buffer, len);
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		}
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		else
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		{
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			/* larger packets are transmitted directly from caller supplied buffer
			   by several calls to gdb_write() to avoid dynamic allocation */
			local_buffer[1] = '#';
			local_buffer[2] = DIGITS[(my_checksum >> 4) & 0xf];
			local_buffer[3] = DIGITS[my_checksum & 0xf];
			gdb_write(connection, local_buffer, 1);
			gdb_write(connection, buffer, len);
			gdb_write(connection, local_buffer+1, 3);
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		}
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		if (gdb_con->noack_mode)
			break;
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		if ((retval = gdb_get_char(connection, &reply)) != ERROR_OK)
			return retval;

		if (reply == '+')
			break;
		else if (reply == '-')
		{
			/* Stop sending output packets for now */
			log_remove_callback(gdb_log_callback, connection);
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			LOG_WARNING("negative reply, retrying");
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		}
		else if (reply == 0x3)
		{
			gdb_con->ctrl_c = 1;
			if ((retval = gdb_get_char(connection, &reply)) != ERROR_OK)
				return retval;
			if (reply == '+')
				break;
			else if (reply == '-')
			{
				/* Stop sending output packets for now */
				log_remove_callback(gdb_log_callback, connection);
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				LOG_WARNING("negative reply, retrying");
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			}
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			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);
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				gdb_con->closed=1;
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				return ERROR_SERVER_REMOTE_CLOSED;
			}
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		} 
		else if( reply == '$' ){
			LOG_ERROR("GDB missing ack(2) - assumed good");
			gdb_putback_char( connection, reply );
			return ERROR_OK;
		} 
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		else
		{
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			LOG_ERROR("unknown character(2) 0x%2.2x in reply, dropping connection", reply);
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			gdb_con->closed=1;
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			return ERROR_SERVER_REMOTE_CLOSED;
		}
	}
	if (gdb_con->closed)
		return ERROR_SERVER_REMOTE_CLOSED;

	return ERROR_OK;
}

int gdb_put_packet(connection_t *connection, char *buffer, int len)
{
	gdb_connection_t *gdb_con = connection->priv;
	gdb_con->busy = 1;
	int retval = gdb_put_packet_inner(connection, buffer, len);
	gdb_con->busy = 0;
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	/* we sent some data, reset timer for keep alive messages */
	kept_alive();

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	return retval;
}

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static __inline__ int fetch_packet(connection_t *connection, int *checksum_ok, int noack, int *len, char *buffer)
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{
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	unsigned char my_checksum = 0;
	char checksum[3];
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	int character;
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	int retval;
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	gdb_connection_t *gdb_con = connection->priv;
	my_checksum = 0;
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	int count = 0;
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	count = 0;
	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 ((gdb_con->buf_cnt > 2) && ((gdb_con->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 = gdb_con->buf_p;
			int run = gdb_con->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;
				}
			}
			gdb_con->buf_p += i;
			gdb_con->buf_cnt -= i;
			if (done)
				break;
		}
		if (count > *len)
		{
			LOG_ERROR("packet buffer too small");
			return ERROR_GDB_BUFFER_TOO_SMALL;
		}

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

		if (character == '#')
			break;

		if (character == '}')
		{
			/* data transmitted in binary mode (X packet)
			 * uses 0x7d as escape character */
			my_checksum += character & 0xff;
			if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
				return retval;
			my_checksum += character & 0xff;
			buffer[count++] = (character ^ 0x20) & 0xff;
		}
		else
		{
			my_checksum += character & 0xff;
			buffer[count++] = character & 0xff;
		}
	}

	*len = count;

	if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
		return retval;
	checksum[0] = character;
	if ((retval = gdb_get_char(connection, &character)) != ERROR_OK)
		return retval;
	checksum[1] = character;
	checksum[2] = 0;
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	if (!noack)
	{
		*checksum_ok=(my_checksum == strtoul(checksum, NULL, 16));
	}
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	return ERROR_OK;
}

int gdb_get_packet_inner(connection_t *connection, char *buffer, int *len)
{
	int character;
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	int retval;
	gdb_connection_t *gdb_con = connection->priv;

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

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

			switch (character)
			{
				case '$':
					break;
				case '+':
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					/* gdb sends a dummy ack '+' at every remote connect - see remote_start_remote (remote.c)
					 * incase anyone tries to debug why they receive this warning every time */
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					LOG_WARNING("acknowledgment received, but no packet pending");
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					break;
				case '-':
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					LOG_WARNING("negative acknowledgment, but no packet pending");
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					break;
				case 0x3:
					gdb_con->ctrl_c = 1;
					*len = 0;
					return ERROR_OK;
				default:
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					LOG_WARNING("ignoring character 0x%x", character);
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					break;
			}
		} while (character != '$');

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

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

	return ERROR_OK;
}

int gdb_get_packet(connection_t *connection, char *buffer, int *len)
{
	gdb_connection_t *gdb_con = connection->priv;
	gdb_con->busy = 1;
	int retval = gdb_get_packet_inner(connection, buffer, len);
	gdb_con->busy = 0;
	return retval;
}
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int gdb_output_con(connection_t *connection, const char* line)
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{
	char *hex_buffer;
	int i, bin_size;

	bin_size = strlen(line);

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	hex_buffer = malloc(bin_size*2 + 2);
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	if (hex_buffer == NULL)
		return ERROR_GDB_BUFFER_TOO_SMALL;
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	hex_buffer[0] = 'O';
	for (i=0; i<bin_size; i++)
		snprintf(hex_buffer + 1 + i*2, 3, "%2.2x", line[i]);
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	hex_buffer[bin_size*2+1] = 0;
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	gdb_put_packet(connection, hex_buffer, bin_size*2 + 1);
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	free(hex_buffer);
	return ERROR_OK;
}

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


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static void gdb_frontend_halted(struct target_s *target, connection_t *connection)
{
	gdb_connection_t *gdb_connection = connection->priv;
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	/* In the GDB protocol when we are stepping or coninuing 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)
	{
		char sig_reply[4];
		int signal;
		/* stop forwarding log packets! */
		log_remove_callback(gdb_log_callback, connection);

		if (gdb_connection->ctrl_c)
		{
			signal = 0x2;
			gdb_connection->ctrl_c = 0;
		}
		else
		{
			signal = gdb_last_signal(target);
		}

		snprintf(sig_reply, 4, "T%2.2x", signal);
		gdb_put_packet(connection, sig_reply, 3);
		gdb_connection->frontend_state = TARGET_HALTED;
	}
}

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int gdb_target_callback_event_handler(struct target_s *target, enum target_event event, void *priv)
{
	connection_t *connection = priv;

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	target_handle_event( target, event );
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	switch (event)
	{
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		case TARGET_EVENT_EARLY_HALTED:
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			gdb_frontend_halted(target, connection);
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			break;
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		case TARGET_EVENT_GDB_FLASH_ERASE_START:
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			target_handle_event( target, TARGET_EVENT_OLD_gdb_program_config );
			jtag_execute_queue();
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			break;
		default:
			break;
	}

	return ERROR_OK;
}
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int gdb_new_connection(connection_t *connection)
{
	gdb_connection_t *gdb_connection = malloc(sizeof(gdb_connection_t));
	gdb_service_t *gdb_service = connection->service->priv;
	int retval;
	int initial_ack;

	connection->priv = gdb_connection;

	/* initialize gdb connection information */
	gdb_connection->buf_p = gdb_connection->buffer;
	gdb_connection->buf_cnt = 0;
	gdb_connection->ctrl_c = 0;
	gdb_connection->frontend_state = TARGET_HALTED;
	gdb_connection->vflash_image = NULL;
	gdb_connection->closed = 0;
	gdb_connection->busy = 0;
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	gdb_connection->noack_mode = 0;
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	/* send ACK to GDB for debug request */
	gdb_write(connection, "+", 1);
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	/* output goes through gdb connection */
	command_set_output_handler(connection->cmd_ctx, gdb_output, connection);

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	/* we must remove all breakpoints registered to the target as a previous
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	 * GDB session could leave dangling breakpoints if e.g. communication
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	 * timed out.
	 */
	breakpoint_clear_target(gdb_service->target);
	watchpoint_clear_target(gdb_service->target);
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	/* register callback to be informed about target events */
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	target_register_event_callback(gdb_target_callback_event_handler, connection);
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	/* a gdb session just attached, try to put the target in halt mode.
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	 *
	 * DANGER!!!!
	 *
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	 * If the halt fails(e.g. target needs a reset, JTAG communication not
	 * working, etc.), then the GDB connect will succeed as
	 * the get_gdb_reg_list() will lie and return a register list with
	 * dummy values.
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	 *
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	 * This allows GDB monitor commands to be run from a GDB init script to
	 * initialize the target
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	 *
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	 * Also, since the halt() is asynchronous target connect will be
	 * instantaneous and thus avoiding annoying timeout problems during
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	 * connect.
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	 */
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	target_halt(gdb_service->target);
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	/* FIX!!!! could extended-remote work better here?
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	 *
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	 *  wait a tiny bit for halted state or we just continue. The
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	 * GDB register packet will then contain garbage
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	 */
	target_wait_state(gdb_service->target, TARGET_HALTED, 500);
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	/* remove the initial ACK from the incoming buffer */
	if ((retval = gdb_get_char(connection, &initial_ack)) != ERROR_OK)
		return retval;

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	/* FIX!!!??? would we actually ever receive a + here???
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	 * Not observed.
	 */
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	if (initial_ack != '+')
		gdb_putback_char(connection, initial_ack);
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	target_call_event_callbacks(gdb_service->target, TARGET_EVENT_GDB_ATTACH );
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	return ERROR_OK;
}

int gdb_connection_closed(connection_t *connection)
{
	gdb_service_t *gdb_service = connection->service->priv;
	gdb_connection_t *gdb_connection = connection->priv;

	/* 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, gdb_service->target);
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	if (connection->priv)
	{
		free(connection->priv);
		connection->priv = NULL;
	}
	else
	{
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		LOG_ERROR("BUG: connection->priv == NULL");
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	}

	target_unregister_event_callback(gdb_target_callback_event_handler, connection);
	log_remove_callback(gdb_log_callback, connection);

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	target_call_event_callbacks(gdb_service->target, TARGET_EVENT_GDB_DETACH );
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	return ERROR_OK;
}

void gdb_send_error(connection_t *connection, u8 the_error)
{
	char err[4];
	snprintf(err, 4, "E%2.2X", the_error );
	gdb_put_packet(connection, err, 3);
}

int gdb_last_signal_packet(connection_t *connection, target_t *target, char* packet, int packet_size)
{
	char sig_reply[4];
	int signal;

	signal = gdb_last_signal(target);

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

	return ERROR_OK;
}

/* Convert register to string of bits. NB! The # of bits in the
 * register might be non-divisible by 8(a byte), in which
 * case an entire byte is shown. */
void gdb_str_to_target(target_t *target, char *tstr, reg_t *reg)
{
	int i;

	u8 *buf;
	int buf_len;
	buf = reg->value;
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	buf_len = CEIL(reg->size, 8);
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	for (i = 0; i < buf_len; i++)
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	{
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		tstr[i*2]   = DIGITS[(buf[i]>>4) & 0xf];
		tstr[i*2+1] = DIGITS[buf[i]&0xf];
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	}
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}

void gdb_target_to_str(target_t *target, char *tstr, char *str)
{
	int str_len = strlen(tstr);
	int i;

	if (str_len % 2)
	{
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		LOG_ERROR("BUG: gdb value with uneven number of characters encountered");
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		exit(-1);
	}

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	for (i = 0; i < str_len; i+=2)
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	{
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		str[str_len - i - 1] = tstr[i + 1];
		str[str_len - i - 2] = tstr[i];
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	}
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}

int gdb_get_registers_packet(connection_t *connection, target_t *target, char* packet, int packet_size)
{
	reg_t **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_
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	LOG_DEBUG("-");
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#endif

	if ((retval = target->type->get_gdb_reg_list(target, &reg_list, &reg_list_size)) != ERROR_OK)
	{
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		return gdb_error(connection, retval);
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	}

	for (i = 0; i < reg_list_size; i++)
	{
		reg_packet_size += reg_list[i]->size;
	}

	reg_packet = malloc(CEIL(reg_packet_size, 8) * 2);
	reg_packet_p = reg_packet;

	for (i = 0; i < reg_list_size; i++)
	{
		gdb_str_to_target(target, reg_packet_p, reg_list[i]);
		reg_packet_p += CEIL(reg_list[i]->size, 8) * 2;
	}

#ifdef _DEBUG_GDB_IO_
	{
		char *reg_packet_p;
		reg_packet_p = strndup(reg_packet, CEIL(reg_packet_size, 8) * 2);
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		LOG_DEBUG("reg_packet: %s", reg_packet_p);
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		free(reg_packet_p);
	}
#endif

	gdb_put_packet(connection, reg_packet, CEIL(reg_packet_size, 8) * 2);
	free(reg_packet);

	free(reg_list);

	return ERROR_OK;
}

int gdb_set_registers_packet(connection_t *connection, target_t *target, char *packet, int packet_size)
{
	int i;
	reg_t **reg_list;
	int reg_list_size;
	int retval;
	char *packet_p;

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	LOG_DEBUG("-");
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#endif

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

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

	if ((retval = target->type->get_gdb_reg_list(target, &reg_list, &reg_list_size)) != ERROR_OK)
	{
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	}

	packet_p = packet;
	for (i = 0; i < reg_list_size; i++)
	{
		u8 *bin_buf;
		char *hex_buf;
		reg_arch_type_t *arch_type;

		/* convert from GDB-string (target-endian) to hex-string (big-endian) */
		hex_buf = malloc(CEIL(reg_list[i]->size, 8) * 2);
		gdb_target_to_str(target, packet_p, hex_buf);

		/* convert hex-string to binary buffer */
		bin_buf = malloc(CEIL(reg_list[i]->size, 8));
		str_to_buf(hex_buf, CEIL(reg_list[i]->size, 8) * 2, bin_buf, reg_list[i]->size, 16);

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		/* get register arch_type, and call set method */
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		arch_type = register_get_arch_type(reg_list[i]->arch_type);
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		arch_type->set(reg_list[i], bin_buf);

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		/* advance packet pointer */
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		packet_p += (CEIL(reg_list[i]->size, 8) * 2);

		free(bin_buf);
		free(hex_buf);
	}

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

	gdb_put_packet(connection, "OK", 2);

	return ERROR_OK;
}

int gdb_get_register_packet(connection_t *connection, target_t *target, char *packet, int packet_size)
{
	char *reg_packet;
	int reg_num = strtoul(packet + 1, NULL, 16);
	reg_t **reg_list;
	int reg_list_size;
	int retval;

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

	if ((retval = target->type->get_gdb_reg_list(target, &reg_list, &reg_list_size)) != ERROR_OK)
	{
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		return gdb_error(connection, retval);
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	}

	if (reg_list_size <= reg_num)
	{
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		LOG_ERROR("gdb requested a non-existing register");
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		exit(-1);
	}

	reg_packet = malloc(CEIL(reg_list[reg_num]->size, 8) * 2);

	gdb_str_to_target(target, reg_packet, reg_list[reg_num]);

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