gdb-server.c

/* -*- tab-width:8 -*- */

/*
 Copyright (C)  2011 Peter Zotov <whitequark@whitequark.org>
 Use of this source code is governed by a BSD-style
 license that can be found in the LICENSE file.
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stlink-common.h>

#include "gdb-remote.h"

#define FLASH_BASE 0x08000000
#define FLASH_PAGE (sl->flash_pgsz)
#define FLASH_PAGE_MASK (~((1 << 10) - 1))
#define FLASH_SIZE (FLASH_PAGE * 128)

static const char hex[] = "0123456789abcdef";

static const char* current_memory_map = NULL;

/*
 * Chip IDs are explained in the appropriate programming manual for the
 * DBGMCU_IDCODE register (0xE0042000)
 */
struct chip_params {
	uint32_t chip_id;
	char* description;
        uint32_t flash_size_reg;
	uint32_t max_flash_size, flash_pagesize;
	uint32_t sram_size;
	uint32_t bootrom_base, bootrom_size;
} const devices[] = {
	{ 0x410, "F1 Medium-density device", 0x1ffff7e0,
	  0x20000,  0x400, 0x5000,  0x1ffff000, 0x800  }, // table 2, pm0063
	{ 0x411, "F2 device", 0, /* No flash size register found in the docs*/
	  0x100000,   0x20000, 0x20000, 0x1ff00000, 0x7800  }, // table 1, pm0059
	{ 0x412, "F1 Low-density device", 0x1ffff7e0,
	  0x8000,   0x400, 0x2800,  0x1ffff000, 0x800  }, // table 1, pm0063
	{ 0x413, "F4 device", 0x1FFF7A10,
	  0x100000,   0x20000, 0x20000,  0x1ff00000, 0x7800  }, // table 1, pm0081
	{ 0x414, "F1 High-density device", 0x1ffff7e0,
	  0x80000,  0x800, 0x10000, 0x1ffff000, 0x800  },  // table 3 pm0063 
          // This ignores the EEPROM! (and uses the page erase size,
          // not the sector write protection...)
	{ 0x416, "L1 Med-density device", 0x1FF8004C, // table 1, pm0062
          0x20000, 0x100, 0x4000, 0x1ff00000, 0x1000 },
	{ 0x418, "F1 Connectivity line device", 0x1ffff7e0,
	  0x40000,  0x800, 0x10000, 0x1fffb000, 0x4800 },
	{ 0x420, "F1 Medium-density value line device", 0x1ffff7e0,
	  0x20000,  0x400, 0x2000,  0x1ffff000, 0x800  },
	{ 0x428, "F1 High-density value line device", 0x1ffff7e0,
	  0x80000,  0x800, 0x8000,  0x1ffff000, 0x800  },
	{ 0x430, "F1 XL-density device", 0x1ffff7e0,  // pm0068
	  0x100000, 0x800, 0x18000, 0x1fffe000, 0x1800 },
	{ 0 }
};

int serve(stlink_t *sl, int port);
char* make_memory_map(const struct chip_params *params, uint32_t flash_size);

int main(int argc, char** argv) {

	stlink_t *sl = NULL;

	const char * HelpStr =	"Usage:\n"
								"\t st-util port [/dev/sgX]\n"
								"\t st-util [port]\n"
								"\t st-util --help\n";

	switch(argc) {

		default: {
			fprintf(stderr, HelpStr, NULL);
			return 1;
		}

		case 3 : {
			//sl = stlink_quirk_open(argv[2], 0);
                        // FIXME - hardcoded to usb....
                        sl = stlink_open_usb(argv[2], 10);
			if(sl == NULL) return 1;
			break;
		}

		case 2 : {
			if (strcmp(argv[1], "--help") == 0) {
				fprintf(stdout, HelpStr, NULL);
				return 1;
			}
		}

		case 1 : { // Search ST-LINK (from /dev/sg0 to /dev/sg99)
			const int DevNumMax = 99;
			int ExistDevCount = 0;

			for(int DevNum = 0; DevNum <= DevNumMax; DevNum++)
			{
				if(DevNum < 10) {
					char DevName[] = "/dev/sgX";
					const int X_index = 7;
					DevName[X_index] = DevNum + '0';
					if ( !access(DevName, F_OK) ) {
						sl = stlink_quirk_open(DevName, 0);
						ExistDevCount++;
					}
				}
				else if(DevNum < 100) {
					char DevName[] = "/dev/sgXY";
					const int X_index = 7;
					const int Y_index = 8;
					DevName[X_index] = DevNum/10 + '0';
					DevName[Y_index] = DevNum%10 + '0';
					if ( !access(DevName, F_OK) ) {
						sl = stlink_quirk_open(DevName, 0);
						ExistDevCount++;
					}
				}
				if(sl != NULL) break;
			}

			if(sl == NULL) {
				fprintf(stdout, "\nNumber of /dev/sgX devices found: %i \n",
						ExistDevCount);
				fprintf(stderr, "ST-LINK not found\n");
				return 1;
			}
			break;
		}
	}

	if(stlink_current_mode(sl) != STLINK_DEV_DEBUG_MODE)
		stlink_enter_swd_mode(sl);

	uint32_t chip_id = stlink_chip_id(sl);
	printf("Chip ID is %08x.\n", chip_id);

	const struct chip_params* params = NULL;

	for(int i = 0; i < sizeof(devices) / sizeof(devices[0]); i++) {
		if(devices[i].chip_id == (chip_id & 0xFFF)) {
			params = &devices[i];
			break;
		}
	}

	if(params == NULL) {
		fprintf(stderr, "Cannot recognize the connected device!\n");
		return 0;
	}

	printf("Device connected: %s\n", params->description);
	printf("Device parameters: SRAM: 0x%x bytes, Flash: up to 0x%x bytes in pages of 0x%x bytes\n",
		params->sram_size, params->max_flash_size, params->flash_pagesize);

	FLASH_PAGE = params->flash_pagesize;

	uint32_t flash_size;

	stlink_read_mem32(sl, params->flash_size_reg, 4);
	flash_size = sl->q_buf[0] | (sl->q_buf[1] << 8);

	printf("Flash size is %d KiB.\n", flash_size);
	// memory map is in 1k blocks.
	current_memory_map = make_memory_map(params, flash_size * 0x400);

	int port;

	if(argc == 1) {
                // not on 64bit?
		//srand((unsigned int)&port);
		port = rand()/65535;
	}
	else {
		port = atoi(argv[1]);
	}

	while(serve(sl, port) == 0);

	stlink_close(sl);

	return 0;
}

static const char* const memory_map_template =
  "<?xml version=\"1.0\"?>"
  "<!DOCTYPE memory-map PUBLIC \"+//IDN gnu.org//DTD GDB Memory Map V1.0//EN\""
  "     \"http://sourceware.org/gdb/gdb-memory-map.dtd\">"
  "<memory-map>"
  "  <memory type=\"rom\" start=\"0x00000000\" length=\"0x%x\"/>"       // code = sram, bootrom or flash; flash is bigger
  "  <memory type=\"ram\" start=\"0x20000000\" length=\"0x%x\"/>"       // sram 8k
  "  <memory type=\"flash\" start=\"0x08000000\" length=\"0x%x\">"
  "    <property name=\"blocksize\">0x%x</property>"
  "  </memory>"
  "  <memory type=\"ram\" start=\"0x40000000\" length=\"0x1fffffff\"/>" // peripheral regs
  "  <memory type=\"ram\" start=\"0xe0000000\" length=\"0x1fffffff\"/>" // cortex regs
  "  <memory type=\"rom\" start=\"0x%08x\" length=\"0x%x\"/>"           // bootrom
  "  <memory type=\"rom\" start=\"0x1ffff800\" length=\"0x8\"/>"        // option byte area
  "</memory-map>";

char* make_memory_map(const struct chip_params *params, uint32_t flash_size) {
	/* This will be freed in serve() */
	char* map = malloc(4096);
	map[0] = '\0';

	snprintf(map, 4096, memory_map_template,
			flash_size,
			params->sram_size,
			flash_size, params->flash_pagesize,
			params->bootrom_base, params->bootrom_size);

	return map;
}


/* 
 * DWT_COMP0     0xE0001020
 * DWT_MASK0     0xE0001024
 * DWT_FUNCTION0 0xE0001028
 * DWT_COMP1     0xE0001030
 * DWT_MASK1     0xE0001034
 * DWT_FUNCTION1 0xE0001038
 * DWT_COMP2     0xE0001040
 * DWT_MASK2     0xE0001044
 * DWT_FUNCTION2 0xE0001048
 * DWT_COMP3     0xE0001050
 * DWT_MASK3     0xE0001054
 * DWT_FUNCTION3 0xE0001058
 */

#define DATA_WATCH_NUM 4

enum watchfun { WATCHDISABLED = 0, WATCHREAD = 5, WATCHWRITE = 6, WATCHACCESS = 7 };

struct code_hw_watchpoint {
	stm32_addr_t addr;
	uint8_t mask;
	enum watchfun fun;
};

struct code_hw_watchpoint data_watches[DATA_WATCH_NUM];

static void init_data_watchpoints(stlink_t *sl) {
	#ifdef DEBUG
	printf("init watchpoints\n");
	#endif

	// set trcena in debug command to turn on dwt unit
	stlink_read_mem32(sl, 0xE000EDFC, 4);
	sl->q_buf[3] |= 1;
	stlink_write_mem32(sl, 0xE000EDFC, 4);

	// make sure all watchpoints are cleared
	memset(sl->q_buf, 0, 4);
	for(int i = 0; i < DATA_WATCH_NUM; i++) {
		data_watches[i].fun = WATCHDISABLED;
		stlink_write_mem32(sl, 0xe0001028 + i * 16, 4);
	}
}

static int add_data_watchpoint(stlink_t *sl, enum watchfun wf, stm32_addr_t addr, unsigned int len)
{
	int i = 0;
	uint32_t mask;

	// computer mask
	// find a free watchpoint
	// configure

	mask = -1;
	i = len;
	while(i) {
		i >>= 1;
		mask++;
	}

	if((mask != -1) && (mask < 16)) {
		for(i = 0; i < DATA_WATCH_NUM; i++) {
			// is this an empty slot ?
			if(data_watches[i].fun == WATCHDISABLED) {
				#ifdef DEBUG
				printf("insert watchpoint %d addr %x wf %u mask %u len %d\n", i, addr, wf, mask, len);
				#endif

				data_watches[i].fun = wf;
				data_watches[i].addr = addr;
				data_watches[i].mask = mask;

				// insert comparator address
				sl->q_buf[0] = (addr & 0xff);
				sl->q_buf[1] = ((addr >> 8) & 0xff);
				sl->q_buf[2] = ((addr >> 16) & 0xff);
				sl->q_buf[3] = ((addr >> 24)  & 0xff);

				stlink_write_mem32(sl, 0xE0001020 + i * 16, 4);

				// insert mask
				memset(sl->q_buf, 0, 4);
				sl->q_buf[0] = mask;
				stlink_write_mem32(sl, 0xE0001024 + i * 16, 4);

				// insert function
				memset(sl->q_buf, 0, 4);
				sl->q_buf[0] = wf;
				stlink_write_mem32(sl, 0xE0001028 + i * 16, 4);

				// just to make sure the matched bit is clear !
				stlink_read_mem32(sl,  0xE0001028 + i * 16, 4);
				return 0;
			}
		}
	}

	#ifdef DEBUG
	printf("failure: add watchpoints addr %x wf %u len %u\n", addr, wf, len);
	#endif
	return -1;
}

static int delete_data_watchpoint(stlink_t *sl, stm32_addr_t addr)
{
	int i;

	for(i = 0 ; i < DATA_WATCH_NUM; i++) {
		if((data_watches[i].addr == addr) && (data_watches[i].fun != WATCHDISABLED)) {
			#ifdef DEBUG
			printf("delete watchpoint %d addr %x\n", i, addr);
			#endif

			memset(sl->q_buf, 0, 4);
			data_watches[i].fun = WATCHDISABLED;
			stlink_write_mem32(sl, 0xe0001028 + i * 16, 4);

			return 0;
		}
	}

	#ifdef DEBUG
	printf("failure: delete watchpoint addr %x\n", addr);
	#endif

	return -1;
}

#define CODE_BREAK_NUM	6
#define CODE_BREAK_LOW	0x01
#define CODE_BREAK_HIGH	0x02

struct code_hw_breakpoint {
	stm32_addr_t addr;
	int          type;
};

struct code_hw_breakpoint code_breaks[CODE_BREAK_NUM];

static void init_code_breakpoints(stlink_t *sl) {
	memset(sl->q_buf, 0, 4);
	sl->q_buf[0] = 0x03; // KEY | ENABLE
	stlink_write_mem32(sl, CM3_REG_FP_CTRL, 4);
        printf("KARL - should read back as 0x03, not 60 02 00 00\n");
        stlink_read_mem32(sl, CM3_REG_FP_CTRL, 4);

	memset(sl->q_buf, 0, 4);
	for(int i = 0; i < CODE_BREAK_NUM; i++) {
		code_breaks[i].type = 0;
		stlink_write_mem32(sl, CM3_REG_FP_COMP0 + i * 4, 4);
	}
}

static int update_code_breakpoint(stlink_t *sl, stm32_addr_t addr, int set) {
	stm32_addr_t fpb_addr = addr & ~0x3;
	int type = addr & 0x2 ? CODE_BREAK_HIGH : CODE_BREAK_LOW;

	if(addr & 1) {
		fprintf(stderr, "update_code_breakpoint: unaligned address %08x\n", addr);
		return -1;
	}

	int id = -1;
	for(int i = 0; i < CODE_BREAK_NUM; i++) {
		if(fpb_addr == code_breaks[i].addr ||
			(set && code_breaks[i].type == 0)) {
			id = i;
			break;
		}
	}

	if(id == -1) {
		if(set) return -1; // Free slot not found
		else	return 0;  // Breakpoint is already removed
	}

	struct code_hw_breakpoint* brk = &code_breaks[id];

	brk->addr = fpb_addr;

	if(set) brk->type |= type;
	else	brk->type &= ~type;

	memset(sl->q_buf, 0, 4);

	if(brk->type == 0) {
		#ifdef DEBUG
		printf("clearing hw break %d\n", id);
		#endif

		stlink_write_mem32(sl, 0xe0002008 + id * 4, 4);
	} else {
		sl->q_buf[0] = ( brk->addr        & 0xff) | 1;
		sl->q_buf[1] = ((brk->addr >> 8)  & 0xff);
		sl->q_buf[2] = ((brk->addr >> 16) & 0xff);
		sl->q_buf[3] = ((brk->addr >> 24) & 0xff) | (brk->type << 6);

		#ifdef DEBUG
		printf("setting hw break %d at %08x (%d)\n",
			id, brk->addr, brk->type);
		printf("reg %02x %02x %02x %02x\n",
			sl->q_buf[3], sl->q_buf[2], sl->q_buf[1], sl->q_buf[0]);
		#endif

		stlink_write_mem32(sl, 0xe0002008 + id * 4, 4);
	}

	return 0;
}


struct flash_block {
	stm32_addr_t addr;
	unsigned     length;
	uint8_t*     data;

	struct flash_block* next;
};

static struct flash_block* flash_root;

static int flash_add_block(stm32_addr_t addr, unsigned length, 
			   stlink_t *sl) {
	if(addr < FLASH_BASE || addr + length > FLASH_BASE + FLASH_SIZE) {
		fprintf(stderr, "flash_add_block: incorrect bounds\n");
		return -1;
	}

	if(addr % FLASH_PAGE != 0 || length % FLASH_PAGE != 0) {
		fprintf(stderr, "flash_add_block: unaligned block\n");
		return -1;
	}

	struct flash_block* new = malloc(sizeof(struct flash_block));
	new->next = flash_root;

	new->addr   = addr;
	new->length = length;
	new->data   = calloc(length, 1);

	flash_root = new;

	return 0;
}

static int flash_populate(stm32_addr_t addr, uint8_t* data, unsigned length) {
	int fit_blocks = 0, fit_length = 0;

	for(struct flash_block* fb = flash_root; fb; fb = fb->next) {
		/* Block: ------X------Y--------
		 * Data:            a-----b
		 *                a--b
		 *            a-----------b
		 * Block intersects with data, if:
		 *  a < Y && b > x
		 */

		unsigned X = fb->addr, Y = fb->addr + fb->length;
		unsigned a = addr, b = addr + length;
		if(a < Y && b > X) {
			// from start of the block
			unsigned start = (a > X ? a : X) - X;
			unsigned end   = (b > Y ? Y : b) - X;

			memcpy(fb->data + start, data, end - start);

			fit_blocks++;
			fit_length += end - start;
		}
	}

	if(fit_blocks == 0) {
		fprintf(stderr, "Unfit data block %08x -> %04x\n", addr, length);
		return -1;
	}

	if(fit_length != length) {
		fprintf(stderr, "warning: data block %08x -> %04x truncated to %04x\n",
			addr, length, fit_length);
		fprintf(stderr, "(this is not an error, just a GDB glitch)\n");
	}

	return 0;
}

static int flash_go(stlink_t *sl) {
	int error = -1;

	// Some kinds of clock settings do not allow writing to flash.
	stlink_reset(sl);

	for(struct flash_block* fb = flash_root; fb; fb = fb->next) {
		#ifdef DEBUG
		printf("flash_do: block %08x -> %04x\n", fb->addr, fb->length);
		#endif

		unsigned length = fb->length;
		for(stm32_addr_t page = fb->addr; page < fb->addr + fb->length; page += FLASH_PAGE) {
			#ifdef DEBUG
			printf("flash_do: page %08x\n", page);
			#endif

			stlink_erase_flash_page(sl, page);

			if(stlink_write_flash(sl, page, fb->data + (page - fb->addr),
					length > FLASH_PAGE ? FLASH_PAGE : length) < 0)
				goto error;
		}

	}

	stlink_reset(sl);

	error = 0;

error:
	for(struct flash_block* fb = flash_root, *next; fb; fb = next) {
		next = fb->next;
		free(fb->data);
		free(fb);
	}

	flash_root = NULL;

	return error;
}

int serve(stlink_t *sl, int port) {
	int sock = socket(AF_INET, SOCK_STREAM, 0);
	if(sock < 0) {
		perror("socket");
		return 1;
	}

	unsigned int val = 1;
	setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));

	struct sockaddr_in serv_addr = {0};
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
	serv_addr.sin_port = htons(port);

	if(bind(sock, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
		perror("bind");
		return 1;
	}

	if(listen(sock, 5) < 0) {
		perror("listen");
		return 1;
	}

	stlink_force_debug(sl);
	stlink_reset(sl);
	init_code_breakpoints(sl);
	init_data_watchpoints(sl);

	printf("Listening at *:%d...\n", port);

	int client = accept(sock, NULL, NULL);
	if(client < 0) {
		perror("accept");
		return 1;
	}

	close(sock);

	printf("GDB connected.\n");

	/*
	 * To allow resetting the chip from GDB it is required to
	 * emulate attaching and detaching to target.
	 */
	unsigned int attached = 1;

	while(1) {
		char* packet;

		int status = gdb_recv_packet(client, &packet);
		if(status < 0) {
			fprintf(stderr, "cannot recv: %d\n", status);
			return 1;
		}

		#ifdef DEBUG
		printf("recv: %s\n", packet);
		#endif

		char* reply = NULL;
                reg regp;

		switch(packet[0]) {
		case 'q': {
			if(packet[1] == 'P' || packet[1] == 'C' || packet[1] == 'L') {
				reply = strdup("");
				break;
			}

			char *separator = strstr(packet, ":"), *params = "";
			if(separator == NULL) {
				separator = packet + strlen(packet);
			} else {
				params = separator + 1;
			}

			unsigned queryNameLength = (separator - &packet[1]);
			char* queryName = calloc(queryNameLength + 1, 1);
			strncpy(queryName, &packet[1], queryNameLength);

			#ifdef DEBUG
			printf("query: %s;%s\n", queryName, params);
			#endif

			if(!strcmp(queryName, "Supported")) {
				reply = strdup("PacketSize=3fff;qXfer:memory-map:read+");
			} else if(!strcmp(queryName, "Xfer")) {
				char *type, *op, *annex, *s_addr, *s_length;
				char *tok = params;

				type     = strsep(&tok, ":");
				op       = strsep(&tok, ":");
				annex    = strsep(&tok, ":");
				s_addr   = strsep(&tok, ",");
				s_length = tok;

				unsigned addr = strtoul(s_addr, NULL, 16),
				       length = strtoul(s_length, NULL, 16);

				#ifdef DEBUG
				printf("Xfer: type:%s;op:%s;annex:%s;addr:%d;length:%d\n",
					type, op, annex, addr, length);
				#endif

				const char* data = NULL;

				if(!strcmp(type, "memory-map") && !strcmp(op, "read"))
					data = current_memory_map;

				if(data) {
					unsigned data_length = strlen(data);
					if(addr + length > data_length)
						length = data_length - addr;

					if(length == 0) {
						reply = strdup("l");
					} else {
						reply = calloc(length + 2, 1);
						reply[0] = 'm';
						strncpy(&reply[1], data, length);
					}
				}
			}

			if(reply == NULL)
				reply = strdup("");

			free(queryName);

			break;
		}

		case 'v': {
			char *params = NULL;
			char *cmdName = strtok_r(packet, ":;", &params);

			cmdName++; // vCommand -> Command

			if(!strcmp(cmdName, "FlashErase")) {
				char *s_addr, *s_length;
				char *tok = params;

				s_addr   = strsep(&tok, ",");
				s_length = tok;

				unsigned addr = strtoul(s_addr, NULL, 16),
				       length = strtoul(s_length, NULL, 16);

				#ifdef DEBUG
				printf("FlashErase: addr:%08x,len:%04x\n",
					addr, length);
				#endif

				if(flash_add_block(addr, length, sl) < 0) {
					reply = strdup("E00");
				} else {
					reply = strdup("OK");
				}
			} else if(!strcmp(cmdName, "FlashWrite")) {
				char *s_addr, *data;
				char *tok = params;

				s_addr = strsep(&tok, ":");
				data   = tok;

				unsigned addr = strtoul(s_addr, NULL, 16);
				unsigned data_length = status - (data - packet);

				// Length of decoded data cannot be more than
				// encoded, as escapes are removed.
				// Additional byte is reserved for alignment fix.
				uint8_t *decoded = calloc(data_length + 1, 1);
				unsigned dec_index = 0;
				for(int i = 0; i < data_length; i++) {
					if(data[i] == 0x7d) {
						i++;
						decoded[dec_index++] = data[i] ^ 0x20;
					} else {
						decoded[dec_index++] = data[i];
					}
				}

				// Fix alignment
				if(dec_index % 2 != 0)
					dec_index++;

				#ifdef DEBUG
				printf("binary packet %d -> %d\n", data_length, dec_index);
				#endif

				if(flash_populate(addr, decoded, dec_index) < 0) {
					reply = strdup("E00");
				} else {
					reply = strdup("OK");
				}
			} else if(!strcmp(cmdName, "FlashDone")) {
				if(flash_go(sl) < 0) {
					reply = strdup("E00");
				} else {
					reply = strdup("OK");
				}
			} else if(!strcmp(cmdName, "Kill")) {
				attached = 0;

				reply = strdup("OK");
			}

			if(reply == NULL)
				reply = strdup("");

			break;
		}

		case 'c':
			stlink_run(sl);

			while(1) {
				int status = gdb_check_for_interrupt(client);
				if(status < 0) {
					fprintf(stderr, "cannot check for int: %d\n", status);
					return 1;
				}

				if(status == 1) {
					stlink_force_debug(sl);
					break;
				}

				stlink_status(sl);
				if(sl->core_stat == STLINK_CORE_HALTED) {
					break;
				}

				usleep(100000);
			}

			reply = strdup("S05"); // TRAP
			break;

		case 's':
			stlink_step(sl);

			reply = strdup("S05"); // TRAP
			break;

		case '?':
			if(attached) {
				reply = strdup("S05"); // TRAP
			} else {
				/* Stub shall reply OK if not attached. */
				reply = strdup("OK");
			}
			break;

		case 'g':
			stlink_read_all_regs(sl, &regp);

			reply = calloc(8 * 16 + 1, 1);
			for(int i = 0; i < 16; i++)
				sprintf(&reply[i * 8], "%08x", htonl(regp.r[i]));

			break;

		case 'p': {
			unsigned id = strtoul(&packet[1], NULL, 16);
                        unsigned myreg = 0xDEADDEAD;

			if(id < 16) {
				stlink_read_reg(sl, id, &regp);
				myreg = htonl(regp.r[id]);
			} else if(id == 0x19) {
				stlink_read_reg(sl, 16, &regp);
				myreg = htonl(regp.xpsr);
			} else {
				reply = strdup("E00");
			}

			reply = calloc(8 + 1, 1);
			sprintf(reply, "%08x", myreg);

			break;
		}

		case 'P': {
			char* s_reg = &packet[1];
			char* s_value = strstr(&packet[1], "=") + 1;

			unsigned reg   = strtoul(s_reg,   NULL, 16);
			unsigned value = strtoul(s_value, NULL, 16);

			if(reg < 16) {
				stlink_write_reg(sl, ntohl(value), reg);
			} else if(reg == 0x19) {
				stlink_write_reg(sl, ntohl(value), 16);
			} else {
				reply = strdup("E00");
			}

			if(!reply) {
				reply = strdup("OK");
			}

			break;
		}

		case 'G':
			for(int i = 0; i < 16; i++) {
				char str[9] = {0};
				strncpy(str, &packet[1 + i * 8], 8);
				uint32_t reg = strtoul(str, NULL, 16);
				stlink_write_reg(sl, ntohl(reg), i);
			}

			reply = strdup("OK");
			break;

		case 'm': {
			char* s_start = &packet[1];
			char* s_count = strstr(&packet[1], ",") + 1;

			stm32_addr_t start = strtoul(s_start, NULL, 16);
			unsigned     count = strtoul(s_count, NULL, 16);

			unsigned adj_start = start % 4;

			stlink_read_mem32(sl, start - adj_start, (count % 4 == 0) ?
						count : count + 4 - (count % 4));

			reply = calloc(count * 2 + 1, 1);
			for(int i = 0; i < count; i++) {
				reply[i * 2 + 0] = hex[sl->q_buf[i + adj_start] >> 4];
				reply[i * 2 + 1] = hex[sl->q_buf[i + adj_start] & 0xf];
			}

			break;
		}

		case 'M': {
			char* s_start = &packet[1];
			char* s_count = strstr(&packet[1], ",") + 1;
			char* hexdata = strstr(packet, ":") + 1;

			stm32_addr_t start = strtoul(s_start, NULL, 16);
			unsigned     count = strtoul(s_count, NULL, 16);

			for(int i = 0; i < count; i ++) {
				char hex[3] = { hexdata[i*2], hexdata[i*2+1], 0 };
				uint8_t byte = strtoul(hex, NULL, 16);
				sl->q_buf[i] = byte;
			}

			if((count % 4) == 0 && (start % 4) == 0) {
				stlink_write_mem32(sl, start, count);
			} else {
				stlink_write_mem8(sl, start, count);
			}

			reply = strdup("OK");

			break;
		}

		case 'Z': {
			char *endptr;
			stm32_addr_t addr = strtoul(&packet[3], &endptr, 16);
			stm32_addr_t len  = strtoul(&endptr[1], NULL, 16);

			switch (packet[1]) {
				case '1':
				if(update_code_breakpoint(sl, addr, 1) < 0) {
					reply = strdup("E00");
				} else {
					reply = strdup("OK");
				}
				break;

				case '2':   // insert write watchpoint
				case '3':   // insert read  watchpoint
				case '4':   // insert access watchpoint
		    		{
					enum watchfun wf;
		 			if(packet[1] == '2') {
						wf = WATCHWRITE;
					} else if(packet[1] == '3') {
						wf = WATCHREAD;
					} else {
						wf = WATCHACCESS;
						if(add_data_watchpoint(sl, wf, addr, len) < 0) {
							reply = strdup("E00");
						} else {
							reply = strdup("OK");
							break;
						}
					}
				}

				default:
				reply = strdup("");
			}
			break;
		}
		case 'z': {
			char *endptr;
			stm32_addr_t addr = strtoul(&packet[3], &endptr, 16);
			//stm32_addr_t len  = strtoul(&endptr[1], NULL, 16);

			switch (packet[1]) {
				case '1': // remove breakpoint
				update_code_breakpoint(sl, addr, 0);
				reply = strdup("OK");
				break;

				case '2' : // remove write watchpoint
				case '3' : // remove read watchpoint
				case '4' : // remove access watchpoint
				if(delete_data_watchpoint(sl, addr) < 0) {
					reply = strdup("E00");
				} else {
					reply = strdup("OK");
					break;
				}

				default:
				reply = strdup("");
			}
			break;
		}

		case '!': {
			/*
			 * Enter extended mode which allows restarting.
			 * We do support that always.
			 */

			reply = strdup("OK");

			break;
		}

		case 'R': {
			/* Reset the core. */

			stlink_reset(sl);
			init_code_breakpoints(sl);
			init_data_watchpoints(sl);

			attached = 1;

			reply = strdup("OK");

			break;
		}

		default:
			reply = strdup("");
		}

		if(reply) {
			#ifdef DEBUG
			printf("send: %s\n", reply);
			#endif

			int result = gdb_send_packet(client, reply);
			if(result != 0) {
				fprintf(stderr, "cannot send: %d\n", result);
				return 1;
			}

			free(reply);
		}

		free(packet);
	}

	return 0;
}