path: root/src/rtos/rtos.c

/***************************************************************************
 *   Copyright (C) 2011 by Broadcom Corporation                            *
 *   Evan Hunter - ehunter@broadcom.com                                    *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 ***************************************************************************/

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

#include "rtos.h"
#include "target/target.h"
#include "helper/log.h"
#include "helper/binarybuffer.h"
#include "server/gdb_server.h"

/* RTOSs */
extern struct rtos_type freertos_rtos;
extern struct rtos_type threadx_rtos;
extern struct rtos_type ecos_rtos;
extern struct rtos_type linux_rtos;
extern struct rtos_type chibios_rtos;
extern struct rtos_type chromium_ec_rtos;
extern struct rtos_type embkernel_rtos;
extern struct rtos_type mqx_rtos;
extern struct rtos_type ucos_iii_rtos;
extern struct rtos_type nuttx_rtos;
extern struct rtos_type hwthread_rtos;
extern struct rtos_type riot_rtos;
extern struct rtos_type zephyr_rtos;

static struct rtos_type *rtos_types[] = {
	&threadx_rtos,
	&freertos_rtos,
	&ecos_rtos,
	&linux_rtos,
	&chibios_rtos,
	&chromium_ec_rtos,
	&embkernel_rtos,
	&mqx_rtos,
	&ucos_iii_rtos,
	&nuttx_rtos,
	&riot_rtos,
	&zephyr_rtos,
	/* keep this as last, as it always matches with rtos auto */
	&hwthread_rtos,
	NULL
};

static int rtos_try_next(struct target *target);

int rtos_thread_packet(struct connection *connection, const char *packet, int packet_size);

int rtos_smp_init(struct target *target)
{
	if (target->rtos->type->smp_init)
		return target->rtos->type->smp_init(target);
	return ERROR_TARGET_INIT_FAILED;
}

static int rtos_target_for_threadid(struct connection *connection,
									threadid_t threadid,
									struct target **t)
{
	struct target *curr = get_target_from_connection(connection);
	if (t)
		*t = curr;

	return ERROR_OK;
}

static int os_alloc(struct target *target, struct rtos_type *ostype,
					struct command_context *cmd_ctx)
{
	struct rtos *os = target->rtos = calloc(1, sizeof(struct rtos));

	if (!os)
		return JIM_ERR;

	os->type = ostype;
	os->current_threadid = -1;
	os->current_thread = 0;
	os->symbols = NULL;
	os->target = target;

	/* RTOS drivers can override the packet handler in _create(). */
	os->gdb_thread_packet = rtos_thread_packet;
	os->gdb_v_packet = NULL;
	os->gdb_target_for_threadid = rtos_target_for_threadid;
	os->cmd_ctx = cmd_ctx;

	return JIM_OK;
}

static void os_free(struct target *target)
{
	if (!target->rtos)
		return;

	free(target->rtos->symbols);
	free(target->rtos);
	target->rtos = NULL;
}

static int os_alloc_create(struct target *target, struct rtos_type *ostype,
						   struct command_context *cmd_ctx)
{
	int ret = os_alloc(target, ostype, cmd_ctx);

	if (ret == JIM_OK) {
		ret = target->rtos->type->create(target);
		if (ret != JIM_OK)
			os_free(target);
	}

	return ret;
}

int rtos_create(struct jim_getopt_info *goi, struct target *target)
{
	int x;
	const char *cp;
	Jim_Obj *res;
	int e;

	if (!goi->isconfigure && goi->argc != 0) {
		Jim_WrongNumArgs(goi->interp, goi->argc, goi->argv, "NO PARAMS");
		return JIM_ERR;
	}

	struct command_context *cmd_ctx = current_command_context(goi->interp);

	os_free(target);

	e = jim_getopt_string(goi, &cp, NULL);
	if (e != JIM_OK)
		return e;

	if (strcmp(cp, "auto") == 0) {
		/* Auto detect tries to look up all symbols for each RTOS,
		 * and runs the RTOS driver's _detect() function when GDB
		 * finds all symbols for any RTOS. See rtos_qsymbol(). */
		target->rtos_auto_detect = true;

		/* rtos_qsymbol() will iterate over all RTOSes. Allocate
		 * target->rtos here, and set it to the first RTOS type. */
		return os_alloc(target, rtos_types[0], cmd_ctx);
	}

	for (x = 0; rtos_types[x]; x++)
		if (strcmp(cp, rtos_types[x]->name) == 0)
			return os_alloc_create(target, rtos_types[x], cmd_ctx);

	Jim_SetResultFormatted(goi->interp, "Unknown RTOS type %s, try one of: ", cp);
	res = Jim_GetResult(goi->interp);
	for (x = 0; rtos_types[x]; x++)
		Jim_AppendStrings(goi->interp, res, rtos_types[x]->name, ", ", NULL);
	Jim_AppendStrings(goi->interp, res, " or auto", NULL);

	return JIM_ERR;
}

void rtos_destroy(struct target *target)
{
	os_free(target);
}

int gdb_thread_packet(struct connection *connection, char const *packet, int packet_size)
{
	struct target *target = get_target_from_connection(connection);
	if (!target->rtos)
		return rtos_thread_packet(connection, packet, packet_size);	/* thread not
										 *found*/
	return target->rtos->gdb_thread_packet(connection, packet, packet_size);
}

static struct symbol_table_elem *next_symbol(struct rtos *os, char *cur_symbol, uint64_t cur_addr)
{
	struct symbol_table_elem *s;

	if (!os->symbols)
		os->type->get_symbol_list_to_lookup(&os->symbols);

	if (!cur_symbol[0])
		return &os->symbols[0];

	for (s = os->symbols; s->symbol_name; s++)
		if (!strcmp(s->symbol_name, cur_symbol)) {
			s->address = cur_addr;
			s++;
			return s;
		}

	return NULL;
}

/* searches for 'symbol' in the lookup table for 'os' and returns TRUE,
 * if 'symbol' is not declared optional */
static bool is_symbol_mandatory(const struct rtos *os, const char *symbol)
{
	for (struct symbol_table_elem *s = os->symbols; s->symbol_name; ++s) {
		if (!strcmp(s->symbol_name, symbol))
			return !s->optional;
	}
	return false;
}

/* rtos_qsymbol() processes and replies to all qSymbol packets from GDB.
 *
 * GDB sends a qSymbol:: packet (empty address, empty name) to notify
 * that it can now answer qSymbol::hexcodedname queries, to look up symbols.
 *
 * If the qSymbol packet has no address that means GDB did not find the
 * symbol, in which case auto-detect will move on to try the next RTOS.
 *
 * rtos_qsymbol() then calls the next_symbol() helper function, which
 * iterates over symbol names for the current RTOS until it finds the
 * symbol in the received GDB packet, and then returns the next entry
 * in the list of symbols.
 *
 * If GDB replied about the last symbol for the RTOS and the RTOS was
 * specified explicitly, then no further symbol lookup is done. When
 * auto-detecting, the RTOS driver _detect() function must return success.
 *
 * rtos_qsymbol() returns 1 if an RTOS has been detected, or 0 otherwise.
 */
int rtos_qsymbol(struct connection *connection, char const *packet, int packet_size)
{
	int rtos_detected = 0;
	uint64_t addr = 0;
	size_t reply_len;
	char reply[GDB_BUFFER_SIZE + 1], cur_sym[GDB_BUFFER_SIZE / 2 + 1] = ""; /* Extra byte for null-termination */
	struct symbol_table_elem *next_sym;
	struct target *target = get_target_from_connection(connection);
	struct rtos *os = target->rtos;

	reply_len = sprintf(reply, "OK");

	if (!os)
		goto done;

	/* Decode any symbol name in the packet*/
	size_t len = unhexify((uint8_t *)cur_sym, strchr(packet + 8, ':') + 1, strlen(strchr(packet + 8, ':') + 1));
	cur_sym[len] = 0;

	if ((strcmp(packet, "qSymbol::") != 0) &&               /* GDB is not offering symbol lookup for the first time */
	    (!sscanf(packet, "qSymbol:%" SCNx64 ":", &addr)) && /* GDB did not find an address for a symbol */
	    is_symbol_mandatory(os, cur_sym)) {					/* the symbol is mandatory for this RTOS */

		/* GDB could not find an address for the previous symbol */
		if (!target->rtos_auto_detect) {
			LOG_WARNING("RTOS %s not detected. (GDB could not find symbol \'%s\')", os->type->name, cur_sym);
			goto done;
		} else {
			/* Autodetecting RTOS - try next RTOS */
			if (!rtos_try_next(target)) {
				LOG_WARNING("No RTOS could be auto-detected!");
				goto done;
			}

			/* Next RTOS selected - invalidate current symbol */
			cur_sym[0] = '\x00';
		}
	}

	LOG_DEBUG("RTOS: Address of symbol '%s' is 0x%" PRIx64, cur_sym, addr);

	next_sym = next_symbol(os, cur_sym, addr);

	/* Should never happen unless the debugger misbehaves */
	if (!next_sym) {
		LOG_WARNING("RTOS: Debugger sent us qSymbol with '%s' that we did not ask for", cur_sym);
		goto done;
	}

	if (!next_sym->symbol_name) {
		/* No more symbols need looking up */

		if (!target->rtos_auto_detect) {
			rtos_detected = 1;
			goto done;
		}

		if (os->type->detect_rtos(target)) {
			LOG_INFO("Auto-detected RTOS: %s", os->type->name);
			rtos_detected = 1;
			goto done;
		} else {
			LOG_WARNING("No RTOS could be auto-detected!");
			goto done;
		}
	}

	if (8 + (strlen(next_sym->symbol_name) * 2) + 1 > sizeof(reply)) {
		LOG_ERROR("ERROR: RTOS symbol '%s' name is too long for GDB!", next_sym->symbol_name);
		goto done;
	}

	LOG_DEBUG("RTOS: Requesting symbol lookup of '%s' from the debugger", next_sym->symbol_name);

	reply_len = snprintf(reply, sizeof(reply), "qSymbol:");
	reply_len += hexify(reply + reply_len,
		(const uint8_t *)next_sym->symbol_name, strlen(next_sym->symbol_name),
		sizeof(reply) - reply_len);

done:
	gdb_put_packet(connection, reply, reply_len);
	return rtos_detected;
}

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

	if (strncmp(packet, "qThreadExtraInfo,", 17) == 0) {
		if ((target->rtos) && (target->rtos->thread_details) &&
				(target->rtos->thread_count != 0)) {
			threadid_t threadid = 0;
			int found = -1;
			sscanf(packet, "qThreadExtraInfo,%" SCNx64, &threadid);

			if ((target->rtos) && (target->rtos->thread_details)) {
				int thread_num;
				for (thread_num = 0; thread_num < target->rtos->thread_count; thread_num++) {
					if (target->rtos->thread_details[thread_num].threadid == threadid) {
						if (target->rtos->thread_details[thread_num].exists)
							found = thread_num;
					}
				}
			}
			if (found == -1) {
				gdb_put_packet(connection, "E01", 3);	/* thread not found */
				return ERROR_OK;
			}

			struct thread_detail *detail = &target->rtos->thread_details[found];

			int str_size = 0;
			if (detail->thread_name_str)
				str_size += strlen(detail->thread_name_str);
			if (detail->extra_info_str)
				str_size += strlen(detail->extra_info_str);

			char *tmp_str = calloc(str_size + 9, sizeof(char));
			char *tmp_str_ptr = tmp_str;

			if (detail->thread_name_str)
				tmp_str_ptr += sprintf(tmp_str_ptr, "Name: %s", detail->thread_name_str);
			if (detail->extra_info_str) {
				if (tmp_str_ptr != tmp_str)
					tmp_str_ptr += sprintf(tmp_str_ptr, ", ");
				tmp_str_ptr += sprintf(tmp_str_ptr, "%s", detail->extra_info_str);
			}

			assert(strlen(tmp_str) ==
				(size_t) (tmp_str_ptr - tmp_str));

			char *hex_str = malloc(strlen(tmp_str) * 2 + 1);
			size_t pkt_len = hexify(hex_str, (const uint8_t *)tmp_str,
				strlen(tmp_str), strlen(tmp_str) * 2 + 1);

			gdb_put_packet(connection, hex_str, pkt_len);
			free(hex_str);
			free(tmp_str);
			return ERROR_OK;

		}
		gdb_put_packet(connection, "", 0);
		return ERROR_OK;
	} else if (strncmp(packet, "qSymbol", 7) == 0) {
		if (rtos_qsymbol(connection, packet, packet_size) == 1) {
			if (target->rtos_auto_detect == true) {
				target->rtos_auto_detect = false;
				target->rtos->type->create(target);
			}
			target->rtos->type->update_threads(target->rtos);
		}
		return ERROR_OK;
	} else if (strncmp(packet, "qfThreadInfo", 12) == 0) {
		int i;
		if (target->rtos) {
			if (target->rtos->thread_count == 0) {
				gdb_put_packet(connection, "l", 1);
			} else {
				/*thread id are 16 char +1 for ',' */
				char *out_str = malloc(17 * target->rtos->thread_count + 1);
				char *tmp_str = out_str;
				for (i = 0; i < target->rtos->thread_count; i++) {
					tmp_str += sprintf(tmp_str, "%c%016" PRIx64, i == 0 ? 'm' : ',',
										target->rtos->thread_details[i].threadid);
				}
				gdb_put_packet(connection, out_str, strlen(out_str));
				free(out_str);
			}
		} else
			gdb_put_packet(connection, "l", 1);

		return ERROR_OK;
	} else if (strncmp(packet, "qsThreadInfo", 12) == 0) {
		gdb_put_packet(connection, "l", 1);
		return ERROR_OK;
	} else if (strncmp(packet, "qAttached", 9) == 0) {
		gdb_put_packet(connection, "1", 1);
		return ERROR_OK;
	} else if (strncmp(packet, "qOffsets", 8) == 0) {
		char offsets[] = "Text=0;Data=0;Bss=0";
		gdb_put_packet(connection, offsets, sizeof(offsets)-1);
		return ERROR_OK;
	} else if (strncmp(packet, "qCRC:", 5) == 0) {
		/* make sure we check this before "qC" packet below
		 * otherwise it gets incorrectly handled */
		return GDB_THREAD_PACKET_NOT_CONSUMED;
	} else if (strncmp(packet, "qC", 2) == 0) {
		if (target->rtos) {
			char buffer[19];
			int size;
			size = snprintf(buffer, 19, "QC%016" PRIx64, target->rtos->current_thread);
			gdb_put_packet(connection, buffer, size);
		} else
			gdb_put_packet(connection, "QC0", 3);
		return ERROR_OK;
	} else if (packet[0] == 'T') {	/* Is thread alive? */
		threadid_t threadid;
		int found = -1;
		sscanf(packet, "T%" SCNx64, &threadid);
		if ((target->rtos) && (target->rtos->thread_details)) {
			int thread_num;
			for (thread_num = 0; thread_num < target->rtos->thread_count; thread_num++) {
				if (target->rtos->thread_details[thread_num].threadid == threadid) {
					if (target->rtos->thread_details[thread_num].exists)
						found = thread_num;
				}
			}
		}
		if (found != -1)
			gdb_put_packet(connection, "OK", 2);	/* thread alive */
		else
			gdb_put_packet(connection, "E01", 3);	/* thread not found */
		return ERROR_OK;
	} else if (packet[0] == 'H') {	/* Set current thread ( 'c' for step and continue, 'g' for
					 * all other operations ) */
		if ((packet[1] == 'g') && (target->rtos)) {
			threadid_t threadid;
			sscanf(packet, "Hg%16" SCNx64, &threadid);
			LOG_DEBUG("RTOS: GDB requested to set current thread to 0x%" PRIx64, threadid);
			/* threadid of 0 indicates target should choose */
			if (threadid == 0)
				target->rtos->current_threadid = target->rtos->current_thread;
			else
				target->rtos->current_threadid = threadid;
		}
		gdb_put_packet(connection, "OK", 2);
		return ERROR_OK;
	}

	return GDB_THREAD_PACKET_NOT_CONSUMED;
}

static int rtos_put_gdb_reg_list(struct connection *connection,
		struct rtos_reg *reg_list, int num_regs)
{
	size_t num_bytes = 1; /* NUL */
	for (int i = 0; i < num_regs; ++i)
		num_bytes += DIV_ROUND_UP(reg_list[i].size, 8) * 2;

	char *hex = malloc(num_bytes);
	char *hex_p = hex;

	for (int i = 0; i < num_regs; ++i) {
		size_t count = DIV_ROUND_UP(reg_list[i].size, 8);
		size_t n = hexify(hex_p, reg_list[i].value, count, num_bytes);
		hex_p += n;
		num_bytes -= n;
	}

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

	return ERROR_OK;
}

/** Look through all registers to find this register. */
int rtos_get_gdb_reg(struct connection *connection, int reg_num)
{
	struct target *target = get_target_from_connection(connection);
	threadid_t current_threadid = target->rtos->current_threadid;
	if ((target->rtos) && (current_threadid != -1) &&
			(current_threadid != 0) &&
			((current_threadid != target->rtos->current_thread) ||
			(target->smp))) {	/* in smp several current thread are possible */
		struct rtos_reg *reg_list;
		int num_regs;

		LOG_DEBUG("getting register %d for thread 0x%" PRIx64
				  ", target->rtos->current_thread=0x%" PRIx64,
										reg_num,
										current_threadid,
										target->rtos->current_thread);

		int retval;
		if (target->rtos->type->get_thread_reg_value) {
			uint32_t reg_size;
			uint8_t *reg_value;
			retval = target->rtos->type->get_thread_reg_value(target->rtos,
					current_threadid, reg_num, &reg_size, &reg_value);
			if (retval != ERROR_OK) {
				LOG_ERROR("RTOS: failed to get register %d", reg_num);
				return retval;
			}

			/* Create a reg_list with one register that can
			 * accommodate the full size of the one we just got the
			 * value for. To do that we allocate extra space off the
			 * end of the struct, relying on the fact that
			 * rtos_reg.value is the last element in the struct. */
			reg_list = calloc(1, sizeof(*reg_list) + DIV_ROUND_UP(reg_size, 8));
			if (!reg_list) {
				free(reg_value);
				LOG_ERROR("Failed to allocated reg_list for %d-byte register.",
					  reg_size);
				return ERROR_FAIL;
			}
			reg_list[0].number = reg_num;
			reg_list[0].size = reg_size;
			memcpy(&reg_list[0].value, reg_value, DIV_ROUND_UP(reg_size, 8));
			free(reg_value);
			num_regs = 1;
		} else {
			retval = target->rtos->type->get_thread_reg_list(target->rtos,
					current_threadid,
					&reg_list,
					&num_regs);
			if (retval != ERROR_OK) {
				LOG_ERROR("RTOS: failed to get register list");
				return retval;
			}
		}

		for (int i = 0; i < num_regs; ++i) {
			if (reg_list[i].number == (uint32_t)reg_num) {
				rtos_put_gdb_reg_list(connection, reg_list + i, 1);
				free(reg_list);
				return ERROR_OK;
			}
		}

		free(reg_list);
	}
	return ERROR_FAIL;
}

/** Return a list of general registers. */
int rtos_get_gdb_reg_list(struct connection *connection)
{
	struct target *target = get_target_from_connection(connection);
	int64_t current_threadid = target->rtos->current_threadid;
	if ((target->rtos) && (current_threadid != -1) &&
			(current_threadid != 0) &&
			((current_threadid != target->rtos->current_thread) ||
			(target->smp))) {	/* in smp several current thread are possible */
		struct rtos_reg *reg_list;
		int num_regs;

		LOG_DEBUG("RTOS: getting register list for thread 0x%" PRIx64
				  ", target->rtos->current_thread=0x%" PRIx64 "\r\n",
										current_threadid,
										target->rtos->current_thread);

		int retval = target->rtos->type->get_thread_reg_list(target->rtos,
				current_threadid,
				&reg_list,
				&num_regs);
		if (retval != ERROR_OK) {
			LOG_ERROR("RTOS: failed to get register list");
			return retval;
		}

		rtos_put_gdb_reg_list(connection, reg_list, num_regs);
		free(reg_list);

		return ERROR_OK;
	}
	return ERROR_FAIL;
}

int rtos_set_reg(struct connection *connection, int reg_num,
		uint8_t *reg_value)
{
	struct target *target = get_target_from_connection(connection);
	int64_t current_threadid = target->rtos->current_threadid;
	if ((target->rtos) &&
			(target->rtos->type->set_reg) &&
			(current_threadid != -1) &&
			(current_threadid != 0)) {
		return target->rtos->type->set_reg(target->rtos, reg_num, reg_value);
	}
	return ERROR_FAIL;
}

int rtos_generic_stack_read(struct target *target,
	const struct rtos_register_stacking *stacking,
	target_addr_t stack_ptr,
	struct rtos_reg **reg_list,
	int *num_regs)
{
	int retval;

	if (stack_ptr == 0) {
		LOG_ERROR("Error: null stack pointer in thread");
		return -5;
	}
	/* Read the stack */
	uint8_t *stack_data = malloc(stacking->stack_registers_size);
	target_addr_t address = stack_ptr;

	if (stacking->stack_growth_direction == 1)
		address -= stacking->stack_registers_size;
	retval = target_read_buffer(target, address, stacking->stack_registers_size, stack_data);
	if (retval != ERROR_OK) {
		free(stack_data);
		LOG_ERROR("Error reading stack frame from thread");
		return retval;
	}
	LOG_DEBUG("RTOS: Read stack frame at " TARGET_ADDR_FMT, address);

#if 0
		LOG_OUTPUT("Stack Data :");
		for (i = 0; i < stacking->stack_registers_size; i++)
			LOG_OUTPUT("%02X", stack_data[i]);
		LOG_OUTPUT("\r\n");
#endif

	target_addr_t new_stack_ptr;
	if (stacking->calculate_process_stack) {
		new_stack_ptr = stacking->calculate_process_stack(target,
				stack_data, stacking, stack_ptr);
	} else {
		new_stack_ptr = stack_ptr - stacking->stack_growth_direction *
			stacking->stack_registers_size;
	}

	*reg_list = calloc(stacking->num_output_registers, sizeof(struct rtos_reg));
	*num_regs = stacking->num_output_registers;

	for (int i = 0; i < stacking->num_output_registers; ++i) {
		(*reg_list)[i].number = stacking->register_offsets[i].number;
		(*reg_list)[i].size = stacking->register_offsets[i].width_bits;

		int offset = stacking->register_offsets[i].offset;
		if (offset == -2)
			buf_cpy(&new_stack_ptr, (*reg_list)[i].value, (*reg_list)[i].size);
		else if (offset != -1)
			buf_cpy(stack_data + offset, (*reg_list)[i].value, (*reg_list)[i].size);

		LOG_DEBUG("register %d has value 0x%" PRIx64, (*reg_list)[i].number,
				  buf_get_u64((*reg_list)[i].value, 0, 64));
	}

	free(stack_data);
/*	LOG_OUTPUT("Output register string: %s\r\n", *hex_reg_list); */
	return ERROR_OK;
}

/* Read an individual register from the RTOS stack. */
int rtos_generic_stack_read_reg(struct target *target,
								const struct rtos_register_stacking *stacking,
								target_addr_t stack_ptr,
								uint32_t reg_num, struct rtos_reg *reg)
{
	LOG_DEBUG("stack_ptr=" TARGET_ADDR_FMT ", reg_num=%d", stack_ptr, reg_num);
	unsigned total_count = MAX(stacking->total_register_count, stacking->num_output_registers);
	unsigned i;
	for (i = 0; i < total_count; i++) {
		if (stacking->register_offsets[i].number == reg_num)
			break;
	}
	if (i >= total_count) {
		/* This register is not on the stack. Return error so a caller somewhere
		 * will just read the register directly from the target. */
		return ERROR_FAIL;
	}

	const struct stack_register_offset *offsets = &stacking->register_offsets[i];
	reg->size = offsets->width_bits;

	unsigned width_bytes = DIV_ROUND_UP(offsets->width_bits, 8);
	if (offsets->offset >= 0) {
		target_addr_t address = stack_ptr;

		if (stacking->stack_growth_direction == 1)
			address -= stacking->stack_registers_size;

		if (target_read_buffer(
				target, address + offsets->offset,
				width_bytes, reg->value) != ERROR_OK)
			return ERROR_FAIL;
		LOG_DEBUG("register %d has value 0x%" PRIx64, reg->number,
				  buf_get_u64(reg->value, 0, 64));
	} else {
		memset(reg->value, 0, width_bytes);
	}

	return ERROR_OK;
}

int rtos_generic_stack_write_reg(struct target *target,
								const struct rtos_register_stacking *stacking,
								target_addr_t stack_ptr,
								uint32_t reg_num, uint8_t *reg_value)
{
	LOG_DEBUG("stack_ptr=" TARGET_ADDR_FMT ", reg_num=%d", stack_ptr, reg_num);
	unsigned total_count = MAX(stacking->total_register_count, stacking->num_output_registers);
	unsigned i;
	for (i = 0; i < total_count; i++) {
		if (stacking->register_offsets[i].number == reg_num)
			break;
	}
	if (i >= total_count) {
		/* This register is not on the stack. Return error so a caller somewhere
		 * will just read the register directly from the target. */
		return ERROR_FAIL;
	}

	const struct stack_register_offset *offsets = &stacking->register_offsets[i];

	unsigned width_bytes = DIV_ROUND_UP(offsets->width_bits, 8);
	if (offsets->offset >= 0) {
		target_addr_t address = stack_ptr;

		if (stacking->stack_growth_direction == 1)
			address -= stacking->stack_registers_size;

		LOG_DEBUG("write 0x%" PRIx64 " to register %d",
				  buf_get_u64(reg_value, 0, offsets->width_bits), reg_num);
		if (target_write_buffer(
				target, address + offsets->offset,
				width_bytes, reg_value) != ERROR_OK)
			return ERROR_FAIL;
	} else if (offsets->offset == -1) {
		/* This register isn't on the stack, but is listed as one of those. We
		 * read it as 0, and ignore writes. */
	} else if (offsets->offset == -2) {
		/* This register requires computation when we "read" it. I'm not sure
		 * how to handle writes. We can't simply return error here because then
		 * the higher level code will end up writing the register in the halted
		 * core, which is definitely not the same as writing it for a thread. */
		LOG_ERROR("Don't know how to write register %d with offset -2 in a thread.",
				  reg_num);
		assert(0);
	} else {
		LOG_ERROR("Don't know how to handle offset <2.");
		assert(0);
	}

	return ERROR_OK;
}

static int rtos_try_next(struct target *target)
{
	struct rtos *os = target->rtos;
	struct rtos_type **type = rtos_types;

	if (!os)
		return 0;

	while (*type && os->type != *type)
		type++;

	if (!*type || !*(++type))
		return 0;

	os->type = *type;

	free(os->symbols);
	os->symbols = NULL;

	return 1;
}

int rtos_update_threads(struct target *target)
{
	if ((target->rtos) && (target->rtos->type))
		target->rtos->type->update_threads(target->rtos);
	return ERROR_OK;
}

void rtos_free_threadlist(struct rtos *rtos)
{
	if (rtos->thread_details) {
		int j;

		for (j = 0; j < rtos->thread_count; j++) {
			struct thread_detail *current_thread = &rtos->thread_details[j];
			free(current_thread->thread_name_str);
			free(current_thread->extra_info_str);
		}
		free(rtos->thread_details);
		rtos->thread_details = NULL;
		rtos->thread_count = 0;
		rtos->current_threadid = -1;
		rtos->current_thread = 0;
	}
}

bool rtos_needs_fake_step(struct target *target, int64_t thread_id)
{
	if (target->rtos->type->needs_fake_step)
		return target->rtos->type->needs_fake_step(target, thread_id);
	return target->rtos->current_thread != thread_id;
}

int rtos_read_buffer(struct target *target, target_addr_t address,
		uint32_t size, uint8_t *buffer)
{
	if (target->rtos->type->read_buffer)
		return target->rtos->type->read_buffer(target->rtos, address, size, buffer);
	return ERROR_NOT_IMPLEMENTED;
}

int rtos_write_buffer(struct target *target, target_addr_t address,
		uint32_t size, const uint8_t *buffer)
{
	if (target->rtos->type->write_buffer)
		return target->rtos->type->write_buffer(target->rtos, address, size, buffer);
	return ERROR_NOT_IMPLEMENTED;
}

struct target *rtos_swbp_target(struct target *target, target_addr_t address,
				uint32_t length, enum breakpoint_type type)
{
	if (target->rtos->type->swbp_target)
		return target->rtos->type->swbp_target(target->rtos, address, length, type);
	return target;
}