target.c

/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
 *   Copyright (C) 2007-2010 Øyvind Harboe                                 *
 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
 *   Copyright (C) 2008, Duane Ellis                                       *
 *   openocd@duaneeellis.com                                               *
 *                                                                         *
 *   Copyright (C) 2008 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 *                                                                         *
 *   Copyright (C) 2008 by Rick Altherr                                    *
 *   kc8apf@kc8apf.net>                                                    *
 *                                                                         *
 *   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 <helper/time_support.h>
#include <jtag/jtag.h>
#include <flash/nor/core.h>

#include "target.h"
#include "target_type.h"
#include "target_request.h"
#include "breakpoints.h"
#include "register.h"
#include "trace.h"
#include "image.h"


static int target_array2mem(Jim_Interp *interp, struct target *target,
		int argc, Jim_Obj *const *argv);
static int target_mem2array(Jim_Interp *interp, struct target *target,
		int argc, Jim_Obj *const *argv);

/* targets */
extern struct target_type arm7tdmi_target;
extern struct target_type arm720t_target;
extern struct target_type arm9tdmi_target;
extern struct target_type arm920t_target;
extern struct target_type arm966e_target;
extern struct target_type arm926ejs_target;
extern struct target_type fa526_target;
extern struct target_type feroceon_target;
extern struct target_type dragonite_target;
extern struct target_type xscale_target;
extern struct target_type cortexm3_target;
extern struct target_type cortexa8_target;
extern struct target_type arm11_target;
extern struct target_type mips_m4k_target;
extern struct target_type avr_target;
extern struct target_type dsp563xx_target;
extern struct target_type testee_target;

struct target_type *target_types[] =
{
	&arm7tdmi_target,
	&arm9tdmi_target,
	&arm920t_target,
	&arm720t_target,
	&arm966e_target,
	&arm926ejs_target,
	&fa526_target,
	&feroceon_target,
	&dragonite_target,
	&xscale_target,
	&cortexm3_target,
	&cortexa8_target,
	&arm11_target,
	&mips_m4k_target,
	&avr_target,
	&dsp563xx_target,
	&testee_target,
	NULL,
};

struct target *all_targets = NULL;
struct target_event_callback *target_event_callbacks = NULL;
struct target_timer_callback *target_timer_callbacks = NULL;

static const Jim_Nvp nvp_assert[] = {
	{ .name = "assert", NVP_ASSERT },
	{ .name = "deassert", NVP_DEASSERT },
	{ .name = "T", NVP_ASSERT },
	{ .name = "F", NVP_DEASSERT },
	{ .name = "t", NVP_ASSERT },
	{ .name = "f", NVP_DEASSERT },
	{ .name = NULL, .value = -1 }
};

static const Jim_Nvp nvp_error_target[] = {
	{ .value = ERROR_TARGET_INVALID, .name = "err-invalid" },
	{ .value = ERROR_TARGET_INIT_FAILED, .name = "err-init-failed" },
	{ .value = ERROR_TARGET_TIMEOUT, .name = "err-timeout" },
	{ .value = ERROR_TARGET_NOT_HALTED, .name = "err-not-halted" },
	{ .value = ERROR_TARGET_FAILURE, .name = "err-failure" },
	{ .value = ERROR_TARGET_UNALIGNED_ACCESS   , .name = "err-unaligned-access" },
	{ .value = ERROR_TARGET_DATA_ABORT , .name = "err-data-abort" },
	{ .value = ERROR_TARGET_RESOURCE_NOT_AVAILABLE , .name = "err-resource-not-available" },
	{ .value = ERROR_TARGET_TRANSLATION_FAULT  , .name = "err-translation-fault" },
	{ .value = ERROR_TARGET_NOT_RUNNING, .name = "err-not-running" },
	{ .value = ERROR_TARGET_NOT_EXAMINED, .name = "err-not-examined" },
	{ .value = -1, .name = NULL }
};

const char *target_strerror_safe(int err)
{
	const Jim_Nvp *n;

	n = Jim_Nvp_value2name_simple(nvp_error_target, err);
	if (n->name == NULL) {
		return "unknown";
	} else {
		return n->name;
	}
}

static const Jim_Nvp nvp_target_event[] = {
	{ .value = TARGET_EVENT_OLD_gdb_program_config , .name = "old-gdb_program_config" },
	{ .value = TARGET_EVENT_OLD_pre_resume         , .name = "old-pre_resume" },

	{ .value = TARGET_EVENT_GDB_HALT, .name = "gdb-halt" },
	{ .value = TARGET_EVENT_HALTED, .name = "halted" },
	{ .value = TARGET_EVENT_RESUMED, .name = "resumed" },
	{ .value = TARGET_EVENT_RESUME_START, .name = "resume-start" },
	{ .value = TARGET_EVENT_RESUME_END, .name = "resume-end" },

	{ .name = "gdb-start", .value = TARGET_EVENT_GDB_START },
	{ .name = "gdb-end", .value = TARGET_EVENT_GDB_END },

	/* historical name */

	{ .value = TARGET_EVENT_RESET_START, .name = "reset-start" },

	{ .value = TARGET_EVENT_RESET_ASSERT_PRE,    .name = "reset-assert-pre" },
	{ .value = TARGET_EVENT_RESET_ASSERT,        .name = "reset-assert" },
	{ .value = TARGET_EVENT_RESET_ASSERT_POST,   .name = "reset-assert-post" },
	{ .value = TARGET_EVENT_RESET_DEASSERT_PRE,  .name = "reset-deassert-pre" },
	{ .value = TARGET_EVENT_RESET_DEASSERT_POST, .name = "reset-deassert-post" },
	{ .value = TARGET_EVENT_RESET_HALT_PRE,      .name = "reset-halt-pre" },
	{ .value = TARGET_EVENT_RESET_HALT_POST,     .name = "reset-halt-post" },
	{ .value = TARGET_EVENT_RESET_WAIT_PRE,      .name = "reset-wait-pre" },
	{ .value = TARGET_EVENT_RESET_WAIT_POST,     .name = "reset-wait-post" },
	{ .value = TARGET_EVENT_RESET_INIT,          .name = "reset-init" },
	{ .value = TARGET_EVENT_RESET_END,           .name = "reset-end" },

	{ .value = TARGET_EVENT_EXAMINE_START, .name = "examine-start" },
	{ .value = TARGET_EVENT_EXAMINE_END, .name = "examine-end" },

	{ .value = TARGET_EVENT_DEBUG_HALTED, .name = "debug-halted" },
	{ .value = TARGET_EVENT_DEBUG_RESUMED, .name = "debug-resumed" },

	{ .value = TARGET_EVENT_GDB_ATTACH, .name = "gdb-attach" },
	{ .value = TARGET_EVENT_GDB_DETACH, .name = "gdb-detach" },

	{ .value = TARGET_EVENT_GDB_FLASH_WRITE_START, .name = "gdb-flash-write-start" },
	{ .value = TARGET_EVENT_GDB_FLASH_WRITE_END  , .name = "gdb-flash-write-end"   },

	{ .value = TARGET_EVENT_GDB_FLASH_ERASE_START, .name = "gdb-flash-erase-start" },
	{ .value = TARGET_EVENT_GDB_FLASH_ERASE_END  , .name = "gdb-flash-erase-end" },

	{ .value = TARGET_EVENT_RESUME_START, .name = "resume-start" },
	{ .value = TARGET_EVENT_RESUMED     , .name = "resume-ok" },
	{ .value = TARGET_EVENT_RESUME_END  , .name = "resume-end" },

	{ .name = NULL, .value = -1 }
};

static const Jim_Nvp nvp_target_state[] = {
	{ .name = "unknown", .value = TARGET_UNKNOWN },
	{ .name = "running", .value = TARGET_RUNNING },
	{ .name = "halted",  .value = TARGET_HALTED },
	{ .name = "reset",   .value = TARGET_RESET },
	{ .name = "debug-running", .value = TARGET_DEBUG_RUNNING },
	{ .name = NULL, .value = -1 },
};

static const Jim_Nvp nvp_target_debug_reason [] = {
	{ .name = "debug-request"            , .value = DBG_REASON_DBGRQ },
	{ .name = "breakpoint"               , .value = DBG_REASON_BREAKPOINT },
	{ .name = "watchpoint"               , .value = DBG_REASON_WATCHPOINT },
	{ .name = "watchpoint-and-breakpoint", .value = DBG_REASON_WPTANDBKPT },
	{ .name = "single-step"              , .value = DBG_REASON_SINGLESTEP },
	{ .name = "target-not-halted"        , .value = DBG_REASON_NOTHALTED  },
	{ .name = "undefined"                , .value = DBG_REASON_UNDEFINED },
	{ .name = NULL, .value = -1 },
};

static const Jim_Nvp nvp_target_endian[] = {
	{ .name = "big",    .value = TARGET_BIG_ENDIAN },
	{ .name = "little", .value = TARGET_LITTLE_ENDIAN },
	{ .name = "be",     .value = TARGET_BIG_ENDIAN },
	{ .name = "le",     .value = TARGET_LITTLE_ENDIAN },
	{ .name = NULL,     .value = -1 },
};

static const Jim_Nvp nvp_reset_modes[] = {
	{ .name = "unknown", .value = RESET_UNKNOWN },
	{ .name = "run"    , .value = RESET_RUN },
	{ .name = "halt"   , .value = RESET_HALT },
	{ .name = "init"   , .value = RESET_INIT },
	{ .name = NULL     , .value = -1 },
};

const char *debug_reason_name(struct target *t)
{
	const char *cp;

	cp = Jim_Nvp_value2name_simple(nvp_target_debug_reason,
			t->debug_reason)->name;
	if (!cp) {
		LOG_ERROR("Invalid debug reason: %d", (int)(t->debug_reason));
		cp = "(*BUG*unknown*BUG*)";
	}
	return cp;
}

const char *
target_state_name( struct target *t )
{
	const char *cp;
	cp = Jim_Nvp_value2name_simple(nvp_target_state, t->state)->name;
	if( !cp ){
		LOG_ERROR("Invalid target state: %d", (int)(t->state));
		cp = "(*BUG*unknown*BUG*)";
	}
	return cp;
}

/* determine the number of the new target */
static int new_target_number(void)
{
	struct target *t;
	int x;

	/* number is 0 based */
	x = -1;
	t = all_targets;
	while (t) {
		if (x < t->target_number) {
			x = t->target_number;
		}
		t = t->next;
	}
	return x + 1;
}

/* read a uint32_t from a buffer in target memory endianness */
uint32_t target_buffer_get_u32(struct target *target, const uint8_t *buffer)
{
	if (target->endianness == TARGET_LITTLE_ENDIAN)
		return le_to_h_u32(buffer);
	else
		return be_to_h_u32(buffer);
}

/* read a uint16_t from a buffer in target memory endianness */
uint16_t target_buffer_get_u16(struct target *target, const uint8_t *buffer)
{
	if (target->endianness == TARGET_LITTLE_ENDIAN)
		return le_to_h_u16(buffer);
	else
		return be_to_h_u16(buffer);
}

/* read a uint8_t from a buffer in target memory endianness */
uint8_t target_buffer_get_u8(struct target *target, const uint8_t *buffer)
{
	return *buffer & 0x0ff;
}

/* write a uint32_t to a buffer in target memory endianness */
void target_buffer_set_u32(struct target *target, uint8_t *buffer, uint32_t value)
{
	if (target->endianness == TARGET_LITTLE_ENDIAN)
		h_u32_to_le(buffer, value);
	else
		h_u32_to_be(buffer, value);
}

/* write a uint16_t to a buffer in target memory endianness */
void target_buffer_set_u16(struct target *target, uint8_t *buffer, uint16_t value)
{
	if (target->endianness == TARGET_LITTLE_ENDIAN)
		h_u16_to_le(buffer, value);
	else
		h_u16_to_be(buffer, value);
}

/* write a uint8_t to a buffer in target memory endianness */
void target_buffer_set_u8(struct target *target, uint8_t *buffer, uint8_t value)
{
	*buffer = value;
}

/* return a pointer to a configured target; id is name or number */
struct target *get_target(const char *id)
{
	struct target *target;

	/* try as tcltarget name */
	for (target = all_targets; target; target = target->next) {
		if (target->cmd_name == NULL)
			continue;
		if (strcmp(id, target->cmd_name) == 0)
			return target;
	}

	/* It's OK to remove this fallback sometime after August 2010 or so */

	/* no match, try as number */
	unsigned num;
	if (parse_uint(id, &num) != ERROR_OK)
		return NULL;

	for (target = all_targets; target; target = target->next) {
		if (target->target_number == (int)num) {
			LOG_WARNING("use '%s' as target identifier, not '%u'",
					target->cmd_name, num);
			return target;
		}
	}

	return NULL;
}

/* returns a pointer to the n-th configured target */
static struct target *get_target_by_num(int num)
{
	struct target *target = all_targets;

	while (target) {
		if (target->target_number == num) {
			return target;
		}
		target = target->next;
	}

	return NULL;
}

struct target* get_current_target(struct command_context *cmd_ctx)
{
	struct target *target = get_target_by_num(cmd_ctx->current_target);

	if (target == NULL)
	{
		LOG_ERROR("BUG: current_target out of bounds");
		exit(-1);
	}

	return target;
}

int target_poll(struct target *target)
{
	int retval;

	/* We can't poll until after examine */
	if (!target_was_examined(target))
	{
		/* Fail silently lest we pollute the log */
		return ERROR_FAIL;
	}

	retval = target->type->poll(target);
	if (retval != ERROR_OK)
		return retval;

	if (target->halt_issued)
	{
		if (target->state == TARGET_HALTED)
		{
			target->halt_issued = false;
		} else
		{
			long long t = timeval_ms() - target->halt_issued_time;
			if (t>1000)
			{
				target->halt_issued = false;
				LOG_INFO("Halt timed out, wake up GDB.");
				target_call_event_callbacks(target, TARGET_EVENT_GDB_HALT);
			}
		}
	}

	return ERROR_OK;
}

int target_halt(struct target *target)
{
	int retval;
	/* We can't poll until after examine */
	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		return ERROR_FAIL;
	}

	retval = target->type->halt(target);
	if (retval != ERROR_OK)
		return retval;

	target->halt_issued = true;
	target->halt_issued_time = timeval_ms();

	return ERROR_OK;
}

/**
 * Make the target (re)start executing using its saved execution
 * context (possibly with some modifications).
 *
 * @param target Which target should start executing.
 * @param current True to use the target's saved program counter instead
 *	of the address parameter
 * @param address Optionally used as the program counter.
 * @param handle_breakpoints True iff breakpoints at the resumption PC
 *	should be skipped.  (For example, maybe execution was stopped by
 *	such a breakpoint, in which case it would be counterprodutive to
 *	let it re-trigger.
 * @param debug_execution False if all working areas allocated by OpenOCD
 *	should be released and/or restored to their original contents.
 *	(This would for example be true to run some downloaded "helper"
 *	algorithm code, which resides in one such working buffer and uses
 *	another for data storage.)
 *
 * @todo Resolve the ambiguity about what the "debug_execution" flag
 * signifies.  For example, Target implementations don't agree on how
 * it relates to invalidation of the register cache, or to whether
 * breakpoints and watchpoints should be enabled.  (It would seem wrong
 * to enable breakpoints when running downloaded "helper" algorithms
 * (debug_execution true), since the breakpoints would be set to match
 * target firmware being debugged, not the helper algorithm.... and
 * enabling them could cause such helpers to malfunction (for example,
 * by overwriting data with a breakpoint instruction.  On the other
 * hand the infrastructure for running such helpers might use this
 * procedure but rely on hardware breakpoint to detect termination.)
 */
int target_resume(struct target *target, int current, uint32_t address, int handle_breakpoints, int debug_execution)
{
	int retval;

	/* We can't poll until after examine */
	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		return ERROR_FAIL;
	}

	/* note that resume *must* be asynchronous. The CPU can halt before
	 * we poll. The CPU can even halt at the current PC as a result of
	 * a software breakpoint being inserted by (a bug?) the application.
	 */
	if ((retval = target->type->resume(target, current, address, handle_breakpoints, debug_execution)) != ERROR_OK)
		return retval;

	/* Invalidate any cached protect/erase/... flash status, since
	 * almost all targets will now be able modify the flash by
	 * themselves.  We want flash drivers and infrastructure to
	 * be able to rely on (non-invalidated) cached state.
	 *
	 * REVISIT do the same for NAND ; maybe other flash flavors too...
	 */
	nor_resume(target);
	return retval;
}

int target_process_reset(struct command_context *cmd_ctx, enum target_reset_mode reset_mode)
{
	char buf[100];
	int retval;
	Jim_Nvp *n;
	n = Jim_Nvp_value2name_simple(nvp_reset_modes, reset_mode);
	if (n->name == NULL) {
		LOG_ERROR("invalid reset mode");
		return ERROR_FAIL;
	}

	/* disable polling during reset to make reset event scripts
	 * more predictable, i.e. dr/irscan & pathmove in events will
	 * not have JTAG operations injected into the middle of a sequence.
	 */
	bool save_poll = jtag_poll_get_enabled();

	jtag_poll_set_enabled(false);

	sprintf(buf, "ocd_process_reset %s", n->name);
	retval = Jim_Eval(cmd_ctx->interp, buf);

	jtag_poll_set_enabled(save_poll);

	if (retval != JIM_OK) {
		Jim_PrintErrorMessage(cmd_ctx->interp);
		return ERROR_FAIL;
	}

	/* We want any events to be processed before the prompt */
	retval = target_call_timer_callbacks_now();

	struct target *target;
	for (target = all_targets; target; target = target->next) {
		target->type->check_reset(target);
	}

	return retval;
}

static int identity_virt2phys(struct target *target,
		uint32_t virtual, uint32_t *physical)
{
	*physical = virtual;
	return ERROR_OK;
}

static int no_mmu(struct target *target, int *enabled)
{
	*enabled = 0;
	return ERROR_OK;
}

static int default_examine(struct target *target)
{
	target_set_examined(target);
	return ERROR_OK;
}

/* no check by default */
static int default_check_reset(struct target *target)
{
	return ERROR_OK;
}

int target_examine_one(struct target *target)
{
	return target->type->examine(target);
}

static int jtag_enable_callback(enum jtag_event event, void *priv)
{
	struct target *target = priv;

	if (event != JTAG_TAP_EVENT_ENABLE || !target->tap->enabled)
		return ERROR_OK;

	jtag_unregister_event_callback(jtag_enable_callback, target);
	return target_examine_one(target);
}


/* Targets that correctly implement init + examine, i.e.
 * no communication with target during init:
 *
 * XScale
 */
int target_examine(void)
{
	int retval = ERROR_OK;
	struct target *target;

	for (target = all_targets; target; target = target->next)
	{
		/* defer examination, but don't skip it */
		if (!target->tap->enabled) {
			jtag_register_event_callback(jtag_enable_callback,
					target);
			continue;
		}
		if ((retval = target_examine_one(target)) != ERROR_OK)
			return retval;
	}
	return retval;
}
const char *target_type_name(struct target *target)
{
	return target->type->name;
}

static int target_write_memory_imp(struct target *target, uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		return ERROR_FAIL;
	}
	return target->type->write_memory_imp(target, address, size, count, buffer);
}

static int target_read_memory_imp(struct target *target, uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		return ERROR_FAIL;
	}
	return target->type->read_memory_imp(target, address, size, count, buffer);
}

static int target_soft_reset_halt_imp(struct target *target)
{
	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		return ERROR_FAIL;
	}
	if (!target->type->soft_reset_halt_imp) {
		LOG_ERROR("Target %s does not support soft_reset_halt",
				target_name(target));
		return ERROR_FAIL;
	}
	return target->type->soft_reset_halt_imp(target);
}

/**
 * Downloads a target-specific native code algorithm to the target,
 * and executes it.  * Note that some targets may need to set up, enable,
 * and tear down a breakpoint (hard or * soft) to detect algorithm
 * termination, while others may support  lower overhead schemes where
 * soft breakpoints embedded in the algorithm automatically terminate the
 * algorithm.
 *
 * @param target used to run the algorithm
 * @param arch_info target-specific description of the algorithm.
 */
int target_run_algorithm(struct target *target,
		int num_mem_params, struct mem_param *mem_params,
		int num_reg_params, struct reg_param *reg_param,
		uint32_t entry_point, uint32_t exit_point,
		int timeout_ms, void *arch_info)
{
	int retval = ERROR_FAIL;

	if (!target_was_examined(target))
	{
		LOG_ERROR("Target not examined yet");
		goto done;
	}
	if (target->type->run_algorithm) {
		LOG_ERROR("Target type '%s' does not support %s",
				target_type_name(target), __func__);
		goto done;
	}

	retval = target->type->run_algorithm(target,
			num_mem_params, mem_params,
			num_reg_params, reg_param,
			entry_point, exit_point, timeout_ms, arch_info);

done:
	return retval;
}


int target_read_memory(struct target *target,
		uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	return target->type->read_memory(target, address, size, count, buffer);
}

int target_read_phys_memory(struct target *target,
		uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	return target->type->read_phys_memory(target, address, size, count, buffer);
}

int target_write_memory(struct target *target,
		uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	return target->type->write_memory(target, address, size, count, buffer);
}

int target_write_phys_memory(struct target *target,
		uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer)
{
	return target->type->write_phys_memory(target, address, size, count, buffer);
}

int target_bulk_write_memory(struct target *target,
		uint32_t address, uint32_t count, uint8_t *buffer)
{
	return target->type->bulk_write_memory(target, address, count, buffer);
}

int target_add_breakpoint(struct target *target,
		struct breakpoint *breakpoint)
{
	if (target->state != TARGET_HALTED) {
		LOG_WARNING("target %s is not halted", target->cmd_name);
		return ERROR_TARGET_NOT_HALTED;
	}
	return target->type->add_breakpoint(target, breakpoint);
}
int target_remove_breakpoint(struct target *target,
		struct breakpoint *breakpoint)
{
	return target->type->remove_breakpoint(target, breakpoint);
}

int target_add_watchpoint(struct target *target,
		struct watchpoint *watchpoint)
{
	if (target->state != TARGET_HALTED) {
		LOG_WARNING("target %s is not halted", target->cmd_name);
		return ERROR_TARGET_NOT_HALTED;
	}
	return target->type->add_watchpoint(target, watchpoint);
}
int target_remove_watchpoint(struct target *target,
		struct watchpoint *watchpoint)
{
	return target->type->remove_watchpoint(target, watchpoint);
}

int target_get_gdb_reg_list(struct target *target,
		struct reg **reg_list[], int *reg_list_size)
{
	return target->type->get_gdb_reg_list(target, reg_list, reg_list_size);
}
int target_step(struct target *target,
		int current, uint32_t address, int handle_breakpoints)
{
	return target->type->step(target, current, address, handle_breakpoints);
}


/**
 * Reset the @c examined flag for the given target.
 * Pure paranoia -- targets are zeroed on allocation.
 */
static void target_reset_examined(struct target *target)
{
	target->examined = false;
}

static int
err_read_phys_memory(struct target *target, uint32_t address,
		uint32_t size, uint32_t count, uint8_t *buffer)
{
	LOG_ERROR("Not implemented: %s", __func__);
	return ERROR_FAIL;
}

static int
err_write_phys_memory(struct target *target, uint32_t address,
		uint32_t size, uint32_t count, uint8_t *buffer)
{
	LOG_ERROR("Not implemented: %s", __func__);
	return ERROR_FAIL;
}

static int handle_target(void *priv);

static int target_init_one(struct command_context *cmd_ctx,
		struct target *target)
{
	target_reset_examined(target);

	struct target_type *type = target->type;
	if (type->examine == NULL)
		type->examine = default_examine;

	if (type->check_reset== NULL)
		type->check_reset = default_check_reset;

	int retval = type->init_target(cmd_ctx, target);
	if (ERROR_OK != retval)
	{
		LOG_ERROR("target '%s' init failed", target_name(target));
		return retval;
	}

	/**
	 * @todo get rid of those *memory_imp() methods, now that all
	 * callers are using target_*_memory() accessors ... and make
	 * sure the "physical" paths handle the same issues.
	 */
	/* a non-invasive way(in terms of patches) to add some code that
	 * runs before the type->write/read_memory implementation
	 */
	type->write_memory_imp = target->type->write_memory;
	type->write_memory = target_write_memory_imp;

	type->read_memory_imp = target->type->read_memory;
	type->read_memory = target_read_memory_imp;

	type->soft_reset_halt_imp = target->type->soft_reset_halt;
	type->soft_reset_halt = target_soft_reset_halt_imp;

	/* Sanity-check MMU support ... stub in what we must, to help
	 * implement it in stages, but warn if we need to do so.
	 */
	if (type->mmu)
	{
		if (type->write_phys_memory == NULL)
		{
			LOG_ERROR("type '%s' is missing write_phys_memory",
					type->name);
			type->write_phys_memory = err_write_phys_memory;
		}
		if (type->read_phys_memory == NULL)
		{
			LOG_ERROR("type '%s' is missing read_phys_memory",
					type->name);
			type->read_phys_memory = err_read_phys_memory;
		}
		if (type->virt2phys == NULL)
		{
			LOG_ERROR("type '%s' is missing virt2phys", type->name);
			type->virt2phys = identity_virt2phys;
		}
	}
	else
	{
		/* Make sure no-MMU targets all behave the same:  make no
		 * distinction between physical and virtual addresses, and
		 * ensure that virt2phys() is always an identity mapping.
		 */
		if (type->write_phys_memory || type->read_phys_memory
				|| type->virt2phys)
		{
			LOG_WARNING("type '%s' has bad MMU hooks", type->name);
		}

		type->mmu = no_mmu;
		type->write_phys_memory = type->write_memory;
		type->read_phys_memory = type->read_memory;
		type->virt2phys = identity_virt2phys;
	}
	return ERROR_OK;
}

int target_init(struct command_context *cmd_ctx)
{
	struct target *target;
	int retval;

	for (target = all_targets; target; target = target->next)
	{
		retval = target_init_one(cmd_ctx, target);
		if (ERROR_OK != retval)
			return retval;
	}

	if (!all_targets)
		return ERROR_OK;

	retval = target_register_user_commands(cmd_ctx);
	if (ERROR_OK != retval)
		return retval;

	retval = target_register_timer_callback(&handle_target,
			100, 1, cmd_ctx->interp);
	if (ERROR_OK != retval)
		return retval;

	return ERROR_OK;
}

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

	static bool target_initialized = false;
	if (target_initialized)
	{
		LOG_INFO("'target init' has already been called");
		return ERROR_OK;
	}
	target_initialized = true;

	LOG_DEBUG("Initializing targets...");
	return target_init(CMD_CTX);
}

int target_register_event_callback(int (*callback)(struct target *target, enum target_event event, void *priv), void *priv)
{
	struct target_event_callback **callbacks_p = &target_event_callbacks;

	if (callback == NULL)
	{
		return ERROR_INVALID_ARGUMENTS;
	}

	if (*callbacks_p)
	{
		while ((*callbacks_p)->next)
			callbacks_p = &((*callbacks_p)->next);
		callbacks_p = &((*callbacks_p)->next);
	}

	(*callbacks_p) = malloc(sizeof(struct target_event_callback));
	(*callbacks_p)->callback = callback;
	(*callbacks_p)->priv = priv;
	(*callbacks_p)->next = NULL;

	return ERROR_OK;
}

int target_register_timer_callback(int (*callback)(void *priv), int time_ms, int periodic, void *priv)
{
	struct target_timer_callback **callbacks_p = &target_timer_callbacks;
	struct timeval now;

	if (callback == NULL)
	{
		return ERROR_INVALID_ARGUMENTS;
	}

	if (*callbacks_p)
	{
		while ((*callbacks_p)->next)
			callbacks_p = &((*callbacks_p)->next);
		callbacks_p = &((*callbacks_p)->next);
	}

	(*callbacks_p) = malloc(sizeof(struct target_timer_callback));
	(*callbacks_p)->callback = callback;
	(*callbacks_p)->periodic = periodic;
	(*callbacks_p)->time_ms = time_ms;

	gettimeofday(&now, NULL);
	(*callbacks_p)->when.tv_usec = now.tv_usec + (time_ms % 1000) * 1000;
	time_ms -= (time_ms % 1000);
	(*callbacks_p)->when.tv_sec = now.tv_sec + (time_ms / 1000);
	if ((*callbacks_p)->when.tv_usec > 1000000)
	{
		(*callbacks_p)->when.tv_usec = (*callbacks_p)->when.tv_usec - 1000000;
		(*callbacks_p)->when.tv_sec += 1;
	}

	(*callbacks_p)->priv = priv;
	(*callbacks_p)->next = NULL;

	return ERROR_OK;
}

int target_unregister_event_callback(int (*callback)(struct target *target, enum target_event event, void *priv), void *priv)
{
	struct target_event_callback **p = &target_event_callbacks;
	struct target_event_callback *c = target_event_callbacks;

	if (callback == NULL)
	{
		return ERROR_INVALID_ARGUMENTS;
	}

	while (c)
	{
		struct target_event_callback *next = c->next;
		if ((c->callback == callback) && (c->priv == priv))
		{
			*p = next;
			free(c);
			return ERROR_OK;
		}
		else
			p = &(c->next);
		c = next;
	}

	return ERROR_OK;
}

int target_unregister_timer_callback(int (*callback)(void *priv), void *priv)
{
	struct target_timer_callback **p = &target_timer_callbacks;
	struct target_timer_callback *c = target_timer_callbacks;

	if (callback == NULL)
	{
		return ERROR_INVALID_ARGUMENTS;
	}

	while (c)
	{
		struct target_timer_callback *next = c->next;
		if ((c->callback == callback) && (c->priv == priv))
		{
			*p = next;
			free(c);
			return ERROR_OK;
		}
		else
			p = &(c->next);
		c = next;
	}

	return ERROR_OK;
}

int target_call_event_callbacks(struct target *target, enum target_event event)
{
	struct target_event_callback *callback = target_event_callbacks;
	struct target_event_callback *next_callback;

	if (event == TARGET_EVENT_HALTED)
	{
		/* execute early halted first */
		target_call_event_callbacks(target, TARGET_EVENT_GDB_HALT);
	}

	LOG_DEBUG("target event %i (%s)",
			  event,
			  Jim_Nvp_value2name_simple(nvp_target_event, event)->name);

	target_handle_event(target, event);

	while (callback)
	{
		next_callback = callback->next;
		callback->callback(target, event, callback->priv);
		callback = next_callback;
	}

	return ERROR_OK;
}

static int target_timer_callback_periodic_restart(
		struct target_timer_callback *cb, struct timeval *now)
{
	int time_ms = cb->time_ms;
	cb->when.tv_usec = now->tv_usec + (time_ms % 1000) * 1000;
	time_ms -= (time_ms % 1000);
	cb->when.tv_sec = now->tv_sec + time_ms / 1000;
	if (cb->when.tv_usec > 1000000)
	{
		cb->when.tv_usec = cb->when.