gdb_server, rtos: Fine-grained RTOS register access

1. Add get_thread_reg() to rtos. It's used in rtos_get_gdb_reg() to read
the value of a single register, instead of reading all register values
by calling get_thread_reg_list().
2. Add set_reg() to rtos. gdb_server uses this to change a single
register value for a specific thread.
3. Add target_get_gdb_reg_list_noread() so it's possible for gdb to get
a list of registers without attempting to read their contents.

The clang static checker doesn't find any new problems with this change.

Change-Id: I77f792d1238cb015b91527ca8cb99593ccc8870e
Signed-off-by: Tim Newsome <tim@sifive.com>
Reviewed-on: http://openocd.zylin.com/5114
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/rtos/rtos.c

@@ -462,6 +462,7 @@ static int rtos_put_gdb_reg_list(struct connection *connection,
 	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);
@@ -473,19 +474,31 @@ int rtos_get_gdb_reg(struct connection *connection, int reg_num)
 		struct rtos_reg *reg_list;
 		int num_regs;
 
-		LOG_DEBUG("RTOS: getting register %d for thread 0x%" PRIx64
+		LOG_DEBUG("getting register %d for thread 0x%" PRIx64
-				  ", target->rtos->current_thread=0x%" PRIx64 "\r\n",
+				  ", target->rtos->current_thread=0x%" PRIx64,
 										reg_num,
 										current_threadid,
 										target->rtos->current_thread);
 
-		int retval = target->rtos->type->get_thread_reg_list(target->rtos,
+		int retval;
-				current_threadid,
+		if (target->rtos->type->get_thread_reg) {
-				&reg_list,
+			reg_list = calloc(1, sizeof(*reg_list));
-				&num_regs);
+			num_regs = 1;
-		if (retval != ERROR_OK) {
+			retval = target->rtos->type->get_thread_reg(target->rtos,
-			LOG_ERROR("RTOS: failed to get register list");
+					current_threadid, reg_num, &reg_list[0]);
-			return retval;
+			if (retval != ERROR_OK) {
+				LOG_ERROR("RTOS: failed to get register %d", reg_num);
+				return retval;
+			}
+		} 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) {
@@ -501,6 +514,7 @@ int rtos_get_gdb_reg(struct connection *connection, int reg_num)
 	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);
@@ -534,6 +548,20 @@ int rtos_get_gdb_reg_list(struct connection *connection)
 	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 != NULL) &&
+			(target->rtos->type->set_reg != NULL) &&
+			(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,
 	int64_t stack_ptr,

src/rtos/rtos.h

@@ -20,6 +20,7 @@
 #define OPENOCD_RTOS_RTOS_H
 
 #include "server/server.h"
+#include "target/target.h"
 #include <jim-nvp.h>
 
 typedef int64_t threadid_t;
@@ -49,7 +50,9 @@ struct rtos {
 	symbol_table_elem_t *symbols;
 	struct target *target;
 	/*  add a context variable instead of global variable */
+	/* The thread currently selected by gdb. */
 	int64_t current_threadid;
+	/* The currently selected thread according to the target. */
 	threadid_t current_thread;
 	struct thread_detail *thread_details;
 	int thread_count;
@@ -70,11 +73,15 @@ struct rtos_type {
 	int (*create)(struct target *target);
 	int (*smp_init)(struct target *target);
 	int (*update_threads)(struct rtos *rtos);
+	/** Return a list of general registers, with their values filled out. */
 	int (*get_thread_reg_list)(struct rtos *rtos, int64_t thread_id,
 			struct rtos_reg **reg_list, int *num_regs);
+	int (*get_thread_reg)(struct rtos *rtos, int64_t thread_id,
+			uint32_t reg_num, struct rtos_reg *reg);
 	int (*get_symbol_list_to_lookup)(symbol_table_elem_t *symbol_list[]);
 	int (*clean)(struct target *target);
 	char * (*ps_command)(struct target *target);
+	int (*set_reg)(struct rtos *rtos, uint32_t reg_num, uint8_t *reg_value);
 };
 
 struct stack_register_offset {
@@ -104,6 +111,8 @@ struct rtos_register_stacking {
 #define GDB_THREAD_PACKET_NOT_CONSUMED (-40)
 
 int rtos_create(Jim_GetOptInfo *goi, struct target *target);
+int rtos_set_reg(struct connection *connection, int reg_num,
+		uint8_t *reg_value);
 int rtos_generic_stack_read(struct target *target,
 		const struct rtos_register_stacking *stacking,
 		int64_t stack_ptr,

src/server/gdb_server.c

@@ -724,7 +724,7 @@ static int gdb_output(struct command_context *context, const char *line)
 static void gdb_signal_reply(struct target *target, struct connection *connection)
 {
 	struct gdb_connection *gdb_connection = connection->priv;
-	char sig_reply[45];
+	char sig_reply[65];
 	char stop_reason[20];
 	char current_thread[25];
 	int sig_reply_len;
@@ -735,17 +735,25 @@ static void gdb_signal_reply(struct target *target, struct connection *connectio
 	if (target->debug_reason == DBG_REASON_EXIT) {
 		sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "W00");
 	} else {
+		struct target *ct;
+		if (target->rtos != NULL) {
+			target->rtos->current_threadid = target->rtos->current_thread;
+			target->rtos->gdb_target_for_threadid(connection, target->rtos->current_threadid, &ct);
+		} else {
+			ct = target;
+		}
+
 		if (gdb_connection->ctrl_c) {
 			signal_var = 0x2;
 		} else
-			signal_var = gdb_last_signal(target);
+			signal_var = gdb_last_signal(ct);
 
 		stop_reason[0] = '\0';
-		if (target->debug_reason == DBG_REASON_WATCHPOINT) {
+		if (ct->debug_reason == DBG_REASON_WATCHPOINT) {
 			enum watchpoint_rw hit_wp_type;
 			target_addr_t hit_wp_address;
 
-			if (watchpoint_hit(target, &hit_wp_type, &hit_wp_address) == ERROR_OK) {
+			if (watchpoint_hit(ct, &hit_wp_type, &hit_wp_address) == ERROR_OK) {
 
 				switch (hit_wp_type) {
 					case WPT_WRITE:
@@ -767,15 +775,9 @@ static void gdb_signal_reply(struct target *target, struct connection *connectio
 		}
 
 		current_thread[0] = '\0';
-		if (target->rtos != NULL) {
+		if (target->rtos != NULL)
-			struct target *ct;
+			snprintf(current_thread, sizeof(current_thread), "thread:%" PRIx64 ";",
-			snprintf(current_thread, sizeof(current_thread), "thread:%016" PRIx64 ";",
 					target->rtos->current_thread);
-			target->rtos->current_threadid = target->rtos->current_thread;
-			target->rtos->gdb_target_for_threadid(connection, target->rtos->current_threadid, &ct);
-			if (!gdb_connection->ctrl_c)
-				signal_var = gdb_last_signal(ct);
-		}
 
 		sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "T%2.2x%s%s",
 				signal_var, stop_reason, current_thread);
@@ -1300,7 +1302,7 @@ static int gdb_get_register_packet(struct connection *connection,
 	if ((target->rtos != NULL) && (ERROR_OK == rtos_get_gdb_reg(connection, reg_num)))
 		return ERROR_OK;
 
-	retval = target_get_gdb_reg_list(target, &reg_list, &reg_list_size,
+	retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
 			REG_CLASS_ALL);
 	if (retval != ERROR_OK)
 		return gdb_error(connection, retval);
@@ -1336,37 +1338,49 @@ static int gdb_set_register_packet(struct connection *connection,
 {
 	struct target *target = get_target_from_connection(connection);
 	char *separator;
-	uint8_t *bin_buf;
 	int reg_num = strtoul(packet + 1, &separator, 16);
 	struct reg **reg_list;
 	int reg_list_size;
 	int retval;
 
+#ifdef _DEBUG_GDB_IO_
 	LOG_DEBUG("-");
-
+#endif
-	retval = target_get_gdb_reg_list(target, &reg_list, &reg_list_size,
-			REG_CLASS_ALL);
-	if (retval != ERROR_OK)
-		return gdb_error(connection, retval);
-
-	if (reg_list_size <= reg_num) {
-		LOG_ERROR("gdb requested a non-existing register");
-		return ERROR_SERVER_REMOTE_CLOSED;
-	}
 
 	if (*separator != '=') {
 		LOG_ERROR("GDB 'set register packet', but no '=' following the register number");
 		return ERROR_SERVER_REMOTE_CLOSED;
 	}
+	size_t chars = strlen(separator + 1);
+	uint8_t *bin_buf = malloc(chars / 2);
+	gdb_target_to_reg(target, separator + 1, chars, bin_buf);
 
-	/* convert from GDB-string (target-endian) to hex-string (big-endian) */
+	if ((target->rtos != NULL) &&
-	bin_buf = malloc(DIV_ROUND_UP(reg_list[reg_num]->size, 8));
+			(ERROR_OK == rtos_set_reg(connection, reg_num, bin_buf))) {
-	int chars = (DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2);
-
-	if ((unsigned int)chars != strlen(separator + 1)) {
-		LOG_ERROR("gdb sent %zu bits for a %d-bit register (%s)",
-				strlen(separator + 1) * 4, chars * 4, reg_list[reg_num]->name);
 		free(bin_buf);
+		gdb_put_packet(connection, "OK", 2);
+		return ERROR_OK;
+	}
+
+	retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
+			REG_CLASS_ALL);
+	if (retval != ERROR_OK) {
+		free(bin_buf);
+		return gdb_error(connection, retval);
+	}
+
+	if (reg_list_size <= reg_num) {
+		LOG_ERROR("gdb requested a non-existing register");
+		free(bin_buf);
+		free(reg_list);
+		return ERROR_SERVER_REMOTE_CLOSED;
+	}
+
+	if (chars != (DIV_ROUND_UP(reg_list[reg_num]->size, 8) * 2)) {
+		LOG_ERROR("gdb sent %d bits for a %d-bit register (%s)",
+				(int) chars * 4, reg_list[reg_num]->size, reg_list[reg_num]->name);
+		free(bin_buf);
+		free(reg_list);
 		return ERROR_SERVER_REMOTE_CLOSED;
 	}
 
@@ -1634,7 +1648,7 @@ static int gdb_breakpoint_watchpoint_packet(struct connection *connection,
 	char *separator;
 	int retval;
 
-	LOG_DEBUG("-");
+	LOG_DEBUG("[%s]", target_name(target));
 
 	type = strtoul(packet + 1, &separator, 16);
 
@@ -2200,7 +2214,7 @@ static int gdb_generate_target_description(struct target *target, char **tdesc_o
 
 	arch_defined_types = calloc(1, sizeof(char *));
 
-	retval = target_get_gdb_reg_list(target, &reg_list,
+	retval = target_get_gdb_reg_list_noread(target, &reg_list,
 			&reg_list_size, REG_CLASS_ALL);
 
 	if (retval != ERROR_OK) {
@@ -2388,7 +2402,7 @@ static int gdb_target_description_supported(struct target *target, int *supporte
 
 	char const *architecture = target_get_gdb_arch(target);
 
-	retval = target_get_gdb_reg_list(target, &reg_list,
+	retval = target_get_gdb_reg_list_noread(target, &reg_list,
 			&reg_list_size, REG_CLASS_ALL);
 	if (retval != ERROR_OK) {
 		LOG_ERROR("get register list failed");
@@ -2783,13 +2797,11 @@ static bool gdb_handle_vcont_packet(struct connection *connection, const char *p
 
 				if (parse[0] == 'c') {
 					parse += 1;
-					packet_size -= 1;
 
 					/* check if thread-id follows */
 					if (parse[0] == ':') {
 						int64_t tid;
 						parse += 1;
-						packet_size -= 1;
 
 						tid = strtoll(parse, &endp, 16);
 						if (tid == thread_id) {
@@ -2879,10 +2891,9 @@ static int gdb_v_packet(struct connection *connection,
 		char const *packet, int packet_size)
 {
 	struct gdb_connection *gdb_connection = connection->priv;
-	struct target *target;
 	int result;
 
-	target = get_target_from_connection(connection);
+	struct target *target = get_target_from_connection(connection);
 
 	if (strncmp(packet, "vCont", 5) == 0) {
 		bool handled;

src/target/register.c

@@ -36,6 +36,29 @@
  * may be separate registers associated with debug or trace modules.
  */
 
+struct reg *register_get_by_number(struct reg_cache *first,
+		uint32_t reg_num, bool search_all)
+{
+	unsigned i;
+	struct reg_cache *cache = first;
+
+	while (cache) {
+		for (i = 0; i < cache->num_regs; i++) {
+			if (cache->reg_list[i].exist == false)
+				continue;
+			if (cache->reg_list[i].number == reg_num)
+				return &(cache->reg_list[i]);
+		}
+
+		if (search_all)
+			cache = cache->next;
+		else
+			break;
+	}
+
+	return NULL;
+}
+
 struct reg *register_get_by_name(struct reg_cache *first,
 		const char *name, bool search_all)
 {

src/target/register.h

@@ -159,6 +159,8 @@ struct reg_arch_type {
 	int (*set)(struct reg *reg, uint8_t *buf);
 };
 
+struct reg *register_get_by_number(struct reg_cache *first,
+		uint32_t reg_num, bool search_all);
 struct reg *register_get_by_name(struct reg_cache *first,
 		const char *name, bool search_all);
 struct reg_cache **register_get_last_cache_p(struct reg_cache **first);

src/target/target.c

@@ -1215,7 +1215,24 @@ int target_get_gdb_reg_list(struct target *target,
 		struct reg **reg_list[], int *reg_list_size,
 		enum target_register_class reg_class)
 {
-	return target->type->get_gdb_reg_list(target, reg_list, reg_list_size, reg_class);
+	int result = target->type->get_gdb_reg_list(target, reg_list,
+			reg_list_size, reg_class);
+	if (result != ERROR_OK) {
+		*reg_list = NULL;
+		*reg_list_size = 0;
+	}
+	return result;
+}
+
+int target_get_gdb_reg_list_noread(struct target *target,
+		struct reg **reg_list[], int *reg_list_size,
+		enum target_register_class reg_class)
+{
+	if (target->type->get_gdb_reg_list_noread &&
+			target->type->get_gdb_reg_list_noread(target, reg_list,
+				reg_list_size, reg_class) == ERROR_OK)
+		return ERROR_OK;
+	return target_get_gdb_reg_list(target, reg_list, reg_list_size, reg_class);
 }
 
 bool target_supports_gdb_connection(struct target *target)
@@ -1587,8 +1604,9 @@ int target_call_event_callbacks(struct target *target, enum target_event event)
 		target_call_event_callbacks(target, TARGET_EVENT_GDB_HALT);
 	}
 
-	LOG_DEBUG("target event %i (%s)", event,
+	LOG_DEBUG("target event %i (%s) for core %s", event,
-			Jim_Nvp_value2name_simple(nvp_target_event, event)->name);
+			Jim_Nvp_value2name_simple(nvp_target_event, event)->name,
+			target_name(target));
 
 	target_handle_event(target, event);
 

src/target/target.h

@@ -502,6 +502,16 @@ int target_get_gdb_reg_list(struct target *target,
 		struct reg **reg_list[], int *reg_list_size,
 		enum target_register_class reg_class);
 
+/**
+ * Obtain the registers for GDB, but don't read register values from the
+ * target.
+ *
+ * This routine is a wrapper for target->type->get_gdb_reg_list_noread.
+ */
+int target_get_gdb_reg_list_noread(struct target *target,
+		struct reg **reg_list[], int *reg_list_size,
+		enum target_register_class reg_class);
+
 /**
  * Check if @a target allows GDB connections.
  *

src/target/target_type.h

@@ -111,6 +111,13 @@ struct target_type {
 	int (*get_gdb_reg_list)(struct target *target, struct reg **reg_list[],
 			int *reg_list_size, enum target_register_class reg_class);
 
+	/**
+	 * Same as get_gdb_reg_list, but doesn't read the register values.
+	 * */
+	int (*get_gdb_reg_list_noread)(struct target *target,
+			struct reg **reg_list[], int *reg_list_size,
+			enum target_register_class reg_class);
+
 	/* target memory access
 	* size: 1 = byte (8bit), 2 = half-word (16bit), 4 = word (32bit)
 	* count: number of items of <size>