gdb server: new feature, add stop reason in stop reply packet for gdb

In GDB remote serial protocol, the stop reply packet could contain more
detail stop reason. The currently defined stop reasons are listed below.

* watch
* rwatch
* awatch
* library
* replaylog

This commit adds stop reason, watch/rwatch/awatch, in stop reply packet for
just hit watchpoint. As manual indicates, at most one stop reason should be present.

The function needs target to implement new hook, hit_watchpoint. The hook will fill
the hit watchpoint in second parameter. The information will assist gdb to locate
the watchpoint. If no such information, gdb needs to scan all watchpoints by itself.

Refer to GDB Manual, D.3 Stop Reply Packets

Change-Id: I1f70a1a9cc772e88e641b6171f1a009629a43bd1
Signed-off-by: Hsiangkai Wang <hsiangkai@gmail.com>
Reviewed-on: http://openocd.zylin.com/1092
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/server/gdb_server.c

@@ -705,7 +705,9 @@ static void gdb_frontend_halted(struct target *target, struct connection *connec
 	 * that are to be ignored.
 	 */
 	if (gdb_connection->frontend_state == TARGET_RUNNING) {
-		char sig_reply[4];
+		char sig_reply[20];
+		char stop_reason[20];
+		int sig_reply_len;
 		int signal_var;
 
 		/* stop forwarding log packets! */
@@ -717,8 +719,36 @@ static void gdb_frontend_halted(struct target *target, struct connection *connec
 		} else
 			signal_var = gdb_last_signal(target);
 
-		snprintf(sig_reply, 4, "T%2.2x", signal_var);
-		gdb_put_packet(connection, sig_reply, 3);
+		stop_reason[0] = '\0';
+		if (target->debug_reason == DBG_REASON_WATCHPOINT) {
+			enum watchpoint_rw hit_wp_type;
+			uint32_t hit_wp_address;
+
+			if (watchpoint_hit(target, &hit_wp_type, &hit_wp_address) == ERROR_OK) {
+
+				switch (hit_wp_type) {
+					case WPT_WRITE:
+						snprintf(stop_reason, sizeof(stop_reason),
+								"watch:%08x;", hit_wp_address);
+						break;
+					case WPT_READ:
+						snprintf(stop_reason, sizeof(stop_reason),
+								"rwatch:%08x;", hit_wp_address);
+						break;
+					case WPT_ACCESS:
+						snprintf(stop_reason, sizeof(stop_reason),
+								"awatch:%08x;", hit_wp_address);
+						break;
+					default:
+						break;
+				}
+			}
+		}
+
+		sig_reply_len = snprintf(sig_reply, sizeof(sig_reply), "T%2.2x%s",
+				signal_var, stop_reason);
+
+		gdb_put_packet(connection, sig_reply, sig_reply_len);
 		gdb_connection->frontend_state = TARGET_HALTED;
 		rtos_update_threads(target);
 	}

src/target/breakpoints.c

@@ -500,3 +500,22 @@ void watchpoint_clear_target(struct target *target)
 	while (target->watchpoints != NULL)
 		watchpoint_free(target, target->watchpoints);
 }
+
+int watchpoint_hit(struct target *target, enum watchpoint_rw *rw, uint32_t *address)
+{
+	int retval;
+	struct watchpoint *hit_watchpoint;
+
+	retval = target_hit_watchpoint(target, &hit_watchpoint);
+	if (retval != ERROR_OK)
+		return ERROR_FAIL;
+
+	*rw = hit_watchpoint->rw;
+	*address = hit_watchpoint->address;
+
+	LOG_DEBUG("Found hit watchpoint at 0x%8.8" PRIx32 " (WPID: %d)",
+		hit_watchpoint->address,
+		hit_watchpoint->unique_id);
+
+	return ERROR_OK;
+}

src/target/breakpoints.h

@@ -72,4 +72,7 @@ int watchpoint_add(struct target *target,
 		enum watchpoint_rw rw, uint32_t value, uint32_t mask);
 void watchpoint_remove(struct target *target, uint32_t address);
 
+/* report type and address of just hit watchpoint */
+int watchpoint_hit(struct target *target, enum watchpoint_rw *rw, uint32_t *address);
+
 #endif /* BREAKPOINTS_H */

src/target/nds32_v2.c

@@ -534,6 +534,42 @@ static int nds32_v2_get_exception_address(struct nds32 *nds32,
 	return ERROR_OK;
 }
 
+/**
+ * find out which watchpoint hits
+ * get exception address and compare the address to watchpoints
+ */
+static int nds32_v2_hit_watchpoint(struct target *target,
+		struct watchpoint **hit_watchpoint)
+{
+	uint32_t exception_address;
+	struct watchpoint *wp;
+	static struct watchpoint scan_all_watchpoint;
+	struct nds32 *nds32 = target_to_nds32(target);
+
+	scan_all_watchpoint.address = 0;
+	scan_all_watchpoint.rw = WPT_WRITE;
+	scan_all_watchpoint.next = 0;
+	scan_all_watchpoint.unique_id = 0x5CA8;
+
+	exception_address = nds32->watched_address;
+
+	if (exception_address == 0) {
+		/* send watch:0 to tell GDB to do software scan for hitting multiple watchpoints */
+		*hit_watchpoint = &scan_all_watchpoint;
+		return ERROR_OK;
+	}
+
+	for (wp = target->watchpoints; wp; wp = wp->next) {
+		if (((exception_address ^ wp->address) & (~wp->mask)) == 0) {
+			/* TODO: dispel false match */
+			*hit_watchpoint = wp;
+			return ERROR_OK;
+		}
+	}
+
+	return ERROR_FAIL;
+}
+
 static int nds32_v2_run_algorithm(struct target *target,
 		int num_mem_params,
 		struct mem_param *mem_params,
@@ -747,6 +783,7 @@ struct target_type nds32_v2_target = {
 	.remove_breakpoint = nds32_v2_remove_breakpoint,
 	.add_watchpoint = nds32_v2_add_watchpoint,
 	.remove_watchpoint = nds32_v2_remove_watchpoint,
+	.hit_watchpoint = nds32_v2_hit_watchpoint,
 
 	/* MMU */
 	.mmu = nds32_mmu,

src/target/nds32_v3.c

@@ -506,6 +506,7 @@ struct target_type nds32_v3_target = {
 	.remove_breakpoint = nds32_v3_remove_breakpoint,
 	.add_watchpoint = nds32_v3_add_watchpoint,
 	.remove_watchpoint = nds32_v3_remove_watchpoint,
+	.hit_watchpoint = nds32_v3_hit_watchpoint,
 
 	/* MMU */
 	.mmu = nds32_mmu,

src/target/nds32_v3_common.c

@@ -294,6 +294,45 @@ int nds32_v3_checksum_memory(struct target *target,
 	return ERROR_FAIL;
 }
 
+/**
+ * find out which watchpoint hits
+ * get exception address and compare the address to watchpoints
+ */
+int nds32_v3_hit_watchpoint(struct target *target,
+		struct watchpoint **hit_watchpoint)
+{
+	static struct watchpoint scan_all_watchpoint;
+
+	uint32_t exception_address;
+	struct watchpoint *wp;
+	struct nds32 *nds32 = target_to_nds32(target);
+
+	exception_address = nds32->watched_address;
+
+	if (exception_address == 0xFFFFFFFF)
+		return ERROR_FAIL;
+
+	if (exception_address == 0) {
+		scan_all_watchpoint.address = 0;
+		scan_all_watchpoint.rw = WPT_WRITE;
+		scan_all_watchpoint.next = 0;
+		scan_all_watchpoint.unique_id = 0x5CA8;
+
+		*hit_watchpoint = &scan_all_watchpoint;
+		return ERROR_OK;
+	}
+
+	for (wp = target->watchpoints; wp; wp = wp->next) {
+		if (((exception_address ^ wp->address) & (~wp->mask)) == 0) {
+			*hit_watchpoint = wp;
+
+			return ERROR_OK;
+		}
+	}
+
+	return ERROR_FAIL;
+}
+
 int nds32_v3_target_create_common(struct target *target, struct nds32 *nds32)
 {
 	nds32->register_map = nds32_v3_register_mapping;

src/target/nds32_v3m.c

@@ -494,6 +494,7 @@ struct target_type nds32_v3m_target = {
 	.remove_breakpoint = nds32_v3m_remove_breakpoint,
 	.add_watchpoint = nds32_v3m_add_watchpoint,
 	.remove_watchpoint = nds32_v3m_remove_watchpoint,
+	.hit_watchpoint = nds32_v3_hit_watchpoint,
 
 	/* MMU */
 	.mmu = nds32_mmu,

src/target/target.c

@@ -1035,6 +1035,23 @@ int target_remove_watchpoint(struct target *target,
 {
 	return target->type->remove_watchpoint(target, watchpoint);
 }
+int target_hit_watchpoint(struct target *target,
+		struct watchpoint **hit_watchpoint)
+{
+	if (target->state != TARGET_HALTED) {
+		LOG_WARNING("target %s is not halted", target->cmd_name);
+		return ERROR_TARGET_NOT_HALTED;
+	}
+
+	if (target->type->hit_watchpoint == NULL) {
+		/* For backward compatible, if hit_watchpoint is not implemented,
+		 * return ERROR_FAIL such that gdb_server will not take the nonsense
+		 * information. */
+		return ERROR_FAIL;
+	}
+
+	return target->type->hit_watchpoint(target, hit_watchpoint);
+}
 
 int target_get_gdb_reg_list(struct target *target,
 		struct reg **reg_list[], int *reg_list_size,

src/target/target.h

@@ -399,6 +399,14 @@ int target_add_watchpoint(struct target *target,
 int target_remove_watchpoint(struct target *target,
 		struct watchpoint *watchpoint);
 
+/**
+ * Find out the just hit @a watchpoint for @a target.
+ *
+ * This routine is a wrapper for target->type->hit_watchpoint.
+ */
+int target_hit_watchpoint(struct target *target,
+		struct watchpoint **watchpoint);
+
 /**
  * Obtain the registers for GDB.
  *

src/target/target_type.h

@@ -174,6 +174,11 @@ struct target_type {
 	 */
 	int (*remove_watchpoint)(struct target *target, struct watchpoint *watchpoint);
 
+	/* Find out just hit watchpoint. After the target hits a watchpoint, the
+	 * information could assist gdb to locate where the modified/accessed memory is.
+	 */
+	int (*hit_watchpoint)(struct target *target, struct watchpoint **hit_watchpoint);
+
 	/**
 	 * Target algorithm support.  Do @b not call this method directly,
 	 * use target_run_algorithm() instead.