rtos: server: target: ask the RTOS which target to set swbp on.

This is the result of squashing two commits from RISC-V OpenOCD:
- [1] ("Ask the RTOS which target to set swbp on. (#673)")
- [2] ("Fix breackpoint_add for rtos swbp (#734)")

The resulting change lets the RTOS pick the "current" target for setting
the software breakpoint on, which matters if address translation differs
between threads.

Link: https://github.com/riscv-collab/riscv-openocd/commit/52ca5d198e3b [1]
Link: https://github.com/riscv-collab/riscv-openocd/commit/8ae41e86e15d [2]
Change-Id: I67ce24d6aa0ca9225436b380065d1e265424e70f
Signed-off-by: Tim Newsome <tim@sifive.com>
Signed-off-by: Evgeniy Naydanov <evgeniy.naydanov@syntacore.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/9176
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

src/rtos/hwthread.c

@@ -29,6 +29,8 @@ static int hwthread_read_buffer(struct rtos *rtos, target_addr_t address,
 static int hwthread_write_buffer(struct rtos *rtos, target_addr_t address,
 		uint32_t size, const uint8_t *buffer);
 static bool hwthread_needs_fake_step(struct target *target, int64_t thread_id);
+struct target *hwthread_swbp_target(struct rtos *rtos, target_addr_t address,
+				    uint32_t length, enum breakpoint_type type);
 
 #define HW_THREAD_NAME_STR_SIZE (32)
 
@@ -60,7 +62,8 @@ const struct rtos_type hwthread_rtos = {
 	.set_reg = hwthread_set_reg,
 	.read_buffer = hwthread_read_buffer,
 	.write_buffer = hwthread_write_buffer,
-	.needs_fake_step = hwthread_needs_fake_step
+	.needs_fake_step = hwthread_needs_fake_step,
+	.swbp_target = hwthread_swbp_target,
 };
 
 struct hwthread_params {
@@ -456,3 +459,9 @@ bool hwthread_needs_fake_step(struct target *target, int64_t thread_id)
 {
 	return false;
 }
+
+struct target *hwthread_swbp_target(struct rtos *rtos, target_addr_t address,
+				    uint32_t length, enum breakpoint_type type)
+{
+	return hwthread_find_thread(rtos->target, rtos->current_thread);
+}

src/rtos/rtos.c

@@ -762,3 +762,11 @@ bool rtos_needs_fake_step(struct target *target, int64_t thread_id)
 		return target->rtos->type->needs_fake_step(target, thread_id);
 	return target->rtos->current_thread != thread_id;
 }
+
+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;
+}

src/rtos/rtos.h

@@ -9,6 +9,7 @@
 #define OPENOCD_RTOS_RTOS_H
 
 #include "server/server.h"
+#include "target/breakpoints.h"
 #include "target/target.h"
 
 typedef int64_t threadid_t;
@@ -86,6 +87,12 @@ struct rtos_type {
 	 * target running a multi-threading OS. If an RTOS can do this, override
 	 * needs_fake_step(). */
 	bool (*needs_fake_step)(struct target *target, int64_t thread_id);
+	/* When a software breakpoint is set, it is set on only one target,
+	 * because we assume memory is shared across them. By default this is the
+	 * first target in the SMP group. Override this function to have
+	 * breakpoint_add() use a different target. */
+	struct target * (*swbp_target)(struct rtos *rtos, target_addr_t address,
+				     uint32_t length, enum breakpoint_type type);
 };
 
 struct stack_register_offset {
@@ -145,6 +152,8 @@ int rtos_read_buffer(struct target *target, target_addr_t address,
 int rtos_write_buffer(struct target *target, target_addr_t address,
 		uint32_t size, const uint8_t *buffer);
 bool rtos_needs_fake_step(struct target *target, int64_t thread_id);
+struct target *rtos_swbp_target(struct target *target, target_addr_t address,
+				uint32_t length, enum breakpoint_type type);
 
 // Keep in alphabetic order this list of rtos
 extern const struct rtos_type chibios_rtos;

src/server/gdb_server.c

@@ -1814,7 +1814,15 @@ static int gdb_breakpoint_watchpoint_packet(struct connection *connection,
 		case 0:
 		case 1:
 			if (packet[0] == 'Z') {
-				retval = breakpoint_add(target, address, size, bp_type);
+				struct target *bp_target = target;
+				if (target->rtos && bp_type == BKPT_SOFT) {
+					bp_target = rtos_swbp_target(target, address, size, bp_type);
+					if (!bp_target) {
+						retval = ERROR_FAIL;
+						break;
+					}
+				}
+				retval = breakpoint_add(bp_target, address, size, bp_type);
 			} else {
 				assert(packet[0] == 'z');
 				retval = breakpoint_remove(target, address);

src/target/breakpoints.c

@@ -210,16 +210,10 @@ int breakpoint_add(struct target *target,
 	unsigned int length,
 	enum breakpoint_type type)
 {
-	if (target->smp) {
-		struct target_list *head;
-
-		if (type == BKPT_SOFT) {
-			head = list_first_entry(target->smp_targets, struct target_list, lh);
-			return breakpoint_add_internal(head->target, address, length, type);
-		}
-
-		foreach_smp_target(head, target->smp_targets) {
-			struct target *curr = head->target;
+	if (target->smp && type == BKPT_HARD) {
+		struct target_list *list_node;
+		foreach_smp_target(list_node, target->smp_targets) {
+			struct target *curr = list_node->target;
 			int retval = breakpoint_add_internal(curr, address, length, type);
 			if (retval != ERROR_OK)
 				return retval;