shell: kernel: add command to unwind a thread

Add a shell command to unwind a thread using its thread id.

uart:~$ kernel threads
Scheduler: 11 since last call
Threads:
*0x80017138 shell_uart
        options: 0x0, priority: 14 timeout: 0
        state: queued, entry: 0x800029ac
        stack size 3072, unused 1316, usage 1756 / 3072 (57 %)

 0x80017ca8 sysworkq
        options: 0x1, priority: -1 timeout: 0
        state: pending, entry: 0x80006842
        stack size 1024, unused 644, usage 380 / 1024 (37 %)

 0x800177e0 idle
        options: 0x1, priority: 15 timeout: 0
        state: , entry: 0x800065ae
        stack size 512, unused 180, usage 332 / 512 (64 %)

 0x80017950 main
        options: 0x1, priority: 0 timeout: 13
        state: suspended, entry: 0x80006326
        stack size 4096, unused 3604, usage 492 / 4096 (12 %)

uart:~$ kernel unwind 0x80017ca8
Unwinding 0x80017ca8 sysworkq
ra: 0x80007114 [z_swap+0x58]
ra: 0x80007ae8 [z_sched_wait+0x10]
ra: 0x8000689a [work_queue_main+0x58]
ra: 0x800006de [z_thread_entry+0x2e]

Signed-off-by: Yong Cong Sin <ycsin@meta.com>

subsys/shell/modules/kernel_service.c

@@ -24,6 +24,7 @@
 #if defined(CONFIG_LOG_RUNTIME_FILTERING)
 #include <zephyr/logging/log_ctrl.h>
 #endif
+#include <zephyr/debug/symtab.h>
 
 #if defined(CONFIG_THREAD_MAX_NAME_LEN)
 #define THREAD_MAX_NAM_LEN CONFIG_THREAD_MAX_NAME_LEN
@@ -203,6 +204,66 @@ static int cmd_kernel_threads(const struct shell *sh,
 	return 0;
 }
 
+#if defined(CONFIG_ARCH_HAS_STACKWALK)
+
+static bool print_trace_address(void *arg, unsigned long ra)
+{
+	const struct shell *sh = arg;
+#ifdef CONFIG_SYMTAB
+	uint32_t offset = 0;
+	const char *name = symtab_find_symbol_name(ra, &offset);
+
+	shell_print(sh, "ra: %p [%s+0x%x]", (void *)ra, name, offset);
+#else
+	shell_print(sh, "ra: %p", (void *)ra);
+#endif
+
+	return true;
+}
+
+struct unwind_entry {
+	const struct k_thread *const thread;
+	bool valid;
+};
+
+static void is_valid_thread(const struct k_thread *cthread, void *user_data)
+{
+	struct unwind_entry *entry = user_data;
+
+	if (cthread == entry->thread) {
+		entry->valid = true;
+	}
+}
+
+static int cmd_kernel_unwind(const struct shell *sh, size_t argc, char **argv)
+{
+	struct k_thread *thread;
+
+	if (argc == 1) {
+		thread = _current;
+	} else {
+		thread = UINT_TO_POINTER(strtoll(argv[1], NULL, 16));
+		struct unwind_entry entry = {
+			.thread = thread,
+			.valid = false,
+		};
+
+		k_thread_foreach_unlocked(is_valid_thread, &entry);
+
+		if (!entry.valid) {
+			shell_error(sh, "Invalid thread id %p", (void *)thread);
+			return -EINVAL;
+		}
+	}
+	shell_print(sh, "Unwinding %p %s", (void *)thread, thread->name);
+
+	arch_stack_walk(print_trace_address, (void *)sh, thread, NULL);
+
+	return 0;
+}
+
+#endif /* CONFIG_ARCH_HAS_STACKWALK */
+
 static void shell_stack_dump(const struct k_thread *thread, void *user_data)
 {
 	const struct shell *sh = (const struct shell *)user_data;
@@ -397,6 +458,9 @@ SHELL_STATIC_SUBCMD_SET_CREATE(sub_kernel,
 		defined(CONFIG_THREAD_MONITOR)
 	SHELL_CMD(stacks, NULL, "List threads stack usage.", cmd_kernel_stacks),
 	SHELL_CMD(threads, NULL, "List kernel threads.", cmd_kernel_threads),
+#if defined(CONFIG_ARCH_HAS_STACKWALK)
+	SHELL_CMD_ARG(unwind, NULL, "Unwind a thread.", cmd_kernel_unwind, 1, 1),
+#endif /* CONFIG_ARCH_HAS_STACKWALK */
 #endif
 #if defined(CONFIG_SYS_HEAP_RUNTIME_STATS) && (K_HEAP_MEM_POOL_SIZE > 0)
 	SHELL_CMD(heap, NULL, "System heap usage statistics.", cmd_kernel_heap),