backtrace: Add a command

Add a new 'backtrace' command which prints the current call stack, which
is useful for debugging. The command is enabled by CONFIG_CMD_BACKTRACE

Add docs and a test.

Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>

cmd/Kconfig

@@ -136,6 +136,14 @@ config CMD_ADDR_FIND
 	  sufficiently large to hold a file. If successful, it sets the
 	  loadaddr variable to this address.
 
+config CMD_BACKTRACE
+	bool "backtrace"
+	depends on BACKTRACE
+	default y if BACKTRACE
+	help
+	  This command prints a backtrace showing the current call stack.
+	  This can be useful for debugging.
+
 config CMD_ADDRMAP
 	bool "addrmap"
 	depends on ADDR_MAP

cmd/Makefile

@@ -14,6 +14,7 @@ obj-y += version.o
 # command
 obj-$(CONFIG_CMD_ARMFFA) += armffa.o
 obj-$(CONFIG_CMD_2048) += 2048.o
+obj-$(CONFIG_CMD_BACKTRACE) += backtrace.o
 obj-$(CONFIG_CMD_ACPI) += acpi.o
 obj-$(CONFIG_CMD_ADDR_FIND) += addr_find.o
 obj-$(CONFIG_CMD_ADDRMAP) += addrmap.o

cmd/backtrace.c

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Backtrace command
+ *
+ * Copyright 2025 Canonical Ltd
+ * Written by Simon Glass <simon.glass@canonical.com>
+ */
+
+#include <backtrace.h>
+#include <command.h>
+
+static int do_backtrace(struct cmd_tbl *cmdtp, int flag, int argc,
+			char *const argv[])
+{
+	int ret;
+
+	ret = backtrace_show();
+	if (ret) {
+		printf("backtrace failed: %d\n", ret);
+		return CMD_RET_FAILURE;
+	}
+
+	return 0;
+}
+
+U_BOOT_CMD(backtrace, 1, 1, do_backtrace,
+	   "Print backtrace",
+	   "\n"
+	   "    - Print a backtrace of the current call stack"
+);