Only in busybox-1.36.1-mod: tags
diff -up -r busybox-1.36.1/util-linux/switch_root.c busybox-1.36.1-mod/util-linux/switch_root.c
--- busybox-1.36.1/util-linux/switch_root.c	2021-09-30 00:04:47.000000000 +0200
+++ busybox-1.36.1-mod/util-linux/switch_root.c	2024-07-01 16:08:28.336541504 +0200
@@ -181,6 +181,8 @@ int switch_root_main(int argc UNUSED_PAR
 	unsigned dry_run = 0;
 	dev_t rootdev;
 
+	printf("HELLO THIS IS SWITCH ROOT STARTING\n");
+
 	// Parse args. '+': stop at first non-option
 	if (ENABLE_SWITCH_ROOT && (!ENABLE_RUN_INIT || applet_name[0] == 's')) {
 //usage:#define switch_root_trivial_usage
@@ -241,12 +243,15 @@ int switch_root_main(int argc UNUSED_PAR
 	if (stat("/init", &st) != 0 || !S_ISREG(st.st_mode)) {
 		bb_error_msg_and_die("'%s' is not a regular file", "/init");
 	}
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 	statfs("/", &stfs); // this never fails
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 	if ((unsigned)stfs.f_type != RAMFS_MAGIC
 	 && (unsigned)stfs.f_type != TMPFS_MAGIC
 	) {
 		bb_simple_error_msg_and_die("root filesystem is not ramfs/tmpfs");
 	}
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 
 	if (!dry_run) {
 		// Zap everything out of rootdev
@@ -258,19 +263,26 @@ int switch_root_main(int argc UNUSED_PAR
 			bb_simple_perror_msg_and_die("error moving root");
 		}
 	}
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
+	printf("XCHROOT\n");
 	xchroot(".");
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 	// The chdir is needed to recalculate "." and ".." links
 	/*xchdir("/"); - done in xchroot */
 
 	// If a new console specified, redirect stdin/stdout/stderr to it
 	if (console) {
+		printf("REDIRECTING CONSOLE\n");
+		printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 		int fd = open_or_warn(console, O_RDWR);
 		if (fd >= 0) {
 			xmove_fd(fd, 0);
 			xdup2(0, 1);
 			xdup2(0, 2);
 		}
+		printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 	}
+	printf("SWITCH ROOT LINE %d OK\n", __LINE__);
 
 	if (dry_run) {
 		// Does NEW_INIT look like it can be executed?
@@ -280,8 +292,11 @@ int switch_root_main(int argc UNUSED_PAR
 		if (access(argv[0], X_OK) == 0)
 			return 0;
 	} else {
+		printf("SWITCH ROOT LINE %d OK\n", __LINE__);
+		printf("LAUNCHING EXECV\n");
 		// Exec NEW_INIT
 		execv(argv[0], argv);
+		printf("RETURNED FROM EXECV???\n");
 	}
 	bb_perror_msg_and_die("can't execute '%s'", argv[0]);
 }