dynamic_debug: early return if _ddebug table is empty

If _ddebug table is empty (in a CONFIG_DYNAMIC_DEBUG build this
shouldn't happen), then warn (error?) and return early.  This skips
empty table scan and parsing of setup-string, including the pr_info
call noting the parse.  By inspection, copy return-code handling from
1st ddebug_add_module() callsite to 2nd.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

lib/dynamic_debug.c

@@ -871,7 +871,11 @@ static int __init dynamic_debug_init(void)
 	int ret = 0;
 	int n = 0;
 
-	if (__start___verbose != __stop___verbose) {
+	if (__start___verbose == __stop___verbose) {
+		pr_warn("_ddebug table is empty in a "
+			"CONFIG_DYNAMIC_DEBUG build");
+		return 1;
+	}
 	iter = __start___verbose;
 	modname = iter->modname;
 	iter_start = iter;
@@ -887,7 +891,8 @@ static int __init dynamic_debug_init(void)
 		n++;
 	}
 	ret = ddebug_add_module(iter_start, n, modname);
-	}
+	if (ret)
+		goto out_free;
 
 	/* ddebug_query boot param got passed -> set it up */
 	if (ddebug_setup_string[0] != '\0') {