objtool: Fix seg fault caused by missing parameter

Fix a seg fault when no parameter is provided to 'objtool orc'.
Signed-off-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/9172803ec7ebb72535bcd0b7f966ae96d515968e.1514666459.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/objtool/builtin-orc.c

@@ -44,6 +44,9 @@ int cmd_orc(int argc, const char **argv)
 	const char *objname;
 
 	argc--; argv++;
+	if (argc <= 0)
+		usage_with_options(orc_usage, check_options);
+
 	if (!strncmp(argv[0], "gen", 3)) {
 		argc = parse_options(argc, argv, check_options, orc_usage, 0);
 		if (argc != 1)
@@ -52,7 +55,6 @@ int cmd_orc(int argc, const char **argv)
 		objname = argv[0];
 
 		return check(objname, no_fp, no_unreachable, true);
-
 	}
 
 	if (!strcmp(argv[0], "dump")) {