elfctl: fix -e invalid operation error handling

Validate the operation prior to parsing the feature string, so that e.g.
-e 0x1 reports invalid operation '0' rather than invalid feature 'x11'.
Also make it an error rather than a warning, so that it is not repeated
if multiple files are specified.

(Previously an invalid operation resulted in a segfault.)

MFC after:	3 days
Sponsored by:	The FreeBSD Foundation

(cherry picked from commit b8185579f457569640f714b6180522619c2f18ea)

1 files changed, 4 insertions, 4 deletions

diff --git a/usr.bin/elfctl/elfctl.c b/usr.bin/elfctl/elfctl.c
index dbd39f612439..1042712f828a 100644
--- a/usr.bin/elfctl/elfctl.c
+++ b/usr.bin/elfctl/elfctl.c
@@ -234,6 +234,10 @@ convert_to_feature_val(char *feature_str, uint32_t *feature_val)
 	input = 0;
 	operation = *feature_str;
 	feature_str++;
+
+	if (operation != '+' && operation != '-' && operation != '=')
+		errx(1, "'%c' not an operator - use '+', '-', '='", operation);
+
 	len = nitems(featurelist);
 	while ((feature = strsep(&feature_str, ",")) != NULL) {
 		for (i = 0; i < len; ++i) {
@@ -282,10 +286,6 @@ convert_to_feature_val(char *feature_str, uint32_t *feature_val)
 		*feature_val = input;
 	} else if (operation == '-') {
 		*feature_val &= ~input;
-	} else {
-		warnx("'%c' not an operator - use '+', '-', '='",
-		    feature_str[0]);
-		return (false);
 	}
 	return (true);
 }