selftests: sysctl: return Kselftest Skip code for skipped tests

When sysctl test is skipped because of unmet dependencies and/or
unsupported configuration, it exits with error which is treated as
a fail by the Kselftest framework. This leads to false negative result
even when the test could not be run.

Change it to return kselftest skip code when a test gets skipped to
clearly report that the test could not be run.

Changed return code to kselftest skip code in skip error legs that check
requirements and module probe test error leg.

Kselftest framework SKIP code is 4 and the framework prints appropriate
messages to indicate that the test is skipped.

Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>

tools/testing/selftests/sysctl/sysctl.sh

@@ -14,6 +14,9 @@
 
 # This performs a series tests against the proc sysctl interface.
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 TEST_NAME="sysctl"
 TEST_DRIVER="test_${TEST_NAME}"
 TEST_DIR=$(dirname $0)
@@ -41,7 +44,7 @@ test_modprobe()
                echo "$0: $DIR not present" >&2
                echo "You must have the following enabled in your kernel:" >&2
                cat $TEST_DIR/config >&2
-               exit 1
+               exit $ksft_skip
        fi
 }
 
@@ -98,28 +101,30 @@ test_reqs()
 	uid=$(id -u)
 	if [ $uid -ne 0 ]; then
 		echo $msg must be run as root >&2
-		exit 0
+		exit $ksft_skip
 	fi
 
 	if ! which perl 2> /dev/null > /dev/null; then
 		echo "$0: You need perl installed"
-		exit 1
+		exit $ksft_skip
 	fi
 	if ! which getconf 2> /dev/null > /dev/null; then
 		echo "$0: You need getconf installed"
-		exit 1
+		exit $ksft_skip
 	fi
 	if ! which diff 2> /dev/null > /dev/null; then
 		echo "$0: You need diff installed"
-		exit 1
+		exit $ksft_skip
 	fi
 }
 
 function load_req_mod()
 {
-	trap "test_modprobe" EXIT
-
 	if [ ! -d $DIR ]; then
+		if ! modprobe -q -n $TEST_DRIVER; then
+			echo "$0: module $TEST_DRIVER not found [SKIP]"
+			exit $ksft_skip
+		fi
 		modprobe $TEST_DRIVER
 		if [ $? -ne 0 ]; then
 			exit
@@ -765,6 +770,7 @@ function parse_args()
 test_reqs
 allow_user_defaults
 check_production_sysctl_writes_strict
+test_modprobe
 load_req_mod
 
 trap "test_finish" EXIT