selftests: static_keys: return Kselftest Skip code for skipped tests

BugLink: https://bugs.launchpad.net/bugs/1792377

[ Upstream commit 87815780 ]

When static_keys 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.

Added an explicit searches for test_static_key_base and test_static_keys
modules and return skip code if they aren't found to differentiate between
the failure to load the module condition and module not found condition.

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

tools/testing/selftests/static_keys/test_static_keys.sh

 #!/bin/sh
 # Runs static keys kernel module tests
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+if ! /sbin/modprobe -q -n test_static_key_base; then
+	echo "static_key: module test_static_key_base is not found [SKIP]"
+	exit $ksft_skip
+fi
+
+if ! /sbin/modprobe -q -n test_static_keys; then
+	echo "static_key: module test_static_keys is not found [SKIP]"
+	exit $ksft_skip
+fi
+
 if /sbin/modprobe -q test_static_key_base; then
 	if /sbin/modprobe -q test_static_keys; then
 		echo "static_key: ok"