selftests/livepatch: add test skip handling

Add a skip() message function that stops the test, logs an explanation,
and sets the "skip" return code (4).

Before loading a livepatch self-test kernel module, first verify that
we've built and installed it by running a 'modprobe --dry-run'.  This
should catch a few environment issues, including !CONFIG_LIVEPATCH and
!CONFIG_TEST_LIVEPATCH.  In these cases, exit gracefully with the new
skip() function.
Reported-by: Jiri Benc <jbenc@redhat.com>
Suggested-by: Shuah Khan <shuah@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/livepatch/functions.sh

@@ -13,6 +13,14 @@ function log() {
 	echo "$1" > /dev/kmsg
 }
 
+# skip(msg) - testing can't proceed
+#	msg - explanation
+function skip() {
+	log "SKIP: $1"
+	echo "SKIP: $1" >&2
+	exit 4
+}
+
 # die(msg) - game over, man
 #	msg - dying words
 function die() {
@@ -43,6 +51,12 @@ function loop_until() {
 	done
 }
 
+function assert_mod() {
+	local mod="$1"
+
+	modprobe --dry-run "$mod" &>/dev/null
+}
+
 function is_livepatch_mod() {
 	local mod="$1"
 
@@ -75,6 +89,9 @@ function __load_mod() {
 function load_mod() {
 	local mod="$1"; shift
 
+	assert_mod "$mod" ||
+		skip "unable to load module ${mod}, verify CONFIG_TEST_LIVEPATCH=m and run self-tests as root"
+
 	is_livepatch_mod "$mod" &&
 		die "use load_lp() to load the livepatch module $mod"
 
@@ -88,6 +105,9 @@ function load_mod() {
 function load_lp_nowait() {
 	local mod="$1"; shift
 
+	assert_mod "$mod" ||
+		skip "unable to load module ${mod}, verify CONFIG_TEST_LIVEPATCH=m and run self-tests as root"
+
 	is_livepatch_mod "$mod" ||
 		die "module $mod is not a livepatch"