kunit: Add 'kunit_shutdown' option

Add a new kernel command-line option, 'kunit_shutdown', which allows the
user to specify that the kernel poweroff, halt, or reboot after
completing all KUnit tests; this is very handy for running KUnit tests
on UML or a VM so that the UML/VM process exits cleanly immediately
after running all tests without needing a special initramfs.

Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Tested-By: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Daniel Latypov <dlatypov@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/executor.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <linux/reboot.h>
 #include <kunit/test.h>
 #include <linux/glob.h>
 #include <linux/moduleparam.h>
@@ -18,6 +19,9 @@ module_param(filter_glob, charp, 0);
 MODULE_PARM_DESC(filter_glob,
 		"Filter which KUnit test suites run at boot-time, e.g. list*");
 
+static char *kunit_shutdown;
+core_param(kunit_shutdown, kunit_shutdown, charp, 0644);
+
 static struct kunit_suite * const *
 kunit_filter_subsuite(struct kunit_suite * const * const subsuite)
 {
@@ -82,6 +86,20 @@ static struct suite_set kunit_filter_suites(void)
 	return filtered;
 }
 
+static void kunit_handle_shutdown(void)
+{
+	if (!kunit_shutdown)
+		return;
+
+	if (!strcmp(kunit_shutdown, "poweroff"))
+		kernel_power_off();
+	else if (!strcmp(kunit_shutdown, "halt"))
+		kernel_halt();
+	else if (!strcmp(kunit_shutdown, "reboot"))
+		kernel_restart(NULL);
+
+}
+
 static void kunit_print_tap_header(struct suite_set *suite_set)
 {
 	struct kunit_suite * const * const *suites, * const *subsuite;
@@ -112,6 +130,8 @@ int kunit_run_all_tests(void)
 		kfree(suite_set.start);
 	}
 
+	kunit_handle_shutdown();
+
 	return 0;
 }