[v4,07/11] kunit: test: create a single centralized executor for all tests

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 47e61e1d53370..d13965eb624d4 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -224,7 +224,7 @@  size_t kunit_suite_num_test_cases(struct kunit_suite *suite);
 unsigned int kunit_test_case_num(struct kunit_suite *suite,
 				 struct kunit_case *test_case);
 
-int __kunit_test_suites_init(struct kunit_suite **suites);
+int __kunit_test_suites_init(struct kunit_suite * const * const suites);
 
 void __kunit_test_suites_exit(struct kunit_suite **suites);
 
@@ -237,34 +237,58 @@  void __kunit_test_suites_exit(struct kunit_suite **suites);
  * Registers @suites_list with the test framework. See &struct kunit_suite for
  * more information.
  *
- * When builtin, KUnit tests are all run as late_initcalls; this means
- * that they cannot test anything where tests must run at a different init
- * phase. One significant restriction resulting from this is that KUnit
- * cannot reliably test anything that is initialize in the late_init phase;
- * another is that KUnit is useless to test things that need to be run in
- * an earlier init phase.
- *
- * An alternative is to build the tests as a module.  Because modules
- * do not support multiple late_initcall()s, we need to initialize an
- * array of suites for a module.
- *
- * TODO(brendanhiggins@google.com): Don't run all KUnit tests as
- * late_initcalls.  I have some future work planned to dispatch all KUnit
- * tests from the same place, and at the very least to do so after
- * everything else is definitely initialized.
+ * If a test suite is built-in, module_init() gets translated into
+ * an initcall which we don't want as the idea is that for builtins
+ * the executor will manage execution.  So ensure we do not define
+ * module_{init|exit} functions for the builtin case when registering
+ * suites via kunit_test_suites() below.
  */
-#define kunit_test_suites(suites_list...)				\
-	static struct kunit_suite *suites[] = {suites_list, NULL};	\
-	static int kunit_test_suites_init(void)				\
+#ifdef MODULE
+#define kunit_test_suites_for_module(__suites)				\
+	static int __init kunit_test_suites_init(void)			\
 	{								\
+		struct kunit_suite *suites[] = (__suites);		\
 		return __kunit_test_suites_init(suites);		\
 	}								\
-	late_initcall(kunit_test_suites_init);				\
+	module_init(kunit_test_suites_init);				\
+									\
 	static void __exit kunit_test_suites_exit(void)			\
 	{								\
 		return __kunit_test_suites_exit(suites);		\
 	}								\
 	module_exit(kunit_test_suites_exit)
+#else
+#define kunit_test_suites_for_module(__suites)
+#endif /* MODULE */
+
+#define __kunit_test_suites(unique_array, unique_suites, ...)		       \
+	static struct kunit_suite *unique_array[] = { __VA_ARGS__, NULL };     \
+	kunit_test_suites_for_module(unique_array);			       \
+	static struct kunit_suite **unique_suites			       \
+	__used __section(.kunit_test_suites) = unique_array
+
+/**
+ * kunit_test_suites() - used to register one or more &struct kunit_suite
+ *			 with KUnit.
+ *
+ * @suites: a statically allocated list of &struct kunit_suite.
+ *
+ * Registers @suites with the test framework. See &struct kunit_suite for
+ * more information.
+ *
+ * When builtin,  KUnit tests are all run via executor; this is done
+ * by placing the array of struct kunit_suite * in the .kunit_test_suites
+ * ELF section.
+ *
+ * An alternative is to build the tests as a module.  Because modules do not
+ * support multiple initcall()s, we need to initialize an array of suites for a
+ * module.
+ *
+ */
+#define kunit_test_suites(...)						\
+	__kunit_test_suites(__UNIQUE_ID(array),				\
+			    __UNIQUE_ID(suites),			\
+			    __VA_ARGS__)
 
 #define kunit_test_suite(suite)	kunit_test_suites(&suite)
 
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 724b94311ca36..c49f4ffb6273a 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -3,7 +3,8 @@  obj-$(CONFIG_KUNIT) +=			kunit.o
 kunit-objs +=				test.o \
 					string-stream.o \
 					assert.o \
-					try-catch.o
+					try-catch.o \
+					executor.o
 
 ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
diff --git a/lib/kunit/executor.c b/lib/kunit/executor.c
new file mode 100644
index 0000000000000..7015e7328dce7
--- /dev/null
+++ b/lib/kunit/executor.c
@@ -0,0 +1,28 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <kunit/test.h>
+
+/*
+ * These symbols point to the .kunit_test_suites section and are defined in
+ * include/asm-generic/vmlinux.lds.h, and consequently must be extern.
+ */
+extern struct kunit_suite * const * const __kunit_suites_start[];
+extern struct kunit_suite * const * const __kunit_suites_end[];
+
+#if IS_BUILTIN(CONFIG_KUNIT)
+
+static int kunit_run_all_tests(void)
+{
+	struct kunit_suite * const * const *suites;
+
+	for (suites = __kunit_suites_start;
+	     suites < __kunit_suites_end;
+	     suites++)
+			__kunit_test_suites_init(*suites);
+
+	return 0;
+}
+
+late_initcall(kunit_run_all_tests);
+
+#endif /* IS_BUILTIN(CONFIG_KUNIT) */
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index ccb2ffad8dcfa..918dff400a9d7 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -380,7 +380,7 @@  static void kunit_init_suite(struct kunit_suite *suite)
 	kunit_debugfs_create_suite(suite);
 }
 
-int __kunit_test_suites_init(struct kunit_suite **suites)
+int __kunit_test_suites_init(struct kunit_suite * const * const suites)
 {
 	unsigned int i;