As tests are added to kunit, it will become less feasible to execute
all built tests together.  By supporting modular tests we provide
a simple way to do selective execution on a running system; specifying

CONFIG_KUNIT=y
CONFIG_KUNIT_EXAMPLE_TEST=m

...means we can simply "insmod example-test.ko" to run the tests.

To achieve this we need to do the following:

o export the required symbols in kunit
o string-stream tests utilize non-exported symbols so for now we skip
   building them when CONFIG_KUNIT_TEST=m.
o drivers/base/power/qos-test.c contains a few unexported interface
   references, namely freq_qos_read_value() and freq_constraints_init().
   Both of these could be potentially defined as static inline functions
   in include/linux/pm_qos.h, but for now we simply avoid supporting
   module build for that test suite.
o support a new way of declaring test suites.  Because a module cannot
   do multiple late_initcall()s, we provide a kunit_test_suites() macro
   to declare multiple suites within the same module at once.
o some test module names would have been too general ("test-test"
   and "example-test" for kunit tests, "inode-test" for ext4 tests);
   rename these as appropriate ("kunit-test", "kunit-example-test"
   and "ext4-inode-test" respectively).

Also define kunit_test_suite() via kunit_test_suites()
as callers in other trees may need the old definition.

Co-developed-by: Knut Omang <redacted>
Signed-off-by: Knut Omang <redacted>
Signed-off-by: Alan Maguire <redacted>
Reviewed-by: Brendan Higgins <redacted>
Acked-by: Theodore Ts'o <tytso@mit.edu> # for ext4 bits
Acked-by: David Gow <redacted> # For list-test
Reported-by: kbuild test robot <redacted>
---
  drivers/base/power/qos-test.c                      |  2 +-
  fs/ext4/Kconfig                                    |  2 +-
  fs/ext4/Makefile                                   |  3 +-
  fs/ext4/inode-test.c                               |  4 ++-
  include/kunit/test.h                               | 37 ++++++++++++++++------
  kernel/sysctl-test.c                               |  4 ++-
  lib/Kconfig.debug                                  |  4 +--
  lib/kunit/Kconfig                                  |  4 +--
  lib/kunit/Makefile                                 | 10 ++++--
  lib/kunit/assert.c                                 |  8 +++++
  lib/kunit/{example-test.c => kunit-example-test.c} |  4 ++-
  lib/kunit/{test-test.c => kunit-test.c}            |  5 +--
  lib/kunit/string-stream-test.c                     |  2 +-
  lib/kunit/test.c                                   |  8 +++++
  lib/kunit/try-catch.c                              |  2 ++
  lib/list-test.c                                    |  4 ++-
  16 files changed, 76 insertions(+), 27 deletions(-)
  rename lib/kunit/{example-test.c => kunit-example-test.c} (97%)
  rename lib/kunit/{test-test.c => kunit-test.c} (98%)

diff --git a/drivers/base/power/qos-test.c b/drivers/base/power/qos-test.c
index 3115db0..79fc6c4 100644
--- a/drivers/base/power/qos-test.c
+++ b/drivers/base/power/qos-test.c

@@ -114,4 +114,4 @@ static void freq_qos_test_readd(struct kunit *test)
  	.name = "qos-kunit-test",
  	.test_cases = pm_qos_test_cases,
  };
-kunit_test_suite(pm_qos_test_module);
+kunit_test_suites(&pm_qos_test_module);

diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index ef42ab0..435510f 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig

@@ -108,7 +108,7 @@ config EXT4_DEBUG
  		echo 1 > /sys/module/ext4/parameters/mballoc_debug
  
  config EXT4_KUNIT_TESTS
-	bool "KUnit tests for ext4"
+	tristate "KUnit tests for ext4"
  	select EXT4_FS
  	depends on KUNIT
  	help

diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 840b91d..4ccb3c9 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile

@@ -13,5 +13,6 @@ ext4-y	:= balloc.o bitmap.o block_validity.o dir.o ext4_jbd2.o extents.o \
  
  ext4-$(CONFIG_EXT4_FS_POSIX_ACL)	+= acl.o
  ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o
-ext4-$(CONFIG_EXT4_KUNIT_TESTS)		+= inode-test.o
+ext4-inode-test-objs			+= inode-test.o
+obj-$(CONFIG_EXT4_KUNIT_TESTS)		+= ext4-inode-test.o
  ext4-$(CONFIG_FS_VERITY)		+= verity.o

diff --git a/fs/ext4/inode-test.c b/fs/ext4/inode-test.c
index 92a9da1..95620bf 100644
--- a/fs/ext4/inode-test.c
+++ b/fs/ext4/inode-test.c

@@ -269,4 +269,6 @@ static void inode_test_xtimestamp_decoding(struct kunit *test)
  	.test_cases = ext4_inode_test_cases,
  };
  
-kunit_test_suite(ext4_inode_test_suite);
+kunit_test_suites(&ext4_inode_test_suite);
+
+MODULE_LICENSE("GPL v2");

diff --git a/include/kunit/test.h b/include/kunit/test.h
index dba4830..2dfb550 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h

@@ -12,6 +12,7 @@
  #include <kunit/assert.h>
  #include <kunit/try-catch.h>
  #include <linux/kernel.h>
+#include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/types.h>
  

@@ -197,31 +198,47 @@ struct kunit {
  int kunit_run_tests(struct kunit_suite *suite);
  
  /**
- * kunit_test_suite() - used to register a &struct kunit_suite with KUnit.
+ * kunit_test_suites() - used to register one or more &struct kunit_suite
+ *			 with KUnit.
   *
- * @suite: a statically allocated &struct kunit_suite.
+ * @suites: a statically allocated list of &struct kunit_suite.
   *
- * Registers @suite with the test framework. See &struct kunit_suite for
+ * Registers @suites with the test framework. See &struct kunit_suite for
   * more information.
   *
- * NOTE: Currently KUnit tests are all run as late_initcalls; this means
+ * 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.
   */
-#define kunit_test_suite(suite)						       \
-	static int kunit_suite_init##suite(void)			       \
-	{								       \
-		return kunit_run_tests(&suite);				       \
-	}								       \
-	late_initcall(kunit_suite_init##suite)
+#define kunit_test_suites(...)						\
+	static struct kunit_suite *suites[] = { __VA_ARGS__, NULL};	\
+	static int kunit_test_suites_init(void)				\
+	{								\
+		unsigned int i;						\
+		for (i = 0; suites[i] != NULL; i++)			\
+			kunit_run_tests(suites[i]);			\
+		return 0;						\
+	}								\
+	late_initcall(kunit_test_suites_init);				\
+	static void __exit kunit_test_suites_exit(void)			\
+	{								\
+		return;							\
+	}								\
+	module_exit(kunit_test_suites_exit)
+
+#define kunit_test_suite(suite)	kunit_test_suites(&suite)