kunit: allow kunit tests to be loaded as a module

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 <knut.omang@oracle.com>
Signed-off-by: Knut Omang <knut.omang@oracle.com>
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Theodore Ts'o <tytso@mit.edu> # for ext4 bits
Acked-by: David Gow <davidgow@google.com> # For list-test
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/kunit/assert.c

@@ -26,6 +26,7 @@ void kunit_base_assert_format(const struct kunit_assert *assert,
 	string_stream_add(stream, "%s FAILED at %s:%d\n",
 			 expect_or_assert, assert->file, assert->line);
 }
+EXPORT_SYMBOL_GPL(kunit_base_assert_format);
 
 void kunit_assert_print_msg(const struct kunit_assert *assert,
 			    struct string_stream *stream)
@@ -33,6 +34,7 @@ void kunit_assert_print_msg(const struct kunit_assert *assert,
 	if (assert->message.fmt)
 		string_stream_add(stream, "\n%pV", &assert->message);
 }
+EXPORT_SYMBOL_GPL(kunit_assert_print_msg);
 
 void kunit_fail_assert_format(const struct kunit_assert *assert,
 			      struct string_stream *stream)
@@ -40,6 +42,7 @@ void kunit_fail_assert_format(const struct kunit_assert *assert,
 	kunit_base_assert_format(assert, stream);
 	string_stream_add(stream, "%pV", &assert->message);
 }
+EXPORT_SYMBOL_GPL(kunit_fail_assert_format);
 
 void kunit_unary_assert_format(const struct kunit_assert *assert,
 			       struct string_stream *stream)
@@ -58,6 +61,7 @@ void kunit_unary_assert_format(const struct kunit_assert *assert,
 				 unary_assert->condition);
 	kunit_assert_print_msg(assert, stream);
 }
+EXPORT_SYMBOL_GPL(kunit_unary_assert_format);
 
 void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
 				     struct string_stream *stream)
@@ -78,6 +82,7 @@ void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
 	}
 	kunit_assert_print_msg(assert, stream);
 }
+EXPORT_SYMBOL_GPL(kunit_ptr_not_err_assert_format);
 
 void kunit_binary_assert_format(const struct kunit_assert *assert,
 				struct string_stream *stream)
@@ -99,6 +104,7 @@ void kunit_binary_assert_format(const struct kunit_assert *assert,
 			 binary_assert->right_value);
 	kunit_assert_print_msg(assert, stream);
 }
+EXPORT_SYMBOL_GPL(kunit_binary_assert_format);
 
 void kunit_binary_ptr_assert_format(const struct kunit_assert *assert,
 				    struct string_stream *stream)
@@ -120,6 +126,7 @@ void kunit_binary_ptr_assert_format(const struct kunit_assert *assert,
 			 binary_assert->right_value);
 	kunit_assert_print_msg(assert, stream);
 }
+EXPORT_SYMBOL_GPL(kunit_binary_ptr_assert_format);
 
 void kunit_binary_str_assert_format(const struct kunit_assert *assert,
 				    struct string_stream *stream)
@@ -141,3 +148,4 @@ void kunit_binary_str_assert_format(const struct kunit_assert *assert,
 			 binary_assert->right_value);
 	kunit_assert_print_msg(assert, stream);
 }
+EXPORT_SYMBOL_GPL(kunit_binary_str_assert_format);