Merge tag 'linux-kselftest-5.5-rc1-kunit' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull kselftest KUnit support gtom Shuah Khan:
 "This adds KUnit, a lightweight unit testing and mocking framework for
  the Linux kernel from Brendan Higgins.

  KUnit is not an end-to-end testing framework. It is currently
  supported on UML and sub-systems can write unit tests and run them in
  UML env. KUnit documentation is included in this update.

  In addition, this Kunit update adds 3 new kunit tests:

   - proc sysctl test from Iurii Zaikin

   - the 'list' doubly linked list test from David Gow

   - ext4 tests for decoding extended timestamps from Iurii Zaikin

  In the future KUnit will be linked to Kselftest framework to provide a
  way to trigger KUnit tests from user-space"

* tag 'linux-kselftest-5.5-rc1-kunit' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: (23 commits)
  lib/list-test: add a test for the 'list' doubly linked list
  ext4: add kunit test for decoding extended timestamps
  Documentation: kunit: Fix verification command
  kunit: Fix '--build_dir' option
  kunit: fix failure to build without printk
  MAINTAINERS: add proc sysctl KUnit test to PROC SYSCTL section
  kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()
  MAINTAINERS: add entry for KUnit the unit testing framework
  Documentation: kunit: add documentation for KUnit
  kunit: defconfig: add defconfigs for building KUnit tests
  kunit: tool: add Python wrappers for running KUnit tests
  kunit: test: add tests for KUnit managed resources
  kunit: test: add the concept of assertions
  kunit: test: add tests for kunit test abort
  kunit: test: add support for test abort
  objtool: add kunit_try_catch_throw to the noreturn list
  kunit: test: add initial tests
  lib: enable building KUnit in lib/
  kunit: test: add the concept of expectations
  kunit: test: add assertion printing library
  ...

Documentation/dev-tools/index.rst

@@ -24,6 +24,7 @@ whole; patches welcome!
    gdb-kernel-debugging
    kgdb
    kselftest
+   kunit/index
 
 
 .. only::  subproject and html

Documentation/dev-tools/kunit/api/index.rst

@@ -0,0 +1,16 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+API Reference
+=============
+.. toctree::
+
+	test
+
+This section documents the KUnit kernel testing API. It is divided into the
+following sections:
+
+================================= ==============================================
+:doc:`test`                       documents all of the standard testing API
+                                  excluding mocking or mocking related features.
+================================= ==============================================

Documentation/dev-tools/kunit/api/test.rst

@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========
+Test API
+========
+
+This file documents all of the standard testing API excluding mocking or mocking
+related features.
+
+.. kernel-doc:: include/kunit/test.h
+   :internal:

Documentation/dev-tools/kunit/faq.rst

@@ -0,0 +1,62 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+Frequently Asked Questions
+==========================
+
+How is this different from Autotest, kselftest, etc?
+====================================================
+KUnit is a unit testing framework. Autotest, kselftest (and some others) are
+not.
+
+A `unit test <https://martinfowler.com/bliki/UnitTest.html>`_ is supposed to
+test a single unit of code in isolation, hence the name. A unit test should be
+the finest granularity of testing and as such should allow all possible code
+paths to be tested in the code under test; this is only possible if the code
+under test is very small and does not have any external dependencies outside of
+the test's control like hardware.
+
+There are no testing frameworks currently available for the kernel that do not
+require installing the kernel on a test machine or in a VM and all require
+tests to be written in userspace and run on the kernel under test; this is true
+for Autotest, kselftest, and some others, disqualifying any of them from being
+considered unit testing frameworks.
+
+Does KUnit support running on architectures other than UML?
+===========================================================
+
+Yes, well, mostly.
+
+For the most part, the KUnit core framework (what you use to write the tests)
+can compile to any architecture; it compiles like just another part of the
+kernel and runs when the kernel boots. However, there is some infrastructure,
+like the KUnit Wrapper (``tools/testing/kunit/kunit.py``) that does not support
+other architectures.
+
+In short, this means that, yes, you can run KUnit on other architectures, but
+it might require more work than using KUnit on UML.
+
+For more information, see :ref:`kunit-on-non-uml`.
+
+What is the difference between a unit test and these other kinds of tests?
+==========================================================================
+Most existing tests for the Linux kernel would be categorized as an integration
+test, or an end-to-end test.
+
+- A unit test is supposed to test a single unit of code in isolation, hence the
+  name. A unit test should be the finest granularity of testing and as such
+  should allow all possible code paths to be tested in the code under test; this
+  is only possible if the code under test is very small and does not have any
+  external dependencies outside of the test's control like hardware.
+- An integration test tests the interaction between a minimal set of components,
+  usually just two or three. For example, someone might write an integration
+  test to test the interaction between a driver and a piece of hardware, or to
+  test the interaction between the userspace libraries the kernel provides and
+  the kernel itself; however, one of these tests would probably not test the
+  entire kernel along with hardware interactions and interactions with the
+  userspace.
+- An end-to-end test usually tests the entire system from the perspective of the
+  code under test. For example, someone might write an end-to-end test for the
+  kernel by installing a production configuration of the kernel on production
+  hardware with a production userspace and then trying to exercise some behavior
+  that depends on interactions between the hardware, the kernel, and userspace.

Documentation/dev-tools/kunit/index.rst

@@ -0,0 +1,79 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
+KUnit - Unit Testing for the Linux Kernel
+=========================================
+
+.. toctree::
+	:maxdepth: 2
+
+	start
+	usage
+	api/index
+	faq
+
+What is KUnit?
+==============
+
+KUnit is a lightweight unit testing and mocking framework for the Linux kernel.
+These tests are able to be run locally on a developer's workstation without a VM
+or special hardware.
+
+KUnit is heavily inspired by JUnit, Python's unittest.mock, and
+Googletest/Googlemock for C++. KUnit provides facilities for defining unit test
+cases, grouping related test cases into test suites, providing common
+infrastructure for running tests, and much more.
+
+Get started now: :doc:`start`
+
+Why KUnit?
+==========
+
+A unit test is supposed to test a single unit of code in isolation, hence the
+name. A unit test should be the finest granularity of testing and as such should
+allow all possible code paths to be tested in the code under test; this is only
+possible if the code under test is very small and does not have any external
+dependencies outside of the test's control like hardware.
+
+Outside of KUnit, there are no testing frameworks currently
+available for the kernel that do not require installing the kernel on a test
+machine or in a VM and all require tests to be written in userspace running on
+the kernel; this is true for Autotest, and kselftest, disqualifying
+any of them from being considered unit testing frameworks.
+
+KUnit addresses the problem of being able to run tests without needing a virtual
+machine or actual hardware with User Mode Linux. User Mode Linux is a Linux
+architecture, like ARM or x86; however, unlike other architectures it compiles
+to a standalone program that can be run like any other program directly inside
+of a host operating system; to be clear, it does not require any virtualization
+support; it is just a regular program.
+
+KUnit is fast. Excluding build time, from invocation to completion KUnit can run
+several dozen tests in only 10 to 20 seconds; this might not sound like a big
+deal to some people, but having such fast and easy to run tests fundamentally
+changes the way you go about testing and even writing code in the first place.
+Linus himself said in his `git talk at Google
+<https://gist.github.com/lorn/1272686/revisions#diff-53c65572127855f1b003db4064a94573R874>`_:
+
+	"... a lot of people seem to think that performance is about doing the
+	same thing, just doing it faster, and that is not true. That is not what
+	performance is all about. If you can do something really fast, really
+	well, people will start using it differently."
+
+In this context Linus was talking about branching and merging,
+but this point also applies to testing. If your tests are slow, unreliable, are
+difficult to write, and require a special setup or special hardware to run,
+then you wait a lot longer to write tests, and you wait a lot longer to run
+tests; this means that tests are likely to break, unlikely to test a lot of
+things, and are unlikely to be rerun once they pass. If your tests are really
+fast, you run them all the time, every time you make a change, and every time
+someone sends you some code. Why trust that someone ran all their tests
+correctly on every change when you can just run them yourself in less time than
+it takes to read their test log?
+
+How do I use it?
+================
+
+*   :doc:`start` - for new users of KUnit
+*   :doc:`usage` - for a more detailed explanation of KUnit features
+*   :doc:`api/index` - for the list of KUnit APIs used for testing

Documentation/dev-tools/kunit/start.rst

@@ -0,0 +1,180 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Getting Started
+===============
+
+Installing dependencies
+=======================
+KUnit has the same dependencies as the Linux kernel. As long as you can build
+the kernel, you can run KUnit.
+
+KUnit Wrapper
+=============
+Included with KUnit is a simple Python wrapper that helps format the output to
+easily use and read KUnit output. It handles building and running the kernel, as
+well as formatting the output.
+
+The wrapper can be run with:
+
+.. code-block:: bash
+
+   ./tools/testing/kunit/kunit.py run
+
+Creating a kunitconfig
+======================
+The Python script is a thin wrapper around Kbuild as such, it needs to be
+configured with a ``kunitconfig`` file. This file essentially contains the
+regular Kernel config, with the specific test targets as well.
+
+.. code-block:: bash
+
+	git clone -b master https://kunit.googlesource.com/kunitconfig $PATH_TO_KUNITCONFIG_REPO
+	cd $PATH_TO_LINUX_REPO
+	ln -s $PATH_TO_KUNIT_CONFIG_REPO/kunitconfig kunitconfig
+
+You may want to add kunitconfig to your local gitignore.
+
+Verifying KUnit Works
+---------------------
+
+To make sure that everything is set up correctly, simply invoke the Python
+wrapper from your kernel repo:
+
+.. code-block:: bash
+
+	./tools/testing/kunit/kunit.py run
+
+.. note::
+   You may want to run ``make mrproper`` first.
+
+If everything worked correctly, you should see the following:
+
+.. code-block:: bash
+
+	Generating .config ...
+	Building KUnit Kernel ...
+	Starting KUnit Kernel ...
+
+followed by a list of tests that are run. All of them should be passing.
+
+.. note::
+   Because it is building a lot of sources for the first time, the ``Building
+   kunit kernel`` step may take a while.
+
+Writing your first test
+=======================
+
+In your kernel repo let's add some code that we can test. Create a file
+``drivers/misc/example.h`` with the contents:
+
+.. code-block:: c
+
+	int misc_example_add(int left, int right);
+
+create a file ``drivers/misc/example.c``:
+
+.. code-block:: c
+
+	#include <linux/errno.h>
+
+	#include "example.h"
+
+	int misc_example_add(int left, int right)
+	{
+		return left + right;
+	}
+
+Now add the following lines to ``drivers/misc/Kconfig``:
+
+.. code-block:: kconfig
+
+	config MISC_EXAMPLE
+		bool "My example"
+
+and the following lines to ``drivers/misc/Makefile``:
+
+.. code-block:: make
+
+	obj-$(CONFIG_MISC_EXAMPLE) += example.o
+
+Now we are ready to write the test. The test will be in
+``drivers/misc/example-test.c``:
+
+.. code-block:: c
+
+	#include <kunit/test.h>
+	#include "example.h"
+
+	/* Define the test cases. */
+
+	static void misc_example_add_test_basic(struct kunit *test)
+	{
+		KUNIT_EXPECT_EQ(test, 1, misc_example_add(1, 0));
+		KUNIT_EXPECT_EQ(test, 2, misc_example_add(1, 1));
+		KUNIT_EXPECT_EQ(test, 0, misc_example_add(-1, 1));
+		KUNIT_EXPECT_EQ(test, INT_MAX, misc_example_add(0, INT_MAX));
+		KUNIT_EXPECT_EQ(test, -1, misc_example_add(INT_MAX, INT_MIN));
+	}
+
+	static void misc_example_test_failure(struct kunit *test)
+	{
+		KUNIT_FAIL(test, "This test never passes.");
+	}
+
+	static struct kunit_case misc_example_test_cases[] = {
+		KUNIT_CASE(misc_example_add_test_basic),
+		KUNIT_CASE(misc_example_test_failure),
+		{}
+	};
+
+	static struct kunit_suite misc_example_test_suite = {
+		.name = "misc-example",
+		.test_cases = misc_example_test_cases,
+	};
+	kunit_test_suite(misc_example_test_suite);
+
+Now add the following to ``drivers/misc/Kconfig``:
+
+.. code-block:: kconfig
+
+	config MISC_EXAMPLE_TEST
+		bool "Test for my example"
+		depends on MISC_EXAMPLE && KUNIT
+
+and the following to ``drivers/misc/Makefile``:
+
+.. code-block:: make
+
+	obj-$(CONFIG_MISC_EXAMPLE_TEST) += example-test.o
+
+Now add it to your ``kunitconfig``:
+
+.. code-block:: none
+
+	CONFIG_MISC_EXAMPLE=y
+	CONFIG_MISC_EXAMPLE_TEST=y
+
+Now you can run the test:
+
+.. code-block:: bash
+
+	./tools/testing/kunit/kunit.py
+
+You should see the following failure:
+
+.. code-block:: none
+
+	...
+	[16:08:57] [PASSED] misc-example:misc_example_add_test_basic
+	[16:08:57] [FAILED] misc-example:misc_example_test_failure
+	[16:08:57] EXPECTATION FAILED at drivers/misc/example-test.c:17
+	[16:08:57] 	This test never passes.
+	...
+
+Congrats! You just wrote your first KUnit test!
+
+Next Steps
+==========
+*   Check out the :doc:`usage` page for a more
+    in-depth explanation of KUnit.

MAINTAINERS

@@ -8928,6 +8928,17 @@ S:	Maintained
 F:	tools/testing/selftests/
 F:	Documentation/dev-tools/kselftest*
 
+KERNEL UNIT TESTING FRAMEWORK (KUnit)
+M:	Brendan Higgins <brendanhiggins@google.com>
+L:	linux-kselftest@vger.kernel.org
+L:	kunit-dev@googlegroups.com
+W:	https://google.github.io/kunit-docs/third_party/kernel/docs/
+S:	Maintained
+F:	Documentation/dev-tools/kunit/
+F:	include/kunit/
+F:	lib/kunit/
+F:	tools/testing/kunit/
+
 KERNEL USERMODE HELPER
 M:	Luis Chamberlain <mcgrof@kernel.org>
 L:	linux-kernel@vger.kernel.org
@@ -9505,6 +9516,13 @@ F:	Documentation/misc-devices/lis3lv02d.rst
 F:	drivers/misc/lis3lv02d/
 F:	drivers/platform/x86/hp_accel.c
 
+LIST KUNIT TEST
+M:	David Gow <davidgow@google.com>
+L:	linux-kselftest@vger.kernel.org
+L:	kunit-dev@googlegroups.com
+S:	Maintained
+F:	lib/list-test.c
+
 LIVE PATCHING
 M:	Josh Poimboeuf <jpoimboe@redhat.com>
 M:	Jiri Kosina <jikos@kernel.org>
@@ -13139,12 +13157,14 @@ F:	Documentation/filesystems/proc.txt
 PROC SYSCTL
 M:	Luis Chamberlain <mcgrof@kernel.org>
 M:	Kees Cook <keescook@chromium.org>
+M:	Iurii Zaikin <yzaikin@google.com>
 L:	linux-kernel@vger.kernel.org
 L:	linux-fsdevel@vger.kernel.org
 S:	Maintained
 F:	fs/proc/proc_sysctl.c
 F:	include/linux/sysctl.h
 F:	kernel/sysctl.c
+F:	kernel/sysctl-test.c
 F:	tools/testing/selftests/sysctl/
 
 PS3 NETWORK SUPPORT

arch/um/configs/kunit_defconfig

@@ -0,0 +1,3 @@
+CONFIG_KUNIT=y
+CONFIG_KUNIT_TEST=y
+CONFIG_KUNIT_EXAMPLE_TEST=y

fs/ext4/Kconfig

@@ -106,3 +106,20 @@ config EXT4_DEBUG
 	  If you select Y here, then you will be able to turn on debugging
 	  with a command such as:
 		echo 1 > /sys/module/ext4/parameters/mballoc_debug
+
+config EXT4_KUNIT_TESTS
+	bool "KUnit tests for ext4"
+	select EXT4_FS
+	depends on KUNIT
+	help
+	  This builds the ext4 KUnit tests.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (http://testanything.org/). Only useful for kernel devs
+	  running KUnit test harness and are not for inclusion into a production
+	  build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.

fs/ext4/Makefile

@@ -13,4 +13,5 @@ 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-$(CONFIG_EXT4_KUNIT_TESTS)		+= inode-test.o
 ext4-$(CONFIG_FS_VERITY)		+= verity.o

fs/ext4/inode-test.c

@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test of ext4 inode that verify the seconds part of [a/c/m]
+ * timestamps in ext4 inode structs are decoded correctly.
+ */
+
+#include <kunit/test.h>
+#include <linux/kernel.h>
+#include <linux/time64.h>
+
+#include "ext4.h"
+
+/*
+ * For constructing the nonnegative timestamp lower bound value.
+ * binary: 00000000 00000000 00000000 00000000
+ */
+#define LOWER_MSB_0 0L
+/*
+ * For constructing the nonnegative timestamp upper bound value.
+ * binary: 01111111 11111111 11111111 11111111
+ *
+ */
+#define UPPER_MSB_0 0x7fffffffL
+/*
+ * For constructing the negative timestamp lower bound value.
+ * binary: 10000000 00000000 00000000 00000000
+ */
+#define LOWER_MSB_1 (-0x80000000L)
+/*
+ * For constructing the negative timestamp upper bound value.
+ * binary: 11111111 11111111 11111111 11111111
+ */
+#define UPPER_MSB_1 (-1L)
+/*
+ * Upper bound for nanoseconds value supported by the encoding.
+ * binary: 00111111 11111111 11111111 11111111
+ */
+#define MAX_NANOSECONDS ((1L << 30) - 1)
+
+#define CASE_NAME_FORMAT "%s: msb:%x lower_bound:%x extra_bits: %x"
+
+#define LOWER_BOUND_NEG_NO_EXTRA_BITS_CASE\
+	"1901-12-13 Lower bound of 32bit < 0 timestamp, no extra bits"
+#define UPPER_BOUND_NEG_NO_EXTRA_BITS_CASE\
+	"1969-12-31 Upper bound of 32bit < 0 timestamp, no extra bits"
+#define LOWER_BOUND_NONNEG_NO_EXTRA_BITS_CASE\
+	"1970-01-01 Lower bound of 32bit >=0 timestamp, no extra bits"
+#define UPPER_BOUND_NONNEG_NO_EXTRA_BITS_CASE\
+	"2038-01-19 Upper bound of 32bit >=0 timestamp, no extra bits"
+#define LOWER_BOUND_NEG_LO_1_CASE\
+	"2038-01-19 Lower bound of 32bit <0 timestamp, lo extra sec bit on"
+#define UPPER_BOUND_NEG_LO_1_CASE\
+	"2106-02-07 Upper bound of 32bit <0 timestamp, lo extra sec bit on"
+#define LOWER_BOUND_NONNEG_LO_1_CASE\
+	"2106-02-07 Lower bound of 32bit >=0 timestamp, lo extra sec bit on"
+#define UPPER_BOUND_NONNEG_LO_1_CASE\
+	"2174-02-25 Upper bound of 32bit >=0 timestamp, lo extra sec bit on"
+#define LOWER_BOUND_NEG_HI_1_CASE\
+	"2174-02-25 Lower bound of 32bit <0 timestamp, hi extra sec bit on"
+#define UPPER_BOUND_NEG_HI_1_CASE\
+	"2242-03-16 Upper bound of 32bit <0 timestamp, hi extra sec bit on"
+#define LOWER_BOUND_NONNEG_HI_1_CASE\
+	"2242-03-16 Lower bound of 32bit >=0 timestamp, hi extra sec bit on"
+#define UPPER_BOUND_NONNEG_HI_1_CASE\
+	"2310-04-04 Upper bound of 32bit >=0 timestamp, hi extra sec bit on"
+#define UPPER_BOUND_NONNEG_HI_1_NS_1_CASE\
+	"2310-04-04 Upper bound of 32bit>=0 timestamp, hi extra sec bit 1. 1 ns"
+#define LOWER_BOUND_NONNEG_HI_1_NS_MAX_CASE\
+	"2378-04-22 Lower bound of 32bit>= timestamp. Extra sec bits 1. Max ns"
+#define LOWER_BOUND_NONNEG_EXTRA_BITS_1_CASE\
+	"2378-04-22 Lower bound of 32bit >=0 timestamp. All extra sec bits on"
+#define UPPER_BOUND_NONNEG_EXTRA_BITS_1_CASE\
+	"2446-05-10 Upper bound of 32bit >=0 timestamp. All extra sec bits on"
+
+struct timestamp_expectation {
+	const char *test_case_name;
+	struct timespec64 expected;
+	u32 extra_bits;
+	bool msb_set;
+	bool lower_bound;
+};
+
+static time64_t get_32bit_time(const struct timestamp_expectation * const test)
+{
+	if (test->msb_set) {
+		if (test->lower_bound)
+			return LOWER_MSB_1;
+
+		return UPPER_MSB_1;
+	}
+
+	if (test->lower_bound)
+		return LOWER_MSB_0;
+	return UPPER_MSB_0;
+}
+
+
+/*
+ *  Test data is derived from the table in the Inode Timestamps section of
+ *  Documentation/filesystems/ext4/inodes.rst.
+ */
+static void inode_test_xtimestamp_decoding(struct kunit *test)
+{
+	const struct timestamp_expectation test_data[] = {
+		{
+			.test_case_name = LOWER_BOUND_NEG_NO_EXTRA_BITS_CASE,
+			.msb_set = true,
+			.lower_bound = true,
+			.extra_bits = 0,
+			.expected = {.tv_sec = -0x80000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NEG_NO_EXTRA_BITS_CASE,
+			.msb_set = true,
+			.lower_bound = false,
+			.extra_bits = 0,
+			.expected = {.tv_sec = -1LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NONNEG_NO_EXTRA_BITS_CASE,
+			.msb_set = false,
+			.lower_bound = true,
+			.extra_bits = 0,
+			.expected = {0LL, 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NONNEG_NO_EXTRA_BITS_CASE,
+			.msb_set = false,
+			.lower_bound = false,
+			.extra_bits = 0,
+			.expected = {.tv_sec = 0x7fffffffLL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NEG_LO_1_CASE,
+			.msb_set = true,
+			.lower_bound = true,
+			.extra_bits = 1,
+			.expected = {.tv_sec = 0x80000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NEG_LO_1_CASE,
+			.msb_set = true,
+			.lower_bound = false,
+			.extra_bits = 1,
+			.expected = {.tv_sec = 0xffffffffLL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NONNEG_LO_1_CASE,
+			.msb_set = false,
+			.lower_bound = true,
+			.extra_bits = 1,
+			.expected = {.tv_sec = 0x100000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NONNEG_LO_1_CASE,
+			.msb_set = false,
+			.lower_bound = false,
+			.extra_bits = 1,
+			.expected = {.tv_sec = 0x17fffffffLL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NEG_HI_1_CASE,
+			.msb_set = true,
+			.lower_bound = true,
+			.extra_bits =  2,
+			.expected = {.tv_sec = 0x180000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NEG_HI_1_CASE,
+			.msb_set = true,
+			.lower_bound = false,
+			.extra_bits = 2,
+			.expected = {.tv_sec = 0x1ffffffffLL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NONNEG_HI_1_CASE,
+			.msb_set = false,
+			.lower_bound = true,
+			.extra_bits = 2,
+			.expected = {.tv_sec = 0x200000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NONNEG_HI_1_CASE,
+			.msb_set = false,
+			.lower_bound = false,
+			.extra_bits = 2,
+			.expected = {.tv_sec = 0x27fffffffLL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NONNEG_HI_1_NS_1_CASE,
+			.msb_set = false,
+			.lower_bound = false,
+			.extra_bits = 6,
+			.expected = {.tv_sec = 0x27fffffffLL, .tv_nsec = 1L},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NONNEG_HI_1_NS_MAX_CASE,
+			.msb_set = false,
+			.lower_bound = true,
+			.extra_bits = 0xFFFFFFFF,
+			.expected = {.tv_sec = 0x300000000LL,
+				     .tv_nsec = MAX_NANOSECONDS},
+		},
+
+		{
+			.test_case_name = LOWER_BOUND_NONNEG_EXTRA_BITS_1_CASE,
+			.msb_set = false,
+			.lower_bound = true,
+			.extra_bits = 3,
+			.expected = {.tv_sec = 0x300000000LL, .tv_nsec = 0L},
+		},
+
+		{
+			.test_case_name = UPPER_BOUND_NONNEG_EXTRA_BITS_1_CASE,
+			.msb_set = false,
+			.lower_bound = false,
+			.extra_bits = 3,
+			.expected = {.tv_sec = 0x37fffffffLL, .tv_nsec = 0L},
+		}
+	};
+
+	struct timespec64 timestamp;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_data); ++i) {
+		timestamp.tv_sec = get_32bit_time(&test_data[i]);
+		ext4_decode_extra_time(&timestamp,
+				       cpu_to_le32(test_data[i].extra_bits));
+
+		KUNIT_EXPECT_EQ_MSG(test,
+				    test_data[i].expected.tv_sec,
+				    timestamp.tv_sec,
+				    CASE_NAME_FORMAT,
+				    test_data[i].test_case_name,
+				    test_data[i].msb_set,
+				    test_data[i].lower_bound,
+				    test_data[i].extra_bits);
+		KUNIT_EXPECT_EQ_MSG(test,
+				    test_data[i].expected.tv_nsec,
+				    timestamp.tv_nsec,
+				    CASE_NAME_FORMAT,
+				    test_data[i].test_case_name,
+				    test_data[i].msb_set,
+				    test_data[i].lower_bound,
+				    test_data[i].extra_bits);
+	}
+}
+
+static struct kunit_case ext4_inode_test_cases[] = {
+	KUNIT_CASE(inode_test_xtimestamp_decoding),
+	{}
+};
+
+static struct kunit_suite ext4_inode_test_suite = {
+	.name = "ext4_inode_test",
+	.test_cases = ext4_inode_test_cases,
+};
+
+kunit_test_suite(ext4_inode_test_suite);

include/kunit/assert.h

@@ -0,0 +1,356 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Assertion and expectation serialization API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_ASSERT_H
+#define _KUNIT_ASSERT_H
+
+#include <kunit/string-stream.h>
+#include <linux/err.h>
+
+struct kunit;
+
+/**
+ * enum kunit_assert_type - Type of expectation/assertion.
+ * @KUNIT_ASSERTION: Used to denote that a kunit_assert represents an assertion.
+ * @KUNIT_EXPECTATION: Denotes that a kunit_assert represents an expectation.
+ *
+ * Used in conjunction with a &struct kunit_assert to denote whether it
+ * represents an expectation or an assertion.
+ */
+enum kunit_assert_type {
+	KUNIT_ASSERTION,
+	KUNIT_EXPECTATION,
+};
+
+/**
+ * struct kunit_assert - Data for printing a failed assertion or expectation.
+ * @test: the test case this expectation/assertion is associated with.
+ * @type: the type (either an expectation or an assertion) of this kunit_assert.
+ * @line: the source code line number that the expectation/assertion is at.
+ * @file: the file path of the source file that the expectation/assertion is in.
+ * @message: an optional message to provide additional context.
+ * @format: a function which formats the data in this kunit_assert to a string.
+ *
+ * Represents a failed expectation/assertion. Contains all the data necessary to
+ * format a string to a user reporting the failure.
+ */
+struct kunit_assert {
+	struct kunit *test;
+	enum kunit_assert_type type;
+	int line;
+	const char *file;
+	struct va_format message;
+	void (*format)(const struct kunit_assert *assert,
+		       struct string_stream *stream);
+};
+
+/**
+ * KUNIT_INIT_VA_FMT_NULL - Default initializer for struct va_format.
+ *
+ * Used inside a struct initialization block to initialize struct va_format to
+ * default values where fmt and va are null.
+ */
+#define KUNIT_INIT_VA_FMT_NULL { .fmt = NULL, .va = NULL }
+
+/**
+ * KUNIT_INIT_ASSERT_STRUCT() - Initializer for a &struct kunit_assert.
+ * @kunit: The test case that this expectation/assertion is associated with.
+ * @assert_type: The type (assertion or expectation) of this kunit_assert.
+ * @fmt: The formatting function which builds a string out of this kunit_assert.
+ *
+ * The base initializer for a &struct kunit_assert.
+ */
+#define KUNIT_INIT_ASSERT_STRUCT(kunit, assert_type, fmt) {		       \
+	.test = kunit,							       \
+	.type = assert_type,						       \
+	.file = __FILE__,						       \
+	.line = __LINE__,						       \
+	.message = KUNIT_INIT_VA_FMT_NULL,				       \
+	.format = fmt							       \
+}
+
+void kunit_base_assert_format(const struct kunit_assert *assert,
+			      struct string_stream *stream);
+
+void kunit_assert_print_msg(const struct kunit_assert *assert,
+			    struct string_stream *stream);
+
+/**
+ * struct kunit_fail_assert - Represents a plain fail expectation/assertion.
+ * @assert: The parent of this type.
+ *
+ * Represents a simple KUNIT_FAIL/KUNIT_ASSERT_FAILURE that always fails.
+ */
+struct kunit_fail_assert {
+	struct kunit_assert assert;
+};
+
+void kunit_fail_assert_format(const struct kunit_assert *assert,
+			      struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_FAIL_ASSERT_STRUCT() - Initializer for &struct kunit_fail_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ *
+ * Initializes a &struct kunit_fail_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_FAIL_ASSERT_STRUCT(test, type) {			       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_fail_assert_format)	       \
+}
+
+/**
+ * struct kunit_unary_assert - Represents a KUNIT_{EXPECT|ASSERT}_{TRUE|FALSE}
+ * @assert: The parent of this type.
+ * @condition: A string representation of a conditional expression.
+ * @expected_true: True if of type KUNIT_{EXPECT|ASSERT}_TRUE, false otherwise.
+ *
+ * Represents a simple expectation or assertion that simply asserts something is
+ * true or false. In other words, represents the expectations:
+ * KUNIT_{EXPECT|ASSERT}_{TRUE|FALSE}
+ */
+struct kunit_unary_assert {
+	struct kunit_assert assert;
+	const char *condition;
+	bool expected_true;
+};
+
+void kunit_unary_assert_format(const struct kunit_assert *assert,
+			       struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_UNARY_ASSERT_STRUCT() - Initializes &struct kunit_unary_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ * @cond: A string representation of the expression asserted true or false.
+ * @expect_true: True if of type KUNIT_{EXPECT|ASSERT}_TRUE, false otherwise.
+ *
+ * Initializes a &struct kunit_unary_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_UNARY_ASSERT_STRUCT(test, type, cond, expect_true) {	       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_unary_assert_format),	       \
+	.condition = cond,						       \
+	.expected_true = expect_true					       \
+}
+
+/**
+ * struct kunit_ptr_not_err_assert - An expectation/assertion that a pointer is
+ *	not NULL and not a -errno.
+ * @assert: The parent of this type.
+ * @text: A string representation of the expression passed to the expectation.
+ * @value: The actual evaluated pointer value of the expression.
+ *
+ * Represents an expectation/assertion that a pointer is not null and is does
+ * not contain a -errno. (See IS_ERR_OR_NULL().)
+ */
+struct kunit_ptr_not_err_assert {
+	struct kunit_assert assert;
+	const char *text;
+	const void *value;
+};
+
+void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
+				     struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_PTR_NOT_ERR_ASSERT_STRUCT() - Initializes a
+ *	&struct kunit_ptr_not_err_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ * @txt: A string representation of the expression passed to the expectation.
+ * @val: The actual evaluated pointer value of the expression.
+ *
+ * Initializes a &struct kunit_ptr_not_err_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_PTR_NOT_ERR_STRUCT(test, type, txt, val) {		       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_ptr_not_err_assert_format),   \
+	.text = txt,							       \
+	.value = val							       \
+}
+
+/**
+ * struct kunit_binary_assert - An expectation/assertion that compares two
+ *	non-pointer values (for example, KUNIT_EXPECT_EQ(test, 1 + 1, 2)).
+ * @assert: The parent of this type.
+ * @operation: A string representation of the comparison operator (e.g. "==").
+ * @left_text: A string representation of the expression in the left slot.
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_text: A string representation of the expression in the right slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two non-pointer values. For
+ * example, to expect that 1 + 1 == 2, you can use the expectation
+ * KUNIT_EXPECT_EQ(test, 1 + 1, 2);
+ */
+struct kunit_binary_assert {
+	struct kunit_assert assert;
+	const char *operation;
+	const char *left_text;
+	long long left_value;
+	const char *right_text;
+	long long right_value;
+};
+
+void kunit_binary_assert_format(const struct kunit_assert *assert,
+				struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_BINARY_ASSERT_STRUCT() - Initializes a
+ *	&struct kunit_binary_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ * @op_str: A string representation of the comparison operator (e.g. "==").
+ * @left_str: A string representation of the expression in the left slot.
+ * @left_val: The actual evaluated value of the expression in the left slot.
+ * @right_str: A string representation of the expression in the right slot.
+ * @right_val: The actual evaluated value of the expression in the right slot.
+ *
+ * Initializes a &struct kunit_binary_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_BINARY_ASSERT_STRUCT(test,				       \
+					type,				       \
+					op_str,				       \
+					left_str,			       \
+					left_val,			       \
+					right_str,			       \
+					right_val) {			       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_binary_assert_format),	       \
+	.operation = op_str,						       \
+	.left_text = left_str,						       \
+	.left_value = left_val,						       \
+	.right_text = right_str,					       \
+	.right_value = right_val					       \
+}
+
+/**
+ * struct kunit_binary_ptr_assert - An expectation/assertion that compares two
+ *	pointer values (for example, KUNIT_EXPECT_PTR_EQ(test, foo, bar)).
+ * @assert: The parent of this type.
+ * @operation: A string representation of the comparison operator (e.g. "==").
+ * @left_text: A string representation of the expression in the left slot.
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_text: A string representation of the expression in the right slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two pointer values. For
+ * example, to expect that foo and bar point to the same thing, you can use the
+ * expectation KUNIT_EXPECT_PTR_EQ(test, foo, bar);
+ */
+struct kunit_binary_ptr_assert {
+	struct kunit_assert assert;
+	const char *operation;
+	const char *left_text;
+	const void *left_value;
+	const char *right_text;
+	const void *right_value;
+};
+
+void kunit_binary_ptr_assert_format(const struct kunit_assert *assert,
+				    struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_BINARY_PTR_ASSERT_STRUCT() - Initializes a
+ *	&struct kunit_binary_ptr_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ * @op_str: A string representation of the comparison operator (e.g. "==").
+ * @left_str: A string representation of the expression in the left slot.
+ * @left_val: The actual evaluated value of the expression in the left slot.
+ * @right_str: A string representation of the expression in the right slot.
+ * @right_val: The actual evaluated value of the expression in the right slot.
+ *
+ * Initializes a &struct kunit_binary_ptr_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_BINARY_PTR_ASSERT_STRUCT(test,			       \
+					    type,			       \
+					    op_str,			       \
+					    left_str,			       \
+					    left_val,			       \
+					    right_str,			       \
+					    right_val) {		       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_binary_ptr_assert_format),    \
+	.operation = op_str,						       \
+	.left_text = left_str,						       \
+	.left_value = left_val,						       \
+	.right_text = right_str,					       \
+	.right_value = right_val					       \
+}
+
+/**
+ * struct kunit_binary_str_assert - An expectation/assertion that compares two
+ *	string values (for example, KUNIT_EXPECT_STREQ(test, foo, "bar")).
+ * @assert: The parent of this type.
+ * @operation: A string representation of the comparison operator (e.g. "==").
+ * @left_text: A string representation of the expression in the left slot.
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_text: A string representation of the expression in the right slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two string values. For
+ * example, to expect that the string in foo is equal to "bar", you can use the
+ * expectation KUNIT_EXPECT_STREQ(test, foo, "bar");
+ */
+struct kunit_binary_str_assert {
+	struct kunit_assert assert;
+	const char *operation;
+	const char *left_text;
+	const char *left_value;
+	const char *right_text;
+	const char *right_value;
+};
+
+void kunit_binary_str_assert_format(const struct kunit_assert *assert,
+				    struct string_stream *stream);
+
+/**
+ * KUNIT_INIT_BINARY_STR_ASSERT_STRUCT() - Initializes a
+ *	&struct kunit_binary_str_assert.
+ * @test: The test case that this expectation/assertion is associated with.
+ * @type: The type (assertion or expectation) of this kunit_assert.
+ * @op_str: A string representation of the comparison operator (e.g. "==").
+ * @left_str: A string representation of the expression in the left slot.
+ * @left_val: The actual evaluated value of the expression in the left slot.
+ * @right_str: A string representation of the expression in the right slot.
+ * @right_val: The actual evaluated value of the expression in the right slot.
+ *
+ * Initializes a &struct kunit_binary_str_assert. Intended to be used in
+ * KUNIT_EXPECT_* and KUNIT_ASSERT_* macros.
+ */
+#define KUNIT_INIT_BINARY_STR_ASSERT_STRUCT(test,			       \
+					    type,			       \
+					    op_str,			       \
+					    left_str,			       \
+					    left_val,			       \
+					    right_str,			       \
+					    right_val) {		       \
+	.assert = KUNIT_INIT_ASSERT_STRUCT(test,			       \
+					   type,			       \
+					   kunit_binary_str_assert_format),    \
+	.operation = op_str,						       \
+	.left_text = left_str,						       \
+	.left_value = left_val,						       \
+	.right_text = right_str,					       \
+	.right_value = right_val					       \
+}
+
+#endif /*  _KUNIT_ASSERT_H */

include/kunit/string-stream.h

@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * C++ stream style string builder used in KUnit for building messages.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_STRING_STREAM_H
+#define _KUNIT_STRING_STREAM_H
+
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <stdarg.h>
+
+struct string_stream_fragment {
+	struct kunit *test;
+	struct list_head node;
+	char *fragment;
+};
+
+struct string_stream {
+	size_t length;
+	struct list_head fragments;
+	/* length and fragments are protected by this lock */
+	spinlock_t lock;
+	struct kunit *test;
+	gfp_t gfp;
+};
+
+struct kunit;
+
+struct string_stream *alloc_string_stream(struct kunit *test, gfp_t gfp);
+
+int __printf(2, 3) string_stream_add(struct string_stream *stream,
+				     const char *fmt, ...);
+
+int string_stream_vadd(struct string_stream *stream,
+		       const char *fmt,
+		       va_list args);
+
+char *string_stream_get_string(struct string_stream *stream);
+
+int string_stream_append(struct string_stream *stream,
+			 struct string_stream *other);
+
+bool string_stream_is_empty(struct string_stream *stream);
+
+int string_stream_destroy(struct string_stream *stream);
+
+#endif /* _KUNIT_STRING_STREAM_H */

include/kunit/try-catch.h

@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * An API to allow a function, that may fail, to be executed, and recover in a
+ * controlled manner.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_TRY_CATCH_H
+#define _KUNIT_TRY_CATCH_H
+
+#include <linux/types.h>
+
+typedef void (*kunit_try_catch_func_t)(void *);
+
+struct completion;
+struct kunit;
+
+/**
+ * struct kunit_try_catch - provides a generic way to run code which might fail.
+ * @test: The test case that is currently being executed.
+ * @try_completion: Completion that the control thread waits on while test runs.
+ * @try_result: Contains any errno obtained while running test case.
+ * @try: The function, the test case, to attempt to run.
+ * @catch: The function called if @try bails out.
+ * @context: used to pass user data to the try and catch functions.
+ *
+ * kunit_try_catch provides a generic, architecture independent way to execute
+ * an arbitrary function of type kunit_try_catch_func_t which may bail out by
+ * calling kunit_try_catch_throw(). If kunit_try_catch_throw() is called, @try
+ * is stopped at the site of invocation and @catch is called.
+ *
+ * struct kunit_try_catch provides a generic interface for the functionality
+ * needed to implement kunit->abort() which in turn is needed for implementing
+ * assertions. Assertions allow stating a precondition for a test simplifying
+ * how test cases are written and presented.
+ *
+ * Assertions are like expectations, except they abort (call
+ * kunit_try_catch_throw()) when the specified condition is not met. This is
+ * useful when you look at a test case as a logical statement about some piece
+ * of code, where assertions are the premises for the test case, and the
+ * conclusion is a set of predicates, rather expectations, that must all be
+ * true. If your premises are violated, it does not makes sense to continue.
+ */
+struct kunit_try_catch {
+	/* private: internal use only. */
+	struct kunit *test;
+	struct completion *try_completion;
+	int try_result;
+	kunit_try_catch_func_t try;
+	kunit_try_catch_func_t catch;
+	void *context;
+};
+
+void kunit_try_catch_init(struct kunit_try_catch *try_catch,
+			  struct kunit *test,
+			  kunit_try_catch_func_t try,
+			  kunit_try_catch_func_t catch);
+
+void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context);
+
+void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch);
+
+static inline int kunit_try_catch_get_result(struct kunit_try_catch *try_catch)
+{
+	return try_catch->try_result;
+}
+
+/*
+ * Exposed for testing only.
+ */
+void kunit_generic_try_catch_init(struct kunit_try_catch *try_catch);
+
+#endif /* _KUNIT_TRY_CATCH_H */

kernel/Makefile

@@ -115,6 +115,8 @@ obj-$(CONFIG_TORTURE_TEST) += torture.o
 obj-$(CONFIG_HAS_IOMEM) += iomem.o
 obj-$(CONFIG_RSEQ) += rseq.o
 
+obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
+
 obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o
 KASAN_SANITIZE_stackleak.o := n
 KCOV_INSTRUMENT_stackleak.o := n

kernel/sysctl-test.c

@@ -0,0 +1,392 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test of proc sysctl.
+ */
+
+#include <kunit/test.h>
+#include <linux/sysctl.h>
+
+#define KUNIT_PROC_READ 0
+#define KUNIT_PROC_WRITE 1
+
+static int i_zero;
+static int i_one_hundred = 100;
+
+/*
+ * Test that proc_dointvec will not try to use a NULL .data field even when the
+ * length is non-zero.
+ */
+static void sysctl_test_api_dointvec_null_tbl_data(struct kunit *test)
+{
+	struct ctl_table null_data_table = {
+		.procname = "foo",
+		/*
+		 * Here we are testing that proc_dointvec behaves correctly when
+		 * we give it a NULL .data field. Normally this would point to a
+		 * piece of memory where the value would be stored.
+		 */
+		.data		= NULL,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	/*
+	 * proc_dointvec expects a buffer in user space, so we allocate one. We
+	 * also need to cast it to __user so sparse doesn't get mad.
+	 */
+	void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+							   GFP_USER);
+	size_t len;
+	loff_t pos;
+
+	/*
+	 * We don't care what the starting length is since proc_dointvec should
+	 * not try to read because .data is NULL.
+	 */
+	len = 1234;
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&null_data_table,
+					       KUNIT_PROC_READ, buffer, &len,
+					       &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+	/*
+	 * See above.
+	 */
+	len = 1234;
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&null_data_table,
+					       KUNIT_PROC_WRITE, buffer, &len,
+					       &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Similar to the previous test, we create a struct ctrl_table that has a .data
+ * field that proc_dointvec cannot do anything with; however, this time it is
+ * because we tell proc_dointvec that the size is 0.
+ */
+static void sysctl_test_api_dointvec_table_maxlen_unset(struct kunit *test)
+{
+	int data = 0;
+	struct ctl_table data_maxlen_unset_table = {
+		.procname = "foo",
+		.data		= &data,
+		/*
+		 * So .data is no longer NULL, but we tell proc_dointvec its
+		 * length is 0, so it still shouldn't try to use it.
+		 */
+		.maxlen		= 0,
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+							   GFP_USER);
+	size_t len;
+	loff_t pos;
+
+	/*
+	 * As before, we don't care what buffer length is because proc_dointvec
+	 * cannot do anything because its internal .data buffer has zero length.
+	 */
+	len = 1234;
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&data_maxlen_unset_table,
+					       KUNIT_PROC_READ, buffer, &len,
+					       &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+	/*
+	 * See previous comment.
+	 */
+	len = 1234;
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&data_maxlen_unset_table,
+					       KUNIT_PROC_WRITE, buffer, &len,
+					       &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Here we provide a valid struct ctl_table, but we try to read and write from
+ * it using a buffer of zero length, so it should still fail in a similar way as
+ * before.
+ */
+static void sysctl_test_api_dointvec_table_len_is_zero(struct kunit *test)
+{
+	int data = 0;
+	/* Good table. */
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+							   GFP_USER);
+	/*
+	 * However, now our read/write buffer has zero length.
+	 */
+	size_t len = 0;
+	loff_t pos;
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ, buffer,
+					       &len, &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE, buffer,
+					       &len, &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Test that proc_dointvec refuses to read when the file position is non-zero.
+ */
+static void sysctl_test_api_dointvec_table_read_but_position_set(
+		struct kunit *test)
+{
+	int data = 0;
+	/* Good table. */
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	void __user *buffer = (void __user *)kunit_kzalloc(test, sizeof(int),
+							   GFP_USER);
+	/*
+	 * We don't care about our buffer length because we start off with a
+	 * non-zero file position.
+	 */
+	size_t len = 1234;
+	/*
+	 * proc_dointvec should refuse to read into the buffer since the file
+	 * pos is non-zero.
+	 */
+	loff_t pos = 1;
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ, buffer,
+					       &len, &pos));
+	KUNIT_EXPECT_EQ(test, (size_t)0, len);
+}
+
+/*
+ * Test that we can read a two digit number in a sufficiently size buffer.
+ * Nothing fancy.
+ */
+static void sysctl_test_dointvec_read_happy_single_positive(struct kunit *test)
+{
+	int data = 0;
+	/* Good table. */
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	size_t len = 4;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+	/* Store 13 in the data field. */
+	*((int *)table.data) = 13;
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ,
+					       user_buffer, &len, &pos));
+	KUNIT_ASSERT_EQ(test, (size_t)3, len);
+	buffer[len] = '\0';
+	/* And we read 13 back out. */
+	KUNIT_EXPECT_STREQ(test, "13\n", buffer);
+}
+
+/*
+ * Same as previous test, just now with negative numbers.
+ */
+static void sysctl_test_dointvec_read_happy_single_negative(struct kunit *test)
+{
+	int data = 0;
+	/* Good table. */
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	size_t len = 5;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+	*((int *)table.data) = -16;
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_READ,
+					       user_buffer, &len, &pos));
+	KUNIT_ASSERT_EQ(test, (size_t)4, len);
+	buffer[len] = '\0';
+	KUNIT_EXPECT_STREQ(test, "-16\n", (char *)buffer);
+}
+
+/*
+ * Test that a simple positive write works.
+ */
+static void sysctl_test_dointvec_write_happy_single_positive(struct kunit *test)
+{
+	int data = 0;
+	/* Good table. */
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	char input[] = "9";
+	size_t len = sizeof(input) - 1;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+
+	memcpy(buffer, input, len);
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE,
+					       user_buffer, &len, &pos));
+	KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
+	KUNIT_EXPECT_EQ(test, sizeof(input) - 1, (size_t)pos);
+	KUNIT_EXPECT_EQ(test, 9, *((int *)table.data));
+}
+
+/*
+ * Same as previous test, but now with negative numbers.
+ */
+static void sysctl_test_dointvec_write_happy_single_negative(struct kunit *test)
+{
+	int data = 0;
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	char input[] = "-9";
+	size_t len = sizeof(input) - 1;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+
+	memcpy(buffer, input, len);
+
+	KUNIT_EXPECT_EQ(test, 0, proc_dointvec(&table, KUNIT_PROC_WRITE,
+					       user_buffer, &len, &pos));
+	KUNIT_EXPECT_EQ(test, sizeof(input) - 1, len);
+	KUNIT_EXPECT_EQ(test, sizeof(input) - 1, (size_t)pos);
+	KUNIT_EXPECT_EQ(test, -9, *((int *)table.data));
+}
+
+/*
+ * Test that writing a value smaller than the minimum possible value is not
+ * allowed.
+ */
+static void sysctl_test_api_dointvec_write_single_less_int_min(
+		struct kunit *test)
+{
+	int data = 0;
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	size_t max_len = 32, len = max_len;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, max_len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+	unsigned long abs_of_less_than_min = (unsigned long)INT_MAX
+					     - (INT_MAX + INT_MIN) + 1;
+
+	/*
+	 * We use this rigmarole to create a string that contains a value one
+	 * less than the minimum accepted value.
+	 */
+	KUNIT_ASSERT_LT(test,
+			(size_t)snprintf(buffer, max_len, "-%lu",
+					 abs_of_less_than_min),
+			max_len);
+
+	KUNIT_EXPECT_EQ(test, -EINVAL, proc_dointvec(&table, KUNIT_PROC_WRITE,
+						     user_buffer, &len, &pos));
+	KUNIT_EXPECT_EQ(test, max_len, len);
+	KUNIT_EXPECT_EQ(test, 0, *((int *)table.data));
+}
+
+/*
+ * Test that writing the maximum possible value works.
+ */
+static void sysctl_test_api_dointvec_write_single_greater_int_max(
+		struct kunit *test)
+{
+	int data = 0;
+	struct ctl_table table = {
+		.procname = "foo",
+		.data		= &data,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	};
+	size_t max_len = 32, len = max_len;
+	loff_t pos = 0;
+	char *buffer = kunit_kzalloc(test, max_len, GFP_USER);
+	char __user *user_buffer = (char __user *)buffer;
+	unsigned long greater_than_max = (unsigned long)INT_MAX + 1;
+
+	KUNIT_ASSERT_GT(test, greater_than_max, (unsigned long)INT_MAX);
+	KUNIT_ASSERT_LT(test, (size_t)snprintf(buffer, max_len, "%lu",
+					       greater_than_max),
+			max_len);
+	KUNIT_EXPECT_EQ(test, -EINVAL, proc_dointvec(&table, KUNIT_PROC_WRITE,
+						     user_buffer, &len, &pos));
+	KUNIT_ASSERT_EQ(test, max_len, len);
+	KUNIT_EXPECT_EQ(test, 0, *((int *)table.data));
+}
+
+static struct kunit_case sysctl_test_cases[] = {
+	KUNIT_CASE(sysctl_test_api_dointvec_null_tbl_data),
+	KUNIT_CASE(sysctl_test_api_dointvec_table_maxlen_unset),
+	KUNIT_CASE(sysctl_test_api_dointvec_table_len_is_zero),
+	KUNIT_CASE(sysctl_test_api_dointvec_table_read_but_position_set),
+	KUNIT_CASE(sysctl_test_dointvec_read_happy_single_positive),
+	KUNIT_CASE(sysctl_test_dointvec_read_happy_single_negative),
+	KUNIT_CASE(sysctl_test_dointvec_write_happy_single_positive),
+	KUNIT_CASE(sysctl_test_dointvec_write_happy_single_negative),
+	KUNIT_CASE(sysctl_test_api_dointvec_write_single_less_int_min),
+	KUNIT_CASE(sysctl_test_api_dointvec_write_single_greater_int_max),
+	{}
+};
+
+static struct kunit_suite sysctl_test_suite = {
+	.name = "sysctl_test",
+	.test_cases = sysctl_test_cases,
+};
+
+kunit_test_suite(sysctl_test_suite);

lib/Kconfig.debug

@@ -1664,6 +1664,8 @@ config PROVIDE_OHCI1394_DMA_INIT
 
 	  See Documentation/debugging-via-ohci1394.txt for more information.
 
+source "lib/kunit/Kconfig"
+
 menuconfig RUNTIME_TESTING_MENU
 	bool "Runtime Testing"
 	def_bool y
@@ -1948,6 +1950,35 @@ config TEST_SYSCTL
 
 	  If unsure, say N.
 
+config SYSCTL_KUNIT_TEST
+	bool "KUnit test for sysctl"
+	depends on KUNIT
+	help
+	  This builds the proc sysctl unit test, which runs on boot.
+	  Tests the API contract and implementation correctness of sysctl.
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+config LIST_KUNIT_TEST
+	bool "KUnit Test for Kernel Linked-list structures"
+	depends on KUNIT
+	help
+	  This builds the linked list KUnit test suite.
+	  It tests that the API and basic functionality of the list_head type
+	  and associated macros.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (http://testanything.org/). Only useful for kernel devs
+	  running the KUnit test harness, and not intended for inclusion into a
+	  production build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
 config TEST_UDELAY
 	tristate "udelay test driver"
 	help

lib/Makefile

@@ -92,6 +92,8 @@ obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o
 
 obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/
 
+obj-$(CONFIG_KUNIT) += kunit/
+
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
 CFLAGS_kobject_uevent.o += -DDEBUG
@@ -290,3 +292,6 @@ obj-$(CONFIG_GENERIC_LIB_MULDI3) += muldi3.o
 obj-$(CONFIG_GENERIC_LIB_CMPDI2) += cmpdi2.o
 obj-$(CONFIG_GENERIC_LIB_UCMPDI2) += ucmpdi2.o
 obj-$(CONFIG_OBJAGG) += objagg.o
+
+# KUnit tests
+obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o