5 The kernel contains a set of "self tests" under the tools/testing/selftests/
6 directory. These are intended to be small tests to exercise individual code
7 paths in the kernel. Tests are intended to be run after building, installing
10 Kselftest from mainline can be run on older stable kernels. Running tests
11 from mainline offers the best coverage. Several test rings run mainline
12 kselftest suite on stable releases. The reason is that when a new test
13 gets added to test existing code to regression test a bug, we should be
14 able to run that test on an older kernel. Hence, it is important to keep
15 code that can still test an older kernel and make sure it skips the test
16 gracefully on newer releases.
18 You can find additional information on Kselftest framework, how to
19 write new tests using the framework on Kselftest wiki:
21 https://kselftest.wiki.kernel.org/
23 On some systems, hot-plug tests could hang forever waiting for cpu and
24 memory to be ready to be offlined. A special hot-plug target is created
25 to run the full range of hot-plug tests. In default mode, hot-plug tests run
26 in safe mode with a limited scope. In limited mode, cpu-hotplug test is
27 run on a single cpu as opposed to all hotplug capable cpus, and memory
28 hotplug test is run on 2% of hotplug capable memory instead of 10%.
30 kselftest runs as a userspace process. Tests that can be written/run in
31 userspace may wish to use the `Test Harness`_. Tests that need to be
32 run in kernel space may wish to use a `Test Module`_.
34 Running the selftests (hotplug tests are run in limited mode)
35 =============================================================
39 $ make -C tools/testing/selftests
43 $ make -C tools/testing/selftests run_tests
45 To build and run the tests with a single command, use::
49 Note that some tests will require root privileges.
51 Kselftest supports saving output files in a separate directory and then
52 running tests. To locate output files in a separate directory two syntaxes
53 are supported. In both cases the working directory must be the root of the
54 kernel src. This is applicable to "Running a subset of selftests" section
57 To build, save output files in a separate directory with O= ::
59 $ make O=/tmp/kselftest kselftest
61 To build, save output files in a separate directory with KBUILD_OUTPUT ::
63 $ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest
65 The O= assignment takes precedence over the KBUILD_OUTPUT environment
68 The above commands by default run the tests and print full pass/fail report.
69 Kselftest supports "summary" option to make it easier to understand the test
70 results. Please find the detailed individual test results for each test in
71 /tmp/testname file(s) when summary option is specified. This is applicable
72 to "Running a subset of selftests" section below.
74 To run kselftest with summary option enabled ::
76 $ make summary=1 kselftest
78 Running a subset of selftests
79 =============================
81 You can use the "TARGETS" variable on the make command line to specify
82 single test to run, or a list of tests to run.
84 To run only tests targeted for a single subsystem::
86 $ make -C tools/testing/selftests TARGETS=ptrace run_tests
88 You can specify multiple tests to build and run::
90 $ make TARGETS="size timers" kselftest
92 To build, save output files in a separate directory with O= ::
94 $ make O=/tmp/kselftest TARGETS="size timers" kselftest
96 To build, save output files in a separate directory with KBUILD_OUTPUT ::
98 $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest
100 Additionally you can use the "SKIP_TARGETS" variable on the make command
101 line to specify one or more targets to exclude from the TARGETS list.
103 To run all tests but a single subsystem::
105 $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests
107 You can specify multiple tests to skip::
109 $ make SKIP_TARGETS="size timers" kselftest
111 You can also specify a restricted list of tests to run together with a
114 $ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest
116 See the top-level tools/testing/selftests/Makefile for the list of all
119 Running the full range hotplug selftests
120 ========================================
122 To build the hotplug tests::
124 $ make -C tools/testing/selftests hotplug
126 To run the hotplug tests::
128 $ make -C tools/testing/selftests run_hotplug
130 Note that some tests will require root privileges.
136 You can use the "install" target of "make" (which calls the `kselftest_install.sh`
137 tool) to install selftests in the default location (`tools/testing/selftests/kselftest_install`),
138 or in a user specified location via the `INSTALL_PATH` "make" variable.
140 To install selftests in default location::
142 $ make -C tools/testing/selftests install
144 To install selftests in a user specified location::
146 $ make -C tools/testing/selftests install INSTALL_PATH=/some/other/path
148 Running installed selftests
149 ===========================
151 Found in the install directory, as well as in the Kselftest tarball,
152 is a script named `run_kselftest.sh` to run the tests.
154 You can simply do the following to run the installed Kselftests. Please
155 note some tests will require root privileges::
157 $ cd kselftest_install
160 To see the list of available tests, the `-l` option can be used::
162 $ ./run_kselftest.sh -l
164 The `-c` option can be used to run all the tests from a test collection, or
165 the `-t` option for specific single tests. Either can be used multiple times::
167 $ ./run_kselftest.sh -c bpf -c seccomp -t timers:posix_timers -t timer:nanosleep
169 For other features see the script usage output, seen with the `-h` option.
174 In some cases packaging is desired, such as when tests need to run on a
175 different system. To package selftests, run::
177 $ make -C tools/testing/selftests gen_tar
179 This generates a tarball in the `INSTALL_PATH/kselftest-packages` directory. By
180 default, `.gz` format is used. The tar compression format can be overridden by
181 specifying a `FORMAT` make variable. Any value recognized by `tar's auto-compress`_
182 option is supported, such as::
184 $ make -C tools/testing/selftests gen_tar FORMAT=.xz
186 `make gen_tar` invokes `make install` so you can use it to package a subset of
187 tests by using variables specified in `Running a subset of selftests`_
190 $ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz
192 .. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress
194 Contributing new tests
195 ======================
197 In general, the rules for selftests are
199 * Do as much as you can if you're not root;
201 * Don't take too long;
203 * Don't break the build on any architecture, and
205 * Don't cause the top-level "make run_tests" to fail if your feature is
208 Contributing new tests (details)
209 ================================
211 * Use TEST_GEN_XXX if such binaries or files are generated during
214 TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by
217 TEST_CUSTOM_PROGS should be used by tests that require custom build
218 rules and prevent common build rule use.
220 TEST_PROGS are for test shell scripts. Please ensure shell script has
221 its exec bit set. Otherwise, lib.mk run_tests will generate a warning.
223 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.
225 TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
226 executable which is not tested by default.
227 TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
230 * First use the headers inside the kernel source and/or git repo, and then the
231 system headers. Headers for the kernel release as opposed to headers
232 installed by the distro on the system should be the primary focus to be able
235 * If a test needs specific kernel config options enabled, add a config file in
236 the test directory to enable them.
238 e.g: tools/testing/selftests/android/config
243 Kselftest tests the kernel from userspace. Sometimes things need
244 testing from within the kernel, one method of doing this is to create a
245 test module. We can tie the module into the kselftest framework by
246 using a shell script test runner. ``kselftest/module.sh`` is designed
247 to facilitate this process. There is also a header file provided to
248 assist writing kernel modules that are for use with kselftest:
250 - ``tools/testing/selftests/kselftest_module.h``
251 - ``tools/testing/selftests/kselftest/module.sh``
256 Here we show the typical steps to create a test module and tie it into
257 kselftest. We use kselftests for lib/ as an example.
259 1. Create the test module
261 2. Create the test script that will run (load/unload) the module
262 e.g. ``tools/testing/selftests/lib/printf.sh``
264 3. Add line to config file e.g. ``tools/testing/selftests/lib/config``
266 4. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile``
272 # Assumes you have booted a fresh build of this kernel tree
273 cd /path/to/linux/tree
276 sudo make modules_install
277 make TARGETS=lib kselftest
282 A bare bones test module might look like this:
286 // SPDX-License-Identifier: GPL-2.0+
288 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
290 #include "../tools/testing/selftests/kselftest/module.h"
292 KSTM_MODULE_GLOBALS();
295 * Kernel module for testing the foobinator
298 static int __init test_function()
303 static void __init selftest(void)
305 KSTM_CHECK_ZERO(do_test_case("", 0));
308 KSTM_MODULE_LOADERS(test_foo);
309 MODULE_AUTHOR("John Developer <jd@fooman.org>");
310 MODULE_LICENSE("GPL");
318 # SPDX-License-Identifier: GPL-2.0+
319 $(dirname $0)/../kselftest/module.sh "foo" test_foo
325 The kselftest_harness.h file contains useful helpers to build tests. The
326 test harness is for userspace testing, for kernel space testing see `Test
329 The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as
335 .. kernel-doc:: tools/testing/selftests/kselftest_harness.h
342 .. kernel-doc:: tools/testing/selftests/kselftest_harness.h
343 :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP
344 FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT
350 .. kernel-doc:: tools/testing/selftests/kselftest_harness.h
353 .. kernel-doc:: tools/testing/selftests/kselftest_harness.h
354 :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE
355 ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE
356 ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT
357 EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE
358 EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE