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1======================
2Linux Kernel Selftests
3======================
4
5The kernel contains a set of "self tests" under the tools/testing/selftests/
6directory. These are intended to be small tests to exercise individual code
7paths in the kernel. Tests are intended to be run after building, installing
8and booting a kernel.
9
10Kselftest from mainline can be run on older stable kernels. Running tests
11from mainline offers the best coverage. Several test rings run mainline
12kselftest suite on stable releases. The reason is that when a new test
13gets added to test existing code to regression test a bug, we should be
14able to run that test on an older kernel. Hence, it is important to keep
15code that can still test an older kernel and make sure it skips the test
16gracefully on newer releases.
17
18You can find additional information on Kselftest framework, how to
19write new tests using the framework on Kselftest wiki:
20
21https://kselftest.wiki.kernel.org/
22
23On some systems, hot-plug tests could hang forever waiting for cpu and
24memory to be ready to be offlined. A special hot-plug target is created
25to run the full range of hot-plug tests. In default mode, hot-plug tests run
26in safe mode with a limited scope. In limited mode, cpu-hotplug test is
27run on a single cpu as opposed to all hotplug capable cpus, and memory
28hotplug test is run on 2% of hotplug capable memory instead of 10%.
29
30kselftest runs as a userspace process. Tests that can be written/run in
31userspace may wish to use the `Test Harness`_. Tests that need to be
32run in kernel space may wish to use a `Test Module`_.
33
34Documentation on the tests
35==========================
36
37For documentation on the kselftests themselves, see:
38
39.. toctree::
40
41 testing-devices
42
43Running the selftests (hotplug tests are run in limited mode)
44=============================================================
45
46To build the tests::
47
48 $ make headers
49 $ make -C tools/testing/selftests
50
51To run the tests::
52
53 $ make -C tools/testing/selftests run_tests
54
55To build and run the tests with a single command, use::
56
57 $ make kselftest
58
59Note that some tests will require root privileges.
60
61Kselftest supports saving output files in a separate directory and then
62running tests. To locate output files in a separate directory two syntaxes
63are supported. In both cases the working directory must be the root of the
64kernel src. This is applicable to "Running a subset of selftests" section
65below.
66
67To build, save output files in a separate directory with O= ::
68
69 $ make O=/tmp/kselftest kselftest
70
71To build, save output files in a separate directory with KBUILD_OUTPUT ::
72
73 $ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest
74
75The O= assignment takes precedence over the KBUILD_OUTPUT environment
76variable.
77
78The above commands by default run the tests and print full pass/fail report.
79Kselftest supports "summary" option to make it easier to understand the test
80results. Please find the detailed individual test results for each test in
81/tmp/testname file(s) when summary option is specified. This is applicable
82to "Running a subset of selftests" section below.
83
84To run kselftest with summary option enabled ::
85
86 $ make summary=1 kselftest
87
88Running a subset of selftests
89=============================
90
91You can use the "TARGETS" variable on the make command line to specify
92single test to run, or a list of tests to run.
93
94To run only tests targeted for a single subsystem::
95
96 $ make -C tools/testing/selftests TARGETS=ptrace run_tests
97
98You can specify multiple tests to build and run::
99
100 $ make TARGETS="size timers" kselftest
101
102To build, save output files in a separate directory with O= ::
103
104 $ make O=/tmp/kselftest TARGETS="size timers" kselftest
105
106To build, save output files in a separate directory with KBUILD_OUTPUT ::
107
108 $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest
109
110Additionally you can use the "SKIP_TARGETS" variable on the make command
111line to specify one or more targets to exclude from the TARGETS list.
112
113To run all tests but a single subsystem::
114
115 $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests
116
117You can specify multiple tests to skip::
118
119 $ make SKIP_TARGETS="size timers" kselftest
120
121You can also specify a restricted list of tests to run together with a
122dedicated skiplist::
123
124 $ make TARGETS="breakpoints size timers" SKIP_TARGETS=size kselftest
125
126See the top-level tools/testing/selftests/Makefile for the list of all
127possible targets.
128
129Running the full range hotplug selftests
130========================================
131
132To build the hotplug tests::
133
134 $ make -C tools/testing/selftests hotplug
135
136To run the hotplug tests::
137
138 $ make -C tools/testing/selftests run_hotplug
139
140Note that some tests will require root privileges.
141
142
143Install selftests
144=================
145
146You can use the "install" target of "make" (which calls the `kselftest_install.sh`
147tool) to install selftests in the default location (`tools/testing/selftests/kselftest_install`),
148or in a user specified location via the `INSTALL_PATH` "make" variable.
149
150To install selftests in default location::
151
152 $ make -C tools/testing/selftests install
153
154To install selftests in a user specified location::
155
156 $ make -C tools/testing/selftests install INSTALL_PATH=/some/other/path
157
158Running installed selftests
159===========================
160
161Found in the install directory, as well as in the Kselftest tarball,
162is a script named `run_kselftest.sh` to run the tests.
163
164You can simply do the following to run the installed Kselftests. Please
165note some tests will require root privileges::
166
167 $ cd kselftest_install
168 $ ./run_kselftest.sh
169
170To see the list of available tests, the `-l` option can be used::
171
172 $ ./run_kselftest.sh -l
173
174The `-c` option can be used to run all the tests from a test collection, or
175the `-t` option for specific single tests. Either can be used multiple times::
176
177 $ ./run_kselftest.sh -c size -c seccomp -t timers:posix_timers -t timer:nanosleep
178
179For other features see the script usage output, seen with the `-h` option.
180
181Timeout for selftests
182=====================
183
184Selftests are designed to be quick and so a default timeout is used of 45
185seconds for each test. Tests can override the default timeout by adding
186a settings file in their directory and set a timeout variable there to the
187configured a desired upper timeout for the test. Only a few tests override
188the timeout with a value higher than 45 seconds, selftests strives to keep
189it that way. Timeouts in selftests are not considered fatal because the
190system under which a test runs may change and this can also modify the
191expected time it takes to run a test. If you have control over the systems
192which will run the tests you can configure a test runner on those systems to
193use a greater or lower timeout on the command line as with the `-o` or
194the `--override-timeout` argument. For example to use 165 seconds instead
195one would use::
196
197 $ ./run_kselftest.sh --override-timeout 165
198
199You can look at the TAP output to see if you ran into the timeout. Test
200runners which know a test must run under a specific time can then optionally
201treat these timeouts then as fatal.
202
203Packaging selftests
204===================
205
206In some cases packaging is desired, such as when tests need to run on a
207different system. To package selftests, run::
208
209 $ make -C tools/testing/selftests gen_tar
210
211This generates a tarball in the `INSTALL_PATH/kselftest-packages` directory. By
212default, `.gz` format is used. The tar compression format can be overridden by
213specifying a `FORMAT` make variable. Any value recognized by `tar's auto-compress`_
214option is supported, such as::
215
216 $ make -C tools/testing/selftests gen_tar FORMAT=.xz
217
218`make gen_tar` invokes `make install` so you can use it to package a subset of
219tests by using variables specified in `Running a subset of selftests`_
220section::
221
222 $ make -C tools/testing/selftests gen_tar TARGETS="size" FORMAT=.xz
223
224.. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress
225
226Contributing new tests
227======================
228
229In general, the rules for selftests are
230
231 * Do as much as you can if you're not root;
232
233 * Don't take too long;
234
235 * Don't break the build on any architecture, and
236
237 * Don't cause the top-level "make run_tests" to fail if your feature is
238 unconfigured.
239
240 * The output of tests must conform to the TAP standard to ensure high
241 testing quality and to capture failures/errors with specific details.
242 The kselftest.h and kselftest_harness.h headers provide wrappers for
243 outputting test results. These wrappers should be used for pass,
244 fail, exit, and skip messages. CI systems can easily parse TAP output
245 messages to detect test results.
246
247Contributing new tests (details)
248================================
249
250 * In your Makefile, use facilities from lib.mk by including it instead of
251 reinventing the wheel. Specify flags and binaries generation flags on
252 need basis before including lib.mk. ::
253
254 CFLAGS = $(KHDR_INCLUDES)
255 TEST_GEN_PROGS := close_range_test
256 include ../lib.mk
257
258 * Use TEST_GEN_XXX if such binaries or files are generated during
259 compiling.
260
261 TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by
262 default.
263
264 TEST_GEN_MODS_DIR should be used by tests that require modules to be built
265 before the test starts. The variable will contain the name of the directory
266 containing the modules.
267
268 TEST_CUSTOM_PROGS should be used by tests that require custom build
269 rules and prevent common build rule use.
270
271 TEST_PROGS are for test shell scripts. Please ensure shell script has
272 its exec bit set. Otherwise, lib.mk run_tests will generate a warning.
273
274 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.
275
276 TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
277 executable which is not tested by default.
278
279 TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
280 test.
281
282 TEST_INCLUDES is similar to TEST_FILES, it lists files which should be
283 included when exporting or installing the tests, with the following
284 differences:
285
286 * symlinks to files in other directories are preserved
287 * the part of paths below tools/testing/selftests/ is preserved when
288 copying the files to the output directory
289
290 TEST_INCLUDES is meant to list dependencies located in other directories of
291 the selftests hierarchy.
292
293 * First use the headers inside the kernel source and/or git repo, and then the
294 system headers. Headers for the kernel release as opposed to headers
295 installed by the distro on the system should be the primary focus to be able
296 to find regressions. Use KHDR_INCLUDES in Makefile to include headers from
297 the kernel source.
298
299 * If a test needs specific kernel config options enabled, add a config file in
300 the test directory to enable them.
301
302 e.g: tools/testing/selftests/android/config
303
304 * Create a .gitignore file inside test directory and add all generated objects
305 in it.
306
307 * Add new test name in TARGETS in selftests/Makefile::
308
309 TARGETS += android
310
311 * All changes should pass::
312
313 kselftest-{all,install,clean,gen_tar}
314 kselftest-{all,install,clean,gen_tar} O=abo_path
315 kselftest-{all,install,clean,gen_tar} O=rel_path
316 make -C tools/testing/selftests {all,install,clean,gen_tar}
317 make -C tools/testing/selftests {all,install,clean,gen_tar} O=abs_path
318 make -C tools/testing/selftests {all,install,clean,gen_tar} O=rel_path
319
320Test Module
321===========
322
323Kselftest tests the kernel from userspace. Sometimes things need
324testing from within the kernel, one method of doing this is to create a
325test module. We can tie the module into the kselftest framework by
326using a shell script test runner. ``kselftest/module.sh`` is designed
327to facilitate this process. There is also a header file provided to
328assist writing kernel modules that are for use with kselftest:
329
330- ``tools/testing/selftests/kselftest_module.h``
331- ``tools/testing/selftests/kselftest/module.sh``
332
333Note that test modules should taint the kernel with TAINT_TEST. This will
334happen automatically for modules which are in the ``tools/testing/``
335directory, or for modules which use the ``kselftest_module.h`` header above.
336Otherwise, you'll need to add ``MODULE_INFO(test, "Y")`` to your module
337source. selftests which do not load modules typically should not taint the
338kernel, but in cases where a non-test module is loaded, TEST_TAINT can be
339applied from userspace by writing to ``/proc/sys/kernel/tainted``.
340
341How to use
342----------
343
344Here we show the typical steps to create a test module and tie it into
345kselftest. We use kselftests for lib/ as an example.
346
3471. Create the test module
348
3492. Create the test script that will run (load/unload) the module
350 e.g. ``tools/testing/selftests/lib/printf.sh``
351
3523. Add line to config file e.g. ``tools/testing/selftests/lib/config``
353
3544. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile``
355
3565. Verify it works:
357
358.. code-block:: sh
359
360 # Assumes you have booted a fresh build of this kernel tree
361 cd /path/to/linux/tree
362 make kselftest-merge
363 make modules
364 sudo make modules_install
365 make TARGETS=lib kselftest
366
367Example Module
368--------------
369
370A bare bones test module might look like this:
371
372.. code-block:: c
373
374 // SPDX-License-Identifier: GPL-2.0+
375
376 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
377
378 #include "../tools/testing/selftests/kselftest_module.h"
379
380 KSTM_MODULE_GLOBALS();
381
382 /*
383 * Kernel module for testing the foobinator
384 */
385
386 static int __init test_function()
387 {
388 ...
389 }
390
391 static void __init selftest(void)
392 {
393 KSTM_CHECK_ZERO(do_test_case("", 0));
394 }
395
396 KSTM_MODULE_LOADERS(test_foo);
397 MODULE_AUTHOR("John Developer <jd@fooman.org>");
398 MODULE_LICENSE("GPL");
399 MODULE_INFO(test, "Y");
400
401Example test script
402-------------------
403
404.. code-block:: sh
405
406 #!/bin/bash
407 # SPDX-License-Identifier: GPL-2.0+
408 $(dirname $0)/../kselftest/module.sh "foo" test_foo
409
410
411Test Harness
412============
413
414The kselftest_harness.h file contains useful helpers to build tests. The
415test harness is for userspace testing, for kernel space testing see `Test
416Module`_ above.
417
418The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as
419example.
420
421Example
422-------
423
424.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
425 :doc: example
426
427
428Helpers
429-------
430
431.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
432 :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP
433 FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT
434 FIXTURE_VARIANT_ADD
435
436Operators
437---------
438
439.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
440 :doc: operators
441
442.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
443 :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE
444 ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE
445 ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT
446 EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE
447 EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE
1======================
2Linux Kernel Selftests
3======================
4
5The kernel contains a set of "self tests" under the tools/testing/selftests/
6directory. These are intended to be small tests to exercise individual code
7paths in the kernel. Tests are intended to be run after building, installing
8and booting a kernel.
9
10Kselftest from mainline can be run on older stable kernels. Running tests
11from mainline offers the best coverage. Several test rings run mainline
12kselftest suite on stable releases. The reason is that when a new test
13gets added to test existing code to regression test a bug, we should be
14able to run that test on an older kernel. Hence, it is important to keep
15code that can still test an older kernel and make sure it skips the test
16gracefully on newer releases.
17
18You can find additional information on Kselftest framework, how to
19write new tests using the framework on Kselftest wiki:
20
21https://kselftest.wiki.kernel.org/
22
23On some systems, hot-plug tests could hang forever waiting for cpu and
24memory to be ready to be offlined. A special hot-plug target is created
25to run the full range of hot-plug tests. In default mode, hot-plug tests run
26in safe mode with a limited scope. In limited mode, cpu-hotplug test is
27run on a single cpu as opposed to all hotplug capable cpus, and memory
28hotplug test is run on 2% of hotplug capable memory instead of 10%.
29
30kselftest runs as a userspace process. Tests that can be written/run in
31userspace may wish to use the `Test Harness`_. Tests that need to be
32run in kernel space may wish to use a `Test Module`_.
33
34Running the selftests (hotplug tests are run in limited mode)
35=============================================================
36
37To build the tests::
38
39 $ make headers
40 $ make -C tools/testing/selftests
41
42To run the tests::
43
44 $ make -C tools/testing/selftests run_tests
45
46To build and run the tests with a single command, use::
47
48 $ make kselftest
49
50Note that some tests will require root privileges.
51
52Kselftest supports saving output files in a separate directory and then
53running tests. To locate output files in a separate directory two syntaxes
54are supported. In both cases the working directory must be the root of the
55kernel src. This is applicable to "Running a subset of selftests" section
56below.
57
58To build, save output files in a separate directory with O= ::
59
60 $ make O=/tmp/kselftest kselftest
61
62To build, save output files in a separate directory with KBUILD_OUTPUT ::
63
64 $ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest
65
66The O= assignment takes precedence over the KBUILD_OUTPUT environment
67variable.
68
69The above commands by default run the tests and print full pass/fail report.
70Kselftest supports "summary" option to make it easier to understand the test
71results. Please find the detailed individual test results for each test in
72/tmp/testname file(s) when summary option is specified. This is applicable
73to "Running a subset of selftests" section below.
74
75To run kselftest with summary option enabled ::
76
77 $ make summary=1 kselftest
78
79Running a subset of selftests
80=============================
81
82You can use the "TARGETS" variable on the make command line to specify
83single test to run, or a list of tests to run.
84
85To run only tests targeted for a single subsystem::
86
87 $ make -C tools/testing/selftests TARGETS=ptrace run_tests
88
89You can specify multiple tests to build and run::
90
91 $ make TARGETS="size timers" kselftest
92
93To build, save output files in a separate directory with O= ::
94
95 $ make O=/tmp/kselftest TARGETS="size timers" kselftest
96
97To build, save output files in a separate directory with KBUILD_OUTPUT ::
98
99 $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest
100
101Additionally you can use the "SKIP_TARGETS" variable on the make command
102line to specify one or more targets to exclude from the TARGETS list.
103
104To run all tests but a single subsystem::
105
106 $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests
107
108You can specify multiple tests to skip::
109
110 $ make SKIP_TARGETS="size timers" kselftest
111
112You can also specify a restricted list of tests to run together with a
113dedicated skiplist::
114
115 $ make TARGETS="breakpoints size timers" SKIP_TARGETS=size kselftest
116
117See the top-level tools/testing/selftests/Makefile for the list of all
118possible targets.
119
120Running the full range hotplug selftests
121========================================
122
123To build the hotplug tests::
124
125 $ make -C tools/testing/selftests hotplug
126
127To run the hotplug tests::
128
129 $ make -C tools/testing/selftests run_hotplug
130
131Note that some tests will require root privileges.
132
133
134Install selftests
135=================
136
137You can use the "install" target of "make" (which calls the `kselftest_install.sh`
138tool) to install selftests in the default location (`tools/testing/selftests/kselftest_install`),
139or in a user specified location via the `INSTALL_PATH` "make" variable.
140
141To install selftests in default location::
142
143 $ make -C tools/testing/selftests install
144
145To install selftests in a user specified location::
146
147 $ make -C tools/testing/selftests install INSTALL_PATH=/some/other/path
148
149Running installed selftests
150===========================
151
152Found in the install directory, as well as in the Kselftest tarball,
153is a script named `run_kselftest.sh` to run the tests.
154
155You can simply do the following to run the installed Kselftests. Please
156note some tests will require root privileges::
157
158 $ cd kselftest_install
159 $ ./run_kselftest.sh
160
161To see the list of available tests, the `-l` option can be used::
162
163 $ ./run_kselftest.sh -l
164
165The `-c` option can be used to run all the tests from a test collection, or
166the `-t` option for specific single tests. Either can be used multiple times::
167
168 $ ./run_kselftest.sh -c size -c seccomp -t timers:posix_timers -t timer:nanosleep
169
170For other features see the script usage output, seen with the `-h` option.
171
172Timeout for selftests
173=====================
174
175Selftests are designed to be quick and so a default timeout is used of 45
176seconds for each test. Tests can override the default timeout by adding
177a settings file in their directory and set a timeout variable there to the
178configured a desired upper timeout for the test. Only a few tests override
179the timeout with a value higher than 45 seconds, selftests strives to keep
180it that way. Timeouts in selftests are not considered fatal because the
181system under which a test runs may change and this can also modify the
182expected time it takes to run a test. If you have control over the systems
183which will run the tests you can configure a test runner on those systems to
184use a greater or lower timeout on the command line as with the `-o` or
185the `--override-timeout` argument. For example to use 165 seconds instead
186one would use:
187
188 $ ./run_kselftest.sh --override-timeout 165
189
190You can look at the TAP output to see if you ran into the timeout. Test
191runners which know a test must run under a specific time can then optionally
192treat these timeouts then as fatal.
193
194Packaging selftests
195===================
196
197In some cases packaging is desired, such as when tests need to run on a
198different system. To package selftests, run::
199
200 $ make -C tools/testing/selftests gen_tar
201
202This generates a tarball in the `INSTALL_PATH/kselftest-packages` directory. By
203default, `.gz` format is used. The tar compression format can be overridden by
204specifying a `FORMAT` make variable. Any value recognized by `tar's auto-compress`_
205option is supported, such as::
206
207 $ make -C tools/testing/selftests gen_tar FORMAT=.xz
208
209`make gen_tar` invokes `make install` so you can use it to package a subset of
210tests by using variables specified in `Running a subset of selftests`_
211section::
212
213 $ make -C tools/testing/selftests gen_tar TARGETS="size" FORMAT=.xz
214
215.. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress
216
217Contributing new tests
218======================
219
220In general, the rules for selftests are
221
222 * Do as much as you can if you're not root;
223
224 * Don't take too long;
225
226 * Don't break the build on any architecture, and
227
228 * Don't cause the top-level "make run_tests" to fail if your feature is
229 unconfigured.
230
231Contributing new tests (details)
232================================
233
234 * In your Makefile, use facilities from lib.mk by including it instead of
235 reinventing the wheel. Specify flags and binaries generation flags on
236 need basis before including lib.mk. ::
237
238 CFLAGS = $(KHDR_INCLUDES)
239 TEST_GEN_PROGS := close_range_test
240 include ../lib.mk
241
242 * Use TEST_GEN_XXX if such binaries or files are generated during
243 compiling.
244
245 TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by
246 default.
247
248 TEST_CUSTOM_PROGS should be used by tests that require custom build
249 rules and prevent common build rule use.
250
251 TEST_PROGS are for test shell scripts. Please ensure shell script has
252 its exec bit set. Otherwise, lib.mk run_tests will generate a warning.
253
254 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.
255
256 TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
257 executable which is not tested by default.
258 TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
259 test.
260
261 * First use the headers inside the kernel source and/or git repo, and then the
262 system headers. Headers for the kernel release as opposed to headers
263 installed by the distro on the system should be the primary focus to be able
264 to find regressions. Use KHDR_INCLUDES in Makefile to include headers from
265 the kernel source.
266
267 * If a test needs specific kernel config options enabled, add a config file in
268 the test directory to enable them.
269
270 e.g: tools/testing/selftests/android/config
271
272 * Create a .gitignore file inside test directory and add all generated objects
273 in it.
274
275 * Add new test name in TARGETS in selftests/Makefile::
276
277 TARGETS += android
278
279 * All changes should pass::
280
281 kselftest-{all,install,clean,gen_tar}
282 kselftest-{all,install,clean,gen_tar} O=abo_path
283 kselftest-{all,install,clean,gen_tar} O=rel_path
284 make -C tools/testing/selftests {all,install,clean,gen_tar}
285 make -C tools/testing/selftests {all,install,clean,gen_tar} O=abs_path
286 make -C tools/testing/selftests {all,install,clean,gen_tar} O=rel_path
287
288Test Module
289===========
290
291Kselftest tests the kernel from userspace. Sometimes things need
292testing from within the kernel, one method of doing this is to create a
293test module. We can tie the module into the kselftest framework by
294using a shell script test runner. ``kselftest/module.sh`` is designed
295to facilitate this process. There is also a header file provided to
296assist writing kernel modules that are for use with kselftest:
297
298- ``tools/testing/selftests/kselftest_module.h``
299- ``tools/testing/selftests/kselftest/module.sh``
300
301Note that test modules should taint the kernel with TAINT_TEST. This will
302happen automatically for modules which are in the ``tools/testing/``
303directory, or for modules which use the ``kselftest_module.h`` header above.
304Otherwise, you'll need to add ``MODULE_INFO(test, "Y")`` to your module
305source. selftests which do not load modules typically should not taint the
306kernel, but in cases where a non-test module is loaded, TEST_TAINT can be
307applied from userspace by writing to ``/proc/sys/kernel/tainted``.
308
309How to use
310----------
311
312Here we show the typical steps to create a test module and tie it into
313kselftest. We use kselftests for lib/ as an example.
314
3151. Create the test module
316
3172. Create the test script that will run (load/unload) the module
318 e.g. ``tools/testing/selftests/lib/printf.sh``
319
3203. Add line to config file e.g. ``tools/testing/selftests/lib/config``
321
3224. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile``
323
3245. Verify it works:
325
326.. code-block:: sh
327
328 # Assumes you have booted a fresh build of this kernel tree
329 cd /path/to/linux/tree
330 make kselftest-merge
331 make modules
332 sudo make modules_install
333 make TARGETS=lib kselftest
334
335Example Module
336--------------
337
338A bare bones test module might look like this:
339
340.. code-block:: c
341
342 // SPDX-License-Identifier: GPL-2.0+
343
344 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
345
346 #include "../tools/testing/selftests/kselftest_module.h"
347
348 KSTM_MODULE_GLOBALS();
349
350 /*
351 * Kernel module for testing the foobinator
352 */
353
354 static int __init test_function()
355 {
356 ...
357 }
358
359 static void __init selftest(void)
360 {
361 KSTM_CHECK_ZERO(do_test_case("", 0));
362 }
363
364 KSTM_MODULE_LOADERS(test_foo);
365 MODULE_AUTHOR("John Developer <jd@fooman.org>");
366 MODULE_LICENSE("GPL");
367 MODULE_INFO(test, "Y");
368
369Example test script
370-------------------
371
372.. code-block:: sh
373
374 #!/bin/bash
375 # SPDX-License-Identifier: GPL-2.0+
376 $(dirname $0)/../kselftest/module.sh "foo" test_foo
377
378
379Test Harness
380============
381
382The kselftest_harness.h file contains useful helpers to build tests. The
383test harness is for userspace testing, for kernel space testing see `Test
384Module`_ above.
385
386The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as
387example.
388
389Example
390-------
391
392.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
393 :doc: example
394
395
396Helpers
397-------
398
399.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
400 :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP
401 FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT
402 FIXTURE_VARIANT_ADD
403
404Operators
405---------
406
407.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
408 :doc: operators
409
410.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
411 :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE
412 ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE
413 ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT
414 EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE
415 EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE