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 448