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. 230 231 * The output of tests must conform to the TAP standard to ensure high 232 testing quality and to capture failures/errors with specific details. 233 The kselftest.h and kselftest_harness.h headers provide wrappers for 234 outputting test results. These wrappers should be used for pass, 235 fail, exit, and skip messages. CI systems can easily parse TAP output 236 messages to detect test results. 237 238Contributing new tests (details) 239================================ 240 241 * In your Makefile, use facilities from lib.mk by including it instead of 242 reinventing the wheel. Specify flags and binaries generation flags on 243 need basis before including lib.mk. :: 244 245 CFLAGS = $(KHDR_INCLUDES) 246 TEST_GEN_PROGS := close_range_test 247 include ../lib.mk 248 249 * Use TEST_GEN_XXX if such binaries or files are generated during 250 compiling. 251 252 TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by 253 default. 254 255 TEST_GEN_MODS_DIR should be used by tests that require modules to be built 256 before the test starts. The variable will contain the name of the directory 257 containing the modules. 258 259 TEST_CUSTOM_PROGS should be used by tests that require custom build 260 rules and prevent common build rule use. 261 262 TEST_PROGS are for test shell scripts. Please ensure shell script has 263 its exec bit set. Otherwise, lib.mk run_tests will generate a warning. 264 265 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests. 266 267 TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the 268 executable which is not tested by default. 269 270 TEST_FILES, TEST_GEN_FILES mean it is the file which is used by 271 test. 272 273 TEST_INCLUDES is similar to TEST_FILES, it lists files which should be 274 included when exporting or installing the tests, with the following 275 differences: 276 277 * symlinks to files in other directories are preserved 278 * the part of paths below tools/testing/selftests/ is preserved when 279 copying the files to the output directory 280 281 TEST_INCLUDES is meant to list dependencies located in other directories of 282 the selftests hierarchy. 283 284 * First use the headers inside the kernel source and/or git repo, and then the 285 system headers. Headers for the kernel release as opposed to headers 286 installed by the distro on the system should be the primary focus to be able 287 to find regressions. Use KHDR_INCLUDES in Makefile to include headers from 288 the kernel source. 289 290 * If a test needs specific kernel config options enabled, add a config file in 291 the test directory to enable them. 292 293 e.g: tools/testing/selftests/android/config 294 295 * Create a .gitignore file inside test directory and add all generated objects 296 in it. 297 298 * Add new test name in TARGETS in selftests/Makefile:: 299 300 TARGETS += android 301 302 * All changes should pass:: 303 304 kselftest-{all,install,clean,gen_tar} 305 kselftest-{all,install,clean,gen_tar} O=abo_path 306 kselftest-{all,install,clean,gen_tar} O=rel_path 307 make -C tools/testing/selftests {all,install,clean,gen_tar} 308 make -C tools/testing/selftests {all,install,clean,gen_tar} O=abs_path 309 make -C tools/testing/selftests {all,install,clean,gen_tar} O=rel_path 310 311Test Module 312=========== 313 314Kselftest tests the kernel from userspace. Sometimes things need 315testing from within the kernel, one method of doing this is to create a 316test module. We can tie the module into the kselftest framework by 317using a shell script test runner. ``kselftest/module.sh`` is designed 318to facilitate this process. There is also a header file provided to 319assist writing kernel modules that are for use with kselftest: 320 321- ``tools/testing/selftests/kselftest_module.h`` 322- ``tools/testing/selftests/kselftest/module.sh`` 323 324Note that test modules should taint the kernel with TAINT_TEST. This will 325happen automatically for modules which are in the ``tools/testing/`` 326directory, or for modules which use the ``kselftest_module.h`` header above. 327Otherwise, you'll need to add ``MODULE_INFO(test, "Y")`` to your module 328source. selftests which do not load modules typically should not taint the 329kernel, but in cases where a non-test module is loaded, TEST_TAINT can be 330applied from userspace by writing to ``/proc/sys/kernel/tainted``. 331 332How to use 333---------- 334 335Here we show the typical steps to create a test module and tie it into 336kselftest. We use kselftests for lib/ as an example. 337 3381. Create the test module 339 3402. Create the test script that will run (load/unload) the module 341 e.g. ``tools/testing/selftests/lib/printf.sh`` 342 3433. Add line to config file e.g. ``tools/testing/selftests/lib/config`` 344 3454. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile`` 346 3475. Verify it works: 348 349.. code-block:: sh 350 351 # Assumes you have booted a fresh build of this kernel tree 352 cd /path/to/linux/tree 353 make kselftest-merge 354 make modules 355 sudo make modules_install 356 make TARGETS=lib kselftest 357 358Example Module 359-------------- 360 361A bare bones test module might look like this: 362 363.. code-block:: c 364 365 // SPDX-License-Identifier: GPL-2.0+ 366 367 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 368 369 #include "../tools/testing/selftests/kselftest_module.h" 370 371 KSTM_MODULE_GLOBALS(); 372 373 /* 374 * Kernel module for testing the foobinator 375 */ 376 377 static int __init test_function() 378 { 379 ... 380 } 381 382 static void __init selftest(void) 383 { 384 KSTM_CHECK_ZERO(do_test_case("", 0)); 385 } 386 387 KSTM_MODULE_LOADERS(test_foo); 388 MODULE_AUTHOR("John Developer <jd@fooman.org>"); 389 MODULE_LICENSE("GPL"); 390 MODULE_INFO(test, "Y"); 391 392Example test script 393------------------- 394 395.. code-block:: sh 396 397 #!/bin/bash 398 # SPDX-License-Identifier: GPL-2.0+ 399 $(dirname $0)/../kselftest/module.sh "foo" test_foo 400 401 402Test Harness 403============ 404 405The kselftest_harness.h file contains useful helpers to build tests. The 406test harness is for userspace testing, for kernel space testing see `Test 407Module`_ above. 408 409The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as 410example. 411 412Example 413------- 414 415.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 416 :doc: example 417 418 419Helpers 420------- 421 422.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 423 :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP 424 FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT 425 FIXTURE_VARIANT_ADD 426 427Operators 428--------- 429 430.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 431 :doc: operators 432 433.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 434 :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE 435 ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE 436 ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT 437 EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE 438 EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE 439