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_GEN_MODS_DIR should be used by tests that require modules to be built 249 before the test starts. The variable will contain the name of the directory 250 containing the modules. 251 252 TEST_CUSTOM_PROGS should be used by tests that require custom build 253 rules and prevent common build rule use. 254 255 TEST_PROGS are for test shell scripts. Please ensure shell script has 256 its exec bit set. Otherwise, lib.mk run_tests will generate a warning. 257 258 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests. 259 260 TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the 261 executable which is not tested by default. 262 263 TEST_FILES, TEST_GEN_FILES mean it is the file which is used by 264 test. 265 266 TEST_INCLUDES is similar to TEST_FILES, it lists files which should be 267 included when exporting or installing the tests, with the following 268 differences: 269 270 * symlinks to files in other directories are preserved 271 * the part of paths below tools/testing/selftests/ is preserved when 272 copying the files to the output directory 273 274 TEST_INCLUDES is meant to list dependencies located in other directories of 275 the selftests hierarchy. 276 277 * First use the headers inside the kernel source and/or git repo, and then the 278 system headers. Headers for the kernel release as opposed to headers 279 installed by the distro on the system should be the primary focus to be able 280 to find regressions. Use KHDR_INCLUDES in Makefile to include headers from 281 the kernel source. 282 283 * If a test needs specific kernel config options enabled, add a config file in 284 the test directory to enable them. 285 286 e.g: tools/testing/selftests/android/config 287 288 * Create a .gitignore file inside test directory and add all generated objects 289 in it. 290 291 * Add new test name in TARGETS in selftests/Makefile:: 292 293 TARGETS += android 294 295 * All changes should pass:: 296 297 kselftest-{all,install,clean,gen_tar} 298 kselftest-{all,install,clean,gen_tar} O=abo_path 299 kselftest-{all,install,clean,gen_tar} O=rel_path 300 make -C tools/testing/selftests {all,install,clean,gen_tar} 301 make -C tools/testing/selftests {all,install,clean,gen_tar} O=abs_path 302 make -C tools/testing/selftests {all,install,clean,gen_tar} O=rel_path 303 304Test Module 305=========== 306 307Kselftest tests the kernel from userspace. Sometimes things need 308testing from within the kernel, one method of doing this is to create a 309test module. We can tie the module into the kselftest framework by 310using a shell script test runner. ``kselftest/module.sh`` is designed 311to facilitate this process. There is also a header file provided to 312assist writing kernel modules that are for use with kselftest: 313 314- ``tools/testing/selftests/kselftest_module.h`` 315- ``tools/testing/selftests/kselftest/module.sh`` 316 317Note that test modules should taint the kernel with TAINT_TEST. This will 318happen automatically for modules which are in the ``tools/testing/`` 319directory, or for modules which use the ``kselftest_module.h`` header above. 320Otherwise, you'll need to add ``MODULE_INFO(test, "Y")`` to your module 321source. selftests which do not load modules typically should not taint the 322kernel, but in cases where a non-test module is loaded, TEST_TAINT can be 323applied from userspace by writing to ``/proc/sys/kernel/tainted``. 324 325How to use 326---------- 327 328Here we show the typical steps to create a test module and tie it into 329kselftest. We use kselftests for lib/ as an example. 330 3311. Create the test module 332 3332. Create the test script that will run (load/unload) the module 334 e.g. ``tools/testing/selftests/lib/printf.sh`` 335 3363. Add line to config file e.g. ``tools/testing/selftests/lib/config`` 337 3384. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile`` 339 3405. Verify it works: 341 342.. code-block:: sh 343 344 # Assumes you have booted a fresh build of this kernel tree 345 cd /path/to/linux/tree 346 make kselftest-merge 347 make modules 348 sudo make modules_install 349 make TARGETS=lib kselftest 350 351Example Module 352-------------- 353 354A bare bones test module might look like this: 355 356.. code-block:: c 357 358 // SPDX-License-Identifier: GPL-2.0+ 359 360 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 361 362 #include "../tools/testing/selftests/kselftest_module.h" 363 364 KSTM_MODULE_GLOBALS(); 365 366 /* 367 * Kernel module for testing the foobinator 368 */ 369 370 static int __init test_function() 371 { 372 ... 373 } 374 375 static void __init selftest(void) 376 { 377 KSTM_CHECK_ZERO(do_test_case("", 0)); 378 } 379 380 KSTM_MODULE_LOADERS(test_foo); 381 MODULE_AUTHOR("John Developer <jd@fooman.org>"); 382 MODULE_LICENSE("GPL"); 383 MODULE_INFO(test, "Y"); 384 385Example test script 386------------------- 387 388.. code-block:: sh 389 390 #!/bin/bash 391 # SPDX-License-Identifier: GPL-2.0+ 392 $(dirname $0)/../kselftest/module.sh "foo" test_foo 393 394 395Test Harness 396============ 397 398The kselftest_harness.h file contains useful helpers to build tests. The 399test harness is for userspace testing, for kernel space testing see `Test 400Module`_ above. 401 402The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as 403example. 404 405Example 406------- 407 408.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 409 :doc: example 410 411 412Helpers 413------- 414 415.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 416 :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP 417 FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT 418 FIXTURE_VARIANT_ADD 419 420Operators 421--------- 422 423.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 424 :doc: operators 425 426.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 427 :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE 428 ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE 429 ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT 430 EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE 431 EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE 432