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 -C tools/testing/selftests 40 41To run the tests:: 42 43 $ make -C tools/testing/selftests run_tests 44 45To build and run the tests with a single command, use:: 46 47 $ make kselftest 48 49Note that some tests will require root privileges. 50 51Kselftest supports saving output files in a separate directory and then 52running tests. To locate output files in a separate directory two syntaxes 53are supported. In both cases the working directory must be the root of the 54kernel src. This is applicable to "Running a subset of selftests" section 55below. 56 57To build, save output files in a separate directory with O= :: 58 59 $ make O=/tmp/kselftest kselftest 60 61To build, save output files in a separate directory with KBUILD_OUTPUT :: 62 63 $ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest 64 65The O= assignment takes precedence over the KBUILD_OUTPUT environment 66variable. 67 68The above commands by default run the tests and print full pass/fail report. 69Kselftest supports "summary" option to make it easier to understand the test 70results. Please find the detailed individual test results for each test in 71/tmp/testname file(s) when summary option is specified. This is applicable 72to "Running a subset of selftests" section below. 73 74To run kselftest with summary option enabled :: 75 76 $ make summary=1 kselftest 77 78Running a subset of selftests 79============================= 80 81You can use the "TARGETS" variable on the make command line to specify 82single test to run, or a list of tests to run. 83 84To run only tests targeted for a single subsystem:: 85 86 $ make -C tools/testing/selftests TARGETS=ptrace run_tests 87 88You can specify multiple tests to build and run:: 89 90 $ make TARGETS="size timers" kselftest 91 92To build, save output files in a separate directory with O= :: 93 94 $ make O=/tmp/kselftest TARGETS="size timers" kselftest 95 96To build, save output files in a separate directory with KBUILD_OUTPUT :: 97 98 $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest 99 100Additionally you can use the "SKIP_TARGETS" variable on the make command 101line to specify one or more targets to exclude from the TARGETS list. 102 103To run all tests but a single subsystem:: 104 105 $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests 106 107You can specify multiple tests to skip:: 108 109 $ make SKIP_TARGETS="size timers" kselftest 110 111You can also specify a restricted list of tests to run together with a 112dedicated skiplist:: 113 114 $ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest 115 116See the top-level tools/testing/selftests/Makefile for the list of all 117possible targets. 118 119Running the full range hotplug selftests 120======================================== 121 122To build the hotplug tests:: 123 124 $ make -C tools/testing/selftests hotplug 125 126To run the hotplug tests:: 127 128 $ make -C tools/testing/selftests run_hotplug 129 130Note that some tests will require root privileges. 131 132 133Install selftests 134================= 135 136You can use the "install" target of "make" (which calls the `kselftest_install.sh` 137tool) to install selftests in the default location (`tools/testing/selftests/kselftest_install`), 138or in a user specified location via the `INSTALL_PATH` "make" variable. 139 140To install selftests in default location:: 141 142 $ make -C tools/testing/selftests install 143 144To install selftests in a user specified location:: 145 146 $ make -C tools/testing/selftests install INSTALL_PATH=/some/other/path 147 148Running installed selftests 149=========================== 150 151Found in the install directory, as well as in the Kselftest tarball, 152is a script named `run_kselftest.sh` to run the tests. 153 154You can simply do the following to run the installed Kselftests. Please 155note some tests will require root privileges:: 156 157 $ cd kselftest_install 158 $ ./run_kselftest.sh 159 160To see the list of available tests, the `-l` option can be used:: 161 162 $ ./run_kselftest.sh -l 163 164The `-c` option can be used to run all the tests from a test collection, or 165the `-t` option for specific single tests. Either can be used multiple times:: 166 167 $ ./run_kselftest.sh -c bpf -c seccomp -t timers:posix_timers -t timer:nanosleep 168 169For other features see the script usage output, seen with the `-h` option. 170 171Packaging selftests 172=================== 173 174In some cases packaging is desired, such as when tests need to run on a 175different system. To package selftests, run:: 176 177 $ make -C tools/testing/selftests gen_tar 178 179This generates a tarball in the `INSTALL_PATH/kselftest-packages` directory. By 180default, `.gz` format is used. The tar compression format can be overridden by 181specifying a `FORMAT` make variable. Any value recognized by `tar's auto-compress`_ 182option is supported, such as:: 183 184 $ make -C tools/testing/selftests gen_tar FORMAT=.xz 185 186`make gen_tar` invokes `make install` so you can use it to package a subset of 187tests by using variables specified in `Running a subset of selftests`_ 188section:: 189 190 $ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz 191 192.. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress 193 194Contributing new tests 195====================== 196 197In general, the rules for selftests are 198 199 * Do as much as you can if you're not root; 200 201 * Don't take too long; 202 203 * Don't break the build on any architecture, and 204 205 * Don't cause the top-level "make run_tests" to fail if your feature is 206 unconfigured. 207 208Contributing new tests (details) 209================================ 210 211 * Use TEST_GEN_XXX if such binaries or files are generated during 212 compiling. 213 214 TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by 215 default. 216 217 TEST_CUSTOM_PROGS should be used by tests that require custom build 218 rules and prevent common build rule use. 219 220 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. 222 223 TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests. 224 225 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 228 test. 229 230 * 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 233 to find regressions. 234 235 * If a test needs specific kernel config options enabled, add a config file in 236 the test directory to enable them. 237 238 e.g: tools/testing/selftests/android/config 239 240Test Module 241=========== 242 243Kselftest tests the kernel from userspace. Sometimes things need 244testing from within the kernel, one method of doing this is to create a 245test module. We can tie the module into the kselftest framework by 246using a shell script test runner. ``kselftest/module.sh`` is designed 247to facilitate this process. There is also a header file provided to 248assist writing kernel modules that are for use with kselftest: 249 250- ``tools/testing/selftests/kselftest_module.h`` 251- ``tools/testing/selftests/kselftest/module.sh`` 252 253How to use 254---------- 255 256Here we show the typical steps to create a test module and tie it into 257kselftest. We use kselftests for lib/ as an example. 258 2591. Create the test module 260 2612. Create the test script that will run (load/unload) the module 262 e.g. ``tools/testing/selftests/lib/printf.sh`` 263 2643. Add line to config file e.g. ``tools/testing/selftests/lib/config`` 265 2664. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile`` 267 2685. Verify it works: 269 270.. code-block:: sh 271 272 # Assumes you have booted a fresh build of this kernel tree 273 cd /path/to/linux/tree 274 make kselftest-merge 275 make modules 276 sudo make modules_install 277 make TARGETS=lib kselftest 278 279Example Module 280-------------- 281 282A bare bones test module might look like this: 283 284.. code-block:: c 285 286 // SPDX-License-Identifier: GPL-2.0+ 287 288 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 289 290 #include "../tools/testing/selftests/kselftest/module.h" 291 292 KSTM_MODULE_GLOBALS(); 293 294 /* 295 * Kernel module for testing the foobinator 296 */ 297 298 static int __init test_function() 299 { 300 ... 301 } 302 303 static void __init selftest(void) 304 { 305 KSTM_CHECK_ZERO(do_test_case("", 0)); 306 } 307 308 KSTM_MODULE_LOADERS(test_foo); 309 MODULE_AUTHOR("John Developer <jd@fooman.org>"); 310 MODULE_LICENSE("GPL"); 311 312Example test script 313------------------- 314 315.. code-block:: sh 316 317 #!/bin/bash 318 # SPDX-License-Identifier: GPL-2.0+ 319 $(dirname $0)/../kselftest/module.sh "foo" test_foo 320 321 322Test Harness 323============ 324 325The kselftest_harness.h file contains useful helpers to build tests. The 326test harness is for userspace testing, for kernel space testing see `Test 327Module`_ above. 328 329The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as 330example. 331 332Example 333------- 334 335.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 336 :doc: example 337 338 339Helpers 340------- 341 342.. 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 345 FIXTURE_VARIANT_ADD 346 347Operators 348--------- 349 350.. kernel-doc:: tools/testing/selftests/kselftest_harness.h 351 :doc: operators 352 353.. 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 359