| ====================== |
| Linux Kernel Selftests |
| ====================== |
| |
| The kernel contains a set of "self tests" under the tools/testing/selftests/ |
| directory. These are intended to be small tests to exercise individual code |
| paths in the kernel. Tests are intended to be run after building, installing |
| and booting a kernel. |
| |
| You can find additional information on Kselftest framework, how to |
| write new tests using the framework on Kselftest wiki: |
| |
| https://kselftest.wiki.kernel.org/ |
| |
| On some systems, hot-plug tests could hang forever waiting for cpu and |
| memory to be ready to be offlined. A special hot-plug target is created |
| to run the full range of hot-plug tests. In default mode, hot-plug tests run |
| in safe mode with a limited scope. In limited mode, cpu-hotplug test is |
| run on a single cpu as opposed to all hotplug capable cpus, and memory |
| hotplug test is run on 2% of hotplug capable memory instead of 10%. |
| |
| kselftest runs as a userspace process. Tests that can be written/run in |
| userspace may wish to use the `Test Harness`_. Tests that need to be |
| run in kernel space may wish to use a `Test Module`_. |
| |
| Running the selftests (hotplug tests are run in limited mode) |
| ============================================================= |
| |
| To build the tests:: |
| |
| $ make -C tools/testing/selftests |
| |
| To run the tests:: |
| |
| $ make -C tools/testing/selftests run_tests |
| |
| To build and run the tests with a single command, use:: |
| |
| $ make kselftest |
| |
| Note that some tests will require root privileges. |
| |
| Kselftest supports saving output files in a separate directory and then |
| running tests. To locate output files in a separate directory two syntaxes |
| are supported. In both cases the working directory must be the root of the |
| kernel src. This is applicable to "Running a subset of selftests" section |
| below. |
| |
| To build, save output files in a separate directory with O= :: |
| |
| $ make O=/tmp/kselftest kselftest |
| |
| To build, save output files in a separate directory with KBUILD_OUTPUT :: |
| |
| $ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest |
| |
| The O= assignment takes precedence over the KBUILD_OUTPUT environment |
| variable. |
| |
| The above commands by default run the tests and print full pass/fail report. |
| Kselftest supports "summary" option to make it easier to understand the test |
| results. Please find the detailed individual test results for each test in |
| /tmp/testname file(s) when summary option is specified. This is applicable |
| to "Running a subset of selftests" section below. |
| |
| To run kselftest with summary option enabled :: |
| |
| $ make summary=1 kselftest |
| |
| Running a subset of selftests |
| ============================= |
| |
| You can use the "TARGETS" variable on the make command line to specify |
| single test to run, or a list of tests to run. |
| |
| To run only tests targeted for a single subsystem:: |
| |
| $ make -C tools/testing/selftests TARGETS=ptrace run_tests |
| |
| You can specify multiple tests to build and run:: |
| |
| $ make TARGETS="size timers" kselftest |
| |
| To build, save output files in a separate directory with O= :: |
| |
| $ make O=/tmp/kselftest TARGETS="size timers" kselftest |
| |
| To build, save output files in a separate directory with KBUILD_OUTPUT :: |
| |
| $ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest |
| |
| Additionally you can use the "SKIP_TARGETS" variable on the make command |
| line to specify one or more targets to exclude from the TARGETS list. |
| |
| To run all tests but a single subsystem:: |
| |
| $ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests |
| |
| You can specify multiple tests to skip:: |
| |
| $ make SKIP_TARGETS="size timers" kselftest |
| |
| You can also specify a restricted list of tests to run together with a |
| dedicated skiplist:: |
| |
| $ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest |
| |
| See the top-level tools/testing/selftests/Makefile for the list of all |
| possible targets. |
| |
| Running the full range hotplug selftests |
| ======================================== |
| |
| To build the hotplug tests:: |
| |
| $ make -C tools/testing/selftests hotplug |
| |
| To run the hotplug tests:: |
| |
| $ make -C tools/testing/selftests run_hotplug |
| |
| Note that some tests will require root privileges. |
| |
| |
| Install selftests |
| ================= |
| |
| You can use the kselftest_install.sh tool to install selftests in the |
| default location, which is tools/testing/selftests/kselftest, or in a |
| user specified location. |
| |
| To install selftests in default location:: |
| |
| $ cd tools/testing/selftests |
| $ ./kselftest_install.sh |
| |
| To install selftests in a user specified location:: |
| |
| $ cd tools/testing/selftests |
| $ ./kselftest_install.sh install_dir |
| |
| Running installed selftests |
| =========================== |
| |
| Kselftest install as well as the Kselftest tarball provide a script |
| named "run_kselftest.sh" to run the tests. |
| |
| You can simply do the following to run the installed Kselftests. Please |
| note some tests will require root privileges:: |
| |
| $ cd kselftest |
| $ ./run_kselftest.sh |
| |
| Contributing new tests |
| ====================== |
| |
| In general, the rules for selftests are |
| |
| * Do as much as you can if you're not root; |
| |
| * Don't take too long; |
| |
| * Don't break the build on any architecture, and |
| |
| * Don't cause the top-level "make run_tests" to fail if your feature is |
| unconfigured. |
| |
| Contributing new tests (details) |
| ================================ |
| |
| * Use TEST_GEN_XXX if such binaries or files are generated during |
| compiling. |
| |
| TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by |
| default. |
| |
| TEST_CUSTOM_PROGS should be used by tests that require custom build |
| rules and prevent common build rule use. |
| |
| TEST_PROGS are for test shell scripts. Please ensure shell script has |
| its exec bit set. Otherwise, lib.mk run_tests will generate a warning. |
| |
| TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests. |
| |
| TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the |
| executable which is not tested by default. |
| TEST_FILES, TEST_GEN_FILES mean it is the file which is used by |
| test. |
| |
| * First use the headers inside the kernel source and/or git repo, and then the |
| system headers. Headers for the kernel release as opposed to headers |
| installed by the distro on the system should be the primary focus to be able |
| to find regressions. |
| |
| * If a test needs specific kernel config options enabled, add a config file in |
| the test directory to enable them. |
| |
| e.g: tools/testing/selftests/android/config |
| |
| Test Module |
| =========== |
| |
| Kselftest tests the kernel from userspace. Sometimes things need |
| testing from within the kernel, one method of doing this is to create a |
| test module. We can tie the module into the kselftest framework by |
| using a shell script test runner. ``kselftest/module.sh`` is designed |
| to facilitate this process. There is also a header file provided to |
| assist writing kernel modules that are for use with kselftest: |
| |
| - ``tools/testing/kselftest/kselftest_module.h`` |
| - ``tools/testing/kselftest/kselftest/module.sh`` |
| |
| How to use |
| ---------- |
| |
| Here we show the typical steps to create a test module and tie it into |
| kselftest. We use kselftests for lib/ as an example. |
| |
| 1. Create the test module |
| |
| 2. Create the test script that will run (load/unload) the module |
| e.g. ``tools/testing/selftests/lib/printf.sh`` |
| |
| 3. Add line to config file e.g. ``tools/testing/selftests/lib/config`` |
| |
| 4. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile`` |
| |
| 5. Verify it works: |
| |
| .. code-block:: sh |
| |
| # Assumes you have booted a fresh build of this kernel tree |
| cd /path/to/linux/tree |
| make kselftest-merge |
| make modules |
| sudo make modules_install |
| make TARGETS=lib kselftest |
| |
| Example Module |
| -------------- |
| |
| A bare bones test module might look like this: |
| |
| .. code-block:: c |
| |
| // SPDX-License-Identifier: GPL-2.0+ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include "../tools/testing/selftests/kselftest/module.h" |
| |
| KSTM_MODULE_GLOBALS(); |
| |
| /* |
| * Kernel module for testing the foobinator |
| */ |
| |
| static int __init test_function() |
| { |
| ... |
| } |
| |
| static void __init selftest(void) |
| { |
| KSTM_CHECK_ZERO(do_test_case("", 0)); |
| } |
| |
| KSTM_MODULE_LOADERS(test_foo); |
| MODULE_AUTHOR("John Developer <jd@fooman.org>"); |
| MODULE_LICENSE("GPL"); |
| |
| Example test script |
| ------------------- |
| |
| .. code-block:: sh |
| |
| #!/bin/bash |
| # SPDX-License-Identifier: GPL-2.0+ |
| $(dirname $0)/../kselftest/module.sh "foo" test_foo |
| |
| |
| Test Harness |
| ============ |
| |
| The kselftest_harness.h file contains useful helpers to build tests. The |
| test harness is for userspace testing, for kernel space testing see `Test |
| Module`_ above. |
| |
| The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as |
| example. |
| |
| Example |
| ------- |
| |
| .. kernel-doc:: tools/testing/selftests/kselftest_harness.h |
| :doc: example |
| |
| |
| Helpers |
| ------- |
| |
| .. kernel-doc:: tools/testing/selftests/kselftest_harness.h |
| :functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP |
| FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT |
| FIXTURE_VARIANT_ADD |
| |
| Operators |
| --------- |
| |
| .. kernel-doc:: tools/testing/selftests/kselftest_harness.h |
| :doc: operators |
| |
| .. kernel-doc:: tools/testing/selftests/kselftest_harness.h |
| :functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE |
| ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE |
| ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT |
| EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE |
| EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE |