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.
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 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%.
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.
Build and run from user specific object directory (make O=dir):
$ make O=/tmp/kselftest kselftest
Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=):
$ make KBUILD_OUTPUT=/tmp/kselftest kselftest
The above commands run the tests and print pass/fail summary to make it easier to understand the test results. Please find the detailed individual test results for each test in /tmp/testname file(s).
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
Build and run from user specific object directory (make O=dir):
$ make O=/tmp/kselftest TARGETS="size timers" kselftest
Build and run KBUILD_OUTPUT directory (make KBUILD_OUTPUT=):
$ make KBUILD_OUTPUT=/tmp/kselftest TARGETS="size timers" kselftest
The above commands run the tests and print pass/fail summary to make it easier to understand the test results. Please find the detailed individual test results for each test in /tmp/testname file(s).
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 kselftest_install.sh tool installs selftests in default location which is tools/testing/selftests/kselftest or 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 rule 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/ion/config
Test Harness
The kselftest_harness.h file contains useful helpers to build tests. The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as example.