351 lines
11 KiB
ReStructuredText
351 lines
11 KiB
ReStructuredText
======================
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Linux Kernel Selftests
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======================
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The kernel contains a set of "self tests" under the tools/testing/selftests/
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directory. These are intended to be small tests to exercise individual code
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paths in the kernel. Tests are intended to be run after building, installing
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and booting a kernel.
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You can find additional information on Kselftest framework, how to
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write new tests using the framework on Kselftest wiki:
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https://kselftest.wiki.kernel.org/
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On some systems, hot-plug tests could hang forever waiting for cpu and
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memory to be ready to be offlined. A special hot-plug target is created
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to run the full range of hot-plug tests. In default mode, hot-plug tests run
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in safe mode with a limited scope. In limited mode, cpu-hotplug test is
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run on a single cpu as opposed to all hotplug capable cpus, and memory
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hotplug test is run on 2% of hotplug capable memory instead of 10%.
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kselftest runs as a userspace process. Tests that can be written/run in
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userspace may wish to use the `Test Harness`_. Tests that need to be
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run in kernel space may wish to use a `Test Module`_.
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Running the selftests (hotplug tests are run in limited mode)
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=============================================================
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To build the tests::
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$ make -C tools/testing/selftests
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To run the tests::
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$ make -C tools/testing/selftests run_tests
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To build and run the tests with a single command, use::
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$ make kselftest
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Note that some tests will require root privileges.
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Kselftest supports saving output files in a separate directory and then
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running tests. To locate output files in a separate directory two syntaxes
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are supported. In both cases the working directory must be the root of the
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kernel src. This is applicable to "Running a subset of selftests" section
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below.
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To build, save output files in a separate directory with O= ::
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$ make O=/tmp/kselftest kselftest
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To build, save output files in a separate directory with KBUILD_OUTPUT ::
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$ export KBUILD_OUTPUT=/tmp/kselftest; make kselftest
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The O= assignment takes precedence over the KBUILD_OUTPUT environment
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variable.
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The above commands by default run the tests and print full pass/fail report.
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Kselftest supports "summary" option to make it easier to understand the test
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results. Please find the detailed individual test results for each test in
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/tmp/testname file(s) when summary option is specified. This is applicable
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to "Running a subset of selftests" section below.
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To run kselftest with summary option enabled ::
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$ make summary=1 kselftest
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Running a subset of selftests
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=============================
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You can use the "TARGETS" variable on the make command line to specify
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single test to run, or a list of tests to run.
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To run only tests targeted for a single subsystem::
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$ make -C tools/testing/selftests TARGETS=ptrace run_tests
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You can specify multiple tests to build and run::
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$ make TARGETS="size timers" kselftest
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To build, save output files in a separate directory with O= ::
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$ make O=/tmp/kselftest TARGETS="size timers" kselftest
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To build, save output files in a separate directory with KBUILD_OUTPUT ::
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$ export KBUILD_OUTPUT=/tmp/kselftest; make TARGETS="size timers" kselftest
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Additionally you can use the "SKIP_TARGETS" variable on the make command
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line to specify one or more targets to exclude from the TARGETS list.
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To run all tests but a single subsystem::
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$ make -C tools/testing/selftests SKIP_TARGETS=ptrace run_tests
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You can specify multiple tests to skip::
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$ make SKIP_TARGETS="size timers" kselftest
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You can also specify a restricted list of tests to run together with a
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dedicated skiplist::
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$ make TARGETS="bpf breakpoints size timers" SKIP_TARGETS=bpf kselftest
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See the top-level tools/testing/selftests/Makefile for the list of all
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possible targets.
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Running the full range hotplug selftests
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========================================
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To build the hotplug tests::
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$ make -C tools/testing/selftests hotplug
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To run the hotplug tests::
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$ make -C tools/testing/selftests run_hotplug
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Note that some tests will require root privileges.
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Install selftests
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=================
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You can use the "install" target of "make" (which calls the `kselftest_install.sh`
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tool) to install selftests in the default location (`tools/testing/selftests/kselftest_install`),
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or in a user specified location via the `INSTALL_PATH` "make" variable.
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To install selftests in default location::
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$ make -C tools/testing/selftests install
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To install selftests in a user specified location::
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$ make -C tools/testing/selftests install INSTALL_PATH=/some/other/path
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Running installed selftests
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===========================
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Found in the install directory, as well as in the Kselftest tarball,
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is a script named `run_kselftest.sh` to run the tests.
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You can simply do the following to run the installed Kselftests. Please
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note some tests will require root privileges::
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$ cd kselftest_install
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$ ./run_kselftest.sh
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To see the list of available tests, the `-l` option can be used::
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$ ./run_kselftest.sh -l
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The `-c` option can be used to run all the tests from a test collection, or
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the `-t` option for specific single tests. Either can be used multiple times::
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$ ./run_kselftest.sh -c bpf -c seccomp -t timers:posix_timers -t timer:nanosleep
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For other features see the script usage output, seen with the `-h` option.
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Packaging selftests
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===================
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In some cases packaging is desired, such as when tests need to run on a
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different system. To package selftests, run::
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$ make -C tools/testing/selftests gen_tar
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This generates a tarball in the `INSTALL_PATH/kselftest-packages` directory. By
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default, `.gz` format is used. The tar compression format can be overridden by
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specifying a `FORMAT` make variable. Any value recognized by `tar's auto-compress`_
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option is supported, such as::
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$ make -C tools/testing/selftests gen_tar FORMAT=.xz
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`make gen_tar` invokes `make install` so you can use it to package a subset of
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tests by using variables specified in `Running a subset of selftests`_
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section::
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$ make -C tools/testing/selftests gen_tar TARGETS="bpf" FORMAT=.xz
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.. _tar's auto-compress: https://www.gnu.org/software/tar/manual/html_node/gzip.html#auto_002dcompress
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Contributing new tests
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======================
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In general, the rules for selftests are
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* Do as much as you can if you're not root;
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* Don't take too long;
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* Don't break the build on any architecture, and
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* Don't cause the top-level "make run_tests" to fail if your feature is
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unconfigured.
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Contributing new tests (details)
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================================
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* Use TEST_GEN_XXX if such binaries or files are generated during
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compiling.
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TEST_PROGS, TEST_GEN_PROGS mean it is the executable tested by
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default.
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TEST_CUSTOM_PROGS should be used by tests that require custom build
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rules and prevent common build rule use.
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TEST_PROGS are for test shell scripts. Please ensure shell script has
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its exec bit set. Otherwise, lib.mk run_tests will generate a warning.
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TEST_CUSTOM_PROGS and TEST_PROGS will be run by common run_tests.
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TEST_PROGS_EXTENDED, TEST_GEN_PROGS_EXTENDED mean it is the
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executable which is not tested by default.
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TEST_FILES, TEST_GEN_FILES mean it is the file which is used by
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test.
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* First use the headers inside the kernel source and/or git repo, and then the
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system headers. Headers for the kernel release as opposed to headers
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installed by the distro on the system should be the primary focus to be able
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to find regressions.
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* If a test needs specific kernel config options enabled, add a config file in
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the test directory to enable them.
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e.g: tools/testing/selftests/android/config
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Test Module
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===========
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Kselftest tests the kernel from userspace. Sometimes things need
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testing from within the kernel, one method of doing this is to create a
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test module. We can tie the module into the kselftest framework by
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using a shell script test runner. ``kselftest/module.sh`` is designed
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to facilitate this process. There is also a header file provided to
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assist writing kernel modules that are for use with kselftest:
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- ``tools/testing/selftests/kselftest_module.h``
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- ``tools/testing/selftests/kselftest/module.sh``
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How to use
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----------
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Here we show the typical steps to create a test module and tie it into
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kselftest. We use kselftests for lib/ as an example.
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1. Create the test module
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2. Create the test script that will run (load/unload) the module
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e.g. ``tools/testing/selftests/lib/printf.sh``
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3. Add line to config file e.g. ``tools/testing/selftests/lib/config``
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4. Add test script to makefile e.g. ``tools/testing/selftests/lib/Makefile``
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5. Verify it works:
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.. code-block:: sh
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# Assumes you have booted a fresh build of this kernel tree
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cd /path/to/linux/tree
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make kselftest-merge
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make modules
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sudo make modules_install
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make TARGETS=lib kselftest
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Example Module
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--------------
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A bare bones test module might look like this:
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.. code-block:: c
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// SPDX-License-Identifier: GPL-2.0+
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include "../tools/testing/selftests/kselftest/module.h"
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KSTM_MODULE_GLOBALS();
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/*
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* Kernel module for testing the foobinator
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*/
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static int __init test_function()
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{
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...
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}
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static void __init selftest(void)
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{
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KSTM_CHECK_ZERO(do_test_case("", 0));
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}
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KSTM_MODULE_LOADERS(test_foo);
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MODULE_AUTHOR("John Developer <jd@fooman.org>");
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MODULE_LICENSE("GPL");
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Example test script
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-------------------
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.. code-block:: sh
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#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0+
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$(dirname $0)/../kselftest/module.sh "foo" test_foo
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Test Harness
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============
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The kselftest_harness.h file contains useful helpers to build tests. The
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test harness is for userspace testing, for kernel space testing see `Test
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Module`_ above.
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The tests from tools/testing/selftests/seccomp/seccomp_bpf.c can be used as
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example.
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Example
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-------
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.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
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:doc: example
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Helpers
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-------
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.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
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:functions: TH_LOG TEST TEST_SIGNAL FIXTURE FIXTURE_DATA FIXTURE_SETUP
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FIXTURE_TEARDOWN TEST_F TEST_HARNESS_MAIN FIXTURE_VARIANT
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FIXTURE_VARIANT_ADD
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Operators
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---------
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.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
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:doc: operators
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.. kernel-doc:: tools/testing/selftests/kselftest_harness.h
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:functions: ASSERT_EQ ASSERT_NE ASSERT_LT ASSERT_LE ASSERT_GT ASSERT_GE
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ASSERT_NULL ASSERT_TRUE ASSERT_NULL ASSERT_TRUE ASSERT_FALSE
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ASSERT_STREQ ASSERT_STRNE EXPECT_EQ EXPECT_NE EXPECT_LT
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EXPECT_LE EXPECT_GT EXPECT_GE EXPECT_NULL EXPECT_TRUE
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EXPECT_FALSE EXPECT_STREQ EXPECT_STRNE
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