233 lines
8.8 KiB
ReStructuredText
233 lines
8.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=================
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kunit_tool How-To
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=================
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What is kunit_tool?
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===================
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kunit_tool is a script (``tools/testing/kunit/kunit.py``) that aids in building
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the Linux kernel as UML (`User Mode Linux
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<http://user-mode-linux.sourceforge.net/>`_), running KUnit tests, parsing
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the test results and displaying them in a user friendly manner.
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kunit_tool addresses the problem of being able to run tests without needing a
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virtual machine or actual hardware with User Mode Linux. User Mode Linux is a
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Linux architecture, like ARM or x86; however, unlike other architectures it
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compiles the kernel as a standalone Linux executable that can be run like any
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other program directly inside of a host operating system. To be clear, it does
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not require any virtualization support: it is just a regular program.
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What is a .kunitconfig?
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=======================
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It's just a defconfig that kunit_tool looks for in the build directory
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(``.kunit`` by default). kunit_tool uses it to generate a .config as you might
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expect. In addition, it verifies that the generated .config contains the CONFIG
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options in the .kunitconfig; the reason it does this is so that it is easy to
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be sure that a CONFIG that enables a test actually ends up in the .config.
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It's also possible to pass a separate .kunitconfig fragment to kunit_tool,
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which is useful if you have several different groups of tests you wish
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to run independently, or if you want to use pre-defined test configs for
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certain subsystems.
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Getting Started with kunit_tool
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===============================
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If a kunitconfig is present at the root directory, all you have to do is:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run
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However, you most likely want to use it with the following options:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run --timeout=30 --jobs=`nproc --all`
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- ``--timeout`` sets a maximum amount of time to allow tests to run.
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- ``--jobs`` sets the number of threads to use to build the kernel.
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.. note::
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This command will work even without a .kunitconfig file: if no
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.kunitconfig is present, a default one will be used instead.
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If you wish to use a different .kunitconfig file (such as one provided for
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testing a particular subsystem), you can pass it as an option.
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run --kunitconfig=fs/ext4/.kunitconfig
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For a list of all the flags supported by kunit_tool, you can run:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run --help
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Configuring, Building, and Running Tests
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========================================
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It's also possible to run just parts of the KUnit build process independently,
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which is useful if you want to make manual changes to part of the process.
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A .config can be generated from a .kunitconfig by using the ``config`` argument
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when running kunit_tool:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py config
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Similarly, if you just want to build a KUnit kernel from the current .config,
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you can use the ``build`` argument:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py build
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And, if you already have a built UML kernel with built-in KUnit tests, you can
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run the kernel and display the test results with the ``exec`` argument:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py exec
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The ``run`` command which is discussed above is equivalent to running all three
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of these in sequence.
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All of these commands accept a number of optional command-line arguments. The
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``--help`` flag will give a complete list of these, or keep reading this page
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for a guide to some of the more useful ones.
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Parsing Test Results
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====================
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KUnit tests output their results in TAP (Test Anything Protocol) format.
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kunit_tool will, when running tests, parse this output and print a summary
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which is much more pleasant to read. If you wish to look at the raw test
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results in TAP format, you can pass the ``--raw_output`` argument.
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run --raw_output
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The raw output from test runs may contain other, non-KUnit kernel log
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lines. You can see just KUnit output with ``--raw_output=kunit``:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run --raw_output=kunit
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If you have KUnit results in their raw TAP format, you can parse them and print
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the human-readable summary with the ``parse`` command for kunit_tool. This
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accepts a filename for an argument, or will read from standard input.
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.. code-block:: bash
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# Reading from a file
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./tools/testing/kunit/kunit.py parse /var/log/dmesg
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# Reading from stdin
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dmesg | ./tools/testing/kunit/kunit.py parse
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This is very useful if you wish to run tests in a configuration not supported
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by kunit_tool (such as on real hardware, or an unsupported architecture).
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Filtering Tests
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===============
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It's possible to run only a subset of the tests built into a kernel by passing
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a filter to the ``exec`` or ``run`` commands. For example, if you only wanted
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to run KUnit resource tests, you could use:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run 'kunit-resource*'
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This uses the standard glob format for wildcards.
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Running Tests on QEMU
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=====================
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kunit_tool supports running tests on QEMU as well as via UML (as mentioned
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elsewhere). The default way of running tests on QEMU requires two flags:
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``--arch``
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Selects a collection of configs (Kconfig as well as QEMU configs
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options, etc) that allow KUnit tests to be run on the specified
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architecture in a minimal way; this is usually not much slower than
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using UML. The architecture argument is the same as the name of the
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option passed to the ``ARCH`` variable used by Kbuild. Not all
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architectures are currently supported by this flag, but can be handled
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by the ``--qemu_config`` discussed later. If ``um`` is passed (or this
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this flag is ignored) the tests will run via UML. Non-UML architectures,
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e.g. i386, x86_64, arm, um, etc. Non-UML run on QEMU.
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``--cross_compile``
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Specifies the use of a toolchain by Kbuild. The argument passed here is
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the same passed to the ``CROSS_COMPILE`` variable used by Kbuild. As a
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reminder this will be the prefix for the toolchain binaries such as gcc
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for example ``sparc64-linux-gnu-`` if you have the sparc toolchain
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installed on your system, or
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``$HOME/toolchains/microblaze/gcc-9.2.0-nolibc/microblaze-linux/bin/microblaze-linux-``
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if you have downloaded the microblaze toolchain from the 0-day website
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to a directory in your home directory called ``toolchains``.
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In many cases it is likely that you may want to run an architecture which is
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not supported by the ``--arch`` flag, or you may want to just run KUnit tests
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on QEMU using a non-default configuration. For this use case, you can write
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your own QemuConfig. These QemuConfigs are written in Python. They must have an
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import line ``from ..qemu_config import QemuArchParams`` at the top of the file
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and the file must contain a variable called ``QEMU_ARCH`` that has an instance
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of ``QemuArchParams`` assigned to it. An example can be seen in
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``tools/testing/kunit/qemu_configs/x86_64.py``.
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Once you have a QemuConfig you can pass it into kunit_tool using the
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``--qemu_config`` flag; when used this flag replaces the ``--arch`` flag. If we
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were to do this with the ``x86_64.py`` example from above, the invocation would
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look something like this:
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.. code-block:: bash
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./tools/testing/kunit/kunit.py run \
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--timeout=60 \
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--jobs=12 \
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--qemu_config=./tools/testing/kunit/qemu_configs/x86_64.py
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Other Useful Options
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====================
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kunit_tool has a number of other command-line arguments which can be useful
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when adapting it to fit your environment or needs.
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Some of the more useful ones are:
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``--help``
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Lists all of the available options. Note that different commands
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(``config``, ``build``, ``run``, etc) will have different supported
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options. Place ``--help`` before the command to list common options,
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and after the command for options specific to that command.
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``--build_dir``
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Specifies the build directory that kunit_tool will use. This is where
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the .kunitconfig file is located, as well as where the .config and
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compiled kernel will be placed. Defaults to ``.kunit``.
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``--make_options``
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Specifies additional options to pass to ``make`` when compiling a
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kernel (with the ``build`` or ``run`` commands). For example, to enable
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compiler warnings, you can pass ``--make_options W=1``.
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``--alltests``
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Builds a UML kernel with all config options enabled using ``make
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allyesconfig``. This allows you to run as many tests as is possible,
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but is very slow and prone to breakage as new options are added or
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modified. In most cases, enabling all tests which have satisfied
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dependencies by adding ``CONFIG_KUNIT_ALL_TESTS=1`` to your
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.kunitconfig is preferable.
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There are several other options (and new ones are often added), so do check
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``--help`` if you're looking for something not mentioned here.
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