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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-26 23:22:43 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-26 23:22:43 +0300 |
commit | 2f9ef0559efbee18a10a3ca26eefe57f69918693 (patch) | |
tree | 3c30d105078c06b51de764e703a59f6ae1c2bb5a /Documentation/dev-tools/testing-overview.rst | |
parent | 0c855563182001c829065faa17f8e29e9ceffe13 (diff) | |
parent | 441ca977a84dadac6173db7c07c25db110b76c1e (diff) | |
download | linux-2f9ef0559efbee18a10a3ca26eefe57f69918693.tar.xz |
Merge tag 'docs-5.13' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"It's been a relatively busy cycle in docsland, though more than
usually well contained to Documentation/ itself. Highlights include:
- The Chinese translators have been busy and show no signs of
stopping anytime soon. Italian has also caught up.
- Aditya Srivastava has been working on improvements to the
kernel-doc script.
- Thorsten continues his work on reporting-issues.rst and related
documentation around regression reporting.
- Lots of documentation updates, typo fixes, etc. as usual"
* tag 'docs-5.13' of git://git.lwn.net/linux: (139 commits)
docs/zh_CN: add openrisc translation to zh_CN index
docs/zh_CN: add openrisc index.rst translation
docs/zh_CN: add openrisc todo.rst translation
docs/zh_CN: add openrisc openrisc_port.rst translation
docs/zh_CN: add core api translation to zh_CN index
docs/zh_CN: add core-api index.rst translation
docs/zh_CN: add core-api irq index.rst translation
docs/zh_CN: add core-api irq irqflags-tracing.rst translation
docs/zh_CN: add core-api irq irq-domain.rst translation
docs/zh_CN: add core-api irq irq-affinity.rst translation
docs/zh_CN: add core-api irq concepts.rst translation
docs: sphinx-pre-install: don't barf on beta Sphinx releases
scripts: kernel-doc: improve parsing for kernel-doc comments syntax
docs/zh_CN: two minor fixes in zh_CN/doc-guide/
Documentation: dev-tools: Add Testing Overview
docs/zh_CN: add translations in zh_CN/dev-tools/gcov
docs: reporting-issues: make people CC the regressions list
MAINTAINERS: add regressions mailing list
doc:it_IT: align Italian documentation
docs/zh_CN: sync reporting-issues.rst
...
Diffstat (limited to 'Documentation/dev-tools/testing-overview.rst')
-rw-r--r-- | Documentation/dev-tools/testing-overview.rst | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/Documentation/dev-tools/testing-overview.rst b/Documentation/dev-tools/testing-overview.rst new file mode 100644 index 000000000000..b5b46709969c --- /dev/null +++ b/Documentation/dev-tools/testing-overview.rst @@ -0,0 +1,117 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +Kernel Testing Guide +==================== + + +There are a number of different tools for testing the Linux kernel, so knowing +when to use each of them can be a challenge. This document provides a rough +overview of their differences, and how they fit together. + + +Writing and Running Tests +========================= + +The bulk of kernel tests are written using either the kselftest or KUnit +frameworks. These both provide infrastructure to help make running tests and +groups of tests easier, as well as providing helpers to aid in writing new +tests. + +If you're looking to verify the behaviour of the Kernel — particularly specific +parts of the kernel — then you'll want to use KUnit or kselftest. + + +The Difference Between KUnit and kselftest +------------------------------------------ + +KUnit (Documentation/dev-tools/kunit/index.rst) is an entirely in-kernel system +for "white box" testing: because test code is part of the kernel, it can access +internal structures and functions which aren't exposed to userspace. + +KUnit tests therefore are best written against small, self-contained parts +of the kernel, which can be tested in isolation. This aligns well with the +concept of 'unit' testing. + +For example, a KUnit test might test an individual kernel function (or even a +single codepath through a function, such as an error handling case), rather +than a feature as a whole. + +This also makes KUnit tests very fast to build and run, allowing them to be +run frequently as part of the development process. + +There is a KUnit test style guide which may give further pointers in +Documentation/dev-tools/kunit/style.rst + + +kselftest (Documentation/dev-tools/kselftest.rst), on the other hand, is +largely implemented in userspace, and tests are normal userspace scripts or +programs. + +This makes it easier to write more complicated tests, or tests which need to +manipulate the overall system state more (e.g., spawning processes, etc.). +However, it's not possible to call kernel functions directly from kselftest. +This means that only kernel functionality which is exposed to userspace somehow +(e.g. by a syscall, device, filesystem, etc.) can be tested with kselftest. To +work around this, some tests include a companion kernel module which exposes +more information or functionality. If a test runs mostly or entirely within the +kernel, however, KUnit may be the more appropriate tool. + +kselftest is therefore suited well to tests of whole features, as these will +expose an interface to userspace, which can be tested, but not implementation +details. This aligns well with 'system' or 'end-to-end' testing. + +For example, all new system calls should be accompanied by kselftest tests. + +Code Coverage Tools +=================== + +The Linux Kernel supports two different code coverage measurement tools. These +can be used to verify that a test is executing particular functions or lines +of code. This is useful for determining how much of the kernel is being tested, +and for finding corner-cases which are not covered by the appropriate test. + +:doc:`gcov` is GCC's coverage testing tool, which can be used with the kernel +to get global or per-module coverage. Unlike KCOV, it does not record per-task +coverage. Coverage data can be read from debugfs, and interpreted using the +usual gcov tooling. + +:doc:`kcov` is a feature which can be built in to the kernel to allow +capturing coverage on a per-task level. It's therefore useful for fuzzing and +other situations where information about code executed during, for example, a +single syscall is useful. + + +Dynamic Analysis Tools +====================== + +The kernel also supports a number of dynamic analysis tools, which attempt to +detect classes of issues when they occur in a running kernel. These typically +each look for a different class of bugs, such as invalid memory accesses, +concurrency issues such as data races, or other undefined behaviour like +integer overflows. + +Some of these tools are listed below: + +* kmemleak detects possible memory leaks. See + Documentation/dev-tools/kmemleak.rst +* KASAN detects invalid memory accesses such as out-of-bounds and + use-after-free errors. See Documentation/dev-tools/kasan.rst +* UBSAN detects behaviour that is undefined by the C standard, like integer + overflows. See Documentation/dev-tools/ubsan.rst +* KCSAN detects data races. See Documentation/dev-tools/kcsan.rst +* KFENCE is a low-overhead detector of memory issues, which is much faster than + KASAN and can be used in production. See Documentation/dev-tools/kfence.rst +* lockdep is a locking correctness validator. See + Documentation/locking/lockdep-design.rst +* There are several other pieces of debug instrumentation in the kernel, many + of which can be found in lib/Kconfig.debug + +These tools tend to test the kernel as a whole, and do not "pass" like +kselftest or KUnit tests. They can be combined with KUnit or kselftest by +running tests on a kernel with these tools enabled: you can then be sure +that none of these errors are occurring during the test. + +Some of these tools integrate with KUnit or kselftest and will +automatically fail tests if an issue is detected. + |