lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 8 May 2019 17:43:35 -0700
From:   Frank Rowand <>
To:     Greg KH <>
Cc:     Brendan Higgins <>,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Subject: Re: [PATCH v2 00/17] kunit: introduce KUnit, the Linux kernel unit
 testing framework

On 5/7/19 1:01 AM, Greg KH wrote:
> On Mon, May 06, 2019 at 08:14:12PM -0700, Frank Rowand wrote:
>> On 5/1/19 4:01 PM, Brendan Higgins wrote:
>>> ## TLDR
>>> I rebased the last patchset on 5.1-rc7 in hopes that we can get this in
>>> 5.2.
>>> Shuah, I think you, Greg KH, and myself talked off thread, and we agreed
>>> we would merge through your tree when the time came? Am I remembering
>>> correctly?
>>> ## Background
>>> This patch set proposes KUnit, a lightweight unit testing and mocking
>>> framework for the Linux kernel.
>>> Unlike Autotest and kselftest, KUnit is a true unit testing framework;
>>> it does not require installing the kernel on a test machine or in a VM
>>> and does not require tests to be written in userspace running on a host
>>> kernel. Additionally, KUnit is fast: From invocation to completion KUnit
>>> can run several dozen tests in under a second. Currently, the entire
>>> KUnit test suite for KUnit runs in under a second from the initial
>>> invocation (build time excluded).
>>> KUnit is heavily inspired by JUnit, Python's unittest.mock, and
>>> Googletest/Googlemock for C++. KUnit provides facilities for defining
>>> unit test cases, grouping related test cases into test suites, providing
>>> common infrastructure for running tests, mocking, spying, and much more.
>> As a result of the emails replying to this patch thread, I am now
>> starting to look at kselftest.  My level of understanding is based
>> on some slide presentations, an LWN article,
>> and a _tiny_ bit of looking at kselftest code.
>> tl;dr; I don't really understand kselftest yet.
>> (1) why KUnit exists
>>> ## What's so special about unit testing?
>>> A unit test is supposed to test a single unit of code in isolation,
>>> hence the name. There should be no dependencies outside the control of
>>> the test; this means no external dependencies, which makes tests orders
>>> of magnitudes faster. Likewise, since there are no external dependencies,
>>> there are no hoops to jump through to run the tests. Additionally, this
>>> makes unit tests deterministic: a failing unit test always indicates a
>>> problem. Finally, because unit tests necessarily have finer granularity,
>>> they are able to test all code paths easily solving the classic problem
>>> of difficulty in exercising error handling code.
>> (2) KUnit is not meant to replace kselftest
>>> ## Is KUnit trying to replace other testing frameworks for the kernel?
>>> No. Most existing tests for the Linux kernel are end-to-end tests, which
>>> have their place. A well tested system has lots of unit tests, a
>>> reasonable number of integration tests, and some end-to-end tests. KUnit
>>> is just trying to address the unit test space which is currently not
>>> being addressed.
>> My understanding is that the intent of KUnit is to avoid booting a kernel on
>> real hardware or in a virtual machine.  That seems to be a matter of semantics
>> to me because isn't invoking a UML Linux just running the Linux kernel in
>> a different form of virtualization?
>> So I do not understand why KUnit is an improvement over kselftest.
>> It seems to me that KUnit is just another piece of infrastructure that I
>> am going to have to be familiar with as a kernel developer.  More overhead,
>> more information to stuff into my tiny little brain.
>> I would guess that some developers will focus on just one of the two test
>> environments (and some will focus on both), splitting the development
>> resources instead of pooling them on a common infrastructure.
>> What am I missing?
> kselftest provides no in-kernel framework for testing kernel code
> specifically.  That should be what kunit provides, an "easy" way to
> write in-kernel tests for things.

kselftest provides a mechanism for in-kernel tests via modules.  For
example, see:

  tools/testing/selftests/vm/run_vmtests invokes:
      loads module:
        (which is built from lib/test_vmalloc.c if CONFIG_TEST_VMALLOC)

A very quick and dirty search (likely to miss some tests) finds modules:



> Brendan, did I get it right?
> thanks,
> greg k-h
> .

Powered by blists - more mailing lists