linux-kernel - Re: [PATCH v3 2/3] livepatch: Move tests from lib/livepatch to selftests/livepatch

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Date:   Mon, 11 Dec 2023 14:56:15 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     mpdesouza@...e.com, Joe Lawrence <joe.lawrence@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Cc:     Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>, Petr Mladek <pmladek@...e.com>,
        linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        live-patching@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3 2/3] livepatch: Move tests from lib/livepatch to
 selftests/livepatch

On 12/7/23 12:19, mpdesouza@...e.com wrote:
> On Thu, 2023-12-07 at 10:20 -0500, Joe Lawrence wrote:
>> On 12/6/23 10:05, Miroslav Benes wrote:
>>> On Fri, 1 Dec 2023, Joe Lawrence wrote:
>>>
>>>> On Tue, Oct 31, 2023 at 06:10:52PM -0300, Marcos Paulo de Souza
>>>> wrote:
>>>>> The modules are being moved from lib/livepatch to
>>>>> tools/testing/selftests/livepatch/test_modules.
>>>>>
>>>>> This code moving will allow writing more complex tests, like
>>>>> for example an
>>>>> userspace C code that will call a livepatched kernel function.
>>>>>
>>>>> The modules are now built as out-of-tree
>>>>> modules, but being part of the kernel source means they will be
>>>>> maintained.
>>>>>
>>>>> Another advantage of the code moving is to be able to easily
>>>>> change,
>>>>> debug and rebuild the tests by running make on the
>>>>> selftests/livepatch directory,
>>>>> which is not currently possible since the modules on
>>>>> lib/livepatch are
>>>>> build and installed using the "modules" target.
>>>>>
>>>>> The current approach also keeps the ability to execute the
>>>>> tests manually by
>>>>> executing the scripts inside selftests/livepatch directory, as
>>>>> it's currently
>>>>> supported. If the modules are modified, they needed to be
>>>>> rebuilt before running
>>>>> the scripts though.
>>>>>
>>>>> The modules are built before running the selftests when using
>>>>> the
>>>>> kselftest invocations:
>>>>>
>>>>> 	make kselftest TARGETS=livepatch
>>>>> or
>>>>> 	make -C tools/testing/selftests/livepatch run_tests
>>>>>
>>>>
>>>> Quick question:
>>>>
>>>> - We have been building with CONFIG_LIVEPATCH_TEST=m to generate
>>>> the
>>>>    test modules at kernel build time
>>>>
>>>> - Our packaging filters out the selftest scripts and supporting
>>>> modules
>>>>    from the general kernel RPM package into their subpackages
>>>>
>>>> - Tests are run as part of CKI or other manual tests by
>>>> installing the
>>>>    pre-built packages from the previous step
>>>>
>>>>
>>>> After this patch, we would need to add something like the
>>>> following to
>>>> our kernel build, before packaging:
>>>>
>>>>    $ make KDIR=$(pwd) -C tools/testing/selftests/livepatch/
>>>>           ^^^^
>>>>
>>>> If this is the correct way to build the test modules for *this*
>>>> tree and
>>>> /lib/modules/$(shell uname -r)/build... it might be useful to
>>>> document
>>>> in the commit message as an alternative use case.
> 
> That's right:
> 
> $ make -C tools/testing/selftests/livepatch/
> 
> is indeed the way to build the tests without running them. KDIR will be
> set to  /lib/modules/$(shell uname -r)/build is empty.
> 
> Yes, I can definitely add documentation about it inside the
> tools/testing/selftests/livepatch/README.
> 

How does the default kselftest run work with these changes?

make ksefltest - does this still work as it did before this change?

thanks,
-- Shuah