Re: Converting kselftest test modules to kunit

[John Hubbard <jhubbard@nvidia.com>]

On 7/16/24 10:59 AM, Kees Cook wrote:
> On Tue, Jul 16, 2024 at 01:11:14PM +0500, Muhammad Usama Anjum wrote:
>> On 7/15/24 9:40 PM, Kees Cook wrote:
>>> On Mon, Jul 15, 2024 at 03:09:24PM +0500, Muhammad Usama Anjum wrote:
>>>> Hi Kees and All,
>>>>
>>>> There are several tests in kselftest subsystem which load modules to tests
>>>> the internals of the kernel. Most of these test modules are just loaded by
>>>> the kselftest, their status isn't read and reported to the user logs. Hence
>>>> they don't provide benefit of executing those tests.
>>>>
>>>> I've found patches from Kees where he has been converting such kselftests
>>>> to kunit tests [1]. The probable motivation is to move tests output of
>>>> kselftest subsystem which only triggers tests without correctly reporting
>>>> the results. On the other hand, kunit is there to test the kernel's
>>>> internal functions which can't be done by userspace.
>>>>
>>>> Kselftest:	Test user facing APIs from userspace
>>>> Kunit:		Test kernel's internal functions from kernelspace
>>>
>>> I would say this is a reasonable guide to how these things should
>>> be separated, yes. That said, much of what was kind of ad-hoc kernel
>>> internals testing that was triggered via kselftests is better done via
>>> KUnit these days, but not everything.
>> I started investigated when I found that kselftest doesn't parse the kernel
>> logs to mark these tests pass/fail. (kselftest/lib is good example of it)
>>
>>>
>>>> This brings me to conclusion that kselftest which are loading modules to
>>>> test kernelspace should be converted to kunit tests. I've noted several
>>>> such kselftests.
>>>
>>> I would tend to agree, yes. Which stand out to you? I've mainly been
>>> doing the conversions when I find myself wanting to add new tests, etc.
>> lib
>> 	test_bitmap
>> 	prime_numbers
>> 	test_printf
>> 	test_scanf
> 
> Yeah, these would be nice to convert.
> 
>> 	test_strscpy (already converted, need to remove this test)
> 
> Yup, converted in bb8d9b742aa7 ("string: Merge strscpy KUnit tests into string_kunit.c")
> 
>> lock
>> 	test-ww_mutex module
>> net
>> 	test_blackhole_dev
> 
> I don't know these very well, but yeah worth looking into.
> 
>> user
>> 	test_user_copy (probably already converted, need to remove this test)
> 
> This is done in -next via cf6219ee889f ("usercopy: Convert test_user_copy to KUnit test")
> 
>> firmware
>> 	test_firmware
> 
> This might not work to convert: there's a userspace half for testing
> firmware loading (see the kselftest side...)
> 
>> fpu
>> 	test_fpu
> 
> Seems reasonable.
> 
>> Most of these modules are found in lib/*.
>>
>> Would it be desired to move these to kunit?
> 
> Checking with the authors/maintainer is probably the first thing to do;
> check the git history to see who has been working on them.
> 

Also maybe:

mm
	gup_test

This is a classic case of testing a kernel API via ioctl into the
kernel, so I think it meets your criteria for moving to KUnit.
Having said that, I must now go try out KUnit in a bit more depth
before I'm sure that this will work out. But it should.

thanks,
-- 
John Hubbard
NVIDIA