[Linux-kernel-mentees] common KUnit Kconfig and file naming (was: Re: [PATCH] lib: kunit_test_overflow: add KUnit test of check_*_overflow functions)

David Gow davidgow at google.com
Tue Jun 16 07:25:39 UTC 2020

CONFIG_PM_QOS_KUNIT_TESTOn Mon, Jun 15, 2020 at 1:48 AM Kees Cook
<keescook at chromium.org> wrote:
> On Sat, Jun 13, 2020 at 02:51:17PM +0800, David Gow wrote:
> > Yeah, _KUNIT_TEST was what we've sort-of implicitly decided on for
> > config names, but the documentation does need to happen.
> That works for me. It still feels redundant, but all I really want is a
> standard name. :)
> > We haven't put as much thought into standardising the filenames much, though.
> I actually find this to be much more important because it is more
> end-user-facing (i.e. in module naming, in build logs, in scripts, on
> filesystem, etc -- CONFIG is basically only present during kernel build).
> Trying to do any sorting or greping really needs a way to find all the
> kunit pieces.

Certainly this is more of an issue now we support building KUnit tests
as modules, rather than having them always be built-in.

Having some halfway consistent config-name <-> filename <-> test suite
name could be useful down the line, too. Unfortunately, not
necessarily a 1:1 mapping, e.g.:
- CONFIG_KUNIT_TEST compiles both kunit-test.c and string-stream-test.c
- kunit-test.c has several test suites within it:
kunit-try-catch-test, kunit-resource-test & kunit-log-test.
- CONFIG_EXT4_KUNIT_TESTS currently only builds ext4-inode-test.c, but
as the plural name suggests, might build others later.
- CONFIG_SECURITY_APPARMOR_KUNIT_TEST doesn't actually have its own
source file: the test is built into policy_unpack.c
- &cetera

Indeed, this made me quickly look up the names of suites, and there
are a few inconsistencies there:
- most have "-test" as a suffix
- some have "_test" as a suffix
- some have no suffix

(I'm inclined to say that these don't need a suffix at all.)

Within test suites, we're also largely prefixing all of the tests with
a suite name (even if it's not actually the specified suite name). For
example, CONFIG_PM_QOS_KUNIT_TEST builds
drivers/base/power/qos-test.c which contains a suite called
"qos-kunit-test", with tests prefixed "freq_qos_test_". Some of this
clearly comes down to wanting to namespace things a bit more
("qos-test" as a name could refer to a few things, I imagine), but
specifying how to do so consistently could help.

> > Both of these are slightly complicated by cases like this where tests
> > are being ported from a non-KUnit test to KUnit. There's a small
> > argument there for trying to keep the name the same, though personally
> > I suspect consistency is more important.
> Understood. I think consistency is preferred too, especially since the
> driving reason to make this conversions is to gain consistency with the
> actual tests themselves.

We'll go with that until someone objects: from what I recall, this is
largely what people have been doing anyway.

> > Alas, the plans to document test coding style / conventions kept
> > getting pre-empted: I'll drag it back up to the top of the to-do list,
> > and see if we can't prioritise it. I think we'd hoped to be able to
> > catch these in review, but between a bit of forgetfulness and a few
> > tests going upstream without our seeing them has made it obvious that
> > doesn't work.
> >
> > Once something's documented (and the suitable bikeshedding has
> > subsided), we can consider renaming existing tests if that seems
> > worthwhile.
> Yes please! :)

I'll see if I can find time to draft something this week, then. No
promises, but hopefully there'll at least be something to build on.

> > My feeling is we'll go for:
> > - Kconfig name: ~_KUNIT_TEST
> As mentioned, I'm fine with this, but prefer ~_KUNIT
> > - filename: ~-test.c
> I really don't like this. Several reasons reasons:
> - it does not distinguish it from other tests -- there is no way to
>   identify kunit tests from non-kunit tests from directory listings,
>   build log greps, etc.
> - the current "common" naming has been with a leading "test", ignoring
>   kunit, tools/, and samples/:
>         53 test_*.c
>         27 *_test.c
>         19 *[a-z0-9]test.c
>         19 selftest*.c
>         16 test-*.c
>         11 *-test.c
>         11 test[a-z0-9]*.c
>          8 *-tests.c
>          5 *-selftest.c
>          4 *_test_*.c
>          1 *_selftest_*.c
>          1 *_selftests.c
> (these counts might be a bit off -- my eyes started to cross while
> constructing regexes)
> - dashes are converted to _ in module names, leading to some confusion
>   between .c file and .ko file.
> I'd strongly prefer ~_kunit.c, but could live with _kunit_test.c (even
> though it's redundant).

I suggested -test.c largely because it's seemed to be most popular out
of existing KUnit tests (and certainly out of the ones that already
had-KUNIT_TEST config suffixes), but I definitely see your points.
I think that trying to stick to a "common" test naming is a bit
contradictory with trying to distinguish KUnit tests from other tests,
and I'm leaning to the side of distinguishing them, so I definitely
could be converted to ~_kunit.c.

Brendan, any thoughts?

> > At least for the initial draft documentation, as those seem to be most
> > common, but I think a thread on that would probably be the best place
> > to add it.
> I'm ready! :) (Subject updated)
> > This would also be a good opportunity to document the "standard" KUnit
> > boilerplate help text in the Kconfig options.
> Ah yeah, good idea.
> --
> Kees Cook

-- David

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