linux-kernel - Re: kbuild problem: ERROR: modpost: missing MODULE_LICENSE() in drivers/iio/afe/iio-rescale.o

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Date:   Fri, 20 May 2022 22:39:31 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Liam Beguin <liambeguin@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org, Peter Rosin <peda@...ntia.se>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>
Subject: Re: kbuild problem: ERROR: modpost: missing MODULE_LICENSE() in
 drivers/iio/afe/iio-rescale.o



On 5/20/22 21:14, Masahiro Yamada wrote:
> On Sat, May 21, 2022 at 12:51 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>> Ok, one more.
>> [also adding Liam here]
>>
>> On 5/20/22 20:17, Randy Dunlap wrote:
>>>
>>>
>>> On 5/20/22 20:08, Randy Dunlap wrote:
>>>>
>>>>
>>>> On 5/20/22 19:40, Randy Dunlap wrote:
>>>>> Hi,
>>>>>
>>>>> In March I reported that a randconfig build complained:
>>>>>
>>>>> ERROR: modpost: missing MODULE_LICENSE() in drivers/iio/afe/iio-rescale.o
>>>>>
>>>>> (https://lore.kernel.org/all/16509fb6-e40c-e31b-2c80-264c44b0beb9@infradead.org/)
>>>>>
>>>>> I am still seeing this problem so I tried to dig into it a bit.
>>>>> However, I don't see why get_next_modinfo() and friends don't find the
>>>>> MODULE_LICENSE() since it is in the iio-rescale.o file.
>>>>>
>>>>> (BTW, I see this build error on many different $ARCH [around 15 tested]
>>>>> and with 2 different versions of GCC.)
>>>>>
>>>>> Q1: Is modpost checking both vmlinux and iio-rescale.o for modinfo license
>>>>> strings?
>>>>>
>>>>> It looks like it is, because it appears (?) that modpost is looking at
>>>>> drivers/iio/test/iio-test-rescale.o (<<<<< a kunit test, which is builtin
>>>>> in my .config) and at drivers/iio/afe/iio-rescale.o (which is built as a
>>>>> loadable module).
>>>>>
>>>>> Is this confusing modpost?
>>>>> I renamed drivers/iio/afe/iio-rescale.c to afe-rescale.c and changed its
>>>>> Makefile entry accordingly and the MODULE_LICENSE error goes away.
>>>>
>>>> Oh well. This rename causes drivers/iio/test/iio-test-rescale.c to have
>>>> build errors, so that's not a solution, just some info...
>>>
>>> and that was due to not updating drivers/iio/test/Makefile.
>>> When that is done, the missing MODULE_LICENSE() is back in afe-rescale.o.
>>>
>>>>
>>>>> Is this a modpost error or is kunit messing things up?
>>>>>
>>>>> thanks for looking.
>>
>> Does this look OK? It allows afe/iio-rescale.o to build XOR
>> test/iio-rescale.o (not both of them).
>>
>> --- a/drivers/iio/test/Kconfig
>> +++ b/drivers/iio/test/Kconfig
>> @@ -6,7 +6,7 @@
>>  # Keep in alphabetical order
>>  config IIO_RESCALE_KUNIT_TEST
>>         bool "Test IIO rescale conversion functions"
>> -       depends on KUNIT=y && !IIO_RESCALE
>> +       depends on KUNIT=y && IIO_RESCALE=n
>>         default KUNIT_ALL_TESTS
>>         help
>>           If you want to run tests on the iio-rescale code say Y here.
>>
>>
>> --
>> ~Randy
> 
> 
> 
> As you may have already noticed,
> the root cause is drivers/iio/test/Makefile
> 
> obj-$(CONFIG_IIO_RESCALE_KUNIT_TEST) += iio-test-rescale.o ../afe/iio-rescale.o
> 
> 
> 
> For the combination of
> CONFIG_IIO_RESCALE=m
> CONFIG_IIO_RESCALE_KUNIT_TEST=y,
> 
> drivers/iio/afe/iio-rescale.o is built twice;
> as modular by drivers/iio/afe/Makefile, and
> as built-in by drivers/iio/test/Makefile.
> 
> That's why MODULE_LICENSE() is lost.
> 
> 
> I think your solution will work
> although this Makefile is not recommended.

Yeah, I don't care for how that is done either.

-- 
~Randy