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Date:   Fri, 15 Oct 2021 18:28:03 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: selftests/vm madv_populate.c test

On 15.10.21 18:25, Shuah Khan wrote:
> On 10/15/21 10:19 AM, David Hildenbrand wrote:
>> On 15.10.21 18:15, David Hildenbrand wrote:
>>> On 15.10.21 18:06, David Hildenbrand wrote:
>>>> On 15.10.21 17:47, David Hildenbrand wrote:
>>>>> On 15.10.21 17:45, Shuah Khan wrote:
>>>>>> On 9/18/21 1:41 AM, David Hildenbrand wrote:
>>>>>>> On 18.09.21 00:45, Shuah Khan wrote:
>>>>>>>> Hi David,
>>>>>>>>
>>>>>>>> I am running into the following warning when try to build this test:
>>>>>>>>
>>>>>>>> madv_populate.c:334:2: warning: #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition" [-Wcpp]
>>>>>>>>      334 | #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition"
>>>>>>>>          |  ^~~~~~~
>>>>>>>>
>>>>>>>>
>>>>>>>> I see that the following handling is in place. However there is no
>>>>>>>> other information to explain why the check is necessary.
>>>>>>>>
>>>>>>>> #if defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE)
>>>>>>>>
>>>>>>>> #else /* defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE) */
>>>>>>>>
>>>>>>>> #warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition"
>>>>>>>>
>>>>>>>> I do see these defined in:
>>>>>>>>
>>>>>>>> include/uapi/asm-generic/mman-common.h:#define MADV_POPULATE_READ       22
>>>>>>>> include/uapi/asm-generic/mman-common.h:#define MADV_POPULATE_WRITE      23
>>>>>>>>
>>>>>>>> Is this the case of missing include from madv_populate.c?
>>>>>>>
>>>>>>> Hi Shuan,
>>>>>>>
>>>>>>> note that we're including "#include <sys/mman.h>", which in my
>>>>>>> understanding maps to the version installed on your system instead
>>>>>>> of the one in our build environment.ing.
>>>>>>>
>>>>>>> So as soon as you have a proper kernel + the proper headers installed
>>>>>>> and try to build, it would pick up MADV_POPULATE_READ and
>>>>>>> MADV_POPULATE_WRITE from the updated headers. That makes sense: you
>>>>>>> annot run any MADV_POPULATE_READ/MADV_POPULATE_WRITE tests on a kernel
>>>>>>> that doesn't support it.
>>>>>>>
>>>>>>> See vm/userfaultfd.c where we do something similar.
>>>>>>>
>>>>>>
>>>>>> Kselftest is for testing the kernel with kernel headers. That is the
>>>>>> reason why there is the dependency on header install.
>>>>>>
>>>>>>>
>>>>>>> As soon as we have a proper environment, it seems to work just fine:
>>>>>>>
>>>>>>> Linux vm-0 5.15.0-0.rc1.20210915git3ca706c189db.13.fc36.x86_64 #1 SMP Thu Sep 16 11:32:54 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
>>>>>>> [root@...0 linux]# cat /etc/redhat-release
>>>>>>> Fedora release 36 (Rawhide)
>>>>>>
>>>>>> This is a distro release. We don't want to have dependency on headers
>>>>>> from the distro to run selftests. Hope this makes sense.
>>>>>>
>>>>>> I still see this on my test system running Linux 5.15-rc5.
>>>>>
>>>>> Did you also install Linux headers? I assume no, correct?
>>>>>
>>>>
>>>> What happens in your environment when compiling and running the
>>>> memfd_secret test?
>>>>
>>>> If assume you'll see a "skip" when executing, because it might also
>>>> refer to the local version of linux headers and although it builds, it
>>>> really cannot build something "functional". It just doesn't add a
>>>> "#warning" to make that obvious.
>>>>
>>>
>>> The following works but looks extremely hackish.
>>>
>>> diff --git a/tools/testing/selftests/vm/madv_populate.c
>>> b/tools/testing/selftests/vm/madv_populate.c
>>> index b959e4ebdad4..ab26163db540 100644
>>> --- a/tools/testing/selftests/vm/madv_populate.c
>>> +++ b/tools/testing/selftests/vm/madv_populate.c
>>> @@ -14,12 +14,11 @@
>>>   #include <unistd.h>
>>>   #include <errno.h>
>>>   #include <fcntl.h>
>>> +#include "../../../../usr/include/linux/mman.h"
>>>   #include <sys/mman.h>
>>>
>>>   #include "../kselftest.h"
>>>
>>> -#if defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE)
>>> -
>>>   /*
>>>    * For now, we're using 2 MiB of private anonymous memory for all tests.
>>>    */
>>> @@ -328,15 +327,3 @@ int main(int argc, char **argv)
>>>                                     err, ksft_test_num());
>>>          return ksft_exit_pass();
>>>   }
>>> -
>>> -#else /* defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE) */
>>> -
>>> -#warning "missing MADV_POPULATE_READ or MADV_POPULATE_WRITE definition"
>>> -
>>> -int main(int argc, char **argv)
>>> -{
>>> -       ksft_print_header();
>>> -       ksft_exit_skip("MADV_POPULATE_READ or MADV_POPULATE_WRITE not
>>> defined\n");
>>> -}
>>> -
>>> -#endif /* defined(MADV_POPULATE_READ) && defined(MADV_POPULATE_WRITE) */
>>>
>>>
>>> There has to be some clean way to achieve the same.
>>>
>>
>> Sorry for the spam,
>>
>> diff --git a/tools/testing/selftests/vm/Makefile
>> b/tools/testing/selftests/vm/Makefile
>> index d9605bd10f2d..ce198b329ff5 100644
>> --- a/tools/testing/selftests/vm/Makefile
>> +++ b/tools/testing/selftests/vm/Makefile
>> @@ -23,7 +23,7 @@ MACHINE ?= $(shell echo $(uname_M) | sed -e
>> 's/aarch64.*/arm64/' -e 's/ppc64.*/p
>>   # LDLIBS.
>>   MAKEFLAGS += --no-builtin-rules
>>
>> -CFLAGS = -Wall -I ../../../../usr/include $(EXTRA_CFLAGS)
>> +CFLAGS = -Wall -idirafter ../../../../usr/include $(EXTRA_CFLAGS)
>>   LDLIBS = -lrt -lpthread
>>   TEST_GEN_FILES = compaction_test
>>   TEST_GEN_FILES += gup_test
>>
>>
>> Seems to set the right include path priority.
>>
>>
> 
> Yes. It works on linux-next-20211012
> 
> Do you mind sending a me patch for this?

I just double-checked (after make clean) and there is still something
wrong :( the only think that seems to work is the

+#include "../../../../usr/include/linux/mman.h"
 #include <sys/mman.h>

hack.

Using "-nostdinc" won't work because we need other headers :(

-- 
Thanks,

David / dhildenb

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