linux-kernel - Re: [PATCH 2/2] kunit: add coverage

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Date:   Fri, 24 Jun 2022 11:12:24 -0300
From:   Maíra Canal <maira.canal@....br>
To:     David Gow <davidgow@...gle.com>,
        Daniel Latypov <dlatypov@...gle.com>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 2/2] kunit: add coverage_uml.config to enable GCOV on UML

On 6/24/22 04:55, 'David Gow' via KUnit Development wrote:
> On Fri, Jun 24, 2022 at 8:12 AM 'Daniel Latypov' via KUnit Development
> <kunit-dev@...glegroups.com> wrote:
>>
>> Now that kunit.py's --kunitconfig is repeatable, let's create a file to
>> hold the various options needed to enable coverage under UML.
>>
>> This can be used like so:
>> $ ./tools/testing/kunit/kunit.py run \
>>    --kunitconfig=tools/testing/kunit/configs/all_tests_uml.config \
>>    --kunitconfig=tools/testing/kunit/configs/coverage_uml.config \
>>    --make_options=CC=/usr/bin/gcc-6
>>
>> which on my system is enough to get coverage working [1].
>>

It's great to see this coming to KUnit! As I was testing this series, I 
wasn't able to generate the coverage stats with GCC11. I got a linking 
error from ld:

ERROR:root:/usr/bin/ld: 
/usr/lib/gcc/x86_64-redhat-linux/11/libgcov.a(_gcov.o): in function 
`mangle_path':
(.text+0x19f0): multiple definition of `mangle_path'; 
fs/seq_file.o:/home/mairacanal/linux/.kunit/../fs/seq_file.c:441: first 
defined here
collect2: error: ld returned 1 exit status

By changing the name of the function to `seq_mangle_path`, it is 
possible to solve the linking error and run the tests. But, anyway, no 
.gcda files are generated.

I checked out, and this is a known issue that was already discussed in 
this series [1] (but I guess it didn't move on).

Is there any hope to see better UM support for gcov as using GCC6 is 
quite uncommon nowadays?

[1] 
https://lore.kernel.org/all/20210312095526.197739-1-johannes@sipsolutions.net/

Best regards,
- Maíra Canal

>> This is still a clunky command, but far better than before.
>>
>> [1] at the time of this commit, I get:
>>    Overall coverage rate:
>>      lines......: 11.6% (34112 of 295033 lines)
>>      functions..: 15.3% (3721 of 24368 functions)
>>
>> Signed-off-by: Daniel Latypov <dlatypov@...gle.com>
>> ---
> 
> Looks good to me: depending on whether or not we do something like
> [1], we should add a pci_uml.config as well.
> 
> Alas, I don't have a working gcc 6 install anymore, so I wasn't able
> to test the coverage here, but I at least got an encouraging-looking
> error, and the change looks very sensible, so:
> 
> Reviewed-by: David Gow <davidgow@...gle.com>
> 
> Cheers,
> -- David
> 
> [1] https://lore.kernel.org/linux-kselftest/20220622035326.759935-1-davidgow@google.com/
> 
> 
>>   Documentation/dev-tools/kunit/running_tips.rst  |  3 +--
>>   tools/testing/kunit/configs/coverage_uml.config | 11 +++++++++++
>>   2 files changed, 12 insertions(+), 2 deletions(-)
>>   create mode 100644 tools/testing/kunit/configs/coverage_uml.config
>>
>> diff --git a/Documentation/dev-tools/kunit/running_tips.rst b/Documentation/dev-tools/kunit/running_tips.rst
>> index c36f6760087d..205ea21c9cca 100644
>> --- a/Documentation/dev-tools/kunit/running_tips.rst
>> +++ b/Documentation/dev-tools/kunit/running_tips.rst
>> @@ -123,8 +123,7 @@ Putting it together into a copy-pastable sequence of commands:
>>   .. code-block:: bash
>>
>>          # Append coverage options to the current config
>> -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
>> -       $ ./tools/testing/kunit/kunit.py run
>> +       $ ./tools/testing/kunit/kunit.py run --kunitconfig=.kunit/ --kunitconfig=tools/testing/kunit/configs/coverage_uml.config
>>          # Extract the coverage information from the build dir (.kunit/)
>>          $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/
>>
>> diff --git a/tools/testing/kunit/configs/coverage_uml.config b/tools/testing/kunit/configs/coverage_uml.config
>> new file mode 100644
>> index 000000000000..bacb77664fa8
>> --- /dev/null
>> +++ b/tools/testing/kunit/configs/coverage_uml.config
>> @@ -0,0 +1,11 @@
>> +# This config fragment enables coverage on UML, which is different from the
>> +# normal gcov used in other arches (no debugfs).
>> +# Example usage:
>> +# ./tools/testing/kunit/kunit.py run \
>> +#   --kunitconfig=tools/testing/kunit/configs/all_tests_uml.config \
>> +#   --kunitconfig=tools/testing/kunit/configs/coverage_uml.config
>> +
>> +CONFIG_DEBUG_KERNEL=y
>> +CONFIG_DEBUG_INFO=y
>> +CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
>> +CONFIG_GCOV=y
>> --
>> 2.37.0.rc0.104.g0611611a94-goog
>>
>> --
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>> To view this discussion on the web visit https://groups.google.com/d/msgid/kunit-dev/20220624001247.3255978-2-dlatypov%40google.com.
>