Re: [PATCH 2/2] kunit: add coverage_uml.config to enable GCOV on UML

[Maíra Canal]

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@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx/

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@xxxxxxxxxx>
> > ---
>
> 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@xxxxxxxxxx>
>
> Cheers,
> -- David
>
> [1] https://lore.kernel.org/linux-kselftest/20220622035326.759935-1-davidgow@xxxxxxxxxx/
>
>
> >   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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