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

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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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