Getting a clean BPF selftests run involves ensuring latest trunk LLVM/clang are used, pahole is recent (>=1.16) and config matches the specified config file as closely as possible. Document all of this in the general README.rst file. Also note how to work around timeout failures. Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx> --- tools/testing/selftests/bpf/README.rst | 46 ++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst index 0f67f1b..b00eebb 100644 --- a/tools/testing/selftests/bpf/README.rst +++ b/tools/testing/selftests/bpf/README.rst @@ -1,6 +1,52 @@ ================== BPF Selftest Notes ================== +First verify the built kernel config options match the config options +specified in the config file in this directory. Test failures for +unknown helpers, inability to find BTF etc will be observed otherwise. + +To ensure the maximum number of tests pass, it is best to use the latest +trunk LLVM/clang, i.e. + +git clone https://github.com/llvm/llvm-project + +Build/install trunk LLVM: + +.. code-block:: bash + git clone https://github.com/llvm/llvm-project + cd llvm-project + mkdir build/llvm + cd build/llvm + cmake ../../llvm/ + make + sudo make install + cd ../../ + +Build/install trunk clang: + +.. code-block:: bash + mkdir -p build/clang + cd build/clang + cmake ../../clang + make + sudo make install + +When building the kernel with CONFIG_DEBUG_INFO_BTF, pahole +version 16 or later is also required for BTF function +support. pahole can be built from the source at + +https://github.com/acmel/dwarves + +It is often available in "dwarves/libdwarves" packages also, +but be aware that versions prior to 1.16 will fail with +errors that functions cannot be found in BTF. + +When running selftests, the default timeout of 45 seconds +can be exceeded by some tests. We can override the default +timeout via a "settings" file; for example: + +.. code-block:: bash + echo "timeout=120" > tools/testing/selftests/bpf/settings Additional information about selftest failures are documented here. -- 1.8.3.1
