On Mon, May 18, 2020 at 12:23:10PM +0100, Alan Maguire wrote: > 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 > + these instructions are obsolete and partially incorrect. May be refer to Documentation/bpf/bpf_devel_QA.rst instead? > +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 Is it really the case? I've never seen anything like this.
