From 2ba4badca9977b64c966b0177920daadbd5501fe Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau <kafai@fb.com> Date: Mon, 29 Mar 2021 22:41:56 -0700 Subject: [PATCH] bpf: selftests: Update clang requirement in README.rst for testing kfunc call This patch updates the README.rst to specify the clang requirement to compile the bpf selftests that call kernel function. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20210330054156.2933804-1-kafai@fb.com --- tools/testing/selftests/bpf/README.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst index 3464161c8eea3..65fe318d1e712 100644 --- a/tools/testing/selftests/bpf/README.rst +++ b/tools/testing/selftests/bpf/README.rst @@ -179,3 +179,17 @@ types, which was introduced in `Clang 13`__. The older Clang versions will either crash when compiling these tests, or generate an incorrect BTF. __ https://reviews.llvm.org/D83289 + +Kernel function call test and Clang version +=========================================== + +Some selftests (e.g. kfunc_call and bpf_tcp_ca) require a LLVM support +to generate extern function in BTF. It was introduced in `Clang 13`__. + +Without it, the error from compiling bpf selftests looks like: + +.. code-block:: console + + libbpf: failed to find BTF for extern 'tcp_slow_start' [25] section: -2 + +__ https://reviews.llvm.org/D93563 -- 2.30.2