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bpf: selftests: Update clang requirement in README.rst for testing kfunc call

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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
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Martin KaFai Lau 2021-03-29 22:41:56 -07:00 committed by Alexei Starovoitov
parent 5bdca94ff3
commit 2ba4badca9
1 changed files with 14 additions and 0 deletions
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tools/testing/selftests/bpf/README.rst
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@ -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