selftests/bpf: Document latest Clang fix expectations for linking tests

Document which fixes are required to generate correct static linking
selftests.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-19-andrii@kernel.org

diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst
index 65fe318d1e7123a575e9eee636f9c83d882b39c0..3353778c30f8e3eb20ac261f61418e1cf0300327 100644 (file)
--- a/tools/testing/selftests/bpf/README.rst
+++ b/tools/testing/selftests/bpf/README.rst
@@ -193,3 +193,12 @@ Without it, the error from compiling bpf selftests looks like:
   libbpf: failed to find BTF for extern 'tcp_slow_start' [25] section: -2
 
 __ https://reviews.llvm.org/D93563
+
+Clang dependencies for static linking tests
+===========================================
+
+linked_vars, linked_maps, and linked_funcs tests depend on `Clang fix`__ to
+generate valid BTF information for weak variables. Please make sure you use
+Clang that contains the fix.
+
+__ https://reviews.llvm.org/D100362