Linux 5.4 - bpf test build fails

[Shuah Khan <skhan@linuxfoundation.org>]

Hi Alexei and Daniel,

bpf test doesn't build on Linux 5.4 mainline. Do you know what's
happening here.


make -C tools/testing/selftests/bpf/

-c progs/test_core_reloc_ptr_as_arr.c -o - || echo "clang failed") | \
llc -march=bpf -mcpu=generic  -filetype=obj -o 
/mnt/data/lkml/linux_5.4/tools/testing/selftests/bpf/test_core_reloc_ptr_as_arr.o
progs/test_core_reloc_ptr_as_arr.c:25:6: error: use of unknown builtin
       '__builtin_preserve_access_index' [-Wimplicit-function-declaration]
         if (BPF_CORE_READ(&out->a, &in[2].a))
             ^
./bpf_helpers.h:533:10: note: expanded from macro 'BPF_CORE_READ'
                        __builtin_preserve_access_index(src))
                        ^
progs/test_core_reloc_ptr_as_arr.c:25:6: warning: incompatible integer to
       pointer conversion passing 'int' to parameter of type 'const void *'
       [-Wint-conversion]
         if (BPF_CORE_READ(&out->a, &in[2].a))
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./bpf_helpers.h:533:10: note: expanded from macro 'BPF_CORE_READ'
                        __builtin_preserve_access_index(src))
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning and 1 error generated.
llc: error: llc: <stdin>:1:1: error: expected top-level entity
clang failed

Also

make TARGETS=bpf kselftest fails as well. Dependency between
tools/lib/bpf and the test. How can we avoid this type of
dependency or resolve it in a way it doesn't result in build
failures?

thanks,
-- Shuah