Error: Cannot open file tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
Error: Cannot open file tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
Error: Cannot open file tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
Error: Cannot open file tools/testing/selftests/bpf/progs/string_kfuncs_success.c