[PATCH bpf-next] selftests/bpf: Fix selftest compilation on clang 11

[Jiri Olsa <jolsa@xxxxxxxxxx>]

We can't compile test_core_reloc_module.c selftest with clang 11,
compile fails with:

  CLNG-LLC [test_maps] test_core_reloc_module.o
  progs/test_core_reloc_module.c:57:21: error: use of unknown builtin \
  '__builtin_preserve_type_info' [-Wimplicit-function-declaration]
   out->read_ctx_sz = bpf_core_type_size(struct bpf_testmod_test_read_ctx);

Skipping these tests if __builtin_preserve_type_info() is not
supported by compiler.

Fixes: 6bcd39d366b6 ("selftests/bpf: Add CO-RE relocs selftest relying on kernel module BTF")
Fixes: bc9ed69c79ae ("selftests/bpf: Add tp_btf CO-RE reloc test for modules")
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 .../testing/selftests/bpf/progs/test_core_reloc_module.c  | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_module.c b/tools/testing/selftests/bpf/progs/test_core_reloc_module.c
index 56363959f7b0..f59f175c7baf 100644
--- a/tools/testing/selftests/bpf/progs/test_core_reloc_module.c
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_module.c
@@ -40,6 +40,7 @@ int BPF_PROG(test_core_module_probed,
 	     struct task_struct *task,
 	     struct bpf_testmod_test_read_ctx *read_ctx)
 {
+#if __has_builtin(__builtin_preserve_enum_value)
 	struct core_reloc_module_output *out = (void *)&data.out;
 	__u64 pid_tgid = bpf_get_current_pid_tgid();
 	__u32 real_tgid = (__u32)(pid_tgid >> 32);
@@ -61,6 +62,9 @@ int BPF_PROG(test_core_module_probed,
 	out->len_exists = bpf_core_field_exists(read_ctx->len);
 
 	out->comm_len = BPF_CORE_READ_STR_INTO(&out->comm, task, comm);
+#else
+	data.skip = true;
+#endif
 
 	return 0;
 }
@@ -70,6 +74,7 @@ int BPF_PROG(test_core_module_direct,
 	     struct task_struct *task,
 	     struct bpf_testmod_test_read_ctx *read_ctx)
 {
+#if __has_builtin(__builtin_preserve_enum_value)
 	struct core_reloc_module_output *out = (void *)&data.out;
 	__u64 pid_tgid = bpf_get_current_pid_tgid();
 	__u32 real_tgid = (__u32)(pid_tgid >> 32);
@@ -91,6 +96,9 @@ int BPF_PROG(test_core_module_direct,
 	out->len_exists = bpf_core_field_exists(read_ctx->len);
 
 	out->comm_len = BPF_CORE_READ_STR_INTO(&out->comm, task, comm);
+#else
+	data.skip = true;
+#endif
 
 	return 0;
 }
-- 
2.26.2