selftests/bpf: Test bpf_core_types_are_compat() functionality.

Add several tests to check bpf_core_types_are_compat() functionality:
- candidate type name exists and types match
- candidate type name exists but types don't match
- nested func protos at kernel recursion limit
- nested func protos above kernel recursion limit. Such bpf prog
  is rejected during the load.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220204005519.60361-3-mcroce@linux.microsoft.com

1 files changed, 16 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/core_kern.c b/tools/testing/selftests/bpf/progs/core_kern.c
index 13499cc15c7d..2715fe27d4cf 100644
--- a/tools/testing/selftests/bpf/progs/core_kern.c
+++ b/tools/testing/selftests/bpf/progs/core_kern.c
@@ -101,4 +101,20 @@ int balancer_ingress(struct __sk_buff *ctx)
 	return 0;
 }
 
+typedef int (*func_proto_typedef___match)(long);
+typedef int (*func_proto_typedef___doesnt_match)(char *);
+typedef int (*func_proto_typedef_nested1)(func_proto_typedef___match);
+
+int proto_out[3];
+
+SEC("raw_tracepoint/sys_enter")
+int core_relo_proto(void *ctx)
+{
+	proto_out[0] = bpf_core_type_exists(func_proto_typedef___match);
+	proto_out[1] = bpf_core_type_exists(func_proto_typedef___doesnt_match);
+	proto_out[2] = bpf_core_type_exists(func_proto_typedef_nested1);
+
+	return 0;
+}
+
 char LICENSE[] SEC("license") = "GPL";