selftests/bpf: Copy insn_is_pseudo_func() into testing_helpers

insn_is_pseudo_func() will be used in test_verifier, the original idea is
to move it from libbpf.c to libbpf_internal.h and then include the header
to reuse this function, this just adds more internal code of libbpf used
by selftests. While we have allowed it in some cases to avoid duplication
of more complex logic, it is not justified in this case.

Since insn_is_pseudo_func() and its helper is_ldimm64_insn() are trivial
enough, just copy into testing_helpers.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

Author: seehearfeel

tools/testing/selftests/bpf/testing_helpers.h

@@ -54,4 +54,14 @@ int get_xlated_program(int fd_prog, struct bpf_insn **buf, __u32 *cnt);
 int testing_prog_flags(void);
 bool is_jit_enabled(void);
 
+static inline bool is_ldimm64_insn(struct bpf_insn *insn)
+{
+	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+}
+
+static inline bool insn_is_pseudo_func(struct bpf_insn *insn)
+{
+	return is_ldimm64_insn(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
+}
+
 #endif /* __TESTING_HELPERS_H */