bpf_core_format_spec
spec_len = bpf_core_format_spec(spec_buf, sizeof(spec_buf), &spec);
bpf_core_format_spec(spec_buf, sizeof(spec_buf), local_spec);
bpf_core_format_spec(spec_buf, sizeof(spec_buf), cand_spec);
bpf_core_format_spec(spec_buf, sizeof(spec_buf), cand_spec);
int bpf_core_format_spec(char *buf, size_t buf_sz, const struct bpf_core_spec *spec);