libbpf: Preserve kernel error code and remove kprobe prog type guessing

Instead of rewriting error code returned by the kernel of prog load with
libbpf-sepcific variants pass through the original error.

There is now also no need to have a backup generic -LIBBPF_ERRNO__LOAD
fallback error as bpf_prog_load() guarantees that errno will be properly
set no matter what.

Also drop a completely outdated and pretty useless BPF_PROG_TYPE_KPROBE
guess logic. It's not necessary and neither it's helpful in modern BPF
applications.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-7-andrii@kernel.org

tools/lib/bpf/libbpf.c

@@ -6696,34 +6696,19 @@ static int bpf_object_load_prog_instance(struct bpf_object *obj, struct bpf_prog
 		free(log_buf);
 		goto retry_load;
 	}
-	ret = errno ? -errno : -LIBBPF_ERRNO__LOAD;
+
+	ret = -errno;
 	cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
 	pr_warn("prog '%s': BPF program load failed: %s\n", prog->name, cp);
 	pr_perm_msg(ret);
 
 	if (log_buf && log_buf[0] != '\0') {
-		ret = -LIBBPF_ERRNO__VERIFY;
 		pr_warn("prog '%s': -- BEGIN PROG LOAD LOG --\n%s-- END PROG LOAD LOG --\n",
 			prog->name, log_buf);
 	}
 	if (insns_cnt >= BPF_MAXINSNS) {
 		pr_warn("prog '%s': program too large (%d insns), at most %d insns\n",
 			prog->name, insns_cnt, BPF_MAXINSNS);
-		ret = -LIBBPF_ERRNO__PROG2BIG;
-	} else if (prog->type != BPF_PROG_TYPE_KPROBE) {
-		/* Wrong program type? */
-		int fd;
-
-		load_attr.expected_attach_type = 0;
-		load_attr.log_buf = NULL;
-		load_attr.log_size = 0;
-		fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, prog_name, license,
-				   insns, insns_cnt, &load_attr);
-		if (fd >= 0) {
-			close(fd);
-			ret = -LIBBPF_ERRNO__PROGTYPE;
-			goto out;
-		}
 	}
 
 out: