selftests/bpf: Test bpf_link's get_next_id, get_fd_by_id, and get_obj_info

Extend bpf_obj_id selftest to verify bpf_link's observability APIs.

Signed-off-by: Andrii Nakryiko <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/prog_tests/bpf_obj_id.c

···
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 
+#define nr_iters 2
+
 void test_bpf_obj_id(void)
 {
 	const __u64 array_magic_value = 0xfaceb00c;
 	const __u32 array_key = 0;
-	const int nr_iters = 2;
 	const char *file = "./test_obj_id.o";
 	const char *expected_prog_name = "test_obj_id";
 	const char *expected_map_name = "test_map_id";
 	const __u64 nsec_per_sec = 1000000000;
 
-	struct bpf_object *objs[nr_iters];
+	struct bpf_object *objs[nr_iters] = {};
+	struct bpf_link *links[nr_iters] = {};
+	struct bpf_program *prog;
 	int prog_fds[nr_iters], map_fds[nr_iters];
 	/* +1 to test for the info_len returned by kernel */
 	struct bpf_prog_info prog_infos[nr_iters + 1];
 	struct bpf_map_info map_infos[nr_iters + 1];
+	struct bpf_link_info link_infos[nr_iters + 1];
 	/* Each prog only uses one map. +1 to test nr_map_ids
 	 * returned by kernel.
 	 */
 	__u32 map_ids[nr_iters + 1];
-	char jited_insns[128], xlated_insns[128], zeros[128];
+	char jited_insns[128], xlated_insns[128], zeros[128], tp_name[128];
 	__u32 i, next_id, info_len, nr_id_found, duration = 0;
 	struct timespec real_time_ts, boot_time_ts;
 	int err = 0;
···
 	CHECK(err >= 0 || errno != ENOENT,
 	      "get-fd-by-notexist-map-id", "err %d errno %d\n", err, errno);
 
-	for (i = 0; i < nr_iters; i++)
-		objs[i] = NULL;
+	err = bpf_link_get_fd_by_id(0);
+	CHECK(err >= 0 || errno != ENOENT,
+	      "get-fd-by-notexist-link-id", "err %d errno %d\n", err, errno);
 
 	/* Check bpf_obj_get_info_by_fd() */
 	bzero(zeros, sizeof(zeros));
 	for (i = 0; i < nr_iters; i++) {
 		now = time(NULL);
-		err = bpf_prog_load(file, BPF_PROG_TYPE_SOCKET_FILTER,
+		err = bpf_prog_load(file, BPF_PROG_TYPE_RAW_TRACEPOINT,
 				    &objs[i], &prog_fds[i]);
 		/* test_obj_id.o is a dumb prog. It should never fail
 		 * to load.
···
 					  &array_magic_value, 0);
 		if (CHECK_FAIL(err))
 			goto done;
+
+		prog = bpf_object__find_program_by_title(objs[i],
+							 "raw_tp/sys_enter");
+		if (CHECK_FAIL(!prog))
+			goto done;
+		links[i] = bpf_program__attach(prog);
+		err = libbpf_get_error(links[i]);
+		if (CHECK(err, "prog_attach", "prog #%d, err %d\n", i, err)) {
+			links[i] = NULL;
+			goto done;
+		}
 
 		/* Check getting map info */
 		info_len = sizeof(struct bpf_map_info) * 2;
···
 		load_time = (real_time_ts.tv_sec - boot_time_ts.tv_sec)
 			+ (prog_infos[i].load_time / nsec_per_sec);
 		if (CHECK(err ||
-			  prog_infos[i].type != BPF_PROG_TYPE_SOCKET_FILTER ||
+			  prog_infos[i].type != BPF_PROG_TYPE_RAW_TRACEPOINT ||
 			  info_len != sizeof(struct bpf_prog_info) ||
 			  (env.jit_enabled && !prog_infos[i].jited_prog_len) ||
 			  (env.jit_enabled &&
···
 			  *(int *)(long)prog_infos[i].map_ids != map_infos[i].id ||
 			  strcmp((char *)prog_infos[i].name, expected_prog_name),
 			  "get-prog-info(fd)",
-			  "err %d errno %d i %d type %d(%d) info_len %u(%zu) jit_enabled %d jited_prog_len %u xlated_prog_len %u jited_prog %d xlated_prog %d load_time %lu(%lu) uid %u(%u) nr_map_ids %u(%u) map_id %u(%u) name %s(%s)\n",
+			  "err %d errno %d i %d type %d(%d) info_len %u(%zu) "
+			  "jit_enabled %d jited_prog_len %u xlated_prog_len %u "
+			  "jited_prog %d xlated_prog %d load_time %lu(%lu) "
+			  "uid %u(%u) nr_map_ids %u(%u) map_id %u(%u) "
+			  "name %s(%s)\n",
 			  err, errno, i,
 			  prog_infos[i].type, BPF_PROG_TYPE_SOCKET_FILTER,
 			  info_len, sizeof(struct bpf_prog_info),
···
 			  *(int *)(long)prog_infos[i].map_ids, map_infos[i].id,
 			  prog_infos[i].name, expected_prog_name))
 			goto done;
+
+		/* Check getting link info */
+		info_len = sizeof(struct bpf_link_info) * 2;
+		bzero(&link_infos[i], info_len);
+		link_infos[i].raw_tracepoint.tp_name = (__u64)&tp_name;
+		link_infos[i].raw_tracepoint.tp_name_len = sizeof(tp_name);
+		err = bpf_obj_get_info_by_fd(bpf_link__fd(links[i]),
+					     &link_infos[i], &info_len);
+		if (CHECK(err ||
+			  link_infos[i].type != BPF_LINK_TYPE_RAW_TRACEPOINT ||
+			  link_infos[i].prog_id != prog_infos[i].id ||
+			  link_infos[i].raw_tracepoint.tp_name != (__u64)&tp_name ||
+			  strcmp((char *)link_infos[i].raw_tracepoint.tp_name,
+				 "sys_enter") ||
+			  info_len != sizeof(struct bpf_link_info),
+			  "get-link-info(fd)",
+			  "err %d errno %d info_len %u(%zu) type %d(%d) id %d "
+			  "prog_id %d (%d) tp_name %s(%s)\n",
+			  err, errno,
+			  info_len, sizeof(struct bpf_link_info),
+			  link_infos[i].type, BPF_LINK_TYPE_RAW_TRACEPOINT,
+			  link_infos[i].id,
+			  link_infos[i].prog_id, prog_infos[i].id,
+			  (char *)link_infos[i].raw_tracepoint.tp_name,
+			  "sys_enter"))
+			goto done;
+
 	}
 
 	/* Check bpf_prog_get_next_id() */
···
 	      "nr_id_found %u(%u)\n",
 	      nr_id_found, nr_iters);
 
+	/* Check bpf_link_get_next_id() */
+	nr_id_found = 0;
+	next_id = 0;
+	while (!bpf_link_get_next_id(next_id, &next_id)) {
+		struct bpf_link_info link_info;
+		int link_fd, cmp_res;
+
+		info_len = sizeof(link_info);
+		memset(&link_info, 0, info_len);
+
+		link_fd = bpf_link_get_fd_by_id(next_id);
+		if (link_fd < 0 && errno == ENOENT)
+			/* The bpf_link is in the dead row */
+			continue;
+		if (CHECK(link_fd < 0, "get-link-fd(next_id)",
+			  "link_fd %d next_id %u errno %d\n",
+			  link_fd, next_id, errno))
+			break;
+
+		for (i = 0; i < nr_iters; i++)
+			if (link_infos[i].id == next_id)
+				break;
+
+		if (i == nr_iters)
+			continue;
+
+		nr_id_found++;
+
+		err = bpf_obj_get_info_by_fd(link_fd, &link_info, &info_len);
+		cmp_res = memcmp(&link_info, &link_infos[i],
+				offsetof(struct bpf_link_info, raw_tracepoint));
+		CHECK(err || info_len != sizeof(link_info) || cmp_res,
+		      "check get-link-info(next_id->fd)",
+		      "err %d errno %d info_len %u(%zu) memcmp %d\n",
+		      err, errno, info_len, sizeof(struct bpf_link_info),
+		      cmp_res);
+
+		close(link_fd);
+	}
+	CHECK(nr_id_found != nr_iters,
+	      "check total link id found by get_next_id",
+	      "nr_id_found %u(%u)\n", nr_id_found, nr_iters);
+
 done:
-	for (i = 0; i < nr_iters; i++)
+	for (i = 0; i < nr_iters; i++) {
+		bpf_link__destroy(links[i]);
 		bpf_object__close(objs[i]);
+	}
 }

tools/testing/selftests/bpf/progs/test_obj_id.c

···
  */
 #include <stddef.h>
 #include <linux/bpf.h>
-#include <linux/pkt_cls.h>
 #include <bpf/bpf_helpers.h>
-
-/* It is a dumb bpf program such that it must have no
- * issue to be loaded since testing the verifier is
- * not the focus here.
- */
-
-int _version SEC("version") = 1;
 
 struct {
 	__uint(type, BPF_MAP_TYPE_ARRAY);
···
 	__type(value, __u64);
 } test_map_id SEC(".maps");
 
-SEC("test_obj_id_dummy")
-int test_obj_id(struct __sk_buff *skb)
+SEC("raw_tp/sys_enter")
+int test_obj_id(void *ctx)
 {
 	__u32 key = 0;
 	__u64 *value;
 
 	value = bpf_map_lookup_elem(&test_map_id, &key);
 
-	return TC_ACT_OK;
+	return 0;
 }