bpf: btf: Tests for BPF_OBJ_GET_INFO_BY_FD and BPF_BTF_GET_FD_BY_ID

This patch adds test for BPF_BTF_GET_FD_BY_ID and the new
btf_id/btf_key_id/btf_value_id in the "struct bpf_map_info".

It also modifies the existing BPF_OBJ_GET_INFO_BY_FD test
to reflect the new "struct bpf_btf_info".
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/bpf.c

@@ -458,6 +458,16 @@ int bpf_map_get_fd_by_id(__u32 id)
 	return sys_bpf(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr));
 }
 
+int bpf_btf_get_fd_by_id(__u32 id)
+{
+	union bpf_attr attr;
+
+	bzero(&attr, sizeof(attr));
+	attr.btf_id = id;
+
+	return sys_bpf(BPF_BTF_GET_FD_BY_ID, &attr, sizeof(attr));
+}
+
 int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len)
 {
 	union bpf_attr attr;

tools/lib/bpf/bpf.h

@@ -98,6 +98,7 @@ int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id);
 int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
 int bpf_prog_get_fd_by_id(__u32 id);
 int bpf_map_get_fd_by_id(__u32 id);
+int bpf_btf_get_fd_by_id(__u32 id);
 int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len);
 int bpf_prog_query(int target_fd, enum bpf_attach_type type, __u32 query_flags,
 		   __u32 *attach_flags, __u32 *prog_ids, __u32 *prog_cnt);

tools/testing/selftests/bpf/test_btf.c

@@ -1047,9 +1047,13 @@ struct btf_get_info_test {
 	const char *str_sec;
 	__u32 raw_types[MAX_NR_RAW_TYPES];
 	__u32 str_sec_size;
-	int info_size_delta;
+	int btf_size_delta;
+	int (*special_test)(unsigned int test_num);
 };
 
+static int test_big_btf_info(unsigned int test_num);
+static int test_btf_id(unsigned int test_num);
+
 const struct btf_get_info_test get_info_tests[] = {
 {
 	.descr = "== raw_btf_size+1",
@@ -1060,7 +1064,7 @@ const struct btf_get_info_test get_info_tests[] = {
 	},
 	.str_sec = "",
 	.str_sec_size = sizeof(""),
-	.info_size_delta = 1,
+	.btf_size_delta = 1,
 },
 {
 	.descr = "== raw_btf_size-3",
@@ -1071,20 +1075,274 @@ const struct btf_get_info_test get_info_tests[] = {
 	},
 	.str_sec = "",
 	.str_sec_size = sizeof(""),
-	.info_size_delta = -3,
+	.btf_size_delta = -3,
+},
+{
+	.descr = "Large bpf_btf_info",
+	.raw_types = {
+		/* int */				/* [1] */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),
+		BTF_END_RAW,
+	},
+	.str_sec = "",
+	.str_sec_size = sizeof(""),
+	.special_test = test_big_btf_info,
+},
+{
+	.descr = "BTF ID",
+	.raw_types = {
+		/* int */				/* [1] */
+		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),
+		/* unsigned int */			/* [2] */
+		BTF_TYPE_INT_ENC(0, 0, 0, 32, 4),
+		BTF_END_RAW,
+	},
+	.str_sec = "",
+	.str_sec_size = sizeof(""),
+	.special_test = test_btf_id,
 },
 };
 
+static inline __u64 ptr_to_u64(const void *ptr)
+{
+	return (__u64)(unsigned long)ptr;
+}
+
+static int test_big_btf_info(unsigned int test_num)
+{
+	const struct btf_get_info_test *test = &get_info_tests[test_num - 1];
+	uint8_t *raw_btf = NULL, *user_btf = NULL;
+	unsigned int raw_btf_size;
+	struct {
+		struct bpf_btf_info info;
+		uint64_t garbage;
+	} info_garbage;
+	struct bpf_btf_info *info;
+	int btf_fd = -1, err;
+	uint32_t info_len;
+
+	raw_btf = btf_raw_create(&hdr_tmpl,
+				 test->raw_types,
+				 test->str_sec,
+				 test->str_sec_size,
+				 &raw_btf_size);
+
+	if (!raw_btf)
+		return -1;
+
+	*btf_log_buf = '\0';
+
+	user_btf = malloc(raw_btf_size);
+	if (CHECK(!user_btf, "!user_btf")) {
+		err = -1;
+		goto done;
+	}
+
+	btf_fd = bpf_load_btf(raw_btf, raw_btf_size,
+			      btf_log_buf, BTF_LOG_BUF_SIZE,
+			      args.always_log);
+	if (CHECK(btf_fd == -1, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+
+	/*
+	 * GET_INFO should error out if the userspace info
+	 * has non zero tailing bytes.
+	 */
+	info = &info_garbage.info;
+	memset(info, 0, sizeof(*info));
+	info_garbage.garbage = 0xdeadbeef;
+	info_len = sizeof(info_garbage);
+	info->btf = ptr_to_u64(user_btf);
+	info->btf_size = raw_btf_size;
+
+	err = bpf_obj_get_info_by_fd(btf_fd, info, &info_len);
+	if (CHECK(!err, "!err")) {
+		err = -1;
+		goto done;
+	}
+
+	/*
+	 * GET_INFO should succeed even info_len is larger than
+	 * the kernel supported as long as tailing bytes are zero.
+	 * The kernel supported info len should also be returned
+	 * to userspace.
+	 */
+	info_garbage.garbage = 0;
+	err = bpf_obj_get_info_by_fd(btf_fd, info, &info_len);
+	if (CHECK(err || info_len != sizeof(*info),
+		  "err:%d errno:%d info_len:%u sizeof(*info):%lu",
+		  err, errno, info_len, sizeof(*info))) {
+		err = -1;
+		goto done;
+	}
+
+	fprintf(stderr, "OK");
+
+done:
+	if (*btf_log_buf && (err || args.always_log))
+		fprintf(stderr, "\n%s", btf_log_buf);
+
+	free(raw_btf);
+	free(user_btf);
+
+	if (btf_fd != -1)
+		close(btf_fd);
+
+	return err;
+}
+
+static int test_btf_id(unsigned int test_num)
+{
+	const struct btf_get_info_test *test = &get_info_tests[test_num - 1];
+	struct bpf_create_map_attr create_attr = {};
+	uint8_t *raw_btf = NULL, *user_btf[2] = {};
+	int btf_fd[2] = {-1, -1}, map_fd = -1;
+	struct bpf_map_info map_info = {};
+	struct bpf_btf_info info[2] = {};
+	unsigned int raw_btf_size;
+	uint32_t info_len;
+	int err, i, ret;
+
+	raw_btf = btf_raw_create(&hdr_tmpl,
+				 test->raw_types,
+				 test->str_sec,
+				 test->str_sec_size,
+				 &raw_btf_size);
+
+	if (!raw_btf)
+		return -1;
+
+	*btf_log_buf = '\0';
+
+	for (i = 0; i < 2; i++) {
+		user_btf[i] = malloc(raw_btf_size);
+		if (CHECK(!user_btf[i], "!user_btf[%d]", i)) {
+			err = -1;
+			goto done;
+		}
+		info[i].btf = ptr_to_u64(user_btf[i]);
+		info[i].btf_size = raw_btf_size;
+	}
+
+	btf_fd[0] = bpf_load_btf(raw_btf, raw_btf_size,
+				 btf_log_buf, BTF_LOG_BUF_SIZE,
+				 args.always_log);
+	if (CHECK(btf_fd[0] == -1, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+
+	/* Test BPF_OBJ_GET_INFO_BY_ID on btf_id */
+	info_len = sizeof(info[0]);
+	err = bpf_obj_get_info_by_fd(btf_fd[0], &info[0], &info_len);
+	if (CHECK(err, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+
+	btf_fd[1] = bpf_btf_get_fd_by_id(info[0].id);
+	if (CHECK(btf_fd[1] == -1, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+
+	ret = 0;
+	err = bpf_obj_get_info_by_fd(btf_fd[1], &info[1], &info_len);
+	if (CHECK(err || info[0].id != info[1].id ||
+		  info[0].btf_size != info[1].btf_size ||
+		  (ret = memcmp(user_btf[0], user_btf[1], info[0].btf_size)),
+		  "err:%d errno:%d id0:%u id1:%u btf_size0:%u btf_size1:%u memcmp:%d",
+		  err, errno, info[0].id, info[1].id,
+		  info[0].btf_size, info[1].btf_size, ret)) {
+		err = -1;
+		goto done;
+	}
+
+	/* Test btf members in struct bpf_map_info */
+	create_attr.name = "test_btf_id";
+	create_attr.map_type = BPF_MAP_TYPE_ARRAY;
+	create_attr.key_size = sizeof(int);
+	create_attr.value_size = sizeof(unsigned int);
+	create_attr.max_entries = 4;
+	create_attr.btf_fd = btf_fd[0];
+	create_attr.btf_key_id = 1;
+	create_attr.btf_value_id = 2;
+
+	map_fd = bpf_create_map_xattr(&create_attr);
+	if (CHECK(map_fd == -1, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+
+	info_len = sizeof(map_info);
+	err = bpf_obj_get_info_by_fd(map_fd, &map_info, &info_len);
+	if (CHECK(err || map_info.btf_id != info[0].id ||
+		  map_info.btf_key_id != 1 || map_info.btf_value_id != 2,
+		  "err:%d errno:%d info.id:%u btf_id:%u btf_key_id:%u btf_value_id:%u",
+		  err, errno, info[0].id, map_info.btf_id, map_info.btf_key_id,
+		  map_info.btf_value_id)) {
+		err = -1;
+		goto done;
+	}
+
+	for (i = 0; i < 2; i++) {
+		close(btf_fd[i]);
+		btf_fd[i] = -1;
+	}
+
+	/* Test BTF ID is removed from the kernel */
+	btf_fd[0] = bpf_btf_get_fd_by_id(map_info.btf_id);
+	if (CHECK(btf_fd[0] == -1, "errno:%d", errno)) {
+		err = -1;
+		goto done;
+	}
+	close(btf_fd[0]);
+	btf_fd[0] = -1;
+
+	/* The map holds the last ref to BTF and its btf_id */
+	close(map_fd);
+	map_fd = -1;
+	btf_fd[0] = bpf_btf_get_fd_by_id(map_info.btf_id);
+	if (CHECK(btf_fd[0] != -1, "BTF lingers")) {
+		err = -1;
+		goto done;
+	}
+
+	fprintf(stderr, "OK");
+
+done:
+	if (*btf_log_buf && (err || args.always_log))
+		fprintf(stderr, "\n%s", btf_log_buf);
+
+	free(raw_btf);
+	if (map_fd != -1)
+		close(map_fd);
+	for (i = 0; i < 2; i++) {
+		free(user_btf[i]);
+		if (btf_fd[i] != -1)
+			close(btf_fd[i]);
+	}
+
+	return err;
+}
+
 static int do_test_get_info(unsigned int test_num)
 {
 	const struct btf_get_info_test *test = &get_info_tests[test_num - 1];
 	unsigned int raw_btf_size, user_btf_size, expected_nbytes;
 	uint8_t *raw_btf = NULL, *user_btf = NULL;
-	int btf_fd = -1, err;
+	struct bpf_btf_info info = {};
+	int btf_fd = -1, err, ret;
+	uint32_t info_len;
 
-	fprintf(stderr, "BTF GET_INFO_BY_ID test[%u] (%s): ",
+	fprintf(stderr, "BTF GET_INFO test[%u] (%s): ",
 		test_num, test->descr);
 
+	if (test->special_test)
+		return test->special_test(test_num);
+
 	raw_btf = btf_raw_create(&hdr_tmpl,
 				 test->raw_types,
 				 test->str_sec,
@@ -1110,19 +1368,24 @@ static int do_test_get_info(unsigned int test_num)
 		goto done;
 	}
 
-	user_btf_size = (int)raw_btf_size + test->info_size_delta;
+	user_btf_size = (int)raw_btf_size + test->btf_size_delta;
 	expected_nbytes = min(raw_btf_size, user_btf_size);
 	if (raw_btf_size > expected_nbytes)
 		memset(user_btf + expected_nbytes, 0xff,
 		       raw_btf_size - expected_nbytes);
 
-	err = bpf_obj_get_info_by_fd(btf_fd, user_btf, &user_btf_size);
-	if (CHECK(err || user_btf_size != raw_btf_size ||
-		  memcmp(raw_btf, user_btf, expected_nbytes),
-		  "err:%d(errno:%d) raw_btf_size:%u user_btf_size:%u expected_nbytes:%u memcmp:%d",
-		  err, errno,
-		  raw_btf_size, user_btf_size, expected_nbytes,
-		  memcmp(raw_btf, user_btf, expected_nbytes))) {
+	info_len = sizeof(info);
+	info.btf = ptr_to_u64(user_btf);
+	info.btf_size = user_btf_size;
+
+	ret = 0;
+	err = bpf_obj_get_info_by_fd(btf_fd, &info, &info_len);
+	if (CHECK(err || !info.id || info_len != sizeof(info) ||
+		  info.btf_size != raw_btf_size ||
+		  (ret = memcmp(raw_btf, user_btf, expected_nbytes)),
+		  "err:%d errno:%d info.id:%u info_len:%u sizeof(info):%lu raw_btf_size:%u info.btf_size:%u expected_nbytes:%u memcmp:%d",
+		  err, errno, info.id, info_len, sizeof(info),
+		  raw_btf_size, info.btf_size, expected_nbytes, ret)) {
 		err = -1;
 		goto done;
 	}