libbpf: Streamline error reporting for high-level APIs

Implement changes to error reporting for high-level libbpf APIs to make them
less surprising and less error-prone to users:
  - in all the cases when error happens, errno is set to an appropriate error
    value;
  - in libbpf 1.0 mode, all pointer-returning APIs return NULL on error and
    error code is communicated through errno; this applies both to APIs that
    already returned NULL before (so now they communicate more detailed error
    codes), as well as for many APIs that used ERR_PTR() macro and encoded
    error numbers as fake pointers.
  - in legacy (default) mode, those APIs that were returning ERR_PTR(err),
    continue doing so, but still set errno.

With these changes, errno can be always used to extract actual error,
regardless of legacy or libbpf 1.0 modes. This is utilized internally in
libbpf in places where libbpf uses it's own high-level APIs.
libbpf_get_error() is adapted to handle both cases completely transparently to
end-users (and is used by libbpf consistently as well).

More context, justification, and discussion can be found in "Libbpf: the road
to v1.0" document ([0]).

  [0] https://docs.google.com/document/d/1UyjTZuPFWiPFyKk1tV5an11_iaRuec6U-ZESZ54nNTY

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210525035935.1461796-5-andrii@kernel.org

1 files changed, 152 insertions, 150 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d57e13a13798..b46760b93bb4 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -443,7 +443,7 @@ struct btf_type *btf_type_by_id(struct btf *btf, __u32 type_id)
 const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
 {
 	if (type_id >= btf->start_id + btf->nr_types)
-		return NULL;
+		return errno = EINVAL, NULL;
 	return btf_type_by_id((struct btf *)btf, type_id);
 }
 
@@ -510,7 +510,7 @@ size_t btf__pointer_size(const struct btf *btf)
 int btf__set_pointer_size(struct btf *btf, size_t ptr_sz)
 {
 	if (ptr_sz != 4 && ptr_sz != 8)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	btf->ptr_sz = ptr_sz;
 	return 0;
 }
@@ -537,7 +537,7 @@ enum btf_endianness btf__endianness(const struct btf *btf)
 int btf__set_endianness(struct btf *btf, enum btf_endianness endian)
 {
 	if (endian != BTF_LITTLE_ENDIAN && endian != BTF_BIG_ENDIAN)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	btf->swapped_endian = is_host_big_endian() != (endian == BTF_BIG_ENDIAN);
 	if (!btf->swapped_endian) {
@@ -568,8 +568,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 	int i;
 
 	t = btf__type_by_id(btf, type_id);
-	for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
-	     i++) {
+	for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t); i++) {
 		switch (btf_kind(t)) {
 		case BTF_KIND_INT:
 		case BTF_KIND_STRUCT:
@@ -592,12 +591,12 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 		case BTF_KIND_ARRAY:
 			array = btf_array(t);
 			if (nelems && array->nelems > UINT32_MAX / nelems)
-				return -E2BIG;
+				return libbpf_err(-E2BIG);
 			nelems *= array->nelems;
 			type_id = array->type;
 			break;
 		default:
-			return -EINVAL;
+			return libbpf_err(-EINVAL);
 		}
 
 		t = btf__type_by_id(btf, type_id);
@@ -605,9 +604,9 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 
 done:
 	if (size < 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (nelems && size > UINT32_MAX / nelems)
-		return -E2BIG;
+		return libbpf_err(-E2BIG);
 
 	return nelems * size;
 }
@@ -640,7 +639,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
 		for (i = 0; i < vlen; i++, m++) {
 			align = btf__align_of(btf, m->type);
 			if (align <= 0)
-				return align;
+				return libbpf_err(align);
 			max_align = max(max_align, align);
 		}
 
@@ -648,7 +647,7 @@ int btf__align_of(const struct btf *btf, __u32 id)
 	}
 	default:
 		pr_warn("unsupported BTF_KIND:%u\n", btf_kind(t));
-		return 0;
+		return errno = EINVAL, 0;
 	}
 }
 
@@ -667,7 +666,7 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
 	}
 
 	if (depth == MAX_RESOLVE_DEPTH || btf_type_is_void_or_null(t))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	return type_id;
 }
@@ -687,7 +686,7 @@ __s32 btf__find_by_name(const struct btf *btf, const char *type_name)
 			return i;
 	}
 
-	return -ENOENT;
+	return libbpf_err(-ENOENT);
 }
 
 __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
@@ -709,7 +708,7 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
 			return i;
 	}
 
-	return -ENOENT;
+	return libbpf_err(-ENOENT);
 }
 
 static bool btf_is_modifiable(const struct btf *btf)
@@ -785,12 +784,12 @@ static struct btf *btf_new_empty(struct btf *base_btf)
 
 struct btf *btf__new_empty(void)
 {
-	return btf_new_empty(NULL);
+	return libbpf_ptr(btf_new_empty(NULL));
 }
 
 struct btf *btf__new_empty_split(struct btf *base_btf)
 {
-	return btf_new_empty(base_btf);
+	return libbpf_ptr(btf_new_empty(base_btf));
 }
 
 static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf)
@@ -846,7 +845,7 @@ done:
 
 struct btf *btf__new(const void *data, __u32 size)
 {
-	return btf_new(data, size, NULL);
+	return libbpf_ptr(btf_new(data, size, NULL));
 }
 
 static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
@@ -937,7 +936,8 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 		goto done;
 	}
 	btf = btf_new(btf_data->d_buf, btf_data->d_size, base_btf);
-	if (IS_ERR(btf))
+	err = libbpf_get_error(btf);
+	if (err)
 		goto done;
 
 	switch (gelf_getclass(elf)) {
@@ -953,9 +953,9 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 	}
 
 	if (btf_ext && btf_ext_data) {
-		*btf_ext = btf_ext__new(btf_ext_data->d_buf,
-					btf_ext_data->d_size);
-		if (IS_ERR(*btf_ext))
+		*btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size);
+		err = libbpf_get_error(*btf_ext);
+		if (err)
 			goto done;
 	} else if (btf_ext) {
 		*btf_ext = NULL;
@@ -965,30 +965,24 @@ done:
 		elf_end(elf);
 	close(fd);
 
-	if (err)
-		return ERR_PTR(err);
-	/*
-	 * btf is always parsed before btf_ext, so no need to clean up
-	 * btf_ext, if btf loading failed
-	 */
-	if (IS_ERR(btf))
+	if (!err)
 		return btf;
-	if (btf_ext && IS_ERR(*btf_ext)) {
-		btf__free(btf);
-		err = PTR_ERR(*btf_ext);
-		return ERR_PTR(err);
-	}
-	return btf;
+
+	if (btf_ext)
+		btf_ext__free(*btf_ext);
+	btf__free(btf);
+
+	return ERR_PTR(err);
 }
 
 struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
 {
-	return btf_parse_elf(path, NULL, btf_ext);
+	return libbpf_ptr(btf_parse_elf(path, NULL, btf_ext));
 }
 
 struct btf *btf__parse_elf_split(const char *path, struct btf *base_btf)
 {
-	return btf_parse_elf(path, base_btf, NULL);
+	return libbpf_ptr(btf_parse_elf(path, base_btf, NULL));
 }
 
 static struct btf *btf_parse_raw(const char *path, struct btf *base_btf)
@@ -1056,36 +1050,39 @@ err_out:
 
 struct btf *btf__parse_raw(const char *path)
 {
-	return btf_parse_raw(path, NULL);
+	return libbpf_ptr(btf_parse_raw(path, NULL));
 }
 
 struct btf *btf__parse_raw_split(const char *path, struct btf *base_btf)
 {
-	return btf_parse_raw(path, base_btf);
+	return libbpf_ptr(btf_parse_raw(path, base_btf));
 }
 
 static struct btf *btf_parse(const char *path, struct btf *base_btf, struct btf_ext **btf_ext)
 {
 	struct btf *btf;
+	int err;
 
 	if (btf_ext)
 		*btf_ext = NULL;
 
 	btf = btf_parse_raw(path, base_btf);
-	if (!IS_ERR(btf) || PTR_ERR(btf) != -EPROTO)
+	err = libbpf_get_error(btf);
+	if (!err)
 		return btf;
-
+	if (err != -EPROTO)
+		return ERR_PTR(err);
 	return btf_parse_elf(path, base_btf, btf_ext);
 }
 
 struct btf *btf__parse(const char *path, struct btf_ext **btf_ext)
 {
-	return btf_parse(path, NULL, btf_ext);
+	return libbpf_ptr(btf_parse(path, NULL, btf_ext));
 }
 
 struct btf *btf__parse_split(const char *path, struct btf *base_btf)
 {
-	return btf_parse(path, base_btf, NULL);
+	return libbpf_ptr(btf_parse(path, base_btf, NULL));
 }
 
 static int compare_vsi_off(const void *_a, const void *_b)
@@ -1178,7 +1175,7 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
 		}
 	}
 
-	return err;
+	return libbpf_err(err);
 }
 
 static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian);
@@ -1191,13 +1188,13 @@ int btf__load(struct btf *btf)
 	int err = 0;
 
 	if (btf->fd >= 0)
-		return -EEXIST;
+		return libbpf_err(-EEXIST);
 
 retry_load:
 	if (log_buf_size) {
 		log_buf = malloc(log_buf_size);
 		if (!log_buf)
-			return -ENOMEM;
+			return libbpf_err(-ENOMEM);
 
 		*log_buf = 0;
 	}
@@ -1229,7 +1226,7 @@ retry_load:
 
 done:
 	free(log_buf);
-	return err;
+	return libbpf_err(err);
 }
 
 int btf__fd(const struct btf *btf)
@@ -1305,7 +1302,7 @@ const void *btf__get_raw_data(const struct btf *btf_ro, __u32 *size)
 
 	data = btf_get_raw_data(btf, &data_sz, btf->swapped_endian);
 	if (!data)
-		return NULL;
+		return errno = -ENOMEM, NULL;
 
 	btf->raw_size = data_sz;
 	if (btf->swapped_endian)
@@ -1323,7 +1320,7 @@ const char *btf__str_by_offset(const struct btf *btf, __u32 offset)
 	else if (offset - btf->start_str_off < btf->hdr->str_len)
 		return btf_strs_data(btf) + (offset - btf->start_str_off);
 	else
-		return NULL;
+		return errno = EINVAL, NULL;
 }
 
 const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
@@ -1388,17 +1385,20 @@ exit_free:
 int btf__get_from_id(__u32 id, struct btf **btf)
 {
 	struct btf *res;
-	int btf_fd;
+	int err, btf_fd;
 
 	*btf = NULL;
 	btf_fd = bpf_btf_get_fd_by_id(id);
 	if (btf_fd < 0)
-		return -errno;
+		return libbpf_err(-errno);
 
 	res = btf_get_from_fd(btf_fd, NULL);
+	err = libbpf_get_error(res);
+
 	close(btf_fd);
-	if (IS_ERR(res))
-		return PTR_ERR(res);
+
+	if (err)
+		return libbpf_err(err);
 
 	*btf = res;
 	return 0;
@@ -1415,31 +1415,30 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 	__s64 key_size, value_size;
 	__s32 container_id;
 
-	if (snprintf(container_name, max_name, "____btf_map_%s", map_name) ==
-	    max_name) {
+	if (snprintf(container_name, max_name, "____btf_map_%s", map_name) == max_name) {
 		pr_warn("map:%s length of '____btf_map_%s' is too long\n",
 			map_name, map_name);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	container_id = btf__find_by_name(btf, container_name);
 	if (container_id < 0) {
 		pr_debug("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
 			 map_name, container_name);
-		return container_id;
+		return libbpf_err(container_id);
 	}
 
 	container_type = btf__type_by_id(btf, container_id);
 	if (!container_type) {
 		pr_warn("map:%s cannot find BTF type for container_id:%u\n",
 			map_name, container_id);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	if (!btf_is_struct(container_type) || btf_vlen(container_type) < 2) {
 		pr_warn("map:%s container_name:%s is an invalid container struct\n",
 			map_name, container_name);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	key = btf_members(container_type);
@@ -1448,25 +1447,25 @@ int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 	key_size = btf__resolve_size(btf, key->type);
 	if (key_size < 0) {
 		pr_warn("map:%s invalid BTF key_type_size\n", map_name);
-		return key_size;
+		return libbpf_err(key_size);
 	}
 
 	if (expected_key_size != key_size) {
 		pr_warn("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
 			map_name, (__u32)key_size, expected_key_size);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	value_size = btf__resolve_size(btf, value->type);
 	if (value_size < 0) {
 		pr_warn("map:%s invalid BTF value_type_size\n", map_name);
-		return value_size;
+		return libbpf_err(value_size);
 	}
 
 	if (expected_value_size != value_size) {
 		pr_warn("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
 			map_name, (__u32)value_size, expected_value_size);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	*key_type_id = key->type;
@@ -1563,11 +1562,11 @@ int btf__find_str(struct btf *btf, const char *s)
 
 	/* BTF needs to be in a modifiable state to build string lookup index */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	off = strset__find_str(btf->strs_set, s);
 	if (off < 0)
-		return off;
+		return libbpf_err(off);
 
 	return btf->start_str_off + off;
 }
@@ -1588,11 +1587,11 @@ int btf__add_str(struct btf *btf, const char *s)
 	}
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	off = strset__add_str(btf->strs_set, s);
 	if (off < 0)
-		return off;
+		return libbpf_err(off);
 
 	btf->hdr->str_len = strset__data_size(btf->strs_set);
 
@@ -1616,7 +1615,7 @@ static int btf_commit_type(struct btf *btf, int data_sz)
 
 	err = btf_add_type_idx_entry(btf, btf->hdr->type_len);
 	if (err)
-		return err;
+		return libbpf_err(err);
 
 	btf->hdr->type_len += data_sz;
 	btf->hdr->str_off += data_sz;
@@ -1653,21 +1652,21 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t
 
 	sz = btf_type_size(src_type);
 	if (sz < 0)
-		return sz;
+		return libbpf_err(sz);
 
 	/* deconstruct BTF, if necessary, and invalidate raw_data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	memcpy(t, src_type, sz);
 
 	err = btf_type_visit_str_offs(t, btf_rewrite_str, &p);
 	if (err)
-		return err;
+		return libbpf_err(err);
 
 	return btf_commit_type(btf, sz);
 }
@@ -1688,21 +1687,21 @@ int btf__add_int(struct btf *btf, const char *name, size_t byte_sz, int encoding
 
 	/* non-empty name */
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	/* byte_sz must be power of 2 */
 	if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 16)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (encoding & ~(BTF_INT_SIGNED | BTF_INT_CHAR | BTF_INT_BOOL))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* deconstruct BTF, if necessary, and invalidate raw_data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type) + sizeof(int);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	/* if something goes wrong later, we might end up with an extra string,
 	 * but that shouldn't be a problem, because BTF can't be constructed
@@ -1736,20 +1735,20 @@ int btf__add_float(struct btf *btf, const char *name, size_t byte_sz)
 
 	/* non-empty name */
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* byte_sz must be one of the explicitly allowed values */
 	if (byte_sz != 2 && byte_sz != 4 && byte_sz != 8 && byte_sz != 12 &&
 	    byte_sz != 16)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	name_off = btf__add_str(btf, name);
 	if (name_off < 0)
@@ -1780,15 +1779,15 @@ static int btf_add_ref_kind(struct btf *btf, int kind, const char *name, int ref
 	int sz, name_off = 0;
 
 	if (validate_type_id(ref_type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	if (name && name[0]) {
 		name_off = btf__add_str(btf, name);
@@ -1831,15 +1830,15 @@ int btf__add_array(struct btf *btf, int index_type_id, int elem_type_id, __u32 n
 	int sz;
 
 	if (validate_type_id(index_type_id) || validate_type_id(elem_type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type) + sizeof(struct btf_array);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	t->name_off = 0;
 	t->info = btf_type_info(BTF_KIND_ARRAY, 0, 0);
@@ -1860,12 +1859,12 @@ static int btf_add_composite(struct btf *btf, int kind, const char *name, __u32
 	int sz, name_off = 0;
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	if (name && name[0]) {
 		name_off = btf__add_str(btf, name);
@@ -1943,30 +1942,30 @@ int btf__add_field(struct btf *btf, const char *name, int type_id,
 
 	/* last type should be union/struct */
 	if (btf->nr_types == 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	t = btf_last_type(btf);
 	if (!btf_is_composite(t))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (validate_type_id(type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	/* best-effort bit field offset/size enforcement */
 	is_bitfield = bit_size || (bit_offset % 8 != 0);
 	if (is_bitfield && (bit_size == 0 || bit_size > 255 || bit_offset > 0xffffff))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* only offset 0 is allowed for unions */
 	if (btf_is_union(t) && bit_offset)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* decompose and invalidate raw data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_member);
 	m = btf_add_type_mem(btf, sz);
 	if (!m)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	if (name && name[0]) {
 		name_off = btf__add_str(btf, name);
@@ -2008,15 +2007,15 @@ int btf__add_enum(struct btf *btf, const char *name, __u32 byte_sz)
 
 	/* byte_sz must be power of 2 */
 	if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 8)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	if (name && name[0]) {
 		name_off = btf__add_str(btf, name);
@@ -2048,25 +2047,25 @@ int btf__add_enum_value(struct btf *btf, const char *name, __s64 value)
 
 	/* last type should be BTF_KIND_ENUM */
 	if (btf->nr_types == 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	t = btf_last_type(btf);
 	if (!btf_is_enum(t))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* non-empty name */
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (value < INT_MIN || value > UINT_MAX)
-		return -E2BIG;
+		return libbpf_err(-E2BIG);
 
 	/* decompose and invalidate raw data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_enum);
 	v = btf_add_type_mem(btf, sz);
 	if (!v)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	name_off = btf__add_str(btf, name);
 	if (name_off < 0)
@@ -2096,7 +2095,7 @@ int btf__add_enum_value(struct btf *btf, const char *name, __s64 value)
 int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind)
 {
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	switch (fwd_kind) {
 	case BTF_FWD_STRUCT:
@@ -2117,7 +2116,7 @@ int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind)
 		 */
 		return btf__add_enum(btf, name, sizeof(int));
 	default:
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 }
 
@@ -2132,7 +2131,7 @@ int btf__add_fwd(struct btf *btf, const char *name, enum btf_fwd_kind fwd_kind)
 int btf__add_typedef(struct btf *btf, const char *name, int ref_type_id)
 {
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	return btf_add_ref_kind(btf, BTF_KIND_TYPEDEF, name, ref_type_id);
 }
@@ -2187,10 +2186,10 @@ int btf__add_func(struct btf *btf, const char *name,
 	int id;
 
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (linkage != BTF_FUNC_STATIC && linkage != BTF_FUNC_GLOBAL &&
 	    linkage != BTF_FUNC_EXTERN)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	id = btf_add_ref_kind(btf, BTF_KIND_FUNC, name, proto_type_id);
 	if (id > 0) {
@@ -2198,7 +2197,7 @@ int btf__add_func(struct btf *btf, const char *name,
 
 		t->info = btf_type_info(BTF_KIND_FUNC, linkage, 0);
 	}
-	return id;
+	return libbpf_err(id);
 }
 
 /*
@@ -2219,15 +2218,15 @@ int btf__add_func_proto(struct btf *btf, int ret_type_id)
 	int sz;
 
 	if (validate_type_id(ret_type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	/* start out with vlen=0; this will be adjusted when adding enum
 	 * values, if necessary
@@ -2254,23 +2253,23 @@ int btf__add_func_param(struct btf *btf, const char *name, int type_id)
 	int sz, name_off = 0;
 
 	if (validate_type_id(type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* last type should be BTF_KIND_FUNC_PROTO */
 	if (btf->nr_types == 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	t = btf_last_type(btf);
 	if (!btf_is_func_proto(t))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* decompose and invalidate raw data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_param);
 	p = btf_add_type_mem(btf, sz);
 	if (!p)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	if (name && name[0]) {
 		name_off = btf__add_str(btf, name);
@@ -2308,21 +2307,21 @@ int btf__add_var(struct btf *btf, const char *name, int linkage, int type_id)
 
 	/* non-empty name */
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (linkage != BTF_VAR_STATIC && linkage != BTF_VAR_GLOBAL_ALLOCATED &&
 	    linkage != BTF_VAR_GLOBAL_EXTERN)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (validate_type_id(type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* deconstruct BTF, if necessary, and invalidate raw_data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type) + sizeof(struct btf_var);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	name_off = btf__add_str(btf, name);
 	if (name_off < 0)
@@ -2357,15 +2356,15 @@ int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz)
 
 	/* non-empty name */
 	if (!name || !name[0])
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_type);
 	t = btf_add_type_mem(btf, sz);
 	if (!t)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	name_off = btf__add_str(btf, name);
 	if (name_off < 0)
@@ -2397,22 +2396,22 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __
 
 	/* last type should be BTF_KIND_DATASEC */
 	if (btf->nr_types == 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	t = btf_last_type(btf);
 	if (!btf_is_datasec(t))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (validate_type_id(var_type_id))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* decompose and invalidate raw data */
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	sz = sizeof(struct btf_var_secinfo);
 	v = btf_add_type_mem(btf, sz);
 	if (!v)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	v->type = var_type_id;
 	v->offset = offset;
@@ -2614,11 +2613,11 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
 
 	err = btf_ext_parse_hdr(data, size);
 	if (err)
-		return ERR_PTR(err);
+		return libbpf_err_ptr(err);
 
 	btf_ext = calloc(1, sizeof(struct btf_ext));
 	if (!btf_ext)
-		return ERR_PTR(-ENOMEM);
+		return libbpf_err_ptr(-ENOMEM);
 
 	btf_ext->data_size = size;
 	btf_ext->data = malloc(size);
@@ -2628,9 +2627,11 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
 	}
 	memcpy(btf_ext->data, data, size);
 
-	if (btf_ext->hdr->hdr_len <
-	    offsetofend(struct btf_ext_header, line_info_len))
+	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, line_info_len)) {
+		err = -EINVAL;
 		goto done;
+	}
+
 	err = btf_ext_setup_func_info(btf_ext);
 	if (err)
 		goto done;
@@ -2639,8 +2640,11 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
 	if (err)
 		goto done;
 
-	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
+	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
+		err = -EINVAL;
 		goto done;
+	}
+
 	err = btf_ext_setup_core_relos(btf_ext);
 	if (err)
 		goto done;
@@ -2648,7 +2652,7 @@ struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
 done:
 	if (err) {
 		btf_ext__free(btf_ext);
-		return ERR_PTR(err);
+		return libbpf_err_ptr(err);
 	}
 
 	return btf_ext;
@@ -2687,7 +2691,7 @@ static int btf_ext_reloc_info(const struct btf *btf,
 		existing_len = (*cnt) * record_size;
 		data = realloc(*info, existing_len + records_len);
 		if (!data)
-			return -ENOMEM;
+			return libbpf_err(-ENOMEM);
 
 		memcpy(data + existing_len, sinfo->data, records_len);
 		/* adjust insn_off only, the rest data will be passed
@@ -2697,15 +2701,14 @@ static int btf_ext_reloc_info(const struct btf *btf,
 			__u32 *insn_off;
 
 			insn_off = data + existing_len + (i * record_size);
-			*insn_off = *insn_off / sizeof(struct bpf_insn) +
-				insns_cnt;
+			*insn_off = *insn_off / sizeof(struct bpf_insn) + insns_cnt;
 		}
 		*info = data;
 		*cnt += sinfo->num_info;
 		return 0;
 	}
 
-	return -ENOENT;
+	return libbpf_err(-ENOENT);
 }
 
 int btf_ext__reloc_func_info(const struct btf *btf,
@@ -2894,11 +2897,11 @@ int btf__dedup(struct btf *btf, struct btf_ext *btf_ext,
 
 	if (IS_ERR(d)) {
 		pr_debug("btf_dedup_new failed: %ld", PTR_ERR(d));
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	if (btf_ensure_modifiable(btf))
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 
 	err = btf_dedup_prep(d);
 	if (err) {
@@ -2938,7 +2941,7 @@ int btf__dedup(struct btf *btf, struct btf_ext *btf_ext,
 
 done:
 	btf_dedup_free(d);
-	return err;
+	return libbpf_err(err);
 }
 
 #define BTF_UNPROCESSED_ID ((__u32)-1)
@@ -4411,7 +4414,7 @@ struct btf *libbpf_find_kernel_btf(void)
 	char path[PATH_MAX + 1];
 	struct utsname buf;
 	struct btf *btf;
-	int i;
+	int i, err;
 
 	uname(&buf);
 
@@ -4425,17 +4428,16 @@ struct btf *libbpf_find_kernel_btf(void)
 			btf = btf__parse_raw(path);
 		else
 			btf = btf__parse_elf(path, NULL);
-
-		pr_debug("loading kernel BTF '%s': %ld\n",
-			 path, IS_ERR(btf) ? PTR_ERR(btf) : 0);
-		if (IS_ERR(btf))
+		err = libbpf_get_error(btf);
+		pr_debug("loading kernel BTF '%s': %d\n", path, err);
+		if (err)
 			continue;
 
 		return btf;
 	}
 
 	pr_warn("failed to find valid kernel BTF\n");
-	return ERR_PTR(-ESRCH);
+	return libbpf_err_ptr(-ESRCH);
 }
 
 int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ctx)