libbpf: Streamline error reporting for high-level APIs

mainline inclusion
from mainline-5.14-rc1
commit e9fc3ce9
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e9fc3ce99b3485586e7e4803b63df8b4c681f897

-------------------------------------------------

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-ZESZ54nNTYSigned-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Acked-by: NToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210525035935.1461796-5-andrii@kernel.org
(cherry picked from commit e9fc3ce9)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/bpf_prog_linfo.c

@@ -106,7 +106,7 @@ struct bpf_prog_linfo *bpf_prog_linfo__new(const struct bpf_prog_info *info)
 	nr_linfo = info->nr_line_info;
 
 	if (!nr_linfo)
-		return NULL;
+		return errno = EINVAL, NULL;
 
 	/*
 	 * The min size that bpf_prog_linfo has to access for
@@ -114,11 +114,11 @@ struct bpf_prog_linfo *bpf_prog_linfo__new(const struct bpf_prog_info *info)
 	 */
 	if (info->line_info_rec_size <
 	    offsetof(struct bpf_line_info, file_name_off))
-		return NULL;
+		return errno = EINVAL, NULL;
 
 	prog_linfo = calloc(1, sizeof(*prog_linfo));
 	if (!prog_linfo)
-		return NULL;
+		return errno = ENOMEM, NULL;
 
 	/* Copy xlated line_info */
 	prog_linfo->nr_linfo = nr_linfo;
@@ -174,7 +174,7 @@ struct bpf_prog_linfo *bpf_prog_linfo__new(const struct bpf_prog_info *info)
 
 err_free:
 	bpf_prog_linfo__free(prog_linfo);
-	return NULL;
+	return errno = EINVAL, NULL;
 }
 
 const struct bpf_line_info *
@@ -186,11 +186,11 @@ bpf_prog_linfo__lfind_addr_func(const struct bpf_prog_linfo *prog_linfo,
 	const __u64 *jited_linfo;
 
 	if (func_idx >= prog_linfo->nr_jited_func)
-		return NULL;
+		return errno = ENOENT, NULL;
 
 	nr_linfo = prog_linfo->nr_jited_linfo_per_func[func_idx];
 	if (nr_skip >= nr_linfo)
-		return NULL;
+		return errno = ENOENT, NULL;
 
 	start = prog_linfo->jited_linfo_func_idx[func_idx] + nr_skip;
 	jited_rec_size = prog_linfo->jited_rec_size;
@@ -198,7 +198,7 @@ bpf_prog_linfo__lfind_addr_func(const struct bpf_prog_linfo *prog_linfo,
 		(start * jited_rec_size);
 	jited_linfo = raw_jited_linfo;
 	if (addr < *jited_linfo)
-		return NULL;
+		return errno = ENOENT, NULL;
 
 	nr_linfo -= nr_skip;
 	rec_size = prog_linfo->rec_size;
@@ -225,13 +225,13 @@ bpf_prog_linfo__lfind(const struct bpf_prog_linfo *prog_linfo,
 
 	nr_linfo = prog_linfo->nr_linfo;
 	if (nr_skip >= nr_linfo)
-		return NULL;
+		return errno = ENOENT, NULL;
 
 	rec_size = prog_linfo->rec_size;
 	raw_linfo = prog_linfo->raw_linfo + (nr_skip * rec_size);
 	linfo = raw_linfo;
 	if (insn_off < linfo->insn_off)
-		return NULL;
+		return errno = ENOENT, NULL;
 
 	nr_linfo -= nr_skip;
 	for (i = 0; i < nr_linfo; i++) {

tools/lib/bpf/btf_dump.c

@@ -128,7 +128,7 @@ struct btf_dump *btf_dump__new(const struct btf *btf,
 
 	d = calloc(1, sizeof(struct btf_dump));
 	if (!d)
-		return ERR_PTR(-ENOMEM);
+		return libbpf_err_ptr(-ENOMEM);
 
 	d->btf = btf;
 	d->btf_ext = btf_ext;
@@ -156,7 +156,7 @@ struct btf_dump *btf_dump__new(const struct btf *btf,
 	return d;
 err:
 	btf_dump__free(d);
-	return ERR_PTR(err);
+	return libbpf_err_ptr(err);
 }
 
 static int btf_dump_resize(struct btf_dump *d)
@@ -236,16 +236,16 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id)
 	int err, i;
 
 	if (id > btf__get_nr_types(d->btf))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = btf_dump_resize(d);
 	if (err)
-		return err;
+		return libbpf_err(err);
 
 	d->emit_queue_cnt = 0;
 	err = btf_dump_order_type(d, id, false);
 	if (err < 0)
-		return err;
+		return libbpf_err(err);
 
 	for (i = 0; i < d->emit_queue_cnt; i++)
 		btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
@@ -1075,11 +1075,11 @@ int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
 	int lvl, err;
 
 	if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = btf_dump_resize(d);
 	if (err)
-		return -EINVAL;
+		return libbpf_err(err);
 
 	fname = OPTS_GET(opts, field_name, "");
 	lvl = OPTS_GET(opts, indent_level, 0);

tools/lib/bpf/libbpf_errno.c

@@ -12,6 +12,7 @@
 #include <string.h>
 
 #include "libbpf.h"
+#include "libbpf_internal.h"
 
 /* make sure libbpf doesn't use kernel-only integer typedefs */
 #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
@@ -39,7 +40,7 @@ static const char *libbpf_strerror_table[NR_ERRNO] = {
 int libbpf_strerror(int err, char *buf, size_t size)
 {
 	if (!buf || !size)
-		return -1;
+		return libbpf_err(-EINVAL);
 
 	err = err > 0 ? err : -err;
 
@@ -48,7 +49,7 @@ int libbpf_strerror(int err, char *buf, size_t size)
 
 		ret = strerror_r(err, buf, size);
 		buf[size - 1] = '\0';
-		return ret;
+		return libbpf_err_errno(ret);
 	}
 
 	if (err < __LIBBPF_ERRNO__END) {
@@ -62,5 +63,5 @@ int libbpf_strerror(int err, char *buf, size_t size)
 
 	snprintf(buf, size, "Unknown libbpf error %d", err);
 	buf[size - 1] = '\0';
-	return -1;
+	return libbpf_err(-ENOENT);
 }

tools/lib/bpf/libbpf_internal.h

@@ -467,4 +467,31 @@ static inline int libbpf_err_errno(int ret)
 	return ret;
 }
 
+/* handle error for pointer-returning APIs, err is assumed to be < 0 always */
+static inline void *libbpf_err_ptr(int err)
+{
+	/* set errno on error, this doesn't break anything */
+	errno = -err;
+
+	if (libbpf_mode & LIBBPF_STRICT_CLEAN_PTRS)
+		return NULL;
+
+	/* legacy: encode err as ptr */
+	return ERR_PTR(err);
+}
+
+/* handle pointer-returning APIs' error handling */
+static inline void *libbpf_ptr(void *ret)
+{
+	/* set errno on error, this doesn't break anything */
+	if (IS_ERR(ret))
+		errno = -PTR_ERR(ret);
+
+	if (libbpf_mode & LIBBPF_STRICT_CLEAN_PTRS)
+		return IS_ERR(ret) ? NULL : ret;
+
+	/* legacy: pass-through original pointer */
+	return ret;
+}
+
 #endif /* __LIBBPF_LIBBPF_INTERNAL_H */

tools/lib/bpf/linker.c

@@ -220,16 +220,16 @@ struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts
 	int err;
 
 	if (!OPTS_VALID(opts, bpf_linker_opts))
-		return NULL;
+		return errno = EINVAL, NULL;
 
 	if (elf_version(EV_CURRENT) == EV_NONE) {
 		pr_warn_elf("libelf initialization failed");
-		return NULL;
+		return errno = EINVAL, NULL;
 	}
 
 	linker = calloc(1, sizeof(*linker));
 	if (!linker)
-		return NULL;
+		return errno = ENOMEM, NULL;
 
 	linker->fd = -1;
 
@@ -241,7 +241,7 @@ struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts
 
 err_out:
 	bpf_linker__free(linker);
-	return NULL;
+	return errno = -err, NULL;
 }
 
 static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name)
@@ -444,10 +444,10 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
 	int err = 0;
 
 	if (!OPTS_VALID(opts, bpf_linker_file_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (!linker->elf)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
 	err = err ?: linker_append_sec_data(linker, &obj);
@@ -467,7 +467,7 @@ int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
 	if (obj.fd >= 0)
 		close(obj.fd);
 
-	return err;
+	return libbpf_err(err);
 }
 
 static bool is_dwarf_sec_name(const char *name)
@@ -2548,11 +2548,11 @@ int bpf_linker__finalize(struct bpf_linker *linker)
 	int err, i;
 
 	if (!linker->elf)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	err = finalize_btf(linker);
 	if (err)
-		return err;
+		return libbpf_err(err);
 
 	/* Finalize strings */
 	strs_sz = strset__data_size(linker->strtab_strs);
@@ -2584,14 +2584,14 @@ int bpf_linker__finalize(struct bpf_linker *linker)
 	if (elf_update(linker->elf, ELF_C_NULL) < 0) {
 		err = -errno;
 		pr_warn_elf("failed to finalize ELF layout");
-		return err;
+		return libbpf_err(err);
 	}
 
 	/* Write out final ELF contents */
 	if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
 		err = -errno;
 		pr_warn_elf("failed to write ELF contents");
-		return err;
+		return libbpf_err(err);
 	}
 
 	elf_end(linker->elf);

tools/lib/bpf/netlink.c

@@ -225,22 +225,26 @@ static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
 int bpf_set_link_xdp_fd_opts(int ifindex, int fd, __u32 flags,
 			     const struct bpf_xdp_set_link_opts *opts)
 {
-	int old_fd = -1;
+	int old_fd = -1, ret;
 
 	if (!OPTS_VALID(opts, bpf_xdp_set_link_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	if (OPTS_HAS(opts, old_fd)) {
 		old_fd = OPTS_GET(opts, old_fd, -1);
 		flags |= XDP_FLAGS_REPLACE;
 	}
 
-	return __bpf_set_link_xdp_fd_replace(ifindex, fd, old_fd, flags);
+	ret = __bpf_set_link_xdp_fd_replace(ifindex, fd, old_fd, flags);
+	return libbpf_err(ret);
 }
 
 int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
 {
-	return __bpf_set_link_xdp_fd_replace(ifindex, fd, 0, flags);
+	int ret;
+
+	ret = __bpf_set_link_xdp_fd_replace(ifindex, fd, 0, flags);
+	return libbpf_err(ret);
 }
 
 static int __dump_link_nlmsg(struct nlmsghdr *nlh,
@@ -321,13 +325,13 @@ int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
 	};
 
 	if (flags & ~XDP_FLAGS_MASK || !info_size)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	/* Check whether the single {HW,DRV,SKB} mode is set */
 	flags &= (XDP_FLAGS_SKB_MODE | XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE);
 	mask = flags - 1;
 	if (flags && flags & mask)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	xdp_id.ifindex = ifindex;
 	xdp_id.flags = flags;
@@ -341,7 +345,7 @@ int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
 		memset((void *) info + sz, 0, info_size - sz);
 	}
 
-	return ret;
+	return libbpf_err(ret);
 }
 
 static __u32 get_xdp_id(struct xdp_link_info *info, __u32 flags)
@@ -369,7 +373,7 @@ int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags)
 	if (!ret)
 		*prog_id = get_xdp_id(&info, flags);
 
-	return ret;
+	return libbpf_err(ret);
 }
 
 typedef int (*qdisc_config_t)(struct nlmsghdr *nh, struct tcmsg *t,
@@ -463,11 +467,14 @@ static int tc_qdisc_delete(struct bpf_tc_hook *hook)
 
 int bpf_tc_hook_create(struct bpf_tc_hook *hook)
 {
+	int ret;
+
 	if (!hook || !OPTS_VALID(hook, bpf_tc_hook) ||
 	    OPTS_GET(hook, ifindex, 0) <= 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
-	return tc_qdisc_create_excl(hook);
+	ret = tc_qdisc_create_excl(hook);
+	return libbpf_err(ret);
 }
 
 static int __bpf_tc_detach(const struct bpf_tc_hook *hook,
@@ -478,18 +485,18 @@ int bpf_tc_hook_destroy(struct bpf_tc_hook *hook)
 {
 	if (!hook || !OPTS_VALID(hook, bpf_tc_hook) ||
 	    OPTS_GET(hook, ifindex, 0) <= 0)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	switch (OPTS_GET(hook, attach_point, 0)) {
 	case BPF_TC_INGRESS:
 	case BPF_TC_EGRESS:
-		return __bpf_tc_detach(hook, NULL, true);
+		return libbpf_err(__bpf_tc_detach(hook, NULL, true));
 	case BPF_TC_INGRESS | BPF_TC_EGRESS:
-		return tc_qdisc_delete(hook);
+		return libbpf_err(tc_qdisc_delete(hook));
 	case BPF_TC_CUSTOM:
-		return -EOPNOTSUPP;
+		return libbpf_err(-EOPNOTSUPP);
 	default:
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 }
 
@@ -574,7 +581,7 @@ int bpf_tc_attach(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 	if (!hook || !opts ||
 	    !OPTS_VALID(hook, bpf_tc_hook) ||
 	    !OPTS_VALID(opts, bpf_tc_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	ifindex      = OPTS_GET(hook, ifindex, 0);
 	parent       = OPTS_GET(hook, parent, 0);
@@ -587,11 +594,11 @@ int bpf_tc_attach(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 	flags        = OPTS_GET(opts, flags, 0);
 
 	if (ifindex <= 0 || !prog_fd || prog_id)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (priority > UINT16_MAX)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (flags & ~BPF_TC_F_REPLACE)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	flags = (flags & BPF_TC_F_REPLACE) ? NLM_F_REPLACE : NLM_F_EXCL;
 	protocol = ETH_P_ALL;
@@ -608,32 +615,32 @@ int bpf_tc_attach(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 
 	ret = tc_get_tcm_parent(attach_point, &parent);
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	req.tc.tcm_parent = parent;
 
 	ret = nlattr_add(&req.nh, sizeof(req), TCA_KIND, "bpf", sizeof("bpf"));
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	nla = nlattr_begin_nested(&req.nh, sizeof(req), TCA_OPTIONS);
 	if (!nla)
-		return -EMSGSIZE;
+		return libbpf_err(-EMSGSIZE);
 	ret = tc_add_fd_and_name(&req.nh, sizeof(req), prog_fd);
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	bpf_flags = TCA_BPF_FLAG_ACT_DIRECT;
 	ret = nlattr_add(&req.nh, sizeof(req), TCA_BPF_FLAGS, &bpf_flags,
 			 sizeof(bpf_flags));
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	nlattr_end_nested(&req.nh, nla);
 
 	info.opts = opts;
 
 	ret = libbpf_netlink_send_recv(&req.nh, get_tc_info, NULL, &info);
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	if (!info.processed)
-		return -ENOENT;
+		return libbpf_err(-ENOENT);
 	return ret;
 }
 
@@ -708,7 +715,13 @@ static int __bpf_tc_detach(const struct bpf_tc_hook *hook,
 int bpf_tc_detach(const struct bpf_tc_hook *hook,
 		  const struct bpf_tc_opts *opts)
 {
-	return !opts ? -EINVAL : __bpf_tc_detach(hook, opts, false);
+	int ret;
+
+	if (!opts)
+		return libbpf_err(-EINVAL);
+
+	ret = __bpf_tc_detach(hook, opts, false);
+	return libbpf_err(ret);
 }
 
 int bpf_tc_query(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
@@ -725,7 +738,7 @@ int bpf_tc_query(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 	if (!hook || !opts ||
 	    !OPTS_VALID(hook, bpf_tc_hook) ||
 	    !OPTS_VALID(opts, bpf_tc_opts))
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	ifindex      = OPTS_GET(hook, ifindex, 0);
 	parent       = OPTS_GET(hook, parent, 0);
@@ -739,9 +752,9 @@ int bpf_tc_query(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 
 	if (ifindex <= 0 || flags || prog_fd || prog_id ||
 	    !handle || !priority)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	if (priority > UINT16_MAX)
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 
 	protocol = ETH_P_ALL;
 
@@ -756,19 +769,19 @@ int bpf_tc_query(const struct bpf_tc_hook *hook, struct bpf_tc_opts *opts)
 
 	ret = tc_get_tcm_parent(attach_point, &parent);
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	req.tc.tcm_parent = parent;
 
 	ret = nlattr_add(&req.nh, sizeof(req), TCA_KIND, "bpf", sizeof("bpf"));
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 
 	info.opts = opts;
 
 	ret = libbpf_netlink_send_recv(&req.nh, get_tc_info, NULL, &info);
 	if (ret < 0)
-		return ret;
+		return libbpf_err(ret);
 	if (!info.processed)
-		return -ENOENT;
+		return libbpf_err(-ENOENT);
 	return ret;
 }

tools/lib/bpf/ringbuf.c

@@ -69,23 +69,23 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 		err = -errno;
 		pr_warn("ringbuf: failed to get map info for fd=%d: %d\n",
 			map_fd, err);
-		return err;
+		return libbpf_err(err);
 	}
 
 	if (info.type != BPF_MAP_TYPE_RINGBUF) {
 		pr_warn("ringbuf: map fd=%d is not BPF_MAP_TYPE_RINGBUF\n",
 			map_fd);
-		return -EINVAL;
+		return libbpf_err(-EINVAL);
 	}
 
 	tmp = libbpf_reallocarray(rb->rings, rb->ring_cnt + 1, sizeof(*rb->rings));
 	if (!tmp)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 	rb->rings = tmp;
 
 	tmp = libbpf_reallocarray(rb->events, rb->ring_cnt + 1, sizeof(*rb->events));
 	if (!tmp)
-		return -ENOMEM;
+		return libbpf_err(-ENOMEM);
 	rb->events = tmp;
 
 	r = &rb->rings[rb->ring_cnt];
@@ -103,7 +103,7 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 		err = -errno;
 		pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
 			map_fd, err);
-		return err;
+		return libbpf_err(err);
 	}
 	r->consumer_pos = tmp;
 
@@ -118,7 +118,7 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 		ringbuf_unmap_ring(rb, r);
 		pr_warn("ringbuf: failed to mmap data pages for map fd=%d: %d\n",
 			map_fd, err);
-		return err;
+		return libbpf_err(err);
 	}
 	r->producer_pos = tmp;
 	r->data = tmp + rb->page_size;
@@ -133,7 +133,7 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 		ringbuf_unmap_ring(rb, r);
 		pr_warn("ringbuf: failed to epoll add map fd=%d: %d\n",
 			map_fd, err);
-		return err;
+		return libbpf_err(err);
 	}
 
 	rb->ring_cnt++;
@@ -165,11 +165,11 @@ ring_buffer__new(int map_fd, ring_buffer_sample_fn sample_cb, void *ctx,
 	int err;
 
 	if (!OPTS_VALID(opts, ring_buffer_opts))
-		return NULL;
+		return errno = EINVAL, NULL;
 
 	rb = calloc(1, sizeof(*rb));
 	if (!rb)
-		return NULL;
+		return errno = ENOMEM, NULL;
 
 	rb->page_size = getpagesize();
 
@@ -188,7 +188,7 @@ ring_buffer__new(int map_fd, ring_buffer_sample_fn sample_cb, void *ctx,
 
 err_out:
 	ring_buffer__free(rb);
-	return NULL;
+	return errno = -err, NULL;
 }
 
 static inline int roundup_len(__u32 len)
@@ -260,7 +260,7 @@ int ring_buffer__consume(struct ring_buffer *rb)
 
 		err = ringbuf_process_ring(ring);
 		if (err < 0)
-			return err;
+			return libbpf_err(err);
 		res += err;
 	}
 	if (res > INT_MAX)
@@ -279,7 +279,7 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
 
 	cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms);
 	if (cnt < 0)
-		return -errno;
+		return libbpf_err(-errno);
 
 	for (i = 0; i < cnt; i++) {
 		__u32 ring_id = rb->events[i].data.fd;
@@ -287,7 +287,7 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
 
 		err = ringbuf_process_ring(ring);
 		if (err < 0)
-			return err;
+			return libbpf_err(err);
 		res += err;
 	}
 	if (res > INT_MAX)