[PATCH v2 3/6] libbpf: Introduce bpf_prog_get_fd_by_id_opts()

From: Roberto Sassu
Date: Thu Oct 06 2022 - 07:08:52 EST


From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Introduce bpf_prog_get_fd_by_id_opts(), for symmetry with
bpf_map_get_fd_by_id_opts(), to let the caller pass the newly introduced
data structure bpf_get_fd_by_id_opts. Keep the existing
bpf_prog_get_fd_by_id(), and call bpf_prog_get_fd_by_id_opts() with NULL as
opts argument, to prevent setting open_flags.

Currently, the kernel does not support non-zero open_flags for
bpf_prog_get_fd_by_id_opts(), and a call with them will result in an error
returned by the bpf() system call. The caller should always pass zero
open_flags.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
tools/lib/bpf/bpf.c | 12 +++++++++++-
tools/lib/bpf/bpf.h | 2 ++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c08d7509553d..03be8c96bbac 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -935,19 +935,29 @@ int bpf_link_get_next_id(__u32 start_id, __u32 *next_id)
return bpf_obj_get_next_id(start_id, next_id, BPF_LINK_GET_NEXT_ID);
}

-int bpf_prog_get_fd_by_id(__u32 id)
+int bpf_prog_get_fd_by_id_opts(__u32 id,
+ const struct bpf_get_fd_by_id_opts *opts)
{
const size_t attr_sz = offsetofend(union bpf_attr, open_flags);
union bpf_attr attr;
int fd;

+ if (!OPTS_VALID(opts, bpf_get_fd_by_id_opts))
+ return libbpf_err(-EINVAL);
+
memset(&attr, 0, attr_sz);
attr.prog_id = id;
+ attr.open_flags = OPTS_GET(opts, open_flags, 0);

fd = sys_bpf_fd(BPF_PROG_GET_FD_BY_ID, &attr, attr_sz);
return libbpf_err_errno(fd);
}

+int bpf_prog_get_fd_by_id(__u32 id)
+{
+ return bpf_prog_get_fd_by_id_opts(id, NULL);
+}
+
int bpf_map_get_fd_by_id_opts(__u32 id,
const struct bpf_get_fd_by_id_opts *opts)
{
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 10ce38f0a9ef..4558bafbce14 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -374,6 +374,8 @@ struct bpf_get_fd_by_id_opts {
#define bpf_get_fd_by_id_opts__last_field open_flags

LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
+LIBBPF_API int bpf_prog_get_fd_by_id_opts(__u32 id,
+ const struct bpf_get_fd_by_id_opts *opts);
LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id,
const struct bpf_get_fd_by_id_opts *opts);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 2e665b21d84f..c3604eaa220d 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -372,6 +372,7 @@ LIBBPF_1.0.0 {
LIBBPF_1.1.0 {
global:
bpf_map_get_fd_by_id_opts;
+ bpf_prog_get_fd_by_id_opts;
user_ring_buffer__discard;
user_ring_buffer__free;
user_ring_buffer__new;
--
2.25.1