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libbpf: Introduce bpf_btf_get_fd_by_id_opts()

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Introduce bpf_btf_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_btf_get_fd_by_id(), and call bpf_btf_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_btf_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@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221006110736.84253-5-roberto.sassu@huaweicloud.com
This commit is contained in:
Roberto Sassu 2022-10-06 13:07:34 +02:00 committed by Andrii Nakryiko
parent 8f13f168ea
commit 2ce7cbf2ba
3 changed files with 14 additions and 1 deletions
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12
tools/lib/bpf/bpf.c
View File

@ -981,19 +981,29 @@ int bpf_map_get_fd_by_id(__u32 id)
return bpf_map_get_fd_by_id_opts(id, NULL);
}
int bpf_btf_get_fd_by_id(__u32 id)
int bpf_btf_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.btf_id = id;
attr.open_flags = OPTS_GET(opts, open_flags, 0);
fd = sys_bpf_fd(BPF_BTF_GET_FD_BY_ID, &attr, attr_sz);
return libbpf_err_errno(fd);
}
int bpf_btf_get_fd_by_id(__u32 id)
{
return bpf_btf_get_fd_by_id_opts(id, NULL);
}
int bpf_link_get_fd_by_id(__u32 id)
{
const size_t attr_sz = offsetofend(union bpf_attr, open_flags);

2
tools/lib/bpf/bpf.h
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@ -380,6 +380,8 @@ 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);
LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
LIBBPF_API int bpf_btf_get_fd_by_id_opts(__u32 id,
const struct bpf_get_fd_by_id_opts *opts);
LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
LIBBPF_API int bpf_obj_get_info_by_fd(int bpf_fd, void *info, __u32 *info_len);

1
tools/lib/bpf/libbpf.map
View File

@ -371,6 +371,7 @@ LIBBPF_1.0.0 {
LIBBPF_1.1.0 {
global:
bpf_btf_get_fd_by_id_opts;
bpf_map_get_fd_by_id_opts;
bpf_prog_get_fd_by_id_opts;
user_ring_buffer__discard;