On Tue, Oct 4, 2022 at 6:18 AM Roberto Sassu
<roberto.sassu@xxxxxxxxxxxxxxx> wrote:
>
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> Define a new data structure called bpf_get_fd_opts, with the member
> open_flags, to be used by callers of the _opts variants of
> bpf_*_get_fd_by_id() to specify the permissions needed for the file
> descriptor to be obtained.
>
> Also, introduce bpf_map_get_fd_by_id_opts(), to let the caller pass a
> bpf_get_fd_opts structure.
>
> Finally, keep the existing bpf_map_get_fd_by_id(), and call
> bpf_map_get_fd_by_id_opts() with NULL as opts argument, to request
> read-write permissions (current behavior).
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
> tools/lib/bpf/bpf.c | 12 +++++++++++-
> tools/lib/bpf/bpf.h | 10 ++++++++++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 1d49a0352836..4b03063edf1d 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -948,19 +948,29 @@ int bpf_prog_get_fd_by_id(__u32 id)
> return libbpf_err_errno(fd);
> }
>
> -int bpf_map_get_fd_by_id(__u32 id)
> +int bpf_map_get_fd_by_id_opts(__u32 id,
> + const struct bpf_get_fd_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_opts))
> + return libbpf_err(-EINVAL);
> +
> memset(&attr, 0, attr_sz);
> attr.map_id = id;
> + attr.open_flags = OPTS_GET(opts, open_flags, 0);
>
> fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, attr_sz);
> return libbpf_err_errno(fd);
> }
>
> +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)
> {
> const size_t attr_sz = offsetofend(union bpf_attr, open_flags);
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index 9c50beabdd14..c60eda3c88ad 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -365,7 +365,17 @@ LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id);
> LIBBPF_API int bpf_link_get_next_id(__u32 start_id, __u32 *next_id);
> +
> +struct bpf_get_fd_opts {
should we call it "bpf_get_fd_by_id_opts" ? kernel command is
specifically about getting object FD by its external ID, so let's
reflect this in the name?
Otherwise it looks good.
> + size_t sz; /* size of this struct for forward/backward compatibility */
> + __u32 open_flags; /* permissions requested for the operation on fd */
> + size_t :0;
> +};
> +#define bpf_get_fd_opts__last_field open_flags
> +
> LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
> +LIBBPF_API int bpf_map_get_fd_by_id_opts(__u32 id,
> + const struct bpf_get_fd_opts *opts);
> LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
> LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
> LIBBPF_API int bpf_link_get_fd_by_id(__u32 id);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 04fab9f1fdd7..2e665b21d84f 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -371,6 +371,7 @@ LIBBPF_1.0.0 {
>
> LIBBPF_1.1.0 {
> global:
> + bpf_map_get_fd_by_id_opts;
> user_ring_buffer__discard;
> user_ring_buffer__free;
> user_ring_buffer__new;
> --
> 2.25.1
>
