Re: [RFC PATCH bpf-next v7 04/11] libbpf: introduce bpf_map__attach_struct_ops_opts()

[Yonghong Song <yonghong.song@linux.dev>]

On 5/25/26 7:20 PM, Hui Zhu wrote:
> From: Roman Gushchin <roman.gushchin@linux.dev>
>
> Introduce bpf_map__attach_struct_ops_opts(), an extended version of
> bpf_map__attach_struct_ops(), which takes additional struct
> bpf_struct_ops_opts argument.
>
> This allows to pass a target_fd argument and the BPF_F_CGROUP_FD flag
> and attach the struct ops to a cgroup as a result.
>
> Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
> ---
>   tools/lib/bpf/libbpf.c   | 20 +++++++++++++++++---
>   tools/lib/bpf/libbpf.h   | 14 ++++++++++++++
>   tools/lib/bpf/libbpf.map |  1 +
>   3 files changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 1e8688975d16..a1b54da1ded2 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -13683,11 +13683,18 @@ static int bpf_link__detach_struct_ops(struct bpf_link *link)
>   	return close(link->fd);
>   }
>   
> -struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
> +struct bpf_link *bpf_map__attach_struct_ops_opts(const struct bpf_map *map,
> +						 const struct bpf_struct_ops_opts *opts)
>   {
> +	DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts);
>   	struct bpf_link_struct_ops *link;
> +	int err, fd, target_fd;
>   	__u32 zero = 0;
> -	int err, fd;
> +
> +	if (!OPTS_VALID(opts, bpf_struct_ops_opts)) {
> +		pr_warn("map '%s': invalid opts\n", map->name);
> +		return libbpf_err_ptr(-EINVAL);
> +	}
>   
>   	if (!bpf_map__is_struct_ops(map)) {
>   		pr_warn("map '%s': can't attach non-struct_ops map\n", map->name);
> @@ -13724,7 +13731,9 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
>   		return &link->link;
>   	}
>   
> -	fd = bpf_link_create(map->fd, 0, BPF_STRUCT_OPS, NULL);
> +	link_opts.flags = OPTS_GET(opts, flags, 0);
> +	target_fd = OPTS_GET(opts, target_fd, 0);
> +	fd = bpf_link_create(map->fd, target_fd, BPF_STRUCT_OPS, &link_opts);
>   	if (fd < 0) {
>   		free(link);
>   		return libbpf_err_ptr(fd);
> @@ -13736,6 +13745,11 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
>   	return &link->link;
>   }
>   
> +struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
> +{
> +	return bpf_map__attach_struct_ops_opts(map, NULL);
> +}
> +
>   /*
>    * Swap the back struct_ops of a link with a new struct_ops map.
>    */
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index bba4e8464396..18af178547ad 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -945,6 +945,20 @@ bpf_program__attach_cgroup_opts(const struct bpf_program *prog, int cgroup_fd,
>   struct bpf_map;
>   
>   LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map);
> +
> +struct bpf_struct_ops_opts {
> +	/* size of this struct, for forward/backward compatibility */
> +	size_t sz;
> +	__u32 flags;
> +	__u32 target_fd;
> +	__u64 expected_revision;
> +	size_t :0;
> +};
> +#define bpf_struct_ops_opts__last_field expected_revision
> +
> +LIBBPF_API struct bpf_link *
> +bpf_map__attach_struct_ops_opts(const struct bpf_map *map,
> +				const struct bpf_struct_ops_opts *opts);
>   LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map);
>   
>   struct bpf_iter_attach_opts {
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index dfed8d60af05..6105619b5ecf 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -454,6 +454,7 @@ LIBBPF_1.7.0 {
>   		bpf_prog_assoc_struct_ops;
>   		bpf_program__assoc_struct_ops;
>   		btf__permute;
> +		bpf_map__attach_struct_ops_opts;

Function bpf_map__attach_struct_ops_opts should be in
LIBBPF_1.8.0.

>   } LIBBPF_1.6.0;
>   
>   LIBBPF_1.8.0 {