Re: [PATCH bpf-next v3 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE

Andrii Nakryiko
2020-05-08T18:25:04Z

On Wed, May 6, 2020 at 10:41 PM Yonghong Song <yhs@fb.com> wrote:
>
> Given a bpf program, the step to create an anonymous bpf iterator is:
> - create a bpf_iter_link, which combines bpf program and the target.
> In the future, there could be more information recorded in the link.
> A link_fd will be returned to the user space.
> - create an anonymous bpf iterator with the given link_fd.
>
> The bpf_iter_link can be pinned to bpffs mount file system to
> create a file based bpf iterator as well.
>
> The benefit to use of bpf_iter_link:
> - using bpf link simplifies design and implementation as bpf link
> is used for other tracing bpf programs.
> - for file based bpf iterator, bpf_iter_link provides a standard
> way to replace underlying bpf programs.
> - for both anonymous and free based iterators, bpf link query
> capability can be leveraged.
>
> The patch added support of tracing/iter programs for BPF_LINK_CREATE.
> A new link type BPF_LINK_TYPE_ITER is added to facilitate link
> querying. Currently, only prog_id is needed, so there is no
> additional in-kernel show_fdinfo() and fill_link_info() hook
> is needed for BPF_LINK_TYPE_ITER link.
>
> Acked-by: Andrii Nakryiko <andriin@fb.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---

still looks good, but I realized show_fdinfo and fill_link_info is
missing, see request for a follow-up below :)

> include/linux/bpf.h | 1 +
> include/linux/bpf_types.h | 1 +
> include/uapi/linux/bpf.h | 1 +
> kernel/bpf/bpf_iter.c | 62 ++++++++++++++++++++++++++++++++++
> kernel/bpf/syscall.c | 14 ++++++++
> tools/include/uapi/linux/bpf.h | 1 +
> 6 files changed, 80 insertions(+)
>

[...]

> +static const struct bpf_link_ops bpf_iter_link_lops = {
> + .release = bpf_iter_link_release,
> + .dealloc = bpf_iter_link_dealloc,
> +};

Link infra supports .show_fdinfo and .fill_link_info methods, there is
no need to block on this, but it would be great to implement them from
BPF_LINK_TYPE_ITER as well in the same release as a follow-up. Thanks! …