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Date: Fri, 8 May 2020 18:36:10 -0700 From: Yonghong Song <yhs@...com> To: Andrii Nakryiko <andrii.nakryiko@...il.com> CC: Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>, Martin KaFai Lau <kafai@...com>, Networking <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...com>, Daniel Borkmann <daniel@...earbox.net>, Kernel Team <kernel-team@...com> Subject: Re: [PATCH bpf-next v3 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE On 5/8/20 11:24 AM, Andrii Nakryiko wrote: > On Wed, May 6, 2020 at 10:41 PM Yonghong Song <yhs@...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@...com> >> Signed-off-by: Yonghong Song <yhs@...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! The reason I did not implement is due to we do not have additional information beyond prog_id to present. The prog_id itself gives all information about this link. I looked at tracing program show_fdinfo/fill_link_info, the additional attach_type is printed. But attach_type is obvious for BPF_LINK_TYPE_ITER which does not need print. In the future when we add more stuff to parameterize the bpf_iter, will need to implement these two callbacks as well as bpftool. > > > [...] >
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