netdev - Re: [PATCH bpf-next v7 05/10] bpf: support attaching freplace programs to multiple attach points

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Message-ID: <CAEf4BzZO3S+HRSC14tvjp3K5scqkXs1MVma7507VFKB2sp+Cjg@mail.gmail.com>
Date:   Mon, 21 Sep 2020 16:08:15 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        KP Singh <kpsingh@...omium.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v7 05/10] bpf: support attaching freplace
 programs to multiple attach points

On Sat, Sep 19, 2020 at 4:50 AM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@...hat.com>
>
> This enables support for attaching freplace programs to multiple attach
> points. It does this by amending the UAPI for bpf_link_Create with a target
> btf ID that can be used to supply the new attachment point along with the
> target program fd. The target must be compatible with the target that was
> supplied at program load time.
>
> The implementation reuses the checks that were factored out of
> check_attach_btf_id() to ensure compatibility between the BTF types of the
> old and new attachment. If these match, a new bpf_tracing_link will be
> created for the new attach target, allowing multiple attachments to
> co-exist simultaneously.
>
> The code could theoretically support multiple-attach of other types of
> tracing programs as well, but since I don't have a use case for any of
> those, there is no API support for doing so.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---

Acked-by: Andrii Nakryiko <andriin@...com>

>  include/linux/bpf.h            |    2 +
>  include/uapi/linux/bpf.h       |    9 +++-
>  kernel/bpf/syscall.c           |  102 +++++++++++++++++++++++++++++++++-------
>  kernel/bpf/verifier.c          |    9 ++++
>  tools/include/uapi/linux/bpf.h |    9 +++-
>  5 files changed, 108 insertions(+), 23 deletions(-)
>

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