From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
Jiri Olsa <jolsa@redhat.com>,
Eelco Chaudron <echaudro@redhat.com>,
KP Singh <kpsingh@chromium.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH RESEND bpf-next v3 4/9] bpf: support attaching freplace programs to multiple attach points
Date: Mon, 14 Sep 2020 18:08:43 +0200 [thread overview]
Message-ID: <87imcgz6gk.fsf@toke.dk> (raw)
In-Reply-To: <CAEf4BzZMj0sPisgUZ+3qKvqaAxfzzRNHZTpoR-zuDXvKcY3URQ@mail.gmail.com>
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Fri, Sep 11, 2020 at 3:01 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> From: Toke Høiland-Jørgensen <toke@redhat.com>
>>
>> This enables support for attaching freplace programs to multiple attach
>> points. It does this by amending UAPI for bpf_raw_tracepoint_open with a
>> target prog fd and btf ID pair that can be used to supply the new
>> attachment point. 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, the bpf_tracing_prog_attach() function will reject new targets for
>> anything other than PROG_TYPE_EXT programs.
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>
> It feels like using a semi-constructed bpf_tracing_link inside
> prog->aux->tgt_link is just an unnecessary complication, after reading
> this and previous patches. Seems more straightforward and simpler to
> store tgt_attach_type/tgt_prog_type (permanently) and
> tgt_prog/tgt_trampoline (until first attachment) in prog->aux and then
> properly create bpf_link on attach.
I updated v4 with your comments, but kept the link in prog->aux; the
reason being that having a container for the two pointers makes it
possible to atomically swap it out with xchg() as you suggested
previously. Could you please take a look at v4? If you still think it's
better to just keep two separate pointers (and add a lock) in prog->aux,
I can change it to that. But I'd rather avoid the lock if possible...
-Toke
next prev parent reply other threads:[~2020-09-14 16:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 9:59 [PATCH RESEND bpf-next v3 0/9] bpf: Support multi-attach for freplace programs Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 1/9] bpf: change logging calls from verbose() to bpf_log() and use log pointer Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 2/9] bpf: verifier: refactor check_attach_btf_id() Toke Høiland-Jørgensen
2020-09-11 19:13 ` Andrii Nakryiko
2020-09-11 19:50 ` Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 3/9] bpf: wrap prog->aux->linked_prog in a bpf_tracing_link Toke Høiland-Jørgensen
2020-09-11 19:57 ` Andrii Nakryiko
2020-09-11 20:56 ` Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 4/9] bpf: support attaching freplace programs to multiple attach points Toke Høiland-Jørgensen
2020-09-11 21:10 ` Andrii Nakryiko
2020-09-14 16:08 ` Toke Høiland-Jørgensen [this message]
2020-09-14 23:10 ` Andrii Nakryiko
2020-09-15 11:35 ` Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 5/9] bpf: Fix context type resolving for extension programs Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 6/9] tools: add new members to bpf_attr.raw_tracepoint in bpf.h Toke Høiland-Jørgensen
2020-09-11 21:16 ` Andrii Nakryiko
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 7/9] libbpf: add support for supplying target to bpf_raw_tracepoint_open() Toke Høiland-Jørgensen
2020-09-11 21:21 ` Andrii Nakryiko
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 8/9] selftests: add test for multiple attachments of freplace program Toke Høiland-Jørgensen
2020-09-11 9:59 ` [PATCH RESEND bpf-next v3 9/9] selftests/bpf: Adding test for arg dereference in extension trace Toke Høiland-Jørgensen
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