netdev - Re: [PATCH 13/19] bpf: Add support to link multi func tracing program

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 8 Jun 2021 08:42:32 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, Daniel Xu <dxu@...uu.xyz>,
        Viktor Malik <vmalik@...hat.com>
Subject: Re: [PATCH 13/19] bpf: Add support to link multi func tracing program

On Sat, Jun 5, 2021 at 4:11 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Adding support to attach multiple functions to tracing program
> by using the link_create/link_update interface.
>
> Adding multi_btf_ids/multi_btf_ids_cnt pair to link_create struct
> API, that define array of functions btf ids that will be attached
> to prog_fd.
>
> The prog_fd needs to be multi prog tracing program (BPF_F_MULTI_FUNC).
>
> The new link_create interface creates new BPF_LINK_TYPE_TRACING_MULTI
> link type, which creates separate bpf_trampoline and registers it
> as direct function for all specified btf ids.
>
> The new bpf_trampoline is out of scope (bpf_trampoline_lookup) of
> standard trampolines, so all registered functions need to be free
> of direct functions, otherwise the link fails.

Overall the api makes sense to me.
The restriction of multi vs non-multi is too severe though.
The multi trampoline can serve normal fentry/fexit too.
If ip is moved to the end (instead of start) the trampoline
will be able to call into multi and normal fentry/fexit progs. Right?