netdev - Re: [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach

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Message-ID: <CAEf4BzYyvHO_ooGrMFQVwt5xvDo=r3YTgNCK9uRTnNQtZY4q6g@mail.gmail.com>
Date:   Mon, 21 Jun 2021 09:46:09 +0300
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Yonghong Song <yhs@...com>, Jiri Olsa <jolsa@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, Daniel Xu <dxu@...uu.xyz>,
        Viktor Malik <vmalik@...hat.com>
Subject: Re: [RFCv3 00/19] x86/ftrace/bpf: Add batch support for
 direct/tracing attach

On Sun, Jun 20, 2021 at 8:47 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Sun, Jun 20, 2021 at 9:57 AM Yonghong Song <yhs@...com> wrote:
> > >
> > > ah right, should have checked it.. so how about we change
> > > trampoline code to store ip in ctx-8 and make bpf_get_func_ip(ctx)
> > > to return [ctx-8]
> >
> > This should work. Thanks!
>
> +1
> and pls make it always inline into single LDX insn in the verifier.
> For both mass attach and normal fentry/fexit.

Yep.

And we should do it for kprobes (trivial, PT_REGS_IP(ctx)) and
kretprobe (less trivial but simple from inside the kernel, Masami
showed how to do it in one of the previous emails). I hope BPF infra
allows inlining of helpers for some program types but not the others.