netdev - Re: [RFC PATCH bpf-next 1/2] libbpf: Add support for dynamic tracepoint

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]

Message-ID: <lvmetlwqho4pinf5ehoyxbvcwsfgno54vnnuj2jzaitllgft5e@kqu4cgfwjghn>
Date: Tue, 7 Jan 2025 11:16:58 -0700
From: Daniel Xu <dxu@...uu.xyz>
To: Yafang Shao <laoar.shao@...il.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Eddy Z <eddyz87@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Eric Dumazet <edumazet@...gle.com>, bpf <bpf@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next 1/2] libbpf: Add support for dynamic
 tracepoint

Hi Yafang,

On Mon, Jan 06, 2025 at 10:32:15AM +0800, Yafang Shao wrote:
> On Mon, Jan 6, 2025 at 8:16 AM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Sun, Jan 5, 2025 at 4:44 AM Yafang Shao <laoar.shao@...il.com> wrote:
> > >
> > > Dynamic tracepoints can be created using debugfs. For example:
> > >
> > >    echo 'p:myprobe kernel_clone args' >> /sys/kernel/debug/tracing/kprobe_events
> > >
> > > This command creates a new tracepoint under debugfs:
> > >
> > >   $ ls /sys/kernel/debug/tracing/events/kprobes/myprobe/
> > >   enable  filter  format  hist  id  trigger
> > >
> > > Although this dynamic tracepoint appears as a tracepoint, it is internally
> > > implemented as a kprobe. However, it must be attached as a tracepoint to
> > > function correctly in certain contexts.
> >
> > Nack.
> > There are multiple mechanisms to create kprobe/tp via text interfaces.
> > We're not going to mix them with the programmatic libbpf api.
> 
> It appears that bpftrace still lacks support for adding a kprobe/tp
> and then attaching to it directly. Is that correct?
> What do you think about introducing this mechanism into bpftrace? With
> such a feature, we could easily attach to inlined kernel functions
> using bpftrace.

Is the idea to have some other application create dynamic tracepoints
based on kernel debuginfo?

FWIW bpftrace has some initial support for probing inlined kernel
functions w/ DWARF. I don't believe it's enabled by default yet, though
- there's a few limitations. I'll comment in thread below with more
details.

Thanks,
Daniel