linux-kernel - Re: [RFC PATCH bpf-next v1 0/3] bpf: Add BPF program type for overriding tracepoint probes

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Message-ID: <aMvHE-iW5eAwf4km@krava>
Date: Thu, 18 Sep 2025 10:47:15 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Fuyu Zhao <zhaofuyu@...o.com>
Cc: Song Liu <song@...nel.org>, ast@...nel.org, daniel@...earbox.net,
	andrii@...nel.org, martin.lau@...ux.dev, yonghong.song@...ux.dev,
	haoluo@...gle.com, eddyz87@...il.com, kpsingh@...nel.org,
	sdf@...ichev.me, rostedt@...dmis.org, mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com, shuah@...nel.org,
	willemb@...gle.com, kerneljasonxing@...il.com,
	paul.chaignon@...il.com, chen.dylane@...ux.dev, memxor@...il.com,
	martin.kelly@...wdstrike.com, ameryhung@...il.com,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	yikai.lin@...o.com
Subject: Re: [RFC PATCH bpf-next v1 0/3] bpf: Add BPF program type for
 overriding tracepoint probes

On Thu, Sep 18, 2025 at 04:05:51PM +0800, Fuyu Zhao wrote:
> 
> 
> On 9/18/2025 4:02 AM, Song Liu wrote:
> > On Wed, Sep 17, 2025 at 12:23 AM Fuyu Zhao <zhaofuyu@...o.com> wrote:
> >>
> >> Hi everyone,
> >>
> >> This patchset introduces a new BPF program type that allows overriding
> >> a tracepoint probe function registered via register_trace_*.
> >>
> >> Motivation
> >> ----------
> >> Tracepoint probe functions registered via register_trace_* in the kernel
> >> cannot be dynamically modified, changing a probe function requires recompiling
> >> the kernel and rebooting. Nor can BPF programs change an existing
> >> probe function.
> >>
> >> Overiding tracepoint supports a way to apply patches into kernel quickly
> >> (such as applying security ones), through predefined static tracepoints,
> >> without waiting for upstream integration.
> > 
> > IIUC, this work solves the same problem as raw tracepoint (raw_tp) or raw
> > tracepoint with btf (tp_btf).
> > 
> > Did I miss something?
> > 
> > Thanks,
> > Song
> 
> As I understand it, raw tracepoints (raw_tp) and raw tracepoint (raw_tp)
> are designed mainly for tracing the kernel. The goal of this work is to
> provide a way to override the tracepoint callback, so that kernel behavior
> can be adjusted dynamically.

hi,
what's the use case for this? also I'd think you can do that just by
unregister the callback you want to override and register new one?

thanks,
jirka