linux-kernel - Re: [PATCH v4] tracepoint: Have tracepoints created with DECLARE_TRACE() have

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Message-ID: <CAEf4BzammxSa48ZBxQgGQjOBbdVniJcrQ+-52-76TqMYUHx8cg@mail.gmail.com>
Date: Mon, 12 May 2025 15:29:11 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, 
	Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>, bpf@...r.kernel.org, 
	netdev <netdev@...r.kernel.org>, Jiri Olsa <olsajiri@...il.com>, 
	Peter Zijlstra <peterz@...radead.org>, David Ahern <dsahern@...nel.org>, 
	Juri Lelli <juri.lelli@...il.com>, Breno Leitao <leitao@...ian.org>, 
	Alexei Starovoitov <alexei.starovoitov@...il.com>, Gabriele Monaco <gmonaco@...hat.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH v4] tracepoint: Have tracepoints created with
 DECLARE_TRACE() have _tp suffix

On Sat, May 10, 2025 at 1:37 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> From: Steven Rostedt <rostedt@...dmis.org>
>
> Most tracepoints in the kernel are created with TRACE_EVENT(). The
> TRACE_EVENT() macro (and DECLARE_EVENT_CLASS() and DEFINE_EVENT() where in
> reality, TRACE_EVENT() is just a helper macro that calls those other two
> macros), will create not only a tracepoint (the function trace_<event>()
> used in the kernel), it also exposes the tracepoint to user space along
> with defining what fields will be saved by that tracepoint.
>
> There are a few places that tracepoints are created in the kernel that are
> not exposed to userspace via tracefs. They can only be accessed from code
> within the kernel. These tracepoints are created with DEFINE_TRACE()
>
> Most of these tracepoints end with "_tp". This is useful as when the
> developer sees that, they know that the tracepoint is for in-kernel only
> (meaning it can only be accessed inside the kernel, either directly by the
> kernel or indirectly via modules and BPF programs) and is not exposed to
> user space.
>
> Instead of making this only a process to add "_tp", enforce it by making
> the DECLARE_TRACE() append the "_tp" suffix to the tracepoint. This
> requires adding DECLARE_TRACE_EVENT() macros for the TRACE_EVENT() macro
> to use that keeps the original name.
>
> Link: https://lore.kernel.org/all/20250418083351.20a60e64@gandalf.local.home/
>
> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
> Changes since v3: https://lore.kernel.org/20250510092342.77371990@gandalf.local.home
>
> - Added "_tp" suffix in bpf tests to:
>
>   tp_btf/bpf_testmod_test_raw_tp_null in raw_tp_null.c
>   tp_btf/bpf_testmod_test_raw_tp_null in raw_tp_null_fail.c
>   raw_tp.w/bpf_testmod_test_writable_bare in test_module_attach.c
>
>   Hopefully this passes the bpf verifier tests.
>

Yep, BPF CI is happy, changes look good. Thanks!

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>  Documentation/trace/tracepoints.rst           | 17 ++++++---
>  include/linux/tracepoint.h                    | 38 +++++++++++++------
>  include/trace/bpf_probe.h                     |  8 ++--
>  include/trace/define_trace.h                  | 17 ++++++++-
>  include/trace/events/sched.h                  | 30 +++++++--------
>  include/trace/events/tcp.h                    |  2 +-
>  .../testing/selftests/bpf/progs/raw_tp_null.c |  2 +-
>  .../selftests/bpf/progs/raw_tp_null_fail.c    |  2 +-
>  .../selftests/bpf/progs/test_module_attach.c  |  4 +-
>  .../bpf/progs/test_tp_btf_nullable.c          |  4 +-
>  .../selftests/bpf/test_kmods/bpf_testmod.c    |  8 ++--
>  11 files changed, 83 insertions(+), 49 deletions(-)
>

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