linux-kernel - Re: [PATCH v3 0/5] tracing: fprobe: list-style filters,

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Message-Id: <20251008095111.5732b065dcebe53fc80063c5@kernel.org>
Date: Wed, 8 Oct 2025 09:51:11 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Ryan Chung <seokwoo.chung130@...il.com>
Cc: rostedt@...dmis.org, mathieu.desnoyers@...icios.com, shuah@...nel.org,
 hca@...ux.ibm.com, corbet@....net, linux-trace-kernel@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH v3 0/5] tracing: fprobe: list-style filters,

Hi Ryan,

Thanks for update!

On Sun,  5 Oct 2025 08:46:54 +0900
Ryan Chung <seokwoo.chung130@...il.com> wrote:

> This series aims to extend fprobe with list-style filters and a clear
> entry/exist qualifier. Users can now specify a comma-separated symbol
> list with ! exclusions, and use a spec-level suffix to select probe
> type:
> 
> - funcA*, !funcAB, funcC -> entry probes
> - funcA*, !funcAB, funcC:entry -> explicit entry
> - funcA*, !funcAB, funcC:exit -> return/exit across the whole list


Just a note, it should not accept spaces in the list. The space
is the highest level delimiter. I hope actual implementation
does not accept spaces. So something like:

 "funcA*,!funcAB,funcC"
 "funcA*,!funcAB,funcC:entry"
 "funcA*,!funcAB,funcC:exit"


> 
> For compatibility, %return remains supported for single, literal
> symbols. When a list or wildcard is used, an explicit [GROUP/EVENT is
> required and autogeneration is disabled. Autogen names are kept for
> single-symbol specs, with wildcard sanitization. For list/wildcard forms
> we set ctx->funcname = NULL so BTF lookups are not attempted.

OK. So "funcA*%return" and "funcA,funcB%return" will fail.

> 
> The series moves parsing to the parse path, documents the new syntax,
> and adds selftests that accept valid list cases and reject empty tokens,
> stray commas, and %return mixed with lists or wildcards. Selftests also
> verify enable/disable flow and that entry+exit on the same set do not
> double-count attached functions.

Thanks for adding selftests and document, that is important to maintain
features.

> 
> Help wanted: This is my first time contributing ftrace selftests. I
> would appreciate comments and recommendations on test structure and
> coverage.

OK, let me review it.

Thanks,


> 
> Basic coverage is included, but this likely needs broader testing across
> architectures. Feedback and additional test ideas are welcome.
> 
> Changes since v2:
> - Introduce spec-level: :entry/:exit; reject %return with
>   lists/wildcards
> - Require explict [GROUP/]EVENT for list/wildcard; keep autogen only for
>   single literal.
> - Sanitize autogen names for single-symbol wildcards
> - Set ctx->funcname = NULL for list/wildcard to bypass BTF
> - Move list parsing out of __register_trace_fprobe() and into the parse
>   path
> - Update docs and tracefs README and add dynevent selftests for
>   accept/reject and enable/disable flow
> 
> Link: https://lore.kernel.org/lkml/20250904103219.f4937968362bfff1ecd3f004@kernel.org/
> 
> Ryan Chung (5):
>   docs: tracing: fprobe: document list filters and :entry/:exit
>   tracing: fprobe: require explicit [GROUP/]EVENT for list/wildcard
>   tracing: fprobe: support comma-separated symbols and :entry/:exit
>   selftests/ftrace: dynevent: add reject cases for list/:entry/:exit
>   selftests/ftrace: dynevent: add reject cases
> 
>  Documentation/trace/fprobetrace.rst           |  27 +-
>  kernel/trace/trace.c                          |   3 +-
>  kernel/trace/trace_fprobe.c                   | 247 ++++++++++++++----
>  .../test.d/dynevent/add_remove_fprobe.tc      | 121 +++++++++
>  .../test.d/dynevent/fprobe_syntax_errors.tc   |  13 +
>  5 files changed, 349 insertions(+), 62 deletions(-)
> 
> -- 
> 2.43.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>