linux-kernel - Re: [PATCH v4 0/3] Support comma-separated symbols and :entry/:exit

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Message-Id: <20251127151218.4763b25c751bb2aac4b1ee36@kernel.org>
Date: Thu, 27 Nov 2025 15:12:18 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: "Seokwoo Chung (Ryan)" <seokwoo.chung130@...il.com>
Cc: rostedt@...dmis.org, corbet@....net, shuah@...nel.org,
 mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 0/3] Support comma-separated symbols and :entry/:exit

On Wed, 26 Nov 2025 13:41:07 -0500
"Seokwoo Chung (Ryan)" <seokwoo.chung130@...il.com> wrote:

> Extend fprobe to support list-style filters and explicit entry/exit suffixes.
> Currentyl, fprobe only supports a single symbol (or wildcard) per event.
> This patch allows users to specify a comma-separated list of symbols.
> 
> New Syntax:
> - f:[GRP/][EVENT] func1,func2,func3:entry
> - f:[GRP/][EVENT] func1,func2,func3:exit

Thanks for updating!

> 
> Logic changes:
> - Refactor parsing logic into 'parse_fprobe_spec'
> - Support '!' prefix for exclusion
> - Disable BTF lookup ('ctx->funcname = NULL') when a list or wildcard is used,
>   as a single function signature cannot apply to multiple functions.
> - Reject legacy '%return' suffix when used with lists or wildcards
> - Update tracefs/README
> 
> Testing:
> Verified on x86_64 via QEMU. Checked registration of lists, exclusions, and
> explicit suffixes. Verified rejection of invalid syntax including trailing
> commas and mixed legacy/new syntax.
> 
> Seokwoo Chung (Ryan) (3):
>   docs: tracing/fprobe: Document list filters and :entry/:exit
>   tracing/fprobe: Support comma-separated symbols and :entry/:exit

For the next time, please add docs patch after code change because of bisect.
(Or, include the document update into code update.)

>   selftests/ftrace: Add accept cases for fprobe list syntax

Testing after code is good. :)

Thank you,

> 
> Changes in v4:
> - Added validation to reject trailing commas (empty tokens) in symbol lists
> - Added vaildation to reject mixed of list syntax with %return suffix
> - Refactored parse_fprobe_spec to user __free(kfree) for automatic memory
>   cleanup
> - Removed the now-unused parse_symbol_and_return function to avoid compiler
>   warnings.
> - Tigtened %return detection to ensure it only matches as a strict suffix, not a
>   substring
> - Link to v3: https://lore.kernel.org/lkml/20250904103219.f4937968362bfff1ecd3f004@kernel.org/
> 
>  Documentation/trace/fprobetrace.rst           |  17 +-
>  kernel/trace/trace.c                          |   3 +-
>  kernel/trace/trace_fprobe.c                   | 209 ++++++++++++++----
>  .../ftrace/test.d/dynevent/fprobe_list.tc     |  92 ++++++++
>  4 files changed, 269 insertions(+), 52 deletions(-)
>  create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/fprobe_list.tc
> 
> -- 
> 2.43.0
> 


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