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

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Message-ID: <20251126184110.72241-1-seokwoo.chung130@gmail.com>
Date: Wed, 26 Nov 2025 13:41:07 -0500
From: "Seokwoo Chung (Ryan)" <seokwoo.chung130@...il.com>
To: rostedt@...dmis.org,
	mhiramat@...nel.org,
	corbet@....net,
	shuah@...nel.org
Cc: 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,
	"Seokwoo Chung (Ryan)" <seokwoo.chung130@...il.com>
Subject: [PATCH v4 0/3] Support comma-separated symbols and :entry/:exit

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

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
  selftests/ftrace: Add accept cases for fprobe list syntax

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