linux-kernel - [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules

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Message-ID: <20251015203924.731213165@kernel.org>
Date: Wed, 15 Oct 2025 16:38:46 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org,
 linux-kbuild@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Arnd Bergmann <arnd@...db.de>,
 Masahiro Yamada <masahiroy@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nicolas Schier <nicolas.schier@...ux.dev>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Catalin Marinas <catalin.marinas@....com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Randy Dunlap <rdunlap@...radead.org>,
 Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules

From: Steven Rostedt <rostedt@...dmis.org>

If a modules has TRACE_EVENT() but does not use it, add a warning about it
at build time.

Currently, the build must be made by adding "UT=1" to the make command
line in order for this to trigger.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 scripts/Makefile.modfinal   | 7 +++++++
 scripts/tracepoint-update.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 542ba462ed3e..6f909979af91 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -28,6 +28,12 @@ ccflags-remove-y := $(CC_FLAGS_CFI)
 .module-common.o: $(srctree)/scripts/module-common.c FORCE
 	$(call if_changed_rule,cc_o_c)
 
+ifneq ($(WARN_ON_UNUSED_TRACEPOINTS),"")
+cmd_check_tracepoint = ${objtree}/scripts/tracepoint-update $<;
+else
+cmd_check_tracepoint =
+endif
+
 quiet_cmd_ld_ko_o = LD [M]  $@
       cmd_ld_ko_o =							\
 	$(LD) -r $(KBUILD_LDFLAGS)					\
@@ -57,6 +63,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
 ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 	+$(if $(newer-prereqs),$(call cmd,btf_ko))
 endif
+	+$(call cmd,check_tracepoint)
 
 targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o) .module-common.o
 
diff --git a/scripts/tracepoint-update.c b/scripts/tracepoint-update.c
index 6ec30f39d0ad..7e068de9c7f1 100644
--- a/scripts/tracepoint-update.c
+++ b/scripts/tracepoint-update.c
@@ -188,6 +188,13 @@ static int process_tracepoints(void *addr, char const *const fname)
 		}
 	}
 
+	/*
+	 * Modules may not have either section. But if it has one section,
+	 * it should have both of them.
+	 */
+	if (!check_data_sec && !tracepoint_data_sec)
+		return 0;
+
 	if (!check_data_sec) {
 		fprintf(stderr,	"no __tracepoint_check in file: %s\n", fname);
 		return -1;
-- 
2.51.0