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

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Message-ID: <20251015231928.GC3943617@ax162>
Date: Wed, 15 Oct 2025 16:19:28 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Steven Rostedt <rostedt@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org,
	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>,
	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: Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for
 modules

Hi Steve,

On Wed, Oct 15, 2025 at 04:38:46PM -0400, Steven Rostedt wrote:
> 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),"")

Drop the "", nowhere else in Kbuild appears to do this.

> +cmd_check_tracepoint = ${objtree}/scripts/tracepoint-update $<;

Please use $(objtree) to be consistent with the rest of Kbuild.

> +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;
> +

This feels like it could be its own patch but I guess it does not make
much sense without enablement. It might be worth calling this out a bit
more in the commit message.

>  	if (!check_data_sec) {
>  		fprintf(stderr,	"no __tracepoint_check in file: %s\n", fname);
>  		return -1;
> -- 
> 2.51.0
> 
>