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

Steven Rostedt posted 4 patches 2 months ago
There is a newer version of this series
[PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by Steven Rostedt 2 months ago 
From: Steven Rostedt <rostedt@goodmis.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@goodmis.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
Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by kernel test robot 2 months ago 
Hi Steven,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.18-rc1 next-20251015]
[cannot apply to trace/for-next arnd-asm-generic/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/sorttable-Move-ELF-parsing-into-scripts-elf-parse-ch/20251016-044008
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20251015203924.731213165%40kernel.org
patch subject: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
config: microblaze-defconfig (https://download.01.org/0day-ci/archive/20251016/202510161811.9iIH3K15-lkp@intel.com/config)
compiler: microblaze-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251016/202510161811.9iIH3K15-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202510161811.9iIH3K15-lkp@intel.com/

All errors (new ones prefixed by >>):

>> /bin/bash: line 1: ./scripts/tracepoint-update: No such file or directory

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by Nathan Chancellor 2 months ago 
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
> 
>
Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by Steven Rostedt 1 month, 4 weeks ago 
On Wed, 15 Oct 2025 16:19:28 -0700
Nathan Chancellor <nathan@kernel.org> wrote:

> 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.

OK for both.

> 
> > +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.
> 

It was found during debugging. I could make this a separate patch in
preparation for this patch.

-- Steve



> >  	if (!check_data_sec) {
> >  		fprintf(stderr,	"no __tracepoint_check in file: %s\n", fname);
> >  		return -1;
> > -- 
> > 2.51.0
> > 
> >
Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by Nicolas Schier 2 months ago 
On Wed, Oct 15, 2025 at 04:19:28PM -0700, Nathan Chancellor wrote:
> 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

The else part is not required, cp. definition of e.g. cmd_checkdoc in
scripts/Makefile.build.

Kind regards
Nicolas
Re: [PATCH v9 4/4] tracing: Add warnings for unused tracepoints for modules
Posted by Steven Rostedt 1 month, 4 weeks ago 
On Fri, 17 Oct 2025 22:22:32 +0200
Nicolas Schier <nsc@kernel.org> wrote:

> On Wed, Oct 15, 2025 at 04:19:28PM -0700, Nathan Chancellor wrote:
> > 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  
> 
> The else part is not required, cp. definition of e.g. cmd_checkdoc in
> scripts/Makefile.build.

Thanks, will do.

-- Steve

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