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

[Steven Rostedt <rostedt@kernel.org>]

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