From 057caace5214da3b457bbd295e1a2ad34d3685ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= <linux@weissschuh.net>
Date: Wed, 20 May 2026 20:01:55 +0200
Subject: [PATCH] tracing: Create output file from cmd_check_undefined
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As the output file is currently never created, the check will run every
time, even if the inputs have not changed.

Create an empty output file which allows make to skip the execution when
it is not necessary.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20260520-tracing-ringbuffer-check-v1-1-d979cfab1338@weissschuh.net
Fixes: 1211907ac0b5 ("tracing: Generate undef symbols allowlist for simple_ring_buffer")
Fixes: 58b4bd18390e ("tracing: Adjust cmd_check_undefined to show unexpected undefined symbols")
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 9b0834134cae..8d3d96e847d8 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -154,7 +154,8 @@ quiet_cmd_check_undefined = NM      $<
               echo "Unexpected symbols in $<:" >&2; \
               echo "$$undefsyms" >&2; \
               false; \
-          fi
+          fi; \
+          touch $@
 
 $(obj)/%.o.checked: $(obj)/%.o $(obj)/undefsyms_base.o FORCE
 	$(call if_changed,check_undefined)