linux-kernel - [PATCH] codetag: Avoid unused alloc

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Message-ID: <20250313143002.9118-1-petr.pavlu@suse.com>
Date: Thu, 13 Mar 2025 15:29:20 +0100
From: Petr Pavlu <petr.pavlu@...e.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Arnd Bergmann <arnd@...db.de>
Cc: linux-arch@...r.kernel.org,
	linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Petr Pavlu <petr.pavlu@...e.com>
Subject: [PATCH] codetag: Avoid unused alloc_tags sections/symbols

With CONFIG_MEM_ALLOC_PROFILING=n, vmlinux and all modules unnecessarily
contain the symbols __start_alloc_tags and __stop_alloc_tags, which define
an empty range. In the case of modules, the presence of these symbols also
forces the linker to create an empty .codetag.alloc_tags section.

Update codetag.lds.h to make the data conditional on
CONFIG_MEM_ALLOC_PROFILING.

Signed-off-by: Petr Pavlu <petr.pavlu@...e.com>
---
 include/asm-generic/codetag.lds.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/codetag.lds.h b/include/asm-generic/codetag.lds.h
index 372c320c5043..0ea1fa678405 100644
--- a/include/asm-generic/codetag.lds.h
+++ b/include/asm-generic/codetag.lds.h
@@ -2,6 +2,12 @@
 #ifndef __ASM_GENERIC_CODETAG_LDS_H
 #define __ASM_GENERIC_CODETAG_LDS_H
 
+#ifdef CONFIG_MEM_ALLOC_PROFILING
+#define IF_MEM_ALLOC_PROFILING(...) __VA_ARGS__
+#else
+#define IF_MEM_ALLOC_PROFILING(...)
+#endif
+
 #define SECTION_WITH_BOUNDARIES(_name)	\
 	. = ALIGN(8);			\
 	__start_##_name = .;		\
@@ -9,7 +15,7 @@
 	__stop_##_name = .;
 
 #define CODETAG_SECTIONS()		\
-	SECTION_WITH_BOUNDARIES(alloc_tags)
+	IF_MEM_ALLOC_PROFILING(SECTION_WITH_BOUNDARIES(alloc_tags))
 
 /*
  * Module codetags which aren't used after module unload, therefore have the
@@ -28,6 +34,6 @@
  * unload them individually once unused.
  */
 #define MOD_SEPARATE_CODETAG_SECTIONS()		\
-	MOD_SEPARATE_CODETAG_SECTION(alloc_tags)
+	IF_MEM_ALLOC_PROFILING(MOD_SEPARATE_CODETAG_SECTION(alloc_tags))
 
 #endif /* __ASM_GENERIC_CODETAG_LDS_H */

base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
-- 
2.43.0