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.

Link: https://lkml.kernel.org/r/20250618125037.53182-1-petr.pavlu@suse.com
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Casey Chen <cachen@purestorage.com>
Cc: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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))
 
 #define MOD_SEPARATE_CODETAG_SECTION(_name)	\
 	.codetag.##_name : {			\
@@ -22,6 +28,6 @@
  * 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 */