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@suse.com>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>

Author: petrpavlu

include/asm-generic/codetag.lds.h

@@ -2,14 +2,20 @@
 #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 = .;		\
 	KEEP(*(_name))			\
 	__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 */