kconfig option for TRIM_UNUSED_KSYMS

The config option to enable it all.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

init/Kconfig

@@ -2012,6 +2012,22 @@ config MODULE_COMPRESS_XZ
 
 endchoice
 
+config TRIM_UNUSED_KSYMS
+	bool "Trim unused exported kernel symbols"
+	depends on MODULES && !UNUSED_SYMBOLS
+	help
+	  The kernel and some modules make many symbols available for
+	  other modules to use via EXPORT_SYMBOL() and variants. Depending
+	  on the set of modules being selected in your kernel configuration,
+	  many of those exported symbols might never be used.
+
+	  This option allows for unused exported symbols to be dropped from
+	  the build. In turn, this provides the compiler more opportunities
+	  (especially when using LTO) for optimizing the code and reducing
+	  binary size.  This might have some security advantages as well.
+
+	  If unsure say N.
+
 endif # MODULES
 
 config MODULES_TREE_LOOKUP