module: allow symbol exports to be disabled

To allow existing C code to be incorporated into the decompressor or the
UEFI stub, introduce a CPP macro that turns all EXPORT_SYMBOL_xxx
declarations into nops, and #define it in places where such exports are
undesirable.  Note that this gets rid of a rather dodgy redefine of
linux/export.h's header guard.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ard Biesheuvel <[email protected]>
Acked-by: Nicolas Pitre <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Reviewed-by: Will Deacon <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: James Morris <[email protected]>
Cc: James Morris <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Russell King <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Garnier <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/firmware/efi/libstub/Makefile

@@ -24,6 +24,7 @@ KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
 				   -D__NO_FORTIFY \
 				   $(call cc-option,-ffreestanding) \
 				   $(call cc-option,-fno-stack-protector) \
+				   -D__DISABLE_EXPORTS
 
 GCOV_PROFILE			:= n
 KASAN_SANITIZE			:= n