From b14784e7883390c20ed3ff904892255404a5914b Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 7 Jul 2017 17:05:53 +0200
Subject: add an optional config option for stripping all unnecessary symbol exports from the kernel image

lede-commit: bb5a40c64b7c4f4848509fa0a6625055fc9e66cc
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 include/asm-generic/vmlinux.lds.h | 18 +++++++++++++++---
 include/linux/export.h            |  9 ++++++++-
 scripts/Makefile.build            |  2 +-
 3 files changed, 24 insertions(+), 5 deletions(-)

--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -54,6 +54,16 @@
 #define LOAD_OFFSET 0
 #endif
 
+#ifndef SYMTAB_KEEP
+#define SYMTAB_KEEP KEEP(*(SORT(___ksymtab+*)))
+#define SYMTAB_KEEP_GPL KEEP(*(SORT(___ksymtab_gpl+*)))
+#endif
+
+#ifndef SYMTAB_DISCARD
+#define SYMTAB_DISCARD
+#define SYMTAB_DISCARD_GPL
+#endif
+
 #include <linux/export.h>
 
 /* Align . to a 8 byte boundary equals to maximum function alignment. */
@@ -342,14 +352,14 @@
 	/* Kernel symbol table: Normal symbols */			\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
 		VMLINUX_SYMBOL(__start___ksymtab) = .;			\
-		KEEP(*(SORT(___ksymtab+*)))				\
+		SYMTAB_KEEP						\
 		VMLINUX_SYMBOL(__stop___ksymtab) = .;			\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
 	__ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {	\
 		VMLINUX_SYMBOL(__start___ksymtab_gpl) = .;		\
-		KEEP(*(SORT(___ksymtab_gpl+*)))				\
+		SYMTAB_KEEP_GPL						\
 		VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .;		\
 	}								\
 									\
@@ -411,7 +421,7 @@
 									\
 	/* Kernel symbol table: strings */				\
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\
-		*(__ksymtab_strings)					\
+		*(__ksymtab_strings+*)					\
 	}								\
 									\
 	/* __*init sections */						\
@@ -805,6 +815,8 @@
 	EXIT_TEXT							\
 	EXIT_DATA							\
 	EXIT_CALL							\
+	SYMTAB_DISCARD							\
+	SYMTAB_DISCARD_GPL						\
 	*(.discard)							\
 	*(.discard.*)							\
 	}
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -60,12 +60,19 @@ extern struct module __this_module;
 #define __CRC_SYMBOL(sym, sec)
 #endif
 
+#ifdef MODULE
+#define __EXPORT_SUFFIX(sym)
+#else
+#define __EXPORT_SUFFIX(sym) "+" #sym
+#endif
+
 /* For every exported symbol, place a struct in the __ksymtab section */
 #define ___EXPORT_SYMBOL(sym, sec)					\
 	extern typeof(sym) sym;						\
 	__CRC_SYMBOL(sym, sec)						\
 	static const char __kstrtab_##sym[]				\
-	__attribute__((section("__ksymtab_strings"), aligned(1)))	\
+	__attribute__((section("__ksymtab_strings"			\
+	  __EXPORT_SUFFIX(sym)), aligned(1)))				\
 	= VMLINUX_SYMBOL_STR(sym);					\
 	static const struct kernel_symbol __ksymtab_##sym		\
 	__used								\
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -435,7 +435,7 @@ targets += $(extra-y) $(MAKECMDGOALS) $(
 # Linker scripts preprocessor (.lds.S -> .lds)
 # ---------------------------------------------------------------------------
 quiet_cmd_cpp_lds_S = LDS     $@
-      cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
+      cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -U$(ARCH) \
 	                     -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 
 $(obj)/%.lds: $(src)/%.lds.S FORCE