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
+
 /* Align . to a 8 byte boundary equals to maximum function alignment. */
 #define ALIGN_FUNCTION()  . = ALIGN(8)
 
@@ -407,14 +417,14 @@
 	/* Kernel symbol table: Normal symbols */			\
 	__ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {		\
 		__start___ksymtab = .;					\
-		KEEP(*(SORT(___ksymtab+*)))				\
+		SYMTAB_KEEP						\
 		__stop___ksymtab = .;					\
 	}								\
 									\
 	/* Kernel symbol table: GPL-only symbols */			\
 	__ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {	\
 		__start___ksymtab_gpl = .;				\
-		KEEP(*(SORT(___ksymtab_gpl+*)))				\
+		SYMTAB_KEEP_GPL						\
 		__stop___ksymtab_gpl = .;				\
 	}								\
 									\
@@ -476,7 +486,7 @@
 									\
 	/* Kernel symbol table: strings */				\
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\
-		*(__ksymtab_strings)					\
+		*(__ksymtab_strings+*)					\
 	}								\
 									\
 	/* __*init sections */						\
@@ -904,6 +914,8 @@
 	EXIT_TEXT							\
 	EXIT_DATA							\
 	EXIT_CALL							\
+	SYMTAB_DISCARD							\
+	SYMTAB_DISCARD_GPL						\
 	*(.discard)							\
 	*(.discard.*)							\
 	*(.modinfo)							\
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -98,18 +98,26 @@ struct kernel_symbol {
 
 #else
 
+#ifdef MODULE
+#define __EXPORT_SUFFIX(sym)
+#else
+#define __EXPORT_SUFFIX(sym) "+" #sym
+#endif
+
 #define ___export_symbol_common(sym, sec)				\
 	extern typeof(sym) sym;						\
 	__CRC_SYMBOL(sym, sec);						\
 	static const char __kstrtab_##sym[]				\
-	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
+	__attribute__((section("__ksymtab_strings"			\
+	  __EXPORT_SUFFIX(sym)), used, aligned(1)))			\
 	= #sym								\
 
 /* For every exported symbol, place a struct in the __ksymtab section */
 #define ___EXPORT_SYMBOL_NS(sym, sec, ns)				\
 	___export_symbol_common(sym, sec);				\
 	static const char __kstrtabns_##sym[]				\
-	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\
+	__attribute__((section("__ksymtab_strings"			\
+	  __EXPORT_SUFFIX(sym)), used, aligned(1)))			\
 	= #ns;								\
 	__KSYMTAB_ENTRY_NS(sym, sec)
 
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -349,7 +349,7 @@ 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