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
@@ -81,6 +81,16 @@
 #define RO_EXCEPTION_TABLE
 #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 . function alignment. */
 #define ALIGN_FUNCTION()  . = ALIGN(CONFIG_FUNCTION_ALIGNMENT)
 
@@ -486,14 +496,14 @@
 	/* 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 = .;				\
 	}								\
 									\
@@ -513,7 +523,7 @@
 									\
 	/* Kernel symbol table: strings */				\
         __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {	\
-		*(__ksymtab_strings)					\
+		*(__ksymtab_strings+*)					\
 	}								\
 									\
 	/* __*init sections */						\
@@ -1000,6 +1010,8 @@
 #define COMMON_DISCARDS							\
 	SANITIZER_DISCARDS						\
 	PATCHABLE_DISCARDS						\
+	SYMTAB_DISCARD							\
+	SYMTAB_DISCARD_GPL						\
 	*(.discard)							\
 	*(.discard.*)							\
 	*(.export_symbol)						\
--- a/include/linux/export-internal.h
+++ b/include/linux/export-internal.h
@@ -26,6 +26,12 @@
 #define __KSYM_REF(sym)		".long " #sym
 #endif
 
+#ifdef MODULE
+#define __EXPORT_SUFFIX(sym)
+#else
+#define __EXPORT_SUFFIX(sym) "+" #sym
+#endif
+
 /*
  * For every exported symbol, do the following:
  *
@@ -38,7 +44,7 @@
  * former apparently works on all arches according to the binutils source.
  */
 #define __KSYMTAB(name, sym, sec, ns)						\
-	asm("	.section \"__ksymtab_strings\",\"aMS\",%progbits,1"	"\n"	\
+	asm("	.section \"__ksymtab_strings" __EXPORT_SUFFIX(sym) "\",\"aMS\",%progbits,1"	"\n"	\
 	    "__kstrtab_" #name ":"					"\n"	\
 	    "	.asciz \"" #name "\""					"\n"	\
 	    "__kstrtabns_" #name ":"					"\n"	\
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -366,7 +366,7 @@ targets += $(real-dtb-y) $(lib-y) $(alwa
 # 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