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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 . to a 8 byte boundary equals to maximum function alignment. */
#define ALIGN_FUNCTION() . = ALIGN(8)
@@ -485,14 +495,14 @@
/* 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 = .; \
} \
\
@@ -512,7 +522,7 @@
\
/* Kernel symbol table: strings */ \
__ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \
- *(__ksymtab_strings) \
+ *(__ksymtab_strings+*) \
} \
\
/* __*init sections */ \
@@ -1017,6 +1027,8 @@
#define COMMON_DISCARDS \
SANITIZER_DISCARDS \
+ SYMTAB_DISCARD \
+ SYMTAB_DISCARD_GPL \
*(.discard) \
*(.discard.*) \
*(.modinfo) \
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -84,6 +84,12 @@ struct kernel_symbol {
#else
+#ifdef MODULE
+#define __EXPORT_SUFFIX(sym)
+#else
+#define __EXPORT_SUFFIX(sym) "+" #sym
+#endif
+
/*
* For every exported symbol, do the following:
*
@@ -101,7 +107,7 @@ struct kernel_symbol {
extern const char __kstrtab_##sym[]; \
extern const char __kstrtabns_##sym[]; \
__CRC_SYMBOL(sym, sec); \
- asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \
+ asm(" .section \"__ksymtab_strings" __EXPORT_SUFFIX(sym) "\",\"aMS\",%progbits,1 \n" \
"__kstrtab_" #sym ": \n" \
" .asciz \"" #sym "\" \n" \
"__kstrtabns_" #sym ": \n" \
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -26,6 +26,12 @@
#endif
.endm
+#ifdef MODULE
+#define __EXPORT_SUFFIX(name)
+#else
+#define __EXPORT_SUFFIX(name) + #name
+#endif
+
/*
* note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
* section flag requires it. Use '%progbits' instead of '@progbits' since the
@@ -39,7 +45,7 @@
__ksymtab_\name:
__put \val, __kstrtab_\name
.previous
- .section __ksymtab_strings,"aMS",%progbits,1
+ .section __ksymtab_strings __EXPORT_SUFFIX(name),"aMS",%progbits,1
__kstrtab_\name:
.asciz "\name"
.previous
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -397,7 +397,7 @@ 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
|
