1 From b14784e7883390c20ed3ff904892255404a5914b Mon Sep 17 00:00:00 2001
2 From: Felix Fietkau <nbd@nbd.name>
3 Date: Fri, 7 Jul 2017 17:05:53 +0200
4 Subject: add an optional config option for stripping all unnecessary symbol exports from the kernel image
6 lede-commit: bb5a40c64b7c4f4848509fa0a6625055fc9e66cc
7 Signed-off-by: Felix Fietkau <nbd@nbd.name>
9 include/asm-generic/vmlinux.lds.h | 18 +++++++++++++++---
10 include/linux/export.h | 9 ++++++++-
11 scripts/Makefile.build | 2 +-
12 3 files changed, 24 insertions(+), 5 deletions(-)
14 --- a/include/asm-generic/vmlinux.lds.h
15 +++ b/include/asm-generic/vmlinux.lds.h
21 +#define SYMTAB_KEEP KEEP(*(SORT(___ksymtab+*)))
22 +#define SYMTAB_KEEP_GPL KEEP(*(SORT(___ksymtab_gpl+*)))
25 +#ifndef SYMTAB_DISCARD
26 +#define SYMTAB_DISCARD
27 +#define SYMTAB_DISCARD_GPL
30 /* Align . to a 8 byte boundary equals to maximum function alignment. */
31 #define ALIGN_FUNCTION() . = ALIGN(8)
34 /* Kernel symbol table: Normal symbols */ \
35 __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
36 __start___ksymtab = .; \
37 - KEEP(*(SORT(___ksymtab+*))) \
39 __stop___ksymtab = .; \
42 /* Kernel symbol table: GPL-only symbols */ \
43 __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
44 __start___ksymtab_gpl = .; \
45 - KEEP(*(SORT(___ksymtab_gpl+*))) \
47 __stop___ksymtab_gpl = .; \
52 /* Kernel symbol table: strings */ \
53 __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \
54 - *(__ksymtab_strings) \
55 + *(__ksymtab_strings+*) \
58 /* __*init sections */ \
64 + SYMTAB_DISCARD_GPL \
68 --- a/include/linux/export.h
69 +++ b/include/linux/export.h
70 @@ -98,18 +98,26 @@ struct kernel_symbol {
75 +#define __EXPORT_SUFFIX(sym)
77 +#define __EXPORT_SUFFIX(sym) "+" #sym
80 #define ___export_symbol_common(sym, sec) \
81 extern typeof(sym) sym; \
82 __CRC_SYMBOL(sym, sec); \
83 static const char __kstrtab_##sym[] \
84 - __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
85 + __attribute__((section("__ksymtab_strings" \
86 + __EXPORT_SUFFIX(sym)), used, aligned(1))) \
89 /* For every exported symbol, place a struct in the __ksymtab section */
90 #define ___EXPORT_SYMBOL_NS(sym, sec, ns) \
91 ___export_symbol_common(sym, sec); \
92 static const char __kstrtabns_##sym[] \
93 - __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
94 + __attribute__((section("__ksymtab_strings" \
95 + __EXPORT_SUFFIX(sym)), used, aligned(1))) \
97 __KSYMTAB_ENTRY_NS(sym, sec)
99 --- a/scripts/Makefile.build
100 +++ b/scripts/Makefile.build
101 @@ -349,7 +349,7 @@ targets += $(extra-y) $(MAKECMDGOALS) $(
102 # Linker scripts preprocessor (.lds.S -> .lds)
103 # ---------------------------------------------------------------------------
104 quiet_cmd_cpp_lds_S = LDS $@
105 - cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
106 + cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -U$(ARCH) \
107 -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
109 $(obj)/%.lds: $(src)/%.lds.S FORCE