From b14784e7883390c20ed3ff904892255404a5914b Mon Sep 17 00:00:00 2001 From: Felix Fietkau 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 --- 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) @@ -473,14 +483,14 @@ /* 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 = .; \ } \ \ @@ -542,7 +552,7 @@ \ /* Kernel symbol table: strings */ \ __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \ - *(__ksymtab_strings) \ + *(__ksymtab_strings+*) \ } \ \ /* __*init sections */ \ @@ -1019,6 +1029,8 @@ #define COMMON_DISCARDS \ SANITIZER_DISCARDS \ + SYMTAB_DISCARD \ + SYMTAB_DISCARD_GPL \ *(.discard) \ *(.discard.*) \ *(.modinfo) \ --- a/include/linux/export.h +++ b/include/linux/export.h @@ -82,6 +82,12 @@ struct kernel_symbol { #else +#ifdef MODULE +#define __EXPORT_SUFFIX(sym) +#else +#define __EXPORT_SUFFIX(sym) "+" #sym +#endif + /* * For every exported symbol, do the following: * @@ -99,7 +105,7 @@ 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 @@ -373,7 +373,7 @@ targets += $(lib-y) $(always-y) $(MAKECM # 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