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From b14784e7883390c20ed3ff904892255404a5914b Mon Sep 17 00:00:00 2001
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From: Felix Fietkau <nbd@nbd.name>
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Date: Fri, 7 Jul 2017 17:05:53 +0200
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Subject: add an optional config option for stripping all unnecessary symbol exports from the kernel image
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lede-commit: bb5a40c64b7c4f4848509fa0a6625055fc9e66cc
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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---
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include/asm-generic/vmlinux.lds.h | 18 +++++++++++++++---
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include/linux/export.h | 9 ++++++++-
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scripts/Makefile.build | 2 +-
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3 files changed, 24 insertions(+), 5 deletions(-)
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--- a/include/asm-generic/vmlinux.lds.h
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+++ b/include/asm-generic/vmlinux.lds.h
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@@ -54,6 +54,16 @@
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#define LOAD_OFFSET 0
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#endif
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+#ifndef SYMTAB_KEEP
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+#define SYMTAB_KEEP KEEP(*(SORT(___ksymtab+*)))
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+#define SYMTAB_KEEP_GPL KEEP(*(SORT(___ksymtab_gpl+*)))
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+#endif
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+
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+#ifndef SYMTAB_DISCARD
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+#define SYMTAB_DISCARD
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+#define SYMTAB_DISCARD_GPL
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+#endif
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+
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#include <linux/export.h>
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/* Align . to a 8 byte boundary equals to maximum function alignment. */
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@@ -341,14 +351,14 @@
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/* Kernel symbol table: Normal symbols */ \
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__ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___ksymtab) = .; \
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- KEEP(*(SORT(___ksymtab+*))) \
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+ SYMTAB_KEEP \
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VMLINUX_SYMBOL(__stop___ksymtab) = .; \
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} \
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\
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/* Kernel symbol table: GPL-only symbols */ \
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__ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
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- KEEP(*(SORT(___ksymtab_gpl+*))) \
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+ SYMTAB_KEEP_GPL \
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VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
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} \
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\
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@@ -410,7 +420,7 @@
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\
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/* Kernel symbol table: strings */ \
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__ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \
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- *(__ksymtab_strings) \
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+ *(__ksymtab_strings+*) \
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} \
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\
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/* __*init sections */ \
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@@ -793,6 +803,8 @@
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EXIT_TEXT \
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EXIT_DATA \
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EXIT_CALL \
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+ SYMTAB_DISCARD \
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+ SYMTAB_DISCARD_GPL \
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*(.discard) \
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*(.discard.*) \
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}
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--- a/include/linux/export.h
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+++ b/include/linux/export.h
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@@ -60,12 +60,19 @@ extern struct module __this_module;
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#define __CRC_SYMBOL(sym, sec)
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#endif
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+#ifdef MODULE
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+#define __EXPORT_SUFFIX(sym)
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+#else
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+#define __EXPORT_SUFFIX(sym) "+" #sym
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+#endif
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+
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/* For every exported symbol, place a struct in the __ksymtab section */
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#define ___EXPORT_SYMBOL(sym, sec) \
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extern typeof(sym) sym; \
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__CRC_SYMBOL(sym, sec) \
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static const char __kstrtab_##sym[] \
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- __attribute__((section("__ksymtab_strings"), aligned(1))) \
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+ __attribute__((section("__ksymtab_strings" \
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+ __EXPORT_SUFFIX(sym)), aligned(1))) \
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= VMLINUX_SYMBOL_STR(sym); \
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static const struct kernel_symbol __ksymtab_##sym \
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__used \
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--- a/scripts/Makefile.build
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+++ b/scripts/Makefile.build
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@@ -432,7 +432,7 @@ targets += $(extra-y) $(MAKECMDGOALS) $(
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# Linker scripts preprocessor (.lds.S -> .lds)
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# ---------------------------------------------------------------------------
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quiet_cmd_cpp_lds_S = LDS $@
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- cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
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+ cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -U$(ARCH) \
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-D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
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$(obj)/%.lds: $(src)/%.lds.S FORCE
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