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			121 lines
		
	
	
		
			3.2 KiB
		
	
	
	
		
			Diff
		
	
	
	
	
	
			
		
		
	
	
			121 lines
		
	
	
		
			3.2 KiB
		
	
	
	
		
			Diff
		
	
	
	
	
	
From e3d8676f5722b7622685581e06e8f53e6138e3ab Mon Sep 17 00:00:00 2001
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From: Felix Fietkau <nbd@nbd.name>
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Date: Sat, 15 Jul 2017 23:42:36 +0200
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Subject: use -ffunction-sections, -fdata-sections and --gc-sections
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In combination with kernel symbol export stripping this significantly reduces
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the kernel image size. Used on both ARM and MIPS architectures.
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Signed-off-by: Felix Fietkau <nbd@nbd.name>
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Signed-off-by: Jonas Gorski <jogo@openwrt.org>
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Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
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---
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -113,6 +113,7 @@ config ARM
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 	select HAVE_UID16
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 	select HAVE_VIRT_CPU_ACCOUNTING_GEN
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 	select IRQ_FORCED_THREADING
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+	select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
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 	select MODULES_USE_ELF_REL
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 	select NEED_DMA_MAP_STATE
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 	select OF_EARLY_FLATTREE if OF
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--- a/arch/arm/boot/compressed/Makefile
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+++ b/arch/arm/boot/compressed/Makefile
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@@ -98,6 +98,7 @@ $(foreach o, $(libfdt_objs) atags_to_fdt
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 ifdef building_out_of_srctree
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 $(shell rm -f $(addprefix $(obj)/, fdt_rw.c fdt_ro.c fdt_wip.c fdt.c))
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 endif
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+KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
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 targets       := vmlinux vmlinux.lds piggy_data piggy.o \
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 		 lib1funcs.o ashldi3.o bswapsdi2.o \
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--- a/arch/arm/kernel/vmlinux.lds.S
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+++ b/arch/arm/kernel/vmlinux.lds.S
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@@ -100,24 +100,24 @@ SECTIONS
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 	}
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 	.init.arch.info : {
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 		__arch_info_begin = .;
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-		*(.arch.info.init)
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+		KEEP(*(.arch.info.init))
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 		__arch_info_end = .;
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 	}
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 	.init.tagtable : {
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 		__tagtable_begin = .;
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-		*(.taglist.init)
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+		KEEP(*(.taglist.init))
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 		__tagtable_end = .;
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 	}
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 #ifdef CONFIG_SMP_ON_UP
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 	.init.smpalt : {
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 		__smpalt_begin = .;
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-		*(.alt.smp.init)
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+		KEEP(*(.alt.smp.init))
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 		__smpalt_end = .;
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 	}
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 #endif
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 	.init.pv_table : {
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 		__pv_table_begin = .;
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-		*(.pv_table)
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+		KEEP(*(.pv_table))
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 		__pv_table_end = .;
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 	}
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--- a/arch/arm/include/asm/vmlinux.lds.h
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+++ b/arch/arm/include/asm/vmlinux.lds.h
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@@ -23,19 +23,19 @@
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 #define ARM_MMU_DISCARD(x)
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 #else
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 #define ARM_MMU_KEEP(x)
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-#define ARM_MMU_DISCARD(x)	x
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+#define ARM_MMU_DISCARD(x)	KEEP(x)
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 #endif
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 #define PROC_INFO							\
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 		. = ALIGN(4);						\
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 		__proc_info_begin = .;					\
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-		*(.proc.info.init)					\
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+		KEEP(*(.proc.info.init))				\
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 		__proc_info_end = .;
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 #define IDMAP_TEXT							\
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 		ALIGN_FUNCTION();					\
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 		__idmap_text_start = .;					\
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-		*(.idmap.text)						\
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+		KEEP(*(.idmap.text))					\
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 		__idmap_text_end = .;					\
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 #define ARM_DISCARD							\
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@@ -96,12 +96,12 @@
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 	. = ALIGN(8);							\
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 	.ARM.unwind_idx : {						\
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 		__start_unwind_idx = .;					\
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-		*(.ARM.exidx*)						\
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+		KEEP(*(.ARM.exidx*))					\
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 		__stop_unwind_idx = .;					\
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 	}								\
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 	.ARM.unwind_tab : {						\
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 		__start_unwind_tab = .;					\
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-		*(.ARM.extab*)						\
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+		KEEP(*(.ARM.extab*))					\
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 		__stop_unwind_tab = .;					\
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 	}
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@@ -112,14 +112,14 @@
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 #define ARM_VECTORS							\
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 	__vectors_start = .;						\
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 	.vectors 0xffff0000 : AT(__vectors_start) {			\
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-		*(.vectors)						\
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+		KEEP(*(.vectors))					\
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 	}								\
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 	. = __vectors_start + SIZEOF(.vectors);				\
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 	__vectors_end = .;						\
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 									\
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 	__stubs_start = .;						\
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 	.stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {		\
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-		*(.stubs)						\
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+		KEEP(*(.stubs))						\
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 	}								\
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 	. = __stubs_start + SIZEOF(.stubs);				\
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 	__stubs_end = .;						\
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