2020-02-23 12:20:11 +00:00
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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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Makefile | 10 +++----
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arch/arm/Kconfig | 1 +
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arch/arm/boot/compressed/Makefile | 1 +
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arch/arm/kernel/vmlinux.lds.S | 26 ++++++++--------
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arch/mips/Kconfig | 1 +
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arch/mips/kernel/vmlinux.lds.S | 4 +--
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include/asm-generic/vmlinux.lds.h | 63 ++++++++++++++++++++-------------------
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7 files changed, 55 insertions(+), 51 deletions(-)
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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2019-11-25 15:08:31 +00:00
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@@ -111,6 +111,7 @@ config ARM
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2020-02-23 12:20:11 +00:00
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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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2019-11-25 15:08:31 +00:00
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select OF_EARLY_FLATTREE if OF
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2020-02-23 12:20:11 +00:00
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--- a/arch/arm/boot/compressed/Makefile
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+++ b/arch/arm/boot/compressed/Makefile
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2019-11-25 15:08:31 +00:00
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@@ -107,6 +107,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
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2020-02-23 12:20:11 +00:00
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ORIG_CFLAGS := $(KBUILD_CFLAGS)
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KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
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endif
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+KBUILD_CFLAGS_KERNEL := $(patsubst -f%-sections,,$(KBUILD_CFLAGS_KERNEL))
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# -fstack-protector-strong triggers protection checks in this code,
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# but it is being used too early to link to meaningful stack_chk logic.
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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/kernel/vmlinux.lds.h
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+++ b/arch/arm/kernel/vmlinux.lds.h
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@@ -22,13 +22,13 @@
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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 HYPERVISOR_TEXT \
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@@ -39,11 +39,11 @@
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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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. = ALIGN(PAGE_SIZE); \
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__hyp_idmap_text_start = .; \
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- *(.hyp.idmap.text) \
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+ KEEP(*(.hyp.idmap.text)) \
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__hyp_idmap_text_end = .;
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#define ARM_DISCARD \
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@@ -86,12 +86,12 @@
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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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@@ -102,14 +102,14 @@
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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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