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448 lines
14 KiB
448 lines
14 KiB
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/Makefile
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+++ b/Makefile
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@@ -406,6 +406,11 @@ KBUILD_CFLAGS_MODULE := -DMODULE
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KBUILD_LDFLAGS_MODULE = -T $(srctree)/scripts/module-common.lds $(if $(CONFIG_PROFILING),,-s)
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GCC_PLUGINS_CFLAGS :=
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+ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
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+KBUILD_CFLAGS_KERNEL += $(call cc-option,-ffunction-sections,)
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+KBUILD_CFLAGS_KERNEL += $(call cc-option,-fdata-sections,)
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+endif
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+
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# Read KERNELRELEASE from include/config/kernel.release (if it exists)
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KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
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KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
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@@ -636,11 +641,6 @@ KBUILD_CFLAGS += $(call cc-disable-warni
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KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
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KBUILD_CFLAGS += $(call cc-disable-warning, int-in-bool-context)
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-ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
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-KBUILD_CFLAGS += $(call cc-option,-ffunction-sections,)
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-KBUILD_CFLAGS += $(call cc-option,-fdata-sections,)
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-endif
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-
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ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
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KBUILD_CFLAGS += -Os $(call cc-disable-warning,maybe-uninitialized,) $(EXTRA_OPTIMIZATION)
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else
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -81,6 +81,7 @@ config ARM
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select HAVE_UID16
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select HAVE_VIRT_CPU_ACCOUNTING_GEN
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select IRQ_FORCED_THREADING
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+ select LD_DEAD_CODE_DATA_ELIMINATION
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select MODULES_USE_ELF_REL
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select NO_BOOTMEM
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select OF_EARLY_FLATTREE if OF
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--- a/arch/arm/boot/compressed/Makefile
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+++ b/arch/arm/boot/compressed/Makefile
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@@ -102,6 +102,7 @@ ifeq ($(CONFIG_FUNCTION_TRACER),y)
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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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@@ -17,7 +17,7 @@
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#define PROC_INFO \
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. = ALIGN(4); \
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VMLINUX_SYMBOL(__proc_info_begin) = .; \
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- *(.proc.info.init) \
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+ KEEP(*(.proc.info.init)) \
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VMLINUX_SYMBOL(__proc_info_end) = .;
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#define HYPERVISOR_TEXT \
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@@ -28,11 +28,11 @@
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#define IDMAP_TEXT \
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ALIGN_FUNCTION(); \
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VMLINUX_SYMBOL(__idmap_text_start) = .; \
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- *(.idmap.text) \
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+ KEEP(*(.idmap.text)) \
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VMLINUX_SYMBOL(__idmap_text_end) = .; \
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. = ALIGN(PAGE_SIZE); \
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VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \
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- *(.hyp.idmap.text) \
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+ KEEP(*(.hyp.idmap.text)) \
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VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
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#ifdef CONFIG_HOTPLUG_CPU
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@@ -105,7 +105,7 @@ SECTIONS
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_stext = .; /* Text and read-only data */
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IDMAP_TEXT
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__exception_text_start = .;
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- *(.exception.text)
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+ KEEP(*(.exception.text))
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__exception_text_end = .;
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IRQENTRY_TEXT
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SOFTIRQENTRY_TEXT
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@@ -134,7 +134,7 @@ SECTIONS
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__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
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__start___ex_table = .;
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#ifdef CONFIG_MMU
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- *(__ex_table)
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+ KEEP(*(__ex_table))
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#endif
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__stop___ex_table = .;
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}
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@@ -146,12 +146,12 @@ SECTIONS
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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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#endif
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@@ -171,14 +171,14 @@ SECTIONS
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*/
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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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__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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@@ -194,24 +194,24 @@ 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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.init.data : {
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--- a/arch/mips/Kconfig
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+++ b/arch/mips/Kconfig
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@@ -55,6 +55,7 @@ config MIPS
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select CLONE_BACKWARDS
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select HAVE_DEBUG_STACKOVERFLOW
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select HAVE_CC_STACKPROTECTOR
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+ select LD_DEAD_CODE_DATA_ELIMINATION
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select CPU_PM if CPU_IDLE
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select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
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select ARCH_BINFMT_ELF_STATE
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--- a/arch/mips/kernel/vmlinux.lds.S
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+++ b/arch/mips/kernel/vmlinux.lds.S
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@@ -71,7 +71,7 @@ SECTIONS
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/* Exception table for data bus errors */
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__dbe_table : {
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__start___dbe_table = .;
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- *(__dbe_table)
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+ KEEP(*(__dbe_table))
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__stop___dbe_table = .;
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}
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@@ -121,7 +121,7 @@ SECTIONS
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. = ALIGN(4);
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.mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
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__mips_machines_start = .;
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- *(.mips.machines.init)
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+ KEEP(*(.mips.machines.init))
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__mips_machines_end = .;
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}
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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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@@ -105,7 +105,7 @@
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#ifdef CONFIG_FTRACE_MCOUNT_RECORD
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#define MCOUNT_REC() . = ALIGN(8); \
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VMLINUX_SYMBOL(__start_mcount_loc) = .; \
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- *(__mcount_loc) \
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+ KEEP(*(__mcount_loc)) \
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VMLINUX_SYMBOL(__stop_mcount_loc) = .;
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#else
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#define MCOUNT_REC()
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@@ -113,7 +113,7 @@
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#ifdef CONFIG_TRACE_BRANCH_PROFILING
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#define LIKELY_PROFILE() VMLINUX_SYMBOL(__start_annotated_branch_profile) = .; \
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- *(_ftrace_annotated_branch) \
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+ KEEP(*(_ftrace_annotated_branch)) \
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VMLINUX_SYMBOL(__stop_annotated_branch_profile) = .;
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#else
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#define LIKELY_PROFILE()
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@@ -121,7 +121,7 @@
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#ifdef CONFIG_PROFILE_ALL_BRANCHES
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#define BRANCH_PROFILE() VMLINUX_SYMBOL(__start_branch_profile) = .; \
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- *(_ftrace_branch) \
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+ KEEP(*(_ftrace_branch)) \
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VMLINUX_SYMBOL(__stop_branch_profile) = .;
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#else
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#define BRANCH_PROFILE()
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@@ -130,7 +130,7 @@
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#ifdef CONFIG_KPROBES
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#define KPROBE_BLACKLIST() . = ALIGN(8); \
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VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
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- *(_kprobe_blacklist) \
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+ KEEP(*(_kprobe_blacklist)) \
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VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
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#else
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#define KPROBE_BLACKLIST()
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@@ -139,10 +139,10 @@
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#ifdef CONFIG_EVENT_TRACING
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#define FTRACE_EVENTS() . = ALIGN(8); \
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VMLINUX_SYMBOL(__start_ftrace_events) = .; \
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- *(_ftrace_events) \
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+ KEEP(*(_ftrace_events)) \
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VMLINUX_SYMBOL(__stop_ftrace_events) = .; \
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VMLINUX_SYMBOL(__start_ftrace_enum_maps) = .; \
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- *(_ftrace_enum_map) \
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+ KEEP(*(_ftrace_enum_map)) \
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VMLINUX_SYMBOL(__stop_ftrace_enum_maps) = .;
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#else
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#define FTRACE_EVENTS()
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@@ -163,7 +163,7 @@
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#ifdef CONFIG_FTRACE_SYSCALLS
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#define TRACE_SYSCALLS() . = ALIGN(8); \
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VMLINUX_SYMBOL(__start_syscalls_metadata) = .; \
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- *(__syscalls_metadata) \
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+ KEEP(*(__syscalls_metadata)) \
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VMLINUX_SYMBOL(__stop_syscalls_metadata) = .;
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#else
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#define TRACE_SYSCALLS()
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@@ -172,7 +172,7 @@
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#ifdef CONFIG_SERIAL_EARLYCON
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#define EARLYCON_TABLE() STRUCT_ALIGN(); \
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VMLINUX_SYMBOL(__earlycon_table) = .; \
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- *(__earlycon_table) \
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+ KEEP(*(__earlycon_table)) \
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VMLINUX_SYMBOL(__earlycon_table_end) = .;
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#else
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#define EARLYCON_TABLE()
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@@ -185,8 +185,8 @@
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#define _OF_TABLE_1(name) \
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. = ALIGN(8); \
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VMLINUX_SYMBOL(__##name##_of_table) = .; \
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- *(__##name##_of_table) \
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- *(__##name##_of_table_end)
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+ KEEP(*(__##name##_of_table)) \
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+ KEEP(*(__##name##_of_table_end))
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#define CLKSRC_OF_TABLES() OF_TABLE(CONFIG_CLKSRC_OF, clksrc)
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#define IRQCHIP_OF_MATCH_TABLE() OF_TABLE(CONFIG_IRQCHIP, irqchip)
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@@ -209,7 +209,7 @@
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#define KERNEL_DTB() \
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STRUCT_ALIGN(); \
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VMLINUX_SYMBOL(__dtb_start) = .; \
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- *(.dtb.init.rodata) \
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+ KEEP(*(.dtb.init.rodata)) \
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VMLINUX_SYMBOL(__dtb_end) = .;
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/*
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@@ -227,16 +227,17 @@
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/* implement dynamic printk debug */ \
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. = ALIGN(8); \
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VMLINUX_SYMBOL(__start___jump_table) = .; \
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- *(__jump_table) \
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+ KEEP(*(__jump_table)) \
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VMLINUX_SYMBOL(__stop___jump_table) = .; \
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. = ALIGN(8); \
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VMLINUX_SYMBOL(__start___verbose) = .; \
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- *(__verbose) \
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+ KEEP(*(__verbose)) \
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VMLINUX_SYMBOL(__stop___verbose) = .; \
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LIKELY_PROFILE() \
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BRANCH_PROFILE() \
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TRACE_PRINTKS() \
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- TRACEPOINT_STR()
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+ TRACEPOINT_STR() \
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+ *(.data.[a-zA-Z_]*)
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/*
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* Data section helpers
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@@ -304,35 +305,35 @@
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/* PCI quirks */ \
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.pci_fixup : AT(ADDR(.pci_fixup) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start_pci_fixups_early) = .; \
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- *(.pci_fixup_early) \
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+ KEEP(*(.pci_fixup_early)) \
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VMLINUX_SYMBOL(__end_pci_fixups_early) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_header) = .; \
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- *(.pci_fixup_header) \
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+ KEEP(*(.pci_fixup_header)) \
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VMLINUX_SYMBOL(__end_pci_fixups_header) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_final) = .; \
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- *(.pci_fixup_final) \
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+ KEEP(*(.pci_fixup_final)) \
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VMLINUX_SYMBOL(__end_pci_fixups_final) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_enable) = .; \
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- *(.pci_fixup_enable) \
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+ KEEP(*(.pci_fixup_enable)) \
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VMLINUX_SYMBOL(__end_pci_fixups_enable) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_resume) = .; \
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- *(.pci_fixup_resume) \
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+ KEEP(*(.pci_fixup_resume)) \
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VMLINUX_SYMBOL(__end_pci_fixups_resume) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_resume_early) = .; \
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- *(.pci_fixup_resume_early) \
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+ KEEP(*(.pci_fixup_resume_early)) \
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VMLINUX_SYMBOL(__end_pci_fixups_resume_early) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_suspend) = .; \
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- *(.pci_fixup_suspend) \
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+ KEEP(*(.pci_fixup_suspend)) \
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VMLINUX_SYMBOL(__end_pci_fixups_suspend) = .; \
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VMLINUX_SYMBOL(__start_pci_fixups_suspend_late) = .; \
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- *(.pci_fixup_suspend_late) \
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+ KEEP(*(.pci_fixup_suspend_late)) \
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VMLINUX_SYMBOL(__end_pci_fixups_suspend_late) = .; \
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} \
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\
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/* Built-in firmware blobs */ \
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.builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start_builtin_fw) = .; \
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- *(.builtin_fw) \
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+ KEEP(*(.builtin_fw)) \
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VMLINUX_SYMBOL(__end_builtin_fw) = .; \
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} \
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\
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@@ -410,7 +411,7 @@
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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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- KEEP(*(__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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@@ -423,14 +424,14 @@
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/* Built-in module parameters. */ \
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__param : AT(ADDR(__param) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___param) = .; \
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- *(__param) \
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+ KEEP(*(__param)) \
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VMLINUX_SYMBOL(__stop___param) = .; \
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} \
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\
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/* Built-in module versions. */ \
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__modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___modver) = .; \
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- *(__modver) \
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+ KEEP(*(__modver)) \
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VMLINUX_SYMBOL(__stop___modver) = .; \
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. = ALIGN((align)); \
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VMLINUX_SYMBOL(__end_rodata) = .; \
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@@ -496,7 +497,7 @@
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#define ENTRY_TEXT \
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ALIGN_FUNCTION(); \
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VMLINUX_SYMBOL(__entry_text_start) = .; \
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- *(.entry.text) \
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+ KEEP(*(.entry.text)) \
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VMLINUX_SYMBOL(__entry_text_end) = .;
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#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
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@@ -534,7 +535,7 @@
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. = ALIGN(align); \
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__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { \
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VMLINUX_SYMBOL(__start___ex_table) = .; \
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- *(__ex_table) \
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+ KEEP(*(__ex_table)) \
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VMLINUX_SYMBOL(__stop___ex_table) = .; \
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}
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@@ -550,9 +551,9 @@
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#ifdef CONFIG_CONSTRUCTORS
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#define KERNEL_CTORS() . = ALIGN(8); \
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VMLINUX_SYMBOL(__ctors_start) = .; \
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- *(.ctors) \
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+ KEEP(*(.ctors)) \
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*(SORT(.init_array.*)) \
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- *(.init_array) \
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+ KEEP(*(.init_array)) \
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VMLINUX_SYMBOL(__ctors_end) = .;
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#else
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#define KERNEL_CTORS()
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@@ -609,7 +610,7 @@
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#define SBSS(sbss_align) \
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. = ALIGN(sbss_align); \
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.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
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- *(.sbss) \
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+ *(.sbss .sbss.*) \
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*(.scommon) \
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}
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@@ -676,7 +677,7 @@
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. = ALIGN(8); \
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__bug_table : AT(ADDR(__bug_table) - LOAD_OFFSET) { \
|
|
VMLINUX_SYMBOL(__start___bug_table) = .; \
|
|
- *(__bug_table) \
|
|
+ KEEP(*(__bug_table)) \
|
|
VMLINUX_SYMBOL(__stop___bug_table) = .; \
|
|
}
|
|
#else
|
|
@@ -688,7 +689,7 @@
|
|
. = ALIGN(4); \
|
|
.tracedata : AT(ADDR(.tracedata) - LOAD_OFFSET) { \
|
|
VMLINUX_SYMBOL(__tracedata_start) = .; \
|
|
- *(.tracedata) \
|
|
+ KEEP(*(.tracedata)) \
|
|
VMLINUX_SYMBOL(__tracedata_end) = .; \
|
|
}
|
|
#else
|
|
@@ -705,7 +706,7 @@
|
|
#define INIT_SETUP(initsetup_align) \
|
|
. = ALIGN(initsetup_align); \
|
|
VMLINUX_SYMBOL(__setup_start) = .; \
|
|
- *(.init.setup) \
|
|
+ KEEP(*(.init.setup)) \
|
|
VMLINUX_SYMBOL(__setup_end) = .;
|
|
|
|
#define INIT_CALLS_LEVEL(level) \
|
|
|