259 lines
7.5 KiB
Diff
259 lines
7.5 KiB
Diff
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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/Makefile
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+++ b/Makefile
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@@ -410,6 +410,11 @@ KBUILD_AFLAGS_MODULE := -DMODULE
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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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+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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@@ -783,11 +788,6 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
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KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
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endif
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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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# arch Makefile may override CC so keep this after arch Makefile is included
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NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
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CHECKFLAGS += $(NOSTDINC_FLAGS)
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -91,6 +91,7 @@ config ARM
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select HAVE_UID16
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select HAVE_VIRT_CPU_ACCOUNTING_GEN
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select IRQ_FORCED_THREADING
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+ select LD_DEAD_CODE_DATA_ELIMINATION
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select MODULES_USE_ELF_REL
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select NO_BOOTMEM
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select OF_EARLY_FLATTREE if OF
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--- a/arch/arm/boot/compressed/Makefile
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+++ b/arch/arm/boot/compressed/Makefile
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@@ -103,6 +103,7 @@ ifeq ($(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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@@ -18,7 +18,7 @@
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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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@@ -29,11 +29,11 @@
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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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@@ -106,7 +106,7 @@ 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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@@ -135,7 +135,7 @@ 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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@@ -147,12 +147,12 @@ 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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@@ -172,14 +172,14 @@ 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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@@ -195,24 +195,24 @@ 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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@@ -39,6 +39,7 @@ config MIPS
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select HAVE_CBPF_JIT if (!64BIT && !CPU_MICROMIPS)
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select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)
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select HAVE_CC_STACKPROTECTOR
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+ select LD_DEAD_CODE_DATA_ELIMINATION
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select HAVE_CONTEXT_TRACKING
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select HAVE_COPY_THREAD_TLS
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select HAVE_C_RECORDMCOUNT
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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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@@ -72,7 +72,7 @@ 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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@@ -123,7 +123,7 @@ 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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@@ -237,7 +237,8 @@
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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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@@ -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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#define IRQENTRY_TEXT \
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@@ -603,7 +604,7 @@
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. = ALIGN(sbss_align); \
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.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) { \
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*(.dynsbss) \
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- *(.sbss) \
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+ *(.sbss .sbss.*) \
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*(.scommon) \
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}
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