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The current arm32 architecture does not yet support the HAVE_LD_DEAD_CODE_DATA_ELIMINATION feature. arm32 is widely used in embedded scenarios, and enabling this feature would be beneficial for reducing the size of the kernel image. In order to make this work, we keep the necessary tables by annotating them with KEEP, also it requires further changes to linker script to KEEP some tables and wildcard compiler generated sections into the right place. When using ld.lld for linking, KEEP is not recognized within the OVERLAY command, and Ard proposed a concise method to solve this problem. It boots normally with defconfig, vexpress_defconfig and tinyconfig. The size comparison of zImage is as follows: defconfig vexpress_defconfig tinyconfig 5137712 5138024 424192 no dce 5032560 4997824 298384 dce 2.0% 2.7% 29.7% shrink When using smaller config file, there is a significant reduction in the size of the zImage. We also tested this patch on a commercially available single-board computer, and the comparison is as follows: a15eb_config 2161384 no dce 2092240 dce 3.2% shrink The zImage size has been reduced by approximately 3.2%, which is 70KB on 2.1M. Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com> Tested-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
181 lines
3.4 KiB
ArmAsm
181 lines
3.4 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/* ld script to make ARM Linux kernel
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* taken from the i386 version by Russell King
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* Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
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*/
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#ifdef CONFIG_XIP_KERNEL
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#include "vmlinux-xip.lds.S"
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#else
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#include <linux/pgtable.h>
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#include <asm/vmlinux.lds.h>
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#include <asm/cache.h>
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#include <asm/thread_info.h>
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#include <asm/page.h>
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#include <asm/mpu.h>
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OUTPUT_ARCH(arm)
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ENTRY(stext)
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#ifndef __ARMEB__
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jiffies = jiffies_64;
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#else
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jiffies = jiffies_64 + 4;
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#endif
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SECTIONS
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{
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/*
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* XXX: The linker does not define how output sections are
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* assigned to input sections when there are multiple statements
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* matching the same input section name. There is no documented
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* order of matching.
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*
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* unwind exit sections must be discarded before the rest of the
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* unwind sections get included.
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*/
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/DISCARD/ : {
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ARM_DISCARD
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#ifndef CONFIG_SMP_ON_UP
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*(.alt.smp.init)
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#endif
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#ifndef CONFIG_ARM_UNWIND
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*(.ARM.exidx) *(.ARM.exidx.*)
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*(.ARM.extab) *(.ARM.extab.*)
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#endif
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}
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. = KERNEL_OFFSET + TEXT_OFFSET;
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.head.text : {
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_text = .;
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HEAD_TEXT
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}
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#ifdef CONFIG_STRICT_KERNEL_RWX
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. = ALIGN(1<<SECTION_SHIFT);
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#endif
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#ifdef CONFIG_ARM_MPU
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. = ALIGN(PMSAv8_MINALIGN);
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#endif
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.text : { /* Real text segment */
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_stext = .; /* Text and read-only data */
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ARM_TEXT
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}
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#ifdef CONFIG_DEBUG_ALIGN_RODATA
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. = ALIGN(1<<SECTION_SHIFT);
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#endif
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_etext = .; /* End of text section */
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RO_DATA(PAGE_SIZE)
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. = ALIGN(4);
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__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) {
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__start___ex_table = .;
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ARM_MMU_KEEP(KEEP(*(__ex_table)))
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__stop___ex_table = .;
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}
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#ifdef CONFIG_ARM_UNWIND
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ARM_UNWIND_SECTIONS
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#endif
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#ifdef CONFIG_STRICT_KERNEL_RWX
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. = ALIGN(1<<SECTION_SHIFT);
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#else
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. = ALIGN(PAGE_SIZE);
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#endif
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__init_begin = .;
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ARM_VECTORS
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INIT_TEXT_SECTION(8)
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.exit.text : {
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ARM_EXIT_KEEP(EXIT_TEXT)
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}
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.init.proc.info : {
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ARM_CPU_DISCARD(PROC_INFO)
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}
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.init.arch.info : {
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__arch_info_begin = .;
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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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__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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__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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KEEP(*(.pv_table))
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__pv_table_end = .;
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}
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INIT_DATA_SECTION(16)
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.exit.data : {
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ARM_EXIT_KEEP(EXIT_DATA)
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}
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#ifdef CONFIG_SMP
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PERCPU_SECTION(L1_CACHE_BYTES)
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#endif
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#ifdef CONFIG_HAVE_TCM
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ARM_TCM
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#endif
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#ifdef CONFIG_STRICT_KERNEL_RWX
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. = ALIGN(1<<SECTION_SHIFT);
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#else
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. = ALIGN(THREAD_ALIGN);
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#endif
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__init_end = .;
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_sdata = .;
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RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_ALIGN)
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_edata = .;
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BSS_SECTION(0, 0, 0)
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#ifdef CONFIG_ARM_MPU
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. = ALIGN(PMSAv8_MINALIGN);
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#endif
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_end = .;
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STABS_DEBUG
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DWARF_DEBUG
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ARM_DETAILS
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ARM_ASSERTS
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}
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#ifdef CONFIG_STRICT_KERNEL_RWX
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/*
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* Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
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* be the first section-aligned location after __start_rodata. Otherwise,
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* it will be equal to __start_rodata.
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*/
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__start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
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#endif
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/*
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* These must never be empty
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* If you have to comment these two assert statements out, your
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* binutils is too old (for other reasons as well)
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*/
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ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support")
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#ifndef CONFIG_COMPILE_TEST
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ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")
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#endif
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#endif /* CONFIG_XIP_KERNEL */
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