内核的链接脚本文件vmlinux.lds.S

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vmlinux.lds.S是如何组织内核的每个函数存放在内核镜像文件的位置，我们知道你在编译内核生成内核文件的时候，其实这个过程分两步，一个是“编译”，另一个是“链接”的过程，vmlinux.lds.S要做的就是告诉编译器如何链接编译好的各个内核.o文件。

小知识：链接器中的entry

链接器 按以下优先顺序设入口点,找到即停止

1 -e 命令行选项

2 脚本中的entry(symbol)命令

3如定义了start的值,取其值为入口点

4.text的第一个字节的地址

5地址0

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所以你可以从vmlinux.lds.S下面的代码中看到：

OUTPUT_ARCH(arm)

ENTRY(stext)

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表明我们指定stext作为，程序的入口点。

上代码：

SECTIONS

{

#ifdef CONFIG_XIP_KERNEL

. = XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR);

#else

. = PAGE_OFFSET + TEXT_OFFSET;

#endif

.init : { /* Init code and data */

_stext = .;

_sinittext = .;

HEAD_TEXT

INIT_TEXT

ARM_EXIT_KEEP(EXIT_TEXT)

_einittext = .;

ARM_CPU_DISCARD(PROC_INFO)

__arch_info_begin = .;

*(.arch.info.init)

__arch_info_end = .;

__tagtable_begin = .;

*(.taglist.init)

__tagtable_end = .;

#ifdef CONFIG_SMP_ON_UP

__smpalt_begin = .;

*(.alt.smp.init)

__smpalt_end = .;

#endif

__pv_table_begin = .;

*(.pv_table)

__pv_table_end = .;

INIT_SETUP(16)

INIT_CALLS

CON_INITCALL

SECURITY_INITCALL

INIT_RAM_FS

#ifndef CONFIG_XIP_KERNEL

__init_begin = _stext;

INIT_DATA

ARM_EXIT_KEEP(EXIT_DATA)

#endif

}

PERCPU_SECTION(32)

#ifndef CONFIG_XIP_KERNEL

. = ALIGN(PAGE_SIZE);

__init_end = .;

#endif

/*

* unwind exit sections must be discarded before the rest of the

* unwind sections get included.

*/

/DISCARD/ : {

*(.ARM.exidx.exit.text)

*(.ARM.extab.exit.text)

ARM_CPU_DISCARD(*(.ARM.exidx.cpuexit.text))

ARM_CPU_DISCARD(*(.ARM.extab.cpuexit.text))

#ifndef CONFIG_HOTPLUG

*(.ARM.exidx.devexit.text)

*(.ARM.extab.devexit.text)

#endif

#ifndef CONFIG_MMU

*(.fixup)

*(__ex_table)

#endif

}

.text : { /* Real text segment */

_text = .; /* Text and read-only data */

__exception_text_start = .;

*(.exception.text)

__exception_text_end = .;

IRQENTRY_TEXT

TEXT_TEXT

SCHED_TEXT

LOCK_TEXT

KPROBES_TEXT

#ifdef CONFIG_MMU

*(.fixup)

#endif

*(.gnu.warning)

*(.rodata)

*(.rodata.*)

*(.glue_7)

*(.glue_7t)

. = ALIGN(4);

*(.got) /* Global offset table */

ARM_CPU_KEEP(PROC_INFO)

}

RO_DATA(PAGE_SIZE)

#ifdef CONFIG_ARM_UNWIND

/*

* Stack unwinding tables

*/

. = ALIGN(8);

.ARM.unwind_idx : {

__start_unwind_idx = .;

*(.ARM.exidx*)

__stop_unwind_idx = .;

}

.ARM.unwind_tab : {

__start_unwind_tab = .;

*(.ARM.extab*)

__stop_unwind_tab = .;

}

#endif

_etext = .; /* End of text and rodata section */

#ifdef CONFIG_XIP_KERNEL

__data_loc = ALIGN(4); /* location in binary */

. = PAGE_OFFSET + TEXT_OFFSET;

#else

. = ALIGN(THREAD_SIZE);

__data_loc = .;

#endif

.data : AT(__data_loc) {

_data = .; /* address in memory */

_sdata = .;

/*

* first, the init task union, aligned

* to an 8192 byte boundary.

*/

INIT_TASK_DATA(THREAD_SIZE)

#ifdef CONFIG_XIP_KERNEL

. = ALIGN(PAGE_SIZE);

__init_begin = .;

INIT_DATA

ARM_EXIT_KEEP(EXIT_DATA)

. = ALIGN(PAGE_SIZE);

__init_end = .;

#endif

NOSAVE_DATA

CACHELINE_ALIGNED_DATA(32)

READ_MOSTLY_DATA(32)

/*

* The exception fixup table (might need resorting at runtime)

*/

. = ALIGN(32);

__start___ex_table = .;

#ifdef CONFIG_MMU

*(__ex_table)

#endif

__stop___ex_table = .;

/*

* and the usual data section

*/

DATA_DATA

CONSTRUCTORS

_edata = .;

}

_edata_loc = __data_loc + SIZEOF(.data);

#ifdef CONFIG_HAVE_TCM

/*

* We align everything to a page boundary so we can

* free it after init has commenced and TCM contents have

* been copied to its destination.

*/

.tcm_start : {

. = ALIGN(PAGE_SIZE);

__tcm_start = .;

__itcm_start = .;

}

/*

* Link these to the ITCM RAM

* Put VMA to the TCM address and LMA to the common RAM

* and we'll upload the contents from RAM to TCM and free

* the used RAM after that.

*/

.text_itcm ITCM_OFFSET : AT(__itcm_start)

{

__sitcm_text = .;

*(.tcm.text)

*(.tcm.rodata)

. = ALIGN(4);

__eitcm_text = .;

}

/*

* Reset the dot pointer, this is needed to create the

* relative __dtcm_start below (to be used as extern in code).

*/

. = ADDR(.tcm_start) + SIZEOF(.tcm_start) + SIZEOF(.text_itcm);

.dtcm_start : {

__dtcm_start = .;

}

/* TODO: add remainder of ITCM as well, that can be used for data! */

.data_dtcm DTCM_OFFSET : AT(__dtcm_start)

{

. = ALIGN(4);

__sdtcm_data = .;

*(.tcm.data)

. = ALIGN(4);

__edtcm_data = .;

}

/* Reset the dot pointer or the linker gets confused */

. = ADDR(.dtcm_start) + SIZEOF(.data_dtcm);

/* End marker for freeing TCM copy in linked object */

.tcm_end : AT(ADDR(.dtcm_start) + SIZEOF(.data_dtcm)){

. = ALIGN(PAGE_SIZE);

__tcm_end = .;

}

#endif

NOTES

BSS_SECTION(0, 0, 0)

_end = .;

STABS_DEBUG

.comment 0 : { *(.comment) }

/* Default discards */

DISCARDS

#ifndef CONFIG_SMP_ON_UP

/DISCARD/ : {

*(.alt.smp.init)

}

#endif

}

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先看第一个知识点:

（1）. = PAGE_OFFSET + TEXT_OFFSET;

arch/arm/include/asm中的memory.h文件定义了：

#define PAGE_OFFSET UL(CONFIG_PAGE_OFFSET)

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CONFIG_PAGE_OFFSET是在内核配置里面配置的，比如拿ok6410来说，我的配置：

#define CONFIG_PAGE_OFFSET 0xC0000000

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PAGE_OFFSET代表是的内核image的的起始虚拟地址。

在arch/arm/Makefile中有定义：

textofs-y := 0x00008000

TEXT_OFFSET := $(textofs-y)

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TEXT_OFFSET代表的是内核的image存放在内存中地址，注意这个地址为相对于内存的起始地址的偏移量，是个相对的偏移量不是实际的存放内存物理地址。而且这个偏移量取得有讲究，必须为：0xXXXX8000，xxx为任意值。

所以：. = PAGE_OFFSET + TEXT_OFFSET就变成为：.=c0008000，这个地址就是内核存放在内存的虚拟的起始地址。从脚本来看，也就是.stext的地址就是：c0008000，那么我们如何验证我们的这个说法呢，你可以打开linux目录下的System.map文件查看：

00000020 A cpu_v6_suspend_size

c0004000 A swapper_pg_dir

c0008000 T __init_begin

c0008000 T _stext T _sinittext

c0008000 T _stext

c0008000 T stext

c000804c t __create_page_tables

c0008148 t __enable_mmu_loc

c0008154 t __enable_mmu

c0008180 t __turn_mmu_on

c0008198 t __enable_mmu_end

c0008198 t __vet_atags

c00081e0 t __mmap_switched

c0008228 t __mmap_switched_data

c000824c T lookup_processor_type

c0008260 t set_reset_devices

c0008284 t debug_kernel

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从map文件可以知道_stext是内核的入口地址，这个地址就是c0008000，这也验证了我们在第一章讲搭建环境的时候，我为什么要用dnw
c0008000，就是因为我们已经指定好了，内核的存放地址必须为c0008000，针对ok6410来说。

（二）.init内核的初始化代码和数据段

_sinittext = .;

HEAD_TEXT

INIT_TEXT

ARM_EXIT_KEEP(EXIT_TEXT)

_einittext = .;

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从上面的链接脚本可以知道所有：_sinittext开头的，_einittext结尾的HEAD_TEXT， INIT_TEXT，ARM_EXIT_KEEP(EXIT_TEXT)段都是从起始地址c0008000开始存放的。这些宏定义在：include/asm-generic/vmlinux.lds.h中。

__arch_info_begin = .;

*(.arch.info.init)

__arch_info_end = .;

__tagtable_begin = .;

*(.taglist.init)

__tagtable_end = .;

#ifdef CONFIG_SMP_ON_UP

__smpalt_begin = .;

*(.alt.smp.init)

__smpalt_end = .;

#endif

__pv_table_begin = .;

*(.pv_table)

__pv_table_end = .;

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紧接着以此存放的是：*(.arch.info.init)， *(.taglist.init)，*(.alt.smp.init)，*(.pv_table)段的代码，其中我们最熟悉的*(.arch.info.init)段的代码就是：

#define MACHINE_START(_type,_name) \

static const struct machine_desc __mach_desc_##_type \

__used \

__attribute__((__section__(".arch.info.init"))) = { \

.nr = MACH_TYPE_##_type, \

.name = _name,

#define MACHINE_END \

};

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也就是说所有平台的下面这段代码都放到了*(.arch.info.init)段中：

MACHINE_START(MCUOS6410, "MCUOS6410")

/* Maintainer: Ben Dooks <ben-linux@fluff.org> */

.boot_params = S3C64XX_PA_SDRAM + 0x100,

.init_irq = s3c6410_init_irq,

.map_io = mcuos6410_map_io,

.init_machine = mcuos6410_machine_init,

.timer = &s3c24xx_timer,

MACHINE_END

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紧接着存放的是初始化数据段：

#ifndef CONFIG_XIP_KERNEL

__init_begin = _stext;

INIT_DATA

ARM_EXIT_KEEP(EXIT_DATA)

#endif

}

PERCPU_SECTION(32)

#ifndef CONFIG_XIP_KERNEL

. = ALIGN(PAGE_SIZE);

__init_end = .;

#endif

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这个段存放的是所有*(.init.data)，*(.init.rodata)段中的代码。

.init段中的代码段和数据段，在Linux初始化完成之后，这个段的内存都会被请空，被释放。因为他们只需要在初始化的时候使用一次，没有必要再驻留在内存中，浪费空间。为了验证我们以上的分析，我们可以查看system.map这个文件，下面我们看到的从_sinittext开头的，_einittext结尾的所有函数，都会在初始化完成之后被释放：

c0008000 T _sinittext

c0008000 T _stext

c0008000 T stext

c000804c t __create_page_tables

c0008148 t __enable_mmu_loc

c0008154 t __enable_mmu

c0008180 t __turn_mmu_on

c0008198 t __enable_mmu_end

c0008198 t __vet_atags

c00081e0 t __mmap_switched

c0008228 t __mmap_switched_data

c000824c T lookup_processor_type

c0008260 t set_reset_devices

c0008284 t debug_kernel

c00082a8 t quiet_kernel

c00082cc t init_setup

c0008308 t rdinit_setup

c0008344 W smp_setup_processor_id

c0008354 W thread_info_cache_init

c0008364 t loglevel

c0008398 T parse_early_options

c00083d4 t unknown_bootoption

c00085f8 T parse_early_param

c0008648 t do_early_param

c0008724 t kernel_init

c0008850 T start_kernel

c0008b9c t readonly

c0008bd0 t readwrite

c0008c04 t rootwait_setup

c0008c34 t root_data_setup

c0008c54 t fs_names_setup

c0008c74 t load_ramdisk

c0008ca4 t root_dev_setup

c0008ccc t root_delay_setup

c0008cf8 T change_floppy

c0008e20 T mount_block_root

c0009108 T mount_root

c0009174 T prepare_namespace

c0009364 t ramdisk_start_setup

c0009390 t prompt_ramdisk

c00093c0 t error

c00093fc t compr_fill

c0009464 t compr_flush

c00094d4 T rd_load_image

c0009b5c T rd_load_disk

c0009c10 t no_initrd

c0009c34 T initrd_load

c0009f74 t do_linuxrc

c0009fc8 t error

c0009fec t read_into

c000a0a8 t do_start

c000a0d4 t write_buffer

c000a12c t flush_buffer

c000a1d8 t retain_initrd_param

c000a208 t clean_path

c000a268 t do_utime

c000a2ac t do_symlink

c000a378 t unpack_to_rootfs

c000a6d4 t maybe_link

c000a840 t do_name

c000aad8 t do_header

c000adf0 t free_initrd

c000aed0 t populate_rootfs

c000b124 t do_collect

c000b1ec t do_skip

c000b2c0 t do_reset

c000b38c t do_copy

c000b4b8 t lpj_setup

c000b500 T __kuser_helper_start

c000b500 t __kuser_memory_barrier

c000b520 t __kuser_cmpxchg

c000b540 t __kuser_get_tls

c000b55c t __kuser_helper_version

c000b560 T __kuser_helper_end

c000b560 T __stubs_start

c000b560 t vector_irq

c000b5e0 t vector_dabt

c000b660 t vector_pabt

c000b6e0 t vector_und

c000b760 t vector_fiq

c000b764 t vector_addrexcptn

c000b784 T __stubs_end

c000b784 T __vectors_start

c000b7a4 T __vectors_end

c000b7c0 T init_IRQ

c000b7e4 T arch_probe_nr_irqs

c000b818 t nohlt_setup

c000b83c t hlt_setup

c000b860 T reboot_setup

c000b884 t ptrace_break_init

c000b8bc t parse_tag_core

c000b914 t parse_tag_videotext

c000b994 t parse_tag_ramdisk

c000b9fc t parse_tag_serialnr

c000ba30 t parse_tag_revision

c000ba54 t customize_machine

c000ba84 t parse_tag_cmdline

c000baac t topology_init

c000badc t proc_cpu_init

c000bb08 T arm_add_memory

c000bba0 t parse_tag_mem32

c000bbbc t early_mem

c000bc38 T early_print

c000bcb0 T dump_machine_table

c000bd10 T setup_arch

c000c5fc T time_init

c000c630 t timer_init_syscore_ops

c000c650 T trap_init

c000c660 t user_debug_setup

c000c694 T early_trap_init

c000c7a8 T arch_init_kprobes

c000c7cc T arm_kprobe_decode_init

c000c800 T save_atags

c000c824 t init_atags_procfs

c000c934 T unwind_init

c000c97c t arch_hw_breakpoint_init

c000cb8c t register_pmu_driver

c000cba8 t armpmu_reset

c000cbf4 t init_hw_perf_events

c000cd3c t setup_early_printk

c000cd5c t dma_debug_do_init

c000cd70 t consistent_init

c000ce64 T hook_ifault_code

c000ceb8 T hook_fault_code

c000cf10 t exceptions_init

c000cfac t parse_tag_initrd2

c000cfe0 t meminfo_cmp

c000d014 t keepinitrd_setup

c000d038 t early_initrd

c000d09c t parse_tag_initrd

c000d0e8 T mem_init

c000d7cc T bootmem_init

c000da94 T arm_memblock_init

c000dc1c T check_writebuffer_bugs

c000dd64 t early_ecc

c000ddd0 t early_cachepolicy

c000ded0 t early_nowrite

c000df08 t early_nocache

c000df40 t early_vmalloc

c000dfc4 t early_alloc

c000dffc t early_pte_alloc

c000e08c t create_mapping

c000e3e8 T paging_init

c000eabc T iotable_init

c000eaf8 T arm_mm_memblock_reserve

c000eb18 T sanity_check_meminfo

c000ed58 t noalign_setup

c000eda0 t alignment_init

c000ee90 t v6_userpage_init

c000eed4 T v6wbi_tlb_fns

c000eee0 t vic_disable

c000ef28 t vic_clear_interrupts

c000ef6c t vic_set_irq_sources

c000eff0 T vic_init

c000f12c t s3c64xx_sysdev_init

c000f154 T s3c64xx_init_io

c000f1b0 T s3c6400_common_init_uarts

c000f1dc T s3c64xx_register_clocks

c000f264 T s3c6400_setup_clocks

c000f4ec t s3c64xx_gpiolib_add_2bit

c000f504 t s3c64xx_gpiolib_add

c000f54c t s3c64xx_gpiolib_init

c000f5a8 T s3c6410_map_io

c000f5e0 t s3c6410_core_init

c000f5fc T s3c6410_init

c000f624 T s3c6410_init_irq

c000f640 T s3c6410_init_clocks

c000f67c T s3c64xx_init_irq

c000f6f0 t s3c64xx_init_irq_eint

c000f7dc t s3c64xx_dma_init

c000f8c0 t mcuos6410_machine_init

c000f8e0 t mcuos6410_map_io

c000f91c T s3c64xx_ac97_setup_gpio

c000f954 T s3c24xx_init_clocks

c000f9b0 t s3c_arch_init

c000fa08 T s3c24xx_init_uarts

c000fa4c T s3c_init_cpu

c000fb1c T s3c24xx_init_uartdevs

c000fbb4 t s3c2410_timer_init

c000fc94 T s3c_disable_clocks

c000fccc T s3c24xx_register_baseclocks

c000fe08 T s3c_register_clocks

c000fe64 T s3c_pwmclk_init

c000ffd4 T s3c_gpiolib_add

c00100f4 T s3c_set_clksrc

c00101cc T s3c_register_clksrc

c00102d0 T s3c_init_uart_irqs

c00103d4 T s3c_init_vic_timer_irq

c001052c t adc_init

c001056c T s3c_set_platdata

c00105c8 T s3c_i2c0_set_platdata

c0010638 T s3c_nand_set_platdata

c0010784 t sched_init_debug

c00107c4 t init_sched_debug_procfs

c001080c T sched_init_smp

c0010878 T sched_init

c0010ab0 t proc_schedstat_init

c0010af0 t coredump_filter_setup

c0010b24 T fork_init

c0010bc0 T proc_caches_init

c0010cdc t proc_execdomains_init

c0010d1c t oops_setup

c0010d5c t console_suspend_disable

c0010d80 t log_buf_len_setup

c0010de0 t console_setup

c0010f1c t printk_late_init

c0010f9c t keep_bootcon_setup

c0010fcc t ignore_loglevel_setup

c0010ffc T setup_log_buf

c0011184 T softirq_init

c0011214 W arch_early_irq_init

c0011228 t spawn_ksoftirqd

c001127c t reserve_setup

c0011370 t strict_iomem

c00113cc t __reserve_region_with_split

c00114ac T reserve_region_with_split

c00114c0 t ioresources_init

c0011520 t sysctl_init

c0011564 t file_caps_disable

c0011588 T init_timers

c00115e4 t uid_cache_init

c0011670 t setup_print_fatal_signals

c00116a4 T signals_init

c00116e8 T usermodehelper_init

c0011748 t init_workqueues

c00119d8 T pidmap_init

c0011ad8 T pidhash_init

c0011b5c T sort_main_extable

c0011b80 t locate_module_kobject

c0011c80 t param_sysfs_init

c0011ea0 t init_posix_timers

c0012098 t init_posix_cpu_timers

c00121a0 T hrtimers_init

c00121c4 t nsproxy_cache_init

c001220c t ksysfs_init

c00122ac t pm_qos_power_init

c001233c T cred_init

c0012380 t timekeeping_init_ops

c00123a0 T timekeeping_init

c00124b0 t ntp_tick_adj_setup

c00124e4 T ntp_init

c0012520 t init_clocksource_sysfs

c0012580 t boot_override_clocksource

c00125cc t boot_override_clock

c0012628 t clocksource_done_booting

c0012690 W clocksource_default_clock

c00126a8 t init_jiffies_clocksource

c00126c4 t init_timer_list_procfs

c001270c t alarmtimer_init

c0012850 T init_timer_stats

c0012860 t init_tstats_procfs

c00128a8 t futex_init

c0012920 t proc_modules_init

c0012960 t kallsyms_init

c00129a0 t crash_notes_memory_init

c00129e4 t crash_save_vmcoreinfo_init

c0012dac T parse_crashkernel

c0013114 t pid_namespaces_init

c001315c t audit_enable

c0013244 t audit_init

c001338c T audit_register_class

c001345c t init_kprobes

c00135a0 t hung_task_panic_setup

c00135cc t hung_task_init

c0013630 T early_irq_init

c0013708 t irqpoll_setup

c0013744 t irqfixup_setup

c0013784 t irq_gc_init_ops

c00137a4 t rcu_spawn_kthreads

c001380c t relay_init

c0013820 t utsname_sysctl_init

c0013840 t init_lstats_procfs

c0013880 t rb_init_debugfs

c00138c8 t set_cmdline_ftrace

c0013910 t set_ftrace_dump_on_oops

c0013978 t set_buf_size

c00139c8 t clear_boot_tracer

c0013a08 t tracer_init_debugfs

c0013d48 t set_tracing_thresh

c0013da8 t tracer_alloc_buffers

c0013f1c t init_events

c0013fb0 t init_trace_printk_function_export

c0013ffc t init_trace_printk

c0014018 t setup_trace_event

c0014058 t event_trace_init

c001435c t init_kprobe_trace

c00143fc t perf_event_sysfs_init

c00144c0 T perf_event_init

c00145d8 T init_hw_breakpoint

c0014680 T set_dma_reserve

c001469c T page_alloc_init

c00146ac T free_area_init_node

c0014a38 T free_area_init

c0014a5c T setup_per_cpu_pageset

c0014af8 T alloc_large_system_hash

c0014d6c T page_writeback_init

c0014dac T swap_setup

c0014e00 t kswapd_init

c0014e20 T init_tmpfs

c0014f0c t setup_vmstat

c0014fac t bdi_class_init

c0015018 t default_bdi_init

c00150e0 t set_mminit_loglevel

c0015114 t mm_sysfs_init

c0015158 T mminit_verify_pageflags_layout

c001526c T percpu_init_late

c0015304 T pcpu_setup_first_chunk

c0015b78 T pcpu_free_alloc_info

c0015b98 T pcpu_alloc_alloc_info

c0015c2c T setup_per_cpu_areas

c0015cc4 T page_address_init

c0015d68 t disable_randmaps

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c0027334 t __v6_proc_info

c0027334 T _einittext

复制代码

（3）真正的驻留在内存中的内核内代码段

从脚本上来看，所有.text开始，.etext结束区间的段都是内核代码段：

.text : { /* Real text segment */

_text = .; /* Text and read-only data */

__exception_text_start = .;

*(.exception.text)

__exception_text_end = .;

IRQENTRY_TEXT

TEXT_TEXT

SCHED_TEXT

LOCK_TEXT

KPROBES_TEXT

#ifdef CONFIG_MMU

*(.fixup)

#endif

*(.gnu.warning)

*(.rodata)

*(.rodata.*)

*(.glue_7)

*(.glue_7t)

. = ALIGN(4);

*(.got) /* Global offset table */

ARM_CPU_KEEP(PROC_INFO)

}

RO_DATA(PAGE_SIZE)

#ifdef CONFIG_ARM_UNWIND

/*

* Stack unwinding tables

*/

. = ALIGN(8);

.ARM.unwind_idx : {

__start_unwind_idx = .;

*(.ARM.exidx*)

__stop_unwind_idx = .;

}

.ARM.unwind_tab : {

__start_unwind_tab = .;

*(.ARM.extab*)

__stop_unwind_tab = .;

}

#endif

_etext = .; /* End of text and rodata section */

复制代码

这些段中的代码都是事实在在的内核函数。

（4）已经初始化的data数据段：

.data : AT(__data_loc) {

_data = .; /* address in memory */

_sdata = .;

/*

* first, the init task union, aligned

* to an 8192 byte boundary.

*/

INIT_TASK_DATA(THREAD_SIZE)

#ifdef CONFIG_XIP_KERNEL

. = ALIGN(PAGE_SIZE);

__init_begin = .;

INIT_DATA

ARM_EXIT_KEEP(EXIT_DATA)

. = ALIGN(PAGE_SIZE);

__init_end = .;

#endif

NOSAVE_DATA

CACHELINE_ALIGNED_DATA(32)

READ_MOSTLY_DATA(32)

/*

* The exception fixup table (might need resorting at runtime)

*/

. = ALIGN(32);

__start___ex_table = .;

#ifdef CONFIG_MMU

*(__ex_table)

#endif

__stop___ex_table = .;

/*

* and the usual data section

*/

DATA_DATA

CONSTRUCTORS

_edata = .;

复制代码

（5）紧接着以初始化的.data段的是.bss，未经初始化的内核数据段。

BSS_SECTION(0, 0, 0)

_end = .;

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