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
所以你可以从vmlinux.lds.S下面的代码中看到：
- OUTPUT_ARCH(arm)
- ENTRY(stext)
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
- }
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)
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
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)
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
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 = .;
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 = .;
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 \
- };
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
- .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
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
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
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（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 */
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 = .;
（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 = .;