内核(kernel)的链接脚本

Posted 2021-12-29 代二毛

1、链接脚本的产生

kernel的链接脚本和uboot的不同，uboot的链接脚本是源文件的一部分，而kernel的链接脚本在源文件中是找不到的，要经过编译才会产生。链接脚本的名字是vmlinux.lds，由汇编文件vmlinux.lds.S生成。用汇编文件动态生成链接脚本，可以实现条件编译，这样可以根据需求生成不同的内核镜像。
备注：vmlinux.lds.S在arch/xxx/kernel/目录下，其中xxx是CPU的架构。

2、链接脚本

OUTPUT_ARCH(arm)
ENTRY(stext)
jiffies = jiffies_64;
SECTIONS

 . = 0xC0000000 + 0x00008000;
 .init :  /* Init code and data		*/
  _stext = .;
  _sinittext = .;
   *(.head.text)
   *(.init.text) *(.cpuinit.text) *(.meminit.text)
  _einittext = .;
  __proc_info_begin = .;
   *(.proc.info.init)
  __proc_info_end = .;
  __arch_info_begin = .;
   *(.arch.info.init)
  __arch_info_end = .;
  __tagtable_begin = .;
   *(.taglist.init)
  __tagtable_end = .;
  . = ALIGN(16); __setup_start = .; *(.init.setup) __setup_end = .;
  __initcall_start = .; *(.initcallearly.init) __early_initcall_end = .; *(.initcall0.init) *(.initcall0s.init) *(.initcall1.init) *(.initcall1s.init) *(.initcall2.init) *(.initcall2s.init) *(.initcall3.init) *(.initcall3s.init) *(.initcall4.init) *(.initcall4s.init) *(.initcall5.init) *(.initcall5s.init) *(.initcallrootfs.init) *(.initcall6.init) *(.initcall6s.init) *(.initcall7.init) *(.initcall7s.init) __initcall_end = .;
  __con_initcall_start = .; *(.con_initcall.init) __con_initcall_end = .;
  __security_initcall_start = .; *(.security_initcall.init) __security_initcall_end = .;
 
  __init_begin = _stext;
  *(.init.data) *(.cpuinit.data) *(.meminit.data) . = ALIGN(8); __ctors_start = .; *(.ctors) __ctors_end = .; *(.init.rodata) *(.cpuinit.rodata) *(.meminit.rodata)
 
 . = ALIGN((1 << 12)); .data..percpu : AT(ADDR(.data..percpu) - 0)  __per_cpu_load = .; __per_cpu_start = .; *(.data..percpu..first) *(.data..percpu..page_aligned) *(.data..percpu) *(.data..percpu..shared_aligned) __per_cpu_end = .; 
 . = ALIGN((1 << 12));
 __init_end = .;
 /*
	 * 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.exidx.cpuexit.text)
  *(.ARM.extab.cpuexit.text)
 
 .text :  /* Real text segment		*/
  _text = .; /* Text and read-only data	*/
   __exception_text_start = .;
   *(.exception.text)
   __exception_text_end = .;
   . = ALIGN(8); *(.text.hot) *(.text) *(.ref.text) *(.devinit.text) *(.devexit.text) *(.text.unlikely)
   . = ALIGN(8); __sched_text_start = .; *(.sched.text) __sched_text_end = .;
   . = ALIGN(8); __lock_text_start = .; *(.spinlock.text) __lock_text_end = .;
   . = ALIGN(8); __kprobes_text_start = .; *(.kprobes.text) __kprobes_text_end = .;
   *(.fixup)
   *(.gnu.warning)
   *(.rodata)
   *(.rodata.*)
   *(.glue_7)
   *(.glue_7t)
  *(.got) /* Global offset table		*/
 
 . = ALIGN(((1 << 12))); .rodata : AT(ADDR(.rodata) - 0)  __start_rodata = .; *(.rodata) *(.rodata.*) *(__vermagic) *(__markers_strings) *(__tracepoints_strings)  .rodata1 : AT(ADDR(.rodata1) - 0)  *(.rodata1)  .pci_fixup : AT(ADDR(.pci_fixup) - 0)  __start_pci_fixups_early = .; *(.pci_fixup_early) __end_pci_fixups_early = .; __start_pci_fixups_header = .; *(.pci_fixup_header) __end_pci_fixups_header = .; __start_pci_fixups_final = .; *(.pci_fixup_final) __end_pci_fixups_final = .; __start_pci_fixups_enable = .; *(.pci_fixup_enable) __end_pci_fixups_enable = .; __start_pci_fixups_resume = .; *(.pci_fixup_resume) __end_pci_fixups_resume = .; __start_pci_fixups_resume_early = .; *(.pci_fixup_resume_early) __end_pci_fixups_resume_early = .; __start_pci_fixups_suspend = .; *(.pci_fixup_suspend) __end_pci_fixups_suspend = .;  .builtin_fw : AT(ADDR(.builtin_fw) - 0)  __start_builtin_fw = .; *(.builtin_fw) __end_builtin_fw = .;  .rio_ops : AT(ADDR(.rio_ops) - 0)  __start_rio_switch_ops = .; *(.rio_switch_ops) __end_rio_switch_ops = .;  __ksymtab : AT(ADDR(__ksymtab) - 0)  __start___ksymtab = .; *(__ksymtab) __stop___ksymtab = .;  __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - 0)  __start___ksymtab_gpl = .; *(__ksymtab_gpl) __stop___ksymtab_gpl = .;  __ksymtab_unused : AT(ADDR(__ksymtab_unused) - 0)  __start___ksymtab_unused = .; *(__ksymtab_unused) __stop___ksymtab_unused = .;  __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - 0)  __start___ksymtab_unused_gpl = .; *(__ksymtab_unused_gpl) __stop___ksymtab_unused_gpl = .;  __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - 0)  __start___ksymtab_gpl_future = .; *(__ksymtab_gpl_future) __stop___ksymtab_gpl_future = .;  __kcrctab : AT(ADDR(__kcrctab) - 0)  __start___kcrctab = .; *(__kcrctab) __stop___kcrctab = .;  __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - 0)  __start___kcrctab_gpl = .; *(__kcrctab_gpl) __stop___kcrctab_gpl = .;  __kcrctab_unused : AT(ADDR(__kcrctab_unused) - 0)  __start___kcrctab_unused = .; *(__kcrctab_unused) __stop___kcrctab_unused = .;  __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - 0)  __start___kcrctab_unused_gpl = .; *(__kcrctab_unused_gpl) __stop___kcrctab_unused_gpl = .;  __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - 0)  __start___kcrctab_gpl_future = .; *(__kcrctab_gpl_future) __stop___kcrctab_gpl_future = .;  __ksymtab_strings : AT(ADDR(__ksymtab_strings) - 0)  *(__ksymtab_strings)  __init_rodata : AT(ADDR(__init_rodata) - 0)  *(.ref.rodata) *(.devinit.rodata) *(.devexit.rodata)  __param : AT(ADDR(__param) - 0)  __start___param = .; *(__param) __stop___param = .; . = ALIGN(((1 << 12))); __end_rodata = .;  . = ALIGN(((1 << 12)));
 _etext = .; /* End of text and rodata section */
 . = ALIGN(8192);
 __data_loc = .;
 .data : AT(__data_loc) 
  _data = .; /* address in memory */
  _sdata = .;
  /*
		 * first, the init task union, aligned
		 * to an 8192 byte boundary.
		 */
  . = ALIGN(8192); *(.data..init_task)
  . = ALIGN((1 << 12)); __nosave_begin = .; *(.data..nosave) . = ALIGN((1 << 12)); __nosave_end = .;
  . = ALIGN(32); *(.data..cacheline_aligned)
  /*
		 * The exception fixup table (might need resorting at runtime)
		 */
  . = ALIGN(32);
  __start___ex_table = .;
  *(__ex_table)
  __stop___ex_table = .;
  /*
		 * and the usual data section
		 */
  *(.data) *(.ref.data) *(.devinit.data) *(.devexit.data) . = ALIGN(8); __start___markers = .; *(__markers) __stop___markers = .; . = ALIGN(32); __start___tracepoints = .; *(__tracepoints) __stop___tracepoints = .; . = ALIGN(8); __start___verbose = .; *(__verbose) __stop___verbose = .; . = ALIGN(32); . = ALIGN(32);
  CONSTRUCTORS
  _edata = .;
 
 _edata_loc = __data_loc + SIZEOF(.data);
 . = ALIGN(0); __bss_start = .; . = ALIGN(0); .sbss : AT(ADDR(.sbss) - 0)  *(.sbss) *(.scommon)  . = ALIGN(0); .bss : AT(ADDR(.bss) - 0)  *(.bss..page_aligned) *(.dynbss) *(.bss) *(COMMON)  . = ALIGN(0); __bss_stop = .;
 _end = .;
 .stab 0 :  *(.stab)  .stabstr 0 :  *(.stabstr)  .stab.excl 0 :  *(.stab.excl)  .stab.exclstr 0 :  *(.stab.exclstr)  .stab.index 0 :  *(.stab.index)  .stab.indexstr 0 :  *(.stab.indexstr)  .comment 0 :  *(.comment) 
 .comment 0 :  *(.comment) 
 /* Default discards */
 /DISCARD/ :  *(.exit.text) *(.cpuexit.text) *(.memexit.text) *(.exit.data) *(.cpuexit.data) *(.cpuexit.rodata) *(.memexit.data) *(.memexit.rodata) *(.exitcall.exit) *(.discard) 

/*
 * These must never be empty
 * If you have to comment these two assert statements out, your
 * binutils is too old (for other reasons as well)
 */
ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support")
ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")

(1)ENTRY(stext):说明内核的入口是stext标号处；