• linux内核启动过程分析

            分为第一阶段汇编和第二阶段。

    内核启动第一阶段

            先总结出第一阶段主要任务

    • 确保处于SVC模式，且关闭所有中断
    • get processor id/procinfo
    • 创建页表项
    • 使能MMU
    • 跳转start_kernel，开启第二阶段

    内核链接脚本

    arch/arm/kernel/vmlinux.lds

    如下，可以看出内核入口在ENTRY(stext)，stext在汇编中head.S中实现

    1. OUTPUT_ARCH(arm)
    2. ENTRY(stext)
    3. jiffies = jiffies_64;
    4. SECTIONS
    5. {
    6.  /*
    7.      * XXX: The linker does not define how output sections are
    8.      * assigned to input sections when there are multiple statements
    9.      * matching the same input section name.  There is no documented
    10.      * order of matching.
    11.      *
    12.      * unwind exit sections must be discarded before the rest of the
    13.      * unwind sections get included.
    14.      */
    15.  /DISCARD/ : {
    16.   *(.ARM.exidx.exit.text)
    17.   *(.ARM.extab.exit.text)
    18.   *(.exitcall.exit)
    19.   *(.discard)
    20.   *(.discard.*)
    21.  }
    22.  . = 0x80000000 + 0x00008000;
    23.  .head.text : {
    24.   _text = .;
    25.   *(.head.text)
    26.  }
    27.  .text : { /* Real text segment     */
    28.   _stext = .; /* Text and read-only data    */
    29.    . = ALIGN(8); __idmap_text_start = .; *(.idmap.text) __idmap_text_end = .; . = ALIGN((1 << 12)); __hyp_idmap_text_start = .; *(.hyp.idmap.    text) __hyp_idmap_text_end = .;
    30.    __exception_text_start = .;
    31.    *(.exception.text)
    32.    __exception_text_end = .;
    33.  
    34.    . = ALIGN(8); *(.text.hot) *(.text .text.fixup) *(.ref.text) *(.text.unlikely)
    35.    . = ALIGN(8); __sched_text_start = .; *(.sched.text) __sched_text_end = .;
    36.    . = ALIGN(8); __lock_text_start = .; *(.spinlock.text) __lock_text_end = .;

    head.S入口stext

            注释看出，启动内核要求：MMU关闭、DCACHE关闭，ICACHE无所谓，然后传入r0的参数为0，r1是机器ID，r2是tag或者设备树地址指针。02-uboot启动内核前到底做了哪些必要工作_【星星之火】的博客-CSDN博客，在这边文章已经说明了这点，就是Bootloader调用 kernel_entry(0, machid, r2) 传入r0 r1 r2进入到此处。

    1.  59 /*
    2.  60  * Kernel startup entry point.
    3.  61  * ---------------------------
    4.  62  *
    5.  63  * This is normally called from the decompressor code.  The requirements
    6.  64  * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
    7.  65  * r1 = machine nr, r2 = atags or dtb pointer.
    8.  66  *
    9.  67  * This code is mostly position independent, so if you link the kernel at
    10.  68  * 0xc0008000, you call this at __pa(0xc0008000).
    11.  69  *
    12.  70  * See linux/arch/arm/tools/mach-types for the complete list of machine
    13.  71  * numbers for r1.
    14.  72  *
    15.  73  * We're trying to keep crap to a minimum; DO NOT add any machine specific
    16.  74  * crap here - that's what the boot loader (or in extreme, well justified
    17.  75  * circumstances, zImage) is for.
    18.  76  */
    19.  77     .arm
    20.  78 
    21.  79     __HEAD
    22.  80 ENTRY(stext)
    23.  81  ARM_BE8(setend be )            @ ensure we are in BE8 mode
    24.  82 
    25.  83  THUMB( adr r9, BSYM(1f)    )   @ Kernel is always entered in ARM.
    26.  84  THUMB( bx  r9      )   @ If this is a Thumb-2 kernel,
    27.  85  THUMB( .thumb          )   @ switch to Thumb now.
    28.  86  THUMB(1:           )
    29.  87 
    30.  88 #ifdef CONFIG_ARM_VIRT_EXT
    31.  89     bl  __hyp_stub_install
    32.  90 #endif
    33.  91     @ ensure svc mode and all interrupts masked
    34.  92     safe_svcmode_maskall r9
    35.  93 
    36.  94     mrc p15, 0, r9, c0, c0      @ get processor id
    37.  95     bl  __lookup_processor_type     @ r5=procinfo r9=cpuid
    38.  96     movs    r10, r5             @ invalid processor (r5=0)?
    39.  97  THUMB( it  eq )        @ force fixup-able long branch encoding
    40.  98     beq __error_p           @ yes, error 'p'

    SVC模式与禁止中断-safe_svcmode_maskall

    1. arch/arm/include/asm/assembler.h
    2. 320 #if __LINUX_ARM_ARCH__ >= 6 && !defined(CONFIG_CPU_V7M)
    3. 321     mrs \reg , cpsr
    4. 322     eor \reg, \reg, #HYP_MODE
    5. 323     tst \reg, #MODE_MASK
    6. 324     bic \reg , \reg , #MODE_MASK
    7. 325     orr \reg , \reg , #PSR_I_BIT | PSR_F_BIT | SVC_MODE
    8. 326 THUMB(  orr \reg , \reg , #PSR_T_BIT    )
    9. 327     bne 1f
    10. 328     orr \reg, \reg, #PSR_A_BIT
    11. 329     adr lr, BSYM(2f)
    12. 330     msr spsr_cxsf, \reg
    13. 331     __MSR_ELR_HYP(14)
    14. 332     __ERET
    15. 333 1:  msr cpsr_c, \reg
    16. 334 2:
    17. 335 #else

    arm的7种模式

    • 用户模式 USR
    • 系统模式 SYS（特权模式）
    • 管理模式 SVC (特权模式 异常模式)

            操作系统保护模式

    • 快中断 FIQ (特权模式 异常模式)
    • 中断模式 IRQ (特权模式 异常模式)
    • 中止模式 ATB (特权模式 异常模式)
    • 未定义模式 UND (特权模式 异常模式)

    模式设置

            参考ARM® Architecture Reference Manual ARMv7-A and ARMv7-R edition

            设置CPSR的低5位。 

     关闭中断

            系统进行初始化过程中，资源未准备好，产生中断将出现不可预计的错误。关闭中断方法同上寄存器中。

    获取CPU信息

    获取cpu id

            从协处理器p15中的c0寄存器中获取CPU ID

    mrc p15, 0, r9, c0, c0

    获取procinfo信息

            通过如下结构体存储，里面包含了MMU启动信息，所有在早起就需要获取到。在内核文件的“.init.proc.info”段中存放，根据CPU ID查找procinfo信息。

    1.  20 /*
    2.  21  * Note!  struct processor is always defined if we're
    3.  22  * using MULTI_CPU, otherwise this entry is unused,
    4.  23  * but still exists.    
    5.  24  *  
    6.  25  * NOTE! The following structure is defined by assembly
    7.  26  * language, NOT C code.  For more information, check:
    8.  27  *  arch/arm/mm/proc-*.S and arch/arm/kernel/head.S
    9.  28  */ 
    10.  29 struct proc_info_list { 
    11.  30     unsigned int        cpu_val;
    12.  31     unsigned int        cpu_mask;
    13.  32     unsigned long       __cpu_mm_mmu_flags; /* used by head.S */
    14.  33     unsigned long       __cpu_io_mmu_flags; /* used by head.S */
    15.  34     unsigned long       __cpu_flush;        /* used by head.S */
    16.  35     const char      *arch_name;
    17.  36     const char      *elf_name;
    18.  37     unsigned int        elf_hwcap;
    19.  38     const char      *cpu_name;
    20.  39     struct processor    *proc;
    21.  40     struct cpu_tlb_fns  *tlb;
    22.  41     struct cpu_user_fns *user;
    23.  42     struct cpu_cache_fns    *cache;
    24.  43 };

    检查设备树

            __vet_atags中，检查设备树头部4字节是否是magic（d00dfeed）。

    1. 118      * r1 = machine no, r2 = atags or dtb,
    2. 119      * r8 = phys_offset, r9 = cpuid, r10 = procinfo
    3. 120      */
    4. 121     bl  __vet_atags
    5. 122 #ifdef CONFIG_SMP_ON_UP
    6. 123     bl  __fixup_smp
    7. 124 #endif
    8. 125 #ifdef CONFIG_ARM_PATCH_PHYS_VIRT
    9. 126     bl  __fixup_pv_table
    10. 127 #endif
    11. 128     bl  __create_page_tables

    创建临时页表

            内核启动后，要尽快开启MMU，开启MMU之前需要有页表。因此准备好页表环境是开启MMU的前提。由__create_page_tables 来创建。

    1. 108 #ifndef CONFIG_XIP_KERNEL                                                                                                                         ~                   
    2. 109     adr r3, 2f                                                                                                                                    ~                   
    3. 110     ldmia   r3, {r4, r8}                                                                                                                          ~                   
    4. 111     sub r4, r3, r4          @ (PHYS_OFFSET - PAGE_OFFSET)                                                                                         ~                   
    5. 112     add r8, r8, r4          @ PHYS_OFFSET                                                                                                         ~                   
    6. 113 #else                                                                                                                                             ~                   
    7. 114     ldr r8, =PLAT_PHYS_OFFSET       @ always constant in this case                                                                                ~                   
    8. 115 #endif                                                                                                                                            ~                   
    9. 116                                                                                                                                                   ~                   
    10. 117     /*                                                                                                                                            ~                   
    11. 118      * r1 = machine no, r2 = atags or dtb,                                                                                                        ~                   
    12. 119      * r8 = phys_offset, r9 = cpuid, r10 = procinfo                                                                                               ~                   
    13. 120      */                                                                                                                                           ~                   
    14. 121     bl  __vet_atags                                                                                                                               ~                   
    15. 122 #ifdef CONFIG_SMP_ON_UP                                                                                                                           ~                   
    16. 123     bl  __fixup_smp                                                                                                                               ~                   
    17. 124 #endif                                                                                                                                            ~                   
    18. 125 #ifdef CONFIG_ARM_PATCH_PHYS_VIRT                                                                                                                 ~                   
    19. 126     bl  __fixup_pv_table                                                                                                                          ~                   
    20. 127 #endif                                                                                                                                            ~                   
    21. 128     bl  __create_page_tables

    MMU功能

            通过页表完成虚拟地址到物理地址的映射。页表基地址存储在cp15的c2寄存器中。

    段映射

            将4G空间分成4096个1M的段空间。虚拟地址的高12bit是段基址，在页表基地址的基础上得出虚拟地址段页表的位置，在加上虚拟地址的低20bit得出物理地址（MMU硬件自动完成地址转换）。

    映射内容

    • 恒等映射

            开启MMU之前 和开启MMU瞬间，物理地址到虚拟地址的pc指针改变的时候，需要是的虚拟地址和物理地址一致。

    • 内核映射
    • dtb映射

    代码解析

    • 页表物理地址给r4
    • 将页表的16k空间清0
    • __turn_mmu_on函数进行恒等映射，确保开启前后地址一致，该函数的物理地址和虚拟地址一致
    • 内核映射页表
    • 设备树映射页表
    1. 152 /*
    2. 153  * Setup the initial page tables.  We only setup the barest
    3. 154  * amount which are required to get the kernel running, which
    4. 155  * generally means mapping in the kernel code.
    5. 156  *
    6. 157  * r8 = phys_offset, r9 = cpuid, r10 = procinfo
    7. 158  *
    8. 159  * Returns:
    9. 160  *  r0, r3, r5-r7 corrupted
    10. 161  *  r4 = page table (see ARCH_PGD_SHIFT in asm/memory.h)
    11. 162  */
    12. 163 __create_page_tables:
    13. 164     pgtbl   r4, r8              @ page table address 1.页表物理地址给r4
    14. 165 
    15. 166     /*
    16. 167      * Clear the swapper page table 2.清空页表空间
    17. 168      */
    18. 169     mov r0, r4
    19. 170     mov r3, #0
    20. 171     add r6, r0, #PG_DIR_SIZE
    21. 172 1:  str r3, [r0], #4
    22. 173     str r3, [r0], #4
    23. 174     str r3, [r0], #4
    24. 175     str r3, [r0], #4
    25. 176     teq r0, r6
    26. 177     bne 1b
    27. 178 
    28. 179 #ifdef CONFIG_ARM_LPAE
    29. 180     /*
    30. 181      * Build the PGD table (first level) to point to the PMD table. A PGD
    31. 182      * entry is 64-bit wide.
    32. 183      */
    33. 184     mov r0, r4
    34. 185     add r3, r4, #0x1000         @ first PMD table address
    35. 186     orr r3, r3, #3          @ PGD block type
    36. 187     mov r6, #4              @ PTRS_PER_PGD
    37. 188     mov r7, #1 << (55 - 32)     @ L_PGD_SWAPPER
    38. 189 1:
    39. 190 #ifdef CONFIG_CPU_ENDIAN_BE8
    40. 191     str r7, [r0], #4            @ set top PGD entry bits
    41. 192     str r3, [r0], #4            @ set bottom PGD entry bits
    42. 193 #else
    43. 194     str r3, [r0], #4            @ set bottom PGD entry bits
    44. 195     str r7, [r0], #4            @ set top PGD entry bits
    45. 196 #endif
    46. 197     add r3, r3, #0x1000         @ next PMD table
    47. 198     subs    r6, r6, #1
    48. 199     bne 1b
    49. 200 
    50. 201     add r4, r4, #0x1000         @ point to the PMD tables
    51. 202 #ifdef CONFIG_CPU_ENDIAN_BE8
    52. 203     add r4, r4, #4          @ we only write the bottom word
    53. 204 #endif
    54. 205 #endif
    55. 206 
    56. 207     ldr r7, [r10, #PROCINFO_MM_MMUFLAGS] @ mm_mmuflags //将proc中mmuflag信息存到r10
    57. 208 
    58. 209     /*                      3.创建__turn_mmu_on的恒等映射，衔接mmu开启动作
    59. 210      * Create identity mapping to cater for __enable_mmu.
    60. 211      * This identity mapping will be removed by paging_init().
    61. 212      */
    62. 213     adr r0, __turn_mmu_on_loc
    63. 214     ldmia   r0, {r3, r5, r6}
    64. 215     sub r0, r0, r3          @ virt->phys offset
    65. 216     add r5, r5, r0          @ phys __turn_mmu_on
    66. 217     add r6, r6, r0          @ phys __turn_mmu_on_end
    67. 218     mov r5, r5, lsr #SECTION_SHIFT
    68. 219     mov r6, r6, lsr #SECTION_SHIFT
    69. 220 
    70. 221 1:  orr r3, r7, r5, lsl #SECTION_SHIFT  @ flags + kernel base
    71. 222     str r3, [r4, r5, lsl #PMD_ORDER]    @ identity mapping
    72. 223     cmp r5, r6
    73. 224     addlo   r5, r5, #1          @ next section
    74. 225     blo 1b
    75. 226 
    76. 227     /*                    4.内核映射
    77. 228      * Map our RAM from the start to the end of the kernel .bss section.
    78. 229      */
    79. 230     add r0, r4, #PAGE_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
    80. 231     ldr r6, =(_end - 1)
    81. 232     orr r3, r8, r7
    82. 233     add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
    83. 234 1:  str r3, [r0], #1 << PMD_ORDER
    84. 235     add r3, r3, #1 << SECTION_SHIFT
    85. 236     cmp r0, r6
    86. 237     bls 1b
    87. 238 
    88. 239 #ifdef CONFIG_XIP_KERNEL
    89. 242      */
    90. 246     orr r3, r7, r3, lsl #SECTION_SHIFT
    91. 247     add r0, r4,  #(XIP_START & 0xff000000) >> (SECTION_SHIFT - PMD_ORDER)
    92. 248     str r3, [r0, #((XIP_START & 0x00f00000) >> SECTION_SHIFT) << PMD_ORDER]!
    93. 252 1:  cmp r0, r6
    94. 253     add r3, r3, #1 << SECTION_SHIFT
    95. 251     add r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
    96. 252 1:  cmp r0, r6
    97. 253     add r3, r3, #1 << SECTION_SHIFT
    98. 254     strls   r3, [r0], #1 << PMD_ORDER
    99. 255     bls 1b
    100. 256 #endif
    101. 257 
    102. 258     /*                        5.dtb映射页表
    103. 259      * Then map boot params address in r2 if specified.
    104. 260      * We map 2 sections in case the ATAGs/DTB crosses a section boundary.
    105. 261      */
    106. 262     mov r0, r2, lsr #SECTION_SHIFT
    107. 263     movs    r0, r0, lsl #SECTION_SHIFT
    108. 264     subne   r3, r0, r8
    109. 265     addne   r3, r3, #PAGE_OFFSET
    110. 266     addne   r3, r4, r3, lsr #(SECTION_SHIFT - PMD_ORDER)
    111. 267     orrne   r6, r7, r0
    112. 268     strne   r6, [r3], #1 << PMD_ORDER
    113. 269     addne   r6, r6, #1 << SECTION_SHIFT
    114. 270     strne   r6, [r3]

    开启MMU

            通过下面几个函数调用，开启MMU，也就是操作cp15协处理器，最终通过设置协处理器的c1的bit0为1开启MMU。之后跳转到__mmap_switched，准备开启第二阶段。

    1. 130     /*
    2. 131      * The following calls CPU specific code in a position independent
    3. 132      * manner.  See arch/arm/mm/proc-*.S for details.  r10 = base of
    4. 133      * xxx_proc_info structure selected by __lookup_processor_type
    5. 134      * above.  On return, the CPU will be ready for the MMU to be
    6. 135      * turned on, and r0 will hold the CPU control register value.
    7. 136      */
    8. 137     ldr r13, =__mmap_switched       @ address to jump to after
    9. 138                         @ mmu has been enabled
    10. 139     adr lr, BSYM(1f)            @ return (PIC) address
    11. 140     mov r8, r4              @ set TTBR1 to swapper_pg_dir
    12. 141     ldr r12, [r10, #PROCINFO_INITFUNC]
    13. 142     add r12, r12, r10
    14. 143     ret r12
    15. 144 1:  b   __enable_mmu

    1. 428 __enable_mmu:
    2. 429 #if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
    3. 430     orr r0, r0, #CR_A
    4. 431 #else
    5. 432     bic r0, r0, #CR_A
    6. 433 #endif
    7. 434 #ifdef CONFIG_CPU_DCACHE_DISABLE
    8. 435     bic r0, r0, #CR_C
    9. 436 #endif
    10. 437 #ifdef CONFIG_CPU_BPREDICT_DISABLE
    11. 438     bic r0, r0, #CR_Z
    12. 439 #endif
    13. 440 #ifdef CONFIG_CPU_ICACHE_DISABLE
    14. 441     bic r0, r0, #CR_I
    15. 442 #endif
    16. 443 #ifndef CONFIG_ARM_LPAE
    17. 444     mov r5, #(domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
    18. 445               domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
    19. 446               domain_val(DOMAIN_TABLE, DOMAIN_MANAGER) | \
    20. 447               domain_val(DOMAIN_IO, DOMAIN_CLIENT))
    21. 448     mcr p15, 0, r5, c3, c0, 0       @ load domain access register
    22. 449     mcr p15, 0, r4, c2, c0, 0       @ load page table pointer
    23. 450 #endif
    24. 451     b   __turn_mmu_on
    25. 452 ENDPROC(__enable_mmu)

    1. 454 /*
    2. 455  * Enable the MMU.  This completely changes the structure of the visible
    3. 456  * memory space.  You will not be able to trace execution through this.
    4. 457  * If you have an enquiry about this, *please* check the linux-arm-kernel
    5. 458  * mailing list archives BEFORE sending another post to the list.
    6. 459  *
    7. 460  *  r0  = cp#15 control register
    8. 461  *  r1  = machine ID
    9. 462  *  r2  = atags or dtb pointer
    10. 463  *  r9  = processor ID
    11. 464  *  r13 = *virtual* address to jump to upon completion
    12. 465  *
    13. 466  * other registers depend on the function called upon completion
    14. 467  */
    15. 468     .align  5
    16. 469     .pushsection    .idmap.text, "ax"
    17. 470 ENTRY(__turn_mmu_on)
    18. 471     mov r0, r0
    19. 472     instr_sync
    20. 473     mcr p15, 0, r0, c1, c0, 0       @ write control reg
    21. 474     mrc p15, 0, r3, c0, c0, 0       @ read id reg
    22. 475     instr_sync
    23. 476     mov r3, r3
    24. 477     mov r3, r13
    25. 478     ret r3
    26. 479 __turn_mmu_on_end:
    27. 480 ENDPROC(__turn_mmu_on)
    28. 481     .popsection

    跳转start_kernel前__mmap_switched

            映射好__turn_mmu_on、内核、设备树后，开启MMU，一切开始运行在虚拟地址中，MMU开始工作。之后可以进入到C函数进行常规初始化。head.S调用__mmap_switched，完成C环境初始化后，跳转start_kernel。

    1.  71 /*
    2.  72  * The following fragment of code is executed with the MMU on in MMU mode,
    3.  73  * and uses absolute addresses; this is not position independent.
    4.  74  *
    5.  75  *  r0  = cp#15 control register
    6.  76  *  r1  = machine ID
    7.  77  *  r2  = atags/dtb pointer
    8.  78  *  r9  = processor ID
    9.  79  */
    10.  80     __INIT
    11.  81 __mmap_switched:
    12.  82     adr r3, __mmap_switched_data
    13.  83 
    14.  84     ldmia   r3!, {r4, r5, r6, r7}
    15.  85     cmp r4, r5              @ Copy data segment if needed
    16.  86 1:  cmpne   r5, r6
    17.  87     ldrne   fp, [r4], #4
    18.  88     strne   fp, [r5], #4
    19.  89     bne 1b
    20.  90 
    21.  91     mov fp, #0              @ Clear BSS (and zero fp)
    22.  92 1:  cmp r6, r7
    23.  93     strcc   fp, [r6],#4
    24.  94     bcc 1b
    25.  95 
    26.  96  ARM(   ldmia   r3, {r4, r5, r6, r7, sp})
    27.  97  THUMB( ldmia   r3, {r4, r5, r6, r7}    )
    28.  98  THUMB( ldr sp, [r3, #16]       )
    29.  99     str r9, [r4]            @ Save processor ID
    30. 100     str r1, [r5]            @ Save machine type
    31. 101     str r2, [r6]            @ Save atags pointer
    32. 102     cmp r7, #0
    33. 103     strne   r0, [r7]            @ Save control register values
    34. 104     b   start_kernel
    35. 105 ENDPROC(__mmap_switched)

    内核启动第二阶段

            一大顿初始化，想必都很关键。

    1. asmlinkage __visible void __init start_kernel(void)
    2. {
    3. 	char *command_line;
    4. 	char *after_dashes;
    5.  
    6. 	/*
    7. 	 * Need to run as early as possible, to initialize the
    8. 	 * lockdep hash:
    9. 	 */
    10. 	lockdep_init();
    11. 	set_task_stack_end_magic(&init_task);
    12. 	smp_setup_processor_id();
    13. 	debug_objects_early_init();
    14.  
    15. 	/*
    16. 	 * Set up the the initial canary ASAP:
    17. 	 */
    18. 	boot_init_stack_canary();
    19.  
    20. 	cgroup_init_early();
    21.  
    22. 	local_irq_disable();
    23. 	early_boot_irqs_disabled = true;
    24.  
    25. /*
    26.  * Interrupts are still disabled. Do necessary setups, then
    27.  * enable them
    28.  */
    29. 	boot_cpu_init();
    30. 	page_address_init();
    31. 	pr_notice("%s", linux_banner);
    32. 	setup_arch(&command_line);
    33. 	mm_init_cpumask(&init_mm);
    34. 	setup_command_line(command_line);
    35. 	setup_nr_cpu_ids();
    36. 	setup_per_cpu_areas();
    37. 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
    38.  
    39. 	build_all_zonelists(NULL, NULL);
    40. 	page_alloc_init();
    41.  
    42. 	pr_notice("Kernel command line: %s\n", boot_command_line);
    43. 	parse_early_param();
    44. 	after_dashes = parse_args("Booting kernel",
    45. 				  static_command_line, __start___param,
    46. 				  __stop___param - __start___param,
    47. 				  -1, -1, &unknown_bootoption);
    48. 	if (!IS_ERR_OR_NULL(after_dashes))
    49. 		parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
    50. 			   set_init_arg);
    51.  
    52. 	jump_label_init();
    53.  
    54. 	/*
    55. 	 * These use large bootmem allocations and must precede
    56. 	 * kmem_cache_init()
    57. 	 */
    58. 	setup_log_buf(0);
    59. 	pidhash_init();
    60. 	vfs_caches_init_early();
    61. 	sort_main_extable();
    62. 	trap_init();
    63. 	mm_init();
    64.  
    65. 	/*
    66. 	 * Set up the scheduler prior starting any interrupts (such as the
    67. 	 * timer interrupt). Full topology setup happens at smp_init()
    68. 	 * time - but meanwhile we still have a functioning scheduler.
    69. 	 */
    70. 	sched_init();
    71. 	/*
    72. 	 * Disable preemption - early bootup scheduling is extremely
    73. 	 * fragile until we cpu_idle() for the first time.
    74. 	 */
    75. 	preempt_disable();
    76. 	if (WARN(!irqs_disabled(),
    77. 		 "Interrupts were enabled *very* early, fixing it\n"))
    78. 		local_irq_disable();
    79. 	idr_init_cache();
    80. 	rcu_init();
    81.  
    82. 	/* trace_printk() and trace points may be used after this */
    83. 	trace_init();
    84.  
    85. 	context_tracking_init();
    86. 	radix_tree_init();
    87. 	/* init some links before init_ISA_irqs() */
    88. 	early_irq_init();
    89. 	init_IRQ();
    90. 	tick_init();
    91. 	rcu_init_nohz();
    92. 	init_timers();
    93. 	hrtimers_init();
    94. 	softirq_init();
    95. 	timekeeping_init();
    96. 	time_init();
    97. 	sched_clock_postinit();
    98. 	perf_event_init();
    99. 	profile_init();
    100. 	call_function_init();
    101. 	WARN(!irqs_disabled(), "Interrupts were enabled early\n");
    102. 	early_boot_irqs_disabled = false;
    103. 	local_irq_enable();
    104.  
    105. 	kmem_cache_init_late();
    106.  
    107. 	/*
    108. 	 * HACK ALERT! This is early. We're enabling the console before
    109. 	 * we've done PCI setups etc, and console_init() must be aware of
    110. 	 * this. But we do want output early, in case something goes wrong.
    111. 	 */
    112. 	console_init();
    113. 	if (panic_later)
    114. 		panic("Too many boot %s vars at `%s'", panic_later,
    115. 		      panic_param);
    116.  
    117. 	lockdep_info();
    118.  
    119. 	/*
    120. 	 * Need to run this when irqs are enabled, because it wants
    121. 	 * to self-test [hard/soft]-irqs on/off lock inversion bugs
    122. 	 * too:
    123. 	 */
    124. 	locking_selftest();
    125.  
    126. #ifdef CONFIG_BLK_DEV_INITRD
    127. 	if (initrd_start && !initrd_below_start_ok &&
    128. 	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
    129. 		pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
    130. 		    page_to_pfn(virt_to_page((void *)initrd_start)),
    131. 		    min_low_pfn);
    132. 		initrd_start = 0;
    133. 	}
    134. #endif
    135. 	page_ext_init();
    136. 	debug_objects_mem_init();
    137. 	kmemleak_init();
    138. 	setup_per_cpu_pageset();
    139. 	numa_policy_init();
    140. 	if (late_time_init)
    141. 		late_time_init();
    142. 	sched_clock_init();
    143. 	calibrate_delay();
    144. 	pidmap_init();
    145. 	anon_vma_init();
    146. 	acpi_early_init();
    147. 	thread_info_cache_init();
    148. 	cred_init();
    149. 	fork_init();
    150. 	proc_caches_init();
    151. 	buffer_init();
    152. 	key_init();
    153. 	security_init();
    154. 	dbg_late_init();
    155. 	vfs_caches_init(totalram_pages);
    156. 	signals_init();
    157. 	/* rootfs populating might need page-writeback */
    158. 	page_writeback_init();
    159. 	proc_root_init();
    160. 	nsfs_init();
    161. 	cpuset_init();
    162. 	cgroup_init();
    163. 	taskstats_init_early();
    164. 	delayacct_init();
    165.  
    166. 	check_bugs();
    167.  
    168. 	acpi_subsystem_init();
    169. 	sfi_init_late();
    170.  
    171. 	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
    172. 		efi_late_init();
    173. 		efi_free_boot_services();
    174. 	}
    175.  
    176. 	ftrace_init();
    177.  
    178. 	/* Do the rest non-__init'ed, we're now alive */
    179. 	rest_init();
    180. }

    lockdep_init

            初始化全局锁链表

    set_task_stack_end_magic

            在init_task栈底存入魔数0x57AC6E9D，用于栈溢出检测。

    smp_setup_processor_id

            多核检测，暂时不管，单核使用

    debug_objects_early_init

            初始化obj_hash、obj_static_pool全局变量

    boot_init_stack_canary

    cgroup_init_early

            control group早起初始化

    local_irq_disable、early_boot_irqs_disabled

            关闭中断

    boot_cpu_init

            获取cpuid，激活CPU

    page_address_init

            初始化高端内存，arm没有使用

    setup_arch(&command_line)

            处理器变量设置、获取设备树中bootargs，cmdline等初始化相关的参数、初始化init进程的内存描述符init_mm

    mm_init_cpumask

            mm_init里面的初始化cpu mask

    setup_command_line

            保存cmdline

    setup_per_cpu_areas

            为系统cpu变量申请per_cpu

    smp_prepare_boot_cpu

            设置引导CPU

    build_all_zonelists

            内存管理，node，zone

    page_alloc_init

            内存页初始化

    parse_early_param

            解析内核参数

    setup_log_buf

    pidhash_init

    vfs_caches_init_early

    sort_main_extable

    trap_init

    mm_init

    sched_init

            进程调度器初始化

    preempt_disable

            禁止抢占

    idr_init_cache

    rcu_init

    trace_init

    context_tracking_init

    radix_tree_init

    early_irq_init

    init_IRQ

    tick_init

    rcu_init_nohz

    init_timers

    hrtimers_init

    softirq_init

    timekeeping_init

    time_init

    sched_clock_postinit

    perf_event_init

    profile_init

    call_function_init

    early_boot_irqs_disabled

    local_irq_enable

    kmem_cache_init_late

    console_init

    lockdep_info

    locking_selftest

    page_ext_init

    debug_objects_mem_init

    kmemleak_init

    setup_per_cpu_pageset

    numa_policy_init

    sched_clock_init

    calibrate_delay

    pidmap_init

    anon_vma_init

    acpi_early_init

    thread_info_cache_init

    cred_init

    fork_init

    proc_caches_init

    buffer_init

    key_init

    security_init

    dbg_late_init

    vfs_caches_init

    signals_init

    page_writeback_init

    proc_root_init

    nsfs_init

    cpuset_init

    cgroup_init

    taskstats_init_early

    delayacct_init

    check_bugs

    acpi_subsystem_init

    sfi_init_late

    efi_enabled

    ftrace_init

    rest_init

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  • 原文地址：https://blog.csdn.net/fengyuwuzu0519/article/details/126380403