12.u-boot2013.01 smdk2410 启动第一阶段分析.txt

标签：

_start:    b    start_code 

     mrs    r0, cpsr
        bic    r0, r0, #0x1f
        orr    r0, r0, #0xd3
        msr    cpsr, r0

    #  define pWTCON    0x53000000
        ldr    r0, =pWTCON
        mov    r1, #0x0
        str    r1, [r0]

    #  define INTMSK    0x4A000008    /* Interrupt-Controller base addresses */
        mov    r1, #0xffffffff
        ldr    r0, =INTMSK
        str    r1, [r0]

     # if defined(CONFIG_S3C2410)
            ldr    r1, =0x3ff
            ldr    r0, =INTSUBMSK
            str    r1, [r0]
   # endif

   /* FCLK:HCLK:PCLK = 1:2:4 */
        /* default FCLK is 120 MHz ! */
        ldr    r0, =CLKDIVN
        mov    r1, #3
        str    r1, [r0]

   #ifndef CONFIG_SKIP_LOWLEVEL_INIT
        bl    cpu_init_crit                       //在初始化内存之前没有进行时钟的设置
    #endif
    cpu_init_crit：
            a.flush v4 I/D caches
            b.disable MMU stuff and caches
            c.bl    lowlevel_init  //底层的初始化

    bl    _main
                ldr    sp, =(CONFIG_SYS_INIT_SP_ADDR)  //0x30000f80  看确定sp的值分析一节
                bic    sp, sp, #7    /* 8-byte alignment for ABI compliance */
                sub    sp, #GD_SIZE    /* allocate one GD above SP */
                bic    sp, sp, #7    /* 8-byte alignment for ABI compliance */
                

       
        mov    r8, sp        /* GD is above SP */
        mov    r0, #0 

    gd->mon_len = _bss_end_ofs;    
        _bss_end_ofs：的定义
                .globl _bss_end_ofs
                _bss_end_ofs:
                .word __bss_end__ - _start

     for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
            if ((*init_fnc_ptr)() != 0) {
                hang ();
            }
        }

       arch_cpu_init,        /* basic arch cpu dependent setup */
                    mark_bootstage,
                    board_early_init_f,
                    timer_init,        /* initialize timer */
                    env_init,        /* initialize environment */
                    init_baudrate,        /* initialze baudrate settings */
                    serial_init,        /* serial communications setup */
                    console_init_f,        /* stage 1 init of console */
                    display_banner,        /* say that we are here */
                    print_cpuinfo,        /* display cpu info (and speed) */
                    dram_init,        /* configure available RAM banks */
                    NULL,                //表示结束

     int arch_cpu_init(void)
                            __attribute__((weak, alias("__arch_cpu_init")));
                            int __arch_cpu_init(void)
                        {
                            return 0;
                        }

      memset((void *)gd, 0, sizeof(gd_t));//初始化0x30000f00 到0x30000f80之前的内存单元。
                 #define PHYS_SDRAM_1        0x30000000 /* SDRAM Bank #1 */
                 #define CONFIG_SYS_SDRAM_BASE    PHYS_SDRAM_1
                
                 gd->ram_size = PHYS_SDRAM_1_SIZE;       

    /* reserve TLB table */
        gd->tlb_size = 4096 * 4;
        addr -= gd->tlb_size;

      /*
         * reserve memory for U-Boot code, data & bss
         * round down to next 4 kB limit
         */
        addr -= gd->mon_len;
        addr &= ~(4096 - 1);

    * reserve memory for malloc() arena 保留malloc 空间
     */
    addr_sp = addr - TOTAL_MALLOC_LEN;
    
    #define    TOTAL_MALLOC_LEN    (CONFIG_SYS_MALLOC_LEN + CONFIG_ENV_SIZE)

    /*
     * (permanently) allocate a Board Info struct
     * and a permanent copy of the "global" data
     */
    addr_sp -= sizeof (bd_t);
    bd = (bd_t *) addr_sp;
    gd->bd = bd;

  addr_sp -= sizeof (bd_t); //为board Info  保留一块空间

  bd = (bd_t *) addr_sp;    //堆addr_sp进行强制类型的转换。并复制给bd (bd 里边包含了bi_arch_number  见bd gd 结构体分析)    gd->bd = bd; //将bd 赋值给gd的成员bd。
这样就可以通过gd这个全局 的寄存器变量来找到boadr info 信

  addr_sp -= sizeof (gd_t); //为gd_t 保留一块空间 为后续的将低端的GD数据拷贝到高端D==>addr_sp  addr_sp -  sizeof (bd_t)  -  sizeof (gd_t) 地址做准备

  #if defined(CONFIG_OF_SEPARATE) && defined(CONFIG_OF_CONTROL)
        /*
         * If the device tree is sitting immediate above our image then we
         * must relocate it. If it is embedded in the data section, then it
         * will be relocated with other data.
         */
        if (gd->fdt_blob) {
            fdt_size = ALIGN(fdt_totalsize(gd->fdt_blob) + 0x1000, 32);

            addr_sp -= fdt_size;
            new_fdt = (void *)addr_sp;
            debug("Reserving %zu Bytes for FDT at: %08lx\n",
                  fdt_size, addr_sp);
        }
    #endif

      #define PHYS_SDRAM_1        0x30000000 /* SDRAM Bank #1 */
              #define CONFIG_SYS_SDRAM_BASE    PHYS_SDRAM_1
             
             void __dram_init_banksize(void)
        {
            gd->bd->bi_dram[0].start = CONFIG_SYS_SDRAM_BASE; //0x30000000
            gd->bd->bi_dram[0].size =  gd->ram_size;   // 在board_init_f  进行的设置 大小为0x04000000  64M
        }
        void dram_init_banksize(void)
            __attribute__((weak, alias("__dram_init_banksize")));
            
        gd->relocaddr = addr;                    /* Start address of U-Boot in RAM */  //U-boot 在RAM的起始地址
        gd->start_addr_sp = addr_sp;             /* start_addr_stackpointer */            //栈指针的起始地址
        gd->reloc_off = addr - _TEXT_BASE;  //重定位的偏移量  即搬移后u-boot的首地址  

            memcpy(id, (void *)gd, sizeof(gd_t)); //将低端的gd所在的数据，拷贝到高端id处   

        #define GENERATED_GBL_DATA_SIZE (128) /* (sizeof(struct global_data) + 15) & ~15 */
                            #define GENERATED_BD_INFO_SIZE (32) /* (sizeof(struct bd_info) + 15) & ~15 */
                            #define GD_SIZE (128) /* sizeof(struct global_data) */
                            #define GD_BD (0) /* offsetof(struct global_data, bd) */
                            #define GD_RELOCADDR (52) /* offsetof(struct global_data, relocaddr) */
                            #define GD_RELOC_OFF (72) /* offsetof(struct global_data, reloc_off) */
                            #define GD_START_ADDR_SP (68) /* offsetof(struct global_data, start_addr_sp) */

     bic    sp, sp, #7    /* 8-byte alignment for ABI compliance */
        ldr    r8, [r8, #GD_BD]        /* r8 = gd->bd */
        sub    r8, r8, #GD_SIZE        /* new GD is below bd */  此时r8指向的空间为bd的首地址
        
        adr    lr, here //在重定位完成后，返回地址
        ldr    r0, [r8, #GD_RELOC_OFF]        /* lr = gd->start_addr_sp */  [r8, #GD_RELOC_OFF]      得到重定位的偏移量
        add    lr, lr, r0                                                                                                                                        //在here的基础上加上重定位的偏移量
        ldr    r0, [r8, #GD_START_ADDR_SP]    /* r0 = gd->start_addr_sp */                            //void relocate_code (addr_sp, gd, addr_moni)    重定位代码的第一个参数
        mov    r1, r8                /* r1 = gd */                                                                                         //第二个参数    
        ldr    r2, [r8, #GD_RELOCADDR]        /* r2 = gd->relocaddr */                                          //第三个参数，即重定位的位置

     mov    r4, r0    /* save addr_sp */
        mov    r5, r1    /* save addr of gd */
        mov    r6, r2    /* save addr of destination */

 
copy_loop:
    ldmia    r0!, {r9-r10}        /* copy from source address [r0]    */  从r0单元中读出8个字节的数据存在r9 r10 中，同时r0 自动加8
    stmia    r1!, {r9-r10}        /* copy to   target address [r1]    */   将刚才读出的数据放入r1单元的8个
    cmp    r0, r2            /* until source end address [r2]    */          比较数据源地址和 目的地址的尾地址是否相同
    blo    copy_loop                                                                                      //小于则跳转     也就是数据搬移还没有结束               
    

    /*
     * fix .rel.dyn relocations
     */
    ldr    r0, _TEXT_BASE        /* r0 <- Text base */ 读内存指令
    //r0 = 0 //代码段的基地址
    
    sub    r9, r6, r0        /* r9 <- relocation offset */
    //r9 = r6 -r0 =  代码搬移的目标地址 -  代码段的基地址 = 重定位的偏移量
    //r9 =  0x33f34000 - 0 =  0x33f34000
    
    ldr    r10, _dynsym_start_ofs    /* r10 <- sym table ofs */
    //r10 = 符号表的首地址,这个地址是连接脚本中相对于链接脚本中的地址量。
  //r10 = 0x0007cb24  （反汇编得到）
    
    add    r10, r10, r0        /* r10 <- sym table in FLASH */
    //r10 = r10 +r0 = 代码段的基地址 + 符号表的地址  = 符号表在flash 中的地址
    //r10 = 0x0007cb24 + 0 = 0007cb24
    
    ldr    r2, _rel_dyn_start_ofs    /* r2 <- rel dyn start ofs */
    //r2 = rel_dyn的首地址。 这个地址是连接脚本中相对于链接脚本中的地址量。
    //r2 =  0x00073b9c
    
    add    r2, r2, r0        /* r2 <- rel dyn start in FLASH */
    //r2 = r2 +r0 = 在flash中rel_dyn的地址
    //r2 =  0x00073b9c
    
    ldr    r3, _rel_dyn_end_ofs    /* r3 <- rel dyn end ofs */
    add    r3, r3, r0        /* r3 <- rel dyn end in FLASH */
    //在flash中 rel_dyn_end d地址
  // r3 = 0007cb24
 
fixloop:
    ldr    r0, [r2]        /* r0 <- location to fix up, IN FLASH! */
    //将r2单元的数据读到r0 。即rel_dyn在flash的地址
    //第一次循环：r0 = [r2] = [0x00073b9c] = 0x00000020    
    
    add    r0, r0, r9        /* r0 <- location to fix up in RAM */
    // r0 = r0+r9 = 代码段的基地址 +  重定位的偏移量 = 在RAM中的地址
    //第一次循环： r0= r0 + r9 = 0x00000020  + 0x33f34000 =  0x33f34020
    
    ldr    r1, [r2, #4]  
    //r1 = *(r2 +4)  = 取出rel_dyn + 4 单元的数据到r1中
    //第一次循环： r1+= [r1 +4 ]  = [0x00073b9c +4 ] = [0x00073ba0] =  00000017
    
    and    r7, r1, #0xff
    //第一次循环: r7 = r1 & 0xff = 00000017
    
    cmp    r7, #23            /* relative fixup? */
    //第一次循环: 比较r7是否等于23  ==>等于
    
    beq    fixrel
    //第一次循环：跳转到fixrel
    
    cmp    r7, #2            /* absolute fixup? */
    beq    fixabs
    /* ignore unknown type of fixup */
    b    fixnext
fixabs:
    /* absolute fix: set location to (offset) symbol value */
    mov    r1, r1, LSR #4        /* r1 <- symbol index in .dynsym */
    add    r1, r10, r1        /* r1 <- address of symbol in table */
    ldr    r1, [r1, #4]        /* r1 <- symbol value */
    add    r1, r1, r9        /* r1 <- relocated sym addr */
    b    fixnext
fixrel:
    /* relative fix: increase location by offset */
    ldr    r1, [r0]
    //第一此循环：r1 = [r0] = [0x000020  ]   =  000001a0                          //此处的r0 为什么是0x000020  而不是 0x33f34020
     //此处实际的[r0] 应当是0x33f34020.实际中 0x000020 和0x33f34020单元里边的内容值是一样的。都是取出来。然后进行修改里边的代码。
    add    r1, r1, r9
    // 第一此循环： r1 = r1 + r9 = 0x000001a0 + 0x33f34000  = 0x33F341A0
    
fixnext:
    str    r1, [r0]
    //第一此循环： [0x33f34020] =   0x33F341A0
    
    add    r2, r2, #8        /* each rel.dyn entry is 8 bytes */
    //第一此循环：  r2 = r2 +8 =  0x00073b9c + 8 = 0x00073ba4
    
    cmp    r2, r3
    // 第一此循环：  0x0x00073ba4    != 0x0007cb24
    blo    fixloop  
// 第一此循环： 小于继续跳转 到fixloop  

00073b9c <__image_copy_end>:
   73b9c:    00000020     andeq    r0, r0, r0, lsr #32             //第一次循环
   73ba0:    00000017     andeq    r0, r0, r7, lsl r0                // 17 表示的是一个标号。
   73ba4:    00000024     andeq    r0, r0, r4, lsr #32             //第二次循环
   73ba8:    00000017     andeq    r0, r0, r7, lsl r0
   73bac:    00000028     andeq    r0, r0, r8, lsr #32
   73bb0:    00000017     andeq    r0, r0, r7, lsl r0
   73bb4:    0000002c     andeq    r0, r0, ip, lsr #32
   

here:
/* Set up final (full) environment */

    bl    c_runtime_cpu_setup    /* we still call old routine here */

    ldr    r0, =__bss_start    /* this is auto-relocated! */
    ldr    r1, =__bss_end__    /* this is auto-relocated! */

    mov    r2, #0x00000000        /* prepare zero to clear BSS */
    clbss_l:cmp    r0, r1            /* while not at end of BSS */
    strlo    r2, [r0]        /* clear 32-bit BSS word */
    addlo    r0, r0, #4        /* move to next */
    blo    clbss_l

    /* call board_init_r(gd_t *id, ulong dest_addr) */
    mov    r0, r8            /* gd_t */
    ldr    r1, [r8, #GD_RELOCADDR]    /* dest_addr */
    /* call board_init_r */
    ldr    pc, =board_init_r    /* this is auto-relocated! */

       7d8:    e1a00008     mov    r0, r8
     7dc:    e5981034     ldr    r1, [r8, #52]    ; 0x34
     7e0:    e59ff008     ldr    pc, [pc, #8]    ; 7f0 <clbss_l+0x30>
            pc = pc +8 +8 = 0x7f0 

     7f0:    000008ac     andeq    r0, r0, ip, lsr #17

  
000008ac <board_init_r>:
     8ac:    e5982004     ldr    r2, [r8, #4]
     8b0:    e92d4008     push    {r3, lr}
     8b4:    e59f30b4     ldr    r3, [pc, #180]    ; 970 <board_init_r+0xc4>
     8b8:    e3822001     orr    r2, r2, #1
     8bc:    e5882004     str    r2, [r8, #4]
     8c0:    e5932000     ldr    r2, [r3]
     8c4:    e59f30a8     ldr    r3, [pc, #168]    ; 974 <board_init_r+0xc8>
     8c8:    e1a04001     mov    r4, r1
     8cc:    e5832000     str    r2, [r3]
     8d0:    eb0001ad     bl    f8c <__enable_caches>
     8d4:    eb01729f     bl    5d358 <board_init>

12.u-boot2013.01 smdk2410 启动第一阶段分析.txt

标签：

原文地址：http://blog.csdn.net/u013377887/article/details/51915433