uboot dcc

arch\arm\lib crt0.S

1.设置sp为CONFIG_SYS_INIT_SP_ADDR

include/configs/xxx.h

#define CONFIG_SYS_INIT_SP_ADDR     (CONFIG_SYS_INIT_RAM_ADDR + \
                   
CONFIG_SYS_INIT_RAM_SIZE - GENERATED_GBL_DATA_SIZE)

#define CONFIG_SYS_INIT_RAM_ADDR    0x20000
#define CONFIG_SYS_INIT_RAM_SIZE    0x1000

include/generated/generic-asm-offsets.h

#define GENERATED_GBL_DATA_SIZE 192 /* (sizeof(struct global_data) + 15) & ~15  @ */

CONFIG_SYS_INIT_SP_ADDR=0x20F40

2.调用board_init_f_alloc_reserve

没有定义SYS_MALLOC_F_LEN，不执行。这里不对

make distclean后，CONFIG_SYS_MALLOC_F_LEN默认值0x400

top初始值0x20F40

#if CONFIG_VAL(SYS_MALLOC_F_LEN)
    top -= CONFIG_VAL(SYS_MALLOC_F_LEN);  #top=0x20B40
#endif

top = rounddown(top-sizeof(struct global_data), 16);  #top=0x20A80

3.   r9(gd) = sp = top;

gd地址定了。CONFIG_SYS_INIT_SP_ADDR=0x20A80

4.调用board_init_f

注意：串口初始化之后才能打印输出。

setup_dest_addr

#ifdef CONFIG_SYS_SDRAM_BASE
    gd->ram_top = CONFIG_SYS_SDRAM_BASE;
#endif
    gd->ram_top += get_effective_memsize();
    gd->ram_top = board_get_usable_ram_top(gd->mon_len);
    gd->relocaddr = gd->ram_top;
    debug("Ram top: %08lX\n", (ulong)gd->ram_top);

gd->ram_top=0x20000+0x40000=0x60000

gd->relocaddr=gd->ram_top=0x60000

reserve_uboot --> Reserving 192k for U-Boot at: 0002f000  gd->relocaddr到此为止，之后gd->start_addr_sp出场


reserve_malloc --> Reserving 4k for malloc() at: 0002de70


reserve_board --> Reserving 80 Bytes for Board Info at: 0002de20


reserve_global_data --> Reserving 192 Bytes for Global Data at: 0002dd60  gd->new_gd


reloc_fdt --> 因为CONFIG_OF_EMBED，所以不执行什么


reloc_bootstage --> 因为没有定义CONFIG_BOOTSTAGE，所以不执行什么


reserve_arch --> 空

reserve_stacks --> gd->start_addr_sp -= 16; gd->start_addr_sp &= ~0xf;  调用arch_reserve_stacks（定义在arch\arm\lib\stack.c）gd->start_addr_sp -= 16; 一共减32byte

display_new_sp --> New Stack Pointer is: 0002dd40

setup_reloc --> gd->reloc_off = gd->relocaddr - (unsigned long)__image_copy_start;   gd->relocaddr=0002f000 __image_copy_start就是CONFIG_SYS_TEXT_BASE=0x2f000



Relocation Offset is: 00000000

Relocating to 0002f000, new gd at 0002dd60, sp at 0002dd40

ldr    r0, [r9, #GD_START_ADDR_SP]    /* sp = gd->start_addr_sp */
    bic    r0, r0, #7    /* 8-byte alignment for ABI compliance */
    mov    sp, r0   //定义新sp 之前为0x21000
    ldr    r9, [r9, #GD_BD]        /* r9 = gd->bd */
    sub    r9, r9, #GD_SIZE        /* new GD is below bd */

adr    lr, here
    ldr    r0, [r9, #GD_RELOC_OFF]        /* r0 = gd->reloc_off */
    add    lr, lr, r0
#if defined(CONFIG_CPU_V7M)
    orr    lr, #1                /* As required by Thumb-only */
#endif
    ldr    r0, [r9, #GD_RELOCADDR]        /* r0 = gd->relocaddr */
    b    relocate_code

如果gd->relocaddr和__image_copy_start相等

ldr    r1, =__image_copy_start    /* r1 <- SRC &__image_copy_start */
    subs    r4, r0, r1        /* r4 <- relocation offset */
    beq    relocate_done        /* skip relocation */

就跳过搬移。

所以整个过程中，搬移的就只有gd_t。

如何计算defconfig中的CONFIG_SYS_TEXT_BASE

vi u-boot.map

setup_mon_len中
gd->mon_len = (ulong)&__bss_end - (ulong)_start;

reserve_uboot

gd->relocaddr -= gd->mon_len;

__bss_end

0x000000000005f3a0

.__image_copy_start

0x0000000000033000

gd->mon_len=0x2c3a0

gd->relocaddr=gd->ram_top-gd->mon_len(u-boot)=0x60000-0x2c3a0=0x33c60

后三位清零，4K对齐 gd->relocaddr &= ~(4096 - 1);

gd->relocaddr=0x33000

__image_copy_start 即CONFIG_SYS_TEXT_BASE设置为gd->relocaddr=0x33000

即可跳过搬移。