u-boot2014.1内存分布

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TQ2440开发板，u-boot2014.1，当前为smdk_2410默认配置，SDRAM为64MB。

_main中将sp赋值为CONFIG_SYS_INIT_SP_ADDR= 0x30000f60

sp = sp – 0xa0;//160为gd_t结构的大小

mov r9, sp //r9为gd结构体的地址。从以上可以看出sp入栈时递减，且是[--sp] = data

//gd是一个全局变量，存储一些关键的通用变量，当前位置在0x30000EC0,其定义如下：

typedef struct global_data {

bd_t*bd;

unsignedlong flags;

unsignedint baudrate;

unsignedlong cpu_clk; /* CPU clock in Hz! */

unsignedlong bus_clk;

/*We cannot bracket this with CONFIG_PCI due to mpc5xxx */

unsignedlong pci_clk;

unsignedlong mem_clk;

unsignedlong have_console; /* serial_init() wascalled */

unsignedlong env_addr; /* Address of Environment struct */

unsignedlong env_valid; /* Checksum of Environmentvalid? */

unsignedlong ram_top; /* Top address of RAM usedby U-Boot */

unsignedlong relocaddr; /* Start addressof U-Boot in RAM */

phys_size_tram_size; /* RAM size */

unsignedlong mon_len; /* monitor len */

unsignedlong irq_sp; /* irq stackpointer */

unsignedlong start_addr_sp; /*start_addr_stackpointer */

unsignedlong reloc_off;

structglobal_data *new_gd; /* relocated globaldata */

constvoid *fdt_blob; /* Our device tree,NULL if none */

void*new_fdt; /* RelocatedFDT */

unsignedlong fdt_size; /* Space reserved forrelocated FDT */

void**jt; /* jump table */

charenv_buf[32]; /* buffer for getenv()before reloc. */

unsignedlong timebase_h;

unsignedlong timebase_l;

structarch_global_data arch; /*architecture-specific data */

} gd_t;

进入board_init_f函数主要任务为初始化gd

gd->fdt_blob= (void *)getenv_ulong("fdtcontroladdr", 16,(uintptr_t)gd->fdt_blob);//不懂做什么

gd->mon_len= _bss_end_ofs; //此为u-boot程序占用空间，包含bss段

gd->ram_size //可以理解为SDRAM大小比如64MB

addr= CONFIG_SYS_SDRAM_BASE + gd->ram_size;

gd->arch.tlb_size= PGTABLE_SIZE = 4096 * 4; //为

addr&= ~(0x10000 - 1);

gd->arch.tlb_addr= addr;

debug("TLBtable from %08lx to %08lx\n", addr, addr + gd->arch.tlb_size);

/*reserve memory for LCD display (always full pages) */

addr= lcd_setmem(addr);//管它呢，又是减了一点就对了

gd->fb_base= addr;

addr-= gd->mon_len;

addr&= ~(4096 - 1);

debug("Reserving%ldk for U-Boot at: %08lx\n", gd->mon_len >> 10, addr);

* reserve memory for malloc() arena

addr_sp= addr - TOTAL_MALLOC_LEN;

* (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 (gd_t);

id= (gd_t *) addr_sp;

debug("Reserving%zu Bytes for Global Data at: %08lx\n",sizeof (gd_t), addr_sp);

/*setup stackpointer for exeptions */

gd->irq_sp= addr_sp;

/*leave 3 words for abort-stack */

addr_sp-= 12;

/*8-byte alignment for ABI compliance */

addr_sp&= ~0x07;

debug("NewStack Pointer is: %08lx\n", addr_sp);

gd->bd->bi_baudrate= gd->baudrate;

/*Ram ist board specific, so move it to board code ... */

dram_init_banksize();

display_dram_config(); /* and display it */

gd->relocaddr= addr;

gd->start_addr_sp= addr_sp;

gd->reloc_off= addr - _TEXT_BASE;

debug("relocationOffset is: %08lx\n", gd->reloc_off);

if(new_fdt) {

memcpy(new_fdt,gd->fdt_blob, fdt_size);

gd->fdt_blob= new_fdt;

}

memcpy(id,(void *)gd, sizeof(gd_t));

以上程序为地址定位信息，然后打开debug，查看信息如下：

monitor len: 0009E848//此为u-boot程序占用空间，包含bss段

ramsize: 04000000

//即为64MB，所以sdram最后0x30000000+0x4000000-1=0x33ffffff

TLB table from 33ff0000 to 33ff4000//处于SDRAM的最末端

Top of RAM usable for U-Boot at: 33ff0000

Reserving 634k for U-Boot at: 33f51000

Reserving 4160k for malloc() at: 33b41000

Reserving 32 Bytes for Board Info at:33b40fe0

Reserving 160 Bytes for Global Data at:33b40f40//gd结构体新的地址

New Stack Pointer is: 33b40f30//新的堆栈指针，再上面的12个字节留给异常中断

RAM Configuration:

Bank #0: 30000000 64 MiB

relocation Offset is: 33f51000

WARNING: Caches not enabled

monitor flash len: 0005B18C//此为不包含bss段的长度

Now running in RAM - U-Boot at: 33f51000

从上可得，接下来的程序会把原来的堆栈指针和原来的gd结构体指向新的地址，所以比如0x30000f60这个地址只是临时占用。

再接下来的程序会根据以上数据运行relocate_code。

结论为使用u-boot的时候临时使用sdram时用30000000h-330000000h即可。

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