mini2440利用uboot在内存中下载并运行裸机程序
转载请保留链接
1. 代码编写：
test.Ssub sp, sp, #4
str r14, [sp]
ldr r0, =fmt
mov r14, r15
ldr r15, show
ldr r14, [sp]
add sp, sp, #4
mov r15, r14
show:
.word 0x33f962a8
fmt:
.asciz "hello tauren.\n"
2. 代码编译链接
root@tauren:/code/test# arm-linux-as test.S -o test.oroot@tauren:/code/test# arm-linux-ld -Ttext=0x30008000 test.o -o test
root@tauren:/code/test# arm-linux-objcopy -I elf32-littlearm -O binary test /code/tftp/test.bin
3. u-boot代码的下载与执行
[MINI2440]# tftp 0x30008000 test.bin[MINI2440]# go 0x30008000
U-Boot 2009.11 (Jan 05 2016 - 22:14:15)
modified by tekkamanninja ([email protected])
Love Linux forever!!
I2C: ready
DRAM: 64 MB
Flash: 2 MB
NAND: 128 MiB
Video: 240x320x16 20kHz 62Hz
In: serial
Out: serial
Err: serial
Net: dm9000
U-Boot 2009.11 (Jan 05 2016 - 22:14:15)
modified by tekkamanninja
([email protected])
Love Linux forever!!
[MINI2440]# tftp 0x30008000 test.bin
dm9000 i/o: 0x20000300, id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 08:08:11:18:12:27
operating at 100M full duplex mode
Using dm9000 device
TFTP from server 192.168.1.110; our IP address is 192.168.1.108
Filename 'test.bin'.
Load address: 0x30008000
Loading: T #
done
Bytes transferred = 56 (38 hex)
[MINI2440]# go 0x30008000
## Starting application at 0x30008000 ...
hello tauren.
## Application terminated, rc = 0x0
5. 实验总结：
1) 代码中地址0x33f962a8代表的是uboot所对应的printf函数的地址，可以从u-boot.map中查询，只需要把字符串送至printf函数所在的地址即可实现信息打印。2) 代码链接时指定了链接地址为0x30008000，利用arm-linux-objdump –d test反汇编可以看出，这个地址指的是DDR内存中的临时地址。
root@tauren:/code/test# arm-linux-objdump -d test
test: file format elf32-littlearm
Disassembly of section .text:
30008000
30008000: e24dd004 sub sp, sp, #4
30008004: e58de000 str lr, [sp]
30008008: e59f0024 ldr r0, [pc, #36] ; 30008034
3000800c: e1a0e00f mov lr, pc
30008010: e59ff008 ldr pc, [pc, #8] ; 30008020
30008014: e59de000 ldr lr, [sp]
30008018: e28dd004 add sp, sp, #4
3000801c: e1a0f00e mov pc, lr
30008020
30008020: 33f962a8 .word 0x33f962a8
30008024
30008024: 6c6c6568 .word 0x6c6c6568
30008028: 6174206f .word 0x6174206f
3000802c: 6e657275 .word 0x6e657275
30008030: 00000a2e .word 0x00000a2e
30008034: 30008024 .word 0x30008024
3) 链接出的test是elf格式文件，需要利用arm-linux-objcopy去掉头信息，elf32-littlearm指定小端模式。
4) 代码换成C语言 test.c
void (*show)(char *,...) = 0x33f962a8;
int main(void)
{
show("hello world./n");
return 0;
}
编译：
root@tauren:/code/test# arm-linux-gcc -c test.c -o test.o
root@tauren:/code/test# arm-linux-ld -Ttext=0x30008000 -nostdlib test.o -o test
root@tauren:/code/test# arm-linux-objcopy -I elf32-littlearm -O binary test /code/tftp/test.bin
下载：
[MINI2440]# tftp 0x30008000 test.bin
dm9000 i/o: 0x20000300, id: 0x90000a46
DM9000: running in 16 bit mode
MAC: 08:08:11:18:12:27
operating at 100M full duplex mode
Using dm9000 device
TFTP from server 192.168.1.110; our IP address is 192.168.1.108
Filename 'test.bin'.
Load address: 0x30008000
Loading: T ###
done
Bytes transferred = 32844 (804c hex)
[MINI2440]# go 0x30008000
## Starting application at 0x30008000 ...
hello tauren.
## Application terminated, rc = 0x0