基于mini2440的裸机led程序及其链接脚本分析

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@******************************************************************************
@ File：led_on.S
@ 功能：LED点灯程序，点亮LED1
@******************************************************************************
.text
.global _start
_start:
LDR
R0,=0x56000010
@ R0设为GPBCON寄存器。此寄存器
@ 用于选择端口B各引脚的功能：
@ 是输出、是输入、还是其他
MOV
R1,#0x00000400
STR
R1,[R0]
@ 设置GPB5为输出口, 位[10:9]=0b01
LDR
R0,=0x56000014
@ R0设为GPBDAT寄存器。此寄存器
@ 用于读/写端口B各引脚的数据
MOV
R1,#0x00000000
@ 此值改为0x00000020,
@ 可让LED1熄灭
STR
R1,[R0]
@ GPB5输出0，LED1点亮
MAIN:
B
MAIN

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OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
/*OUTPUT_FORMAT("elf32-arm", "elf32-arm", "elf32-arm")*/
OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
. = 0x00000004; //这个可以换不同的地址试试
. = ALIGN(4);
.text
:
{
led_on.o	(.text)
*(.text)
}
. = ALIGN(4);
.rodata : { *(.rodata) }
. = ALIGN(4);
.data : { *(.data) }
}

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len_on.bin : len_on.S
arm-linux-gcc -g -c -o len_on.o len_on.S
arm-linux-ld
-g -Tled.lds len_on.o
-o len_on_elf
arm-linux-objcopy -O binary -S len_on_elf len_on.bin
clean:
rm -f
len_on.bin len_on_elf *.o

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led_on_elf:
file format elf32-littlearm
Disassembly of section .text:
00000004 <_start>:
4:	e59f0014
ldr	r0, [pc, #20]	; 20 <MAIN+0x4>
8:	e3a01b01
mov	r1, #1024	; 0x400
c:	e5801000
str	r1, [r0]
10:	e59f000c
ldr	r0, [pc, #12]	; 24 <MAIN+0x8>
14:	e3a01000
mov	r1, #0	; 0x0
18:	e5801000
str	r1, [r0]
0000001c <MAIN>:
1c:	eafffffe
b	1c <MAIN>
20:	56000010
.word	0x56000010
24:	56000014
.word	0x56000014
Disassembly of section .ARM.attributes:
00000000 <.ARM.attributes>:
0:	00001741
andeq	r1, r0, r1, asr #14
4:	61656100
cmnvs	r5, r0, lsl #2
8:	01006962
tsteq	r0, r2, ror #18
c:	0000000d
andeq	r0, r0, sp
10:	00543405
subseq	r3, r4, r5, lsl #8
14:	01080206
tsteq	r8, r6, lsl #4
Disassembly of section .debug_line:
00000000 <.debug_line>:
0:	0000003a
andeq	r0, r0, sl, lsr r0
4:	001f0002
andseq	r0, pc, r2
8:	01020000
tsteq	r2, r0
c:	000d0efb
strdeq	r0, [sp], -fp
10:	01010101
tsteq	r1, r1, lsl #2
14:	01000000
tsteq	r0, r0
18:	00010000
andeq	r0, r1, r0
1c:	5f64656c
svcpl	0x0064656c
20:	532e6e6f
teqpl	lr, #1776	; 0x6f0
24:	00000000
andeq	r0, r0, r0
28:	02050000
andeq	r0, r5, #0	; 0x0
2c:	00000004
andeq	r0, r0, r4
30:	31010903
tstcc	r1, r3, lsl #18
34:	30302f2f
eorscc	r2, r0, pc, lsr #30
38:	00060230
andeq	r0, r6, r0, lsr r2
3c:	Address 0x0000003c is out of bounds.
Disassembly of section .debug_info:
00000000 <.debug_info>:
0:	00000063
andeq	r0, r0, r3, rrx
4:	00000002
andeq	r0, r0, r2
8:	01040000
tsteq	r4, r0
c:	00000000
andeq	r0, r0, r0
10:	00000004
andeq	r0, r0, r4
14:	00000028
andeq	r0, r0, r8, lsr #32
18:	5f64656c
svcpl	0x0064656c
1c:	532e6e6f
teqpl	lr, #1776	; 0x6f0
20:	6e6d2f00
cdpvs	15, 6, cr2, cr13, cr0, {0}
24:	67682f74
undefined
28:	532f7366
teqpl	pc, #-1744830463	; 0x98000001
2c:	65726168
ldrbvs	r6, [r2, #-360]!
30:	68746957
ldmdavs	r4!, {r0, r1, r2, r4, r6, r8, fp, sp, lr}^
34:	756e694c
strbvc	r6, [lr, #-2380]!
38:	61732f78
cmnvs	r3, r8, ror pc
3c:	656c706d
strbvs	r7, [ip, #-109]!
40:	65775f73
ldrbvs	r5, [r7, #-3955]!
44:	61682f69
cmnvs	r8, r9, ror #30
48:	61776472
cmnvs	r7, r2, ror r4
4c:	6c2f6572
cfstr32vs	mvfx6, [pc], #-456
50:	6f5f6465
svcvs	0x005f6465
54:	4e47006e
cdpmi	0, 4, cr0, cr7, cr14, {3}
58:	53412055
movtpl	r2, #4181	; 0x1055
5c:	312e3220
teqcc	lr, r0, lsr #4
60:	30352e38
eorscc	r2, r5, r8, lsr lr
64:	Address 0x00000064 is out of bounds.
Disassembly of section .debug_abbrev:
00000000 <.debug_abbrev>:
0:	10001101
andne	r1, r0, r1, lsl #2
4:	12011106
andne	r1, r1, #-2147483647	; 0x80000001
8:	1b080301
blne	200c14 <MAIN+0x200bf8>
c:	13082508
movwne	r2, #34056	; 0x8508
10:	00000005
andeq	r0, r0, r5
Disassembly of section .debug_aranges:
00000000 <.debug_aranges>:
0:	0000001c
andeq	r0, r0, ip, lsl r0
4:	00000002
andeq	r0, r0, r2
8:	00040000
andeq	r0, r4, r0
c:	00000000
andeq	r0, r0, r0
10:	00000004
andeq	r0, r0, r4
14:	00000024
andeq	r0, r0, r4, lsr #32

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led_on.bin:
file format binary
Disassembly of section .data:
00000000 <.data>:
0:	e59f0014
ldr	r0, [pc, #20]	; 0x1c
4:	e3a01b01
mov	r1, #1024	; 0x400
8:	e5801000
str	r1, [r0]
c:	e59f000c
ldr	r0, [pc, #12]	; 0x20
10:	e3a01000
mov	r1, #0	; 0x0
14:	e5801000
str	r1, [r0]
18:	eafffffe
b	0x18
1c:	56000010
undefined
20:	56000014
undefined