链接地址
启动过程
示例代码如下：
start.S文件
.globl_start
_start:
/*硬件相关设置*/
ldrr0,=0x70000000
orrr0,r0,#0x13
mcrp15,0,r0,c15,c2,4
/*关看门狗*/
bltest/*位置无关*/
ldrpc,=test/*位置相关*/
ldrr0,=0x7E00400
movr1,#0
strr1,[r0]
/*设置栈*/
ldrsp,=8*1024
blmain
halt:
bhalt
test:
movpc,lr
Led.c文件
voiddelay(){
volatileinti=0x1000;
while(i--);
}
volatileinti=0;
volatileintj=0x12345678;
volatileintk=0;
volatileintg;
intmain(){
volatileunsignedlong*gpkcon=(volatileunsignedlong*)0x7F008800;
volatileunsignedlong*gpkdat=(volatileunsignedlong*)0x7F008808;
*gpkcon=0x1111;
while(1){
*gpkdat=i;
i++;
if(i==16)
i=0;
delay();
}
return0;
}
Leds.lds文件
SECTIONS
{
.=0x50000000;
.text:{
start.o
*(.text)
}
.data:{
*(.data)
}
bss_start=.;
.bss:{
*(.bss)
}
bss_end=.;
}
Makefile文件
led.bin:start.oled.o
arm-linux-ld-Tleds.lds-oled.elfstart.oled.o
arm-linux-objcopy-Obinaryled.elfled.bin
arm-linux-objdump-Dled.elf>led.dis
start.o:start.S
arm-linux-gcc-ostart.ostart.S-c
led.o:led.c
arm-linux-gcc-oled.oled.c-c
clean:
rm*.oled.elfled.binled.dis
Led.dis文件
led.elf:fileformatelf32-littlearm
首地址为0x50000000;
Disassemblyofsection.text:
50000000<_start>:
50000000: e3a00207 mov r0,#1879048192 ;0x70000000
50000004: e3800013 orr r0,r0,#19
50000008: ee0f0f92 mcr 15,0,r0,cr15,cr2,{4}
5000000c: e59f0014 ldr r0,[pc,#20] ;50000028<test+0x4>
50000010: e3a01000 mov r1,#0
50000014: e5801000 str r1,[r0]
50000018: e3a0da02 mov sp,#8192 ;0x2000
5000001c: eb00001e bl 5000009c<main>
50000020<halt>:
50000020: eafffffe b 50000020<halt>
50000024<test>:
50000024: e1a0f00e mov pc,lr
50000028: 07e00400 strbeq r0,[r0,r0,lsl#8]!
5000002c: 00002541 andeq r2,r0,r1,asr#10
50000030: 61656100 cmnvs r5,r0,lsl#2
50000034: 01006962 tsteq r0,r2,ror#18
50000038: 0000001b andeq r0,r0,fp,lslr0
5000003c: 4d524105 ldfmie f4,[r2,#-20] ;0xffffffec
50000040: 36373131 undefinedinstruction0x36373131
50000044: 2d465a4a vstrcs s11,[r6,#-296] ;0xfffffed8
50000048: 09060053 stmdbeq r6,{r0,r1,r4,r6}
5000004c: 01090108 tsteq r9,r8,lsl#2
50000050: 0000020a andeq r0,r0,sl,lsl#4
50000054<delay>:
50000054: e52db004 push {fp} ;(strfp,[sp,#-4]!)
50000058: e28db000 add fp,sp,#0
5000005c: e24dd00c sub sp,sp,#12
50000060: e3a03a01 mov r3,#4096 ;0x1000
50000064: e50b3008 str r3,[fp,#-8]
50000068: e1a00000 nop ;(movr0,r0)
5000006c: e51b3008 ldr r3,[fp,#-8]
50000070: e3530000 cmp r3,#0
50000074: 03a02000 moveq r2,#0
50000078: 13a02001 movne r2,#1
5000007c: e6ef2072 uxtb r2,r2
50000080: e2433001 sub r3,r3,#1
50000084: e50b3008 str r3,[fp,#-8]
50000088: e3520000 cmp r2,#0
5000008c: 1afffff6 bne 5000006c<delay+0x18>
50000090: e28bd000 add sp,fp,#0
50000094: e8bd0800 pop {fp}
50000098: e12fff1e bx lr
5000009c<main>:
5000009c: e92d4800 push {fp,lr}
500000a0: e28db004 add fp,sp,#4
500000a4: e24dd008 sub sp,sp,#8
500000a8: e59f3060 ldr r3,[pc,#96] ;50000110<main+0x74>
500000ac: e50b3008 str r3,[fp,#-8]
500000b0: e59f305c ldr r3,[pc,#92] ;50000114<main+0x78>
500000b4: e50b300c str r3,[fp,#-12]
500000b8: e51b3008 ldr r3,[fp,#-8]
500000bc: e59f2054 ldr r2,[pc,#84] ;50000118<main+0x7c>
500000c0: e5832000 str r2,[r3]
500000c4: e59f3050 ldr r3,[pc,#80] ;5000011c<main+0x80>
500000c8: e5933000 ldr r3,[r3]
500000cc: e1a02003 mov r2,r3
500000d0: e51b300c ldr r3,[fp,#-12]
500000d4: e5832000 str r2,[r3]
500000d8: e59f303c ldr r3,[pc,#60] ;5000011c<main+0x80>
500000dc: e5933000 ldr r3,[r3]
500000e0: e2832001 add r2,r3,#1
500000e4: e59f3030 ldr r3,[pc,#48] ;5000011c<main+0x80>
500000e8: e5832000 str r2,[r3]
500000ec: e59f3028 ldr r3,[pc,#40] ;5000011c<main+0x80>
500000f0: e5933000 ldr r3,[r3]
500000f4: e3530010 cmp r3,#16
500000f8: 1a000002 bne 50000108<main+0x6c>
500000fc: e59f3018 ldr r3,[pc,#24] ;5000011c<main+0x80>
50000100: e3a02000 mov r2,#0
50000104: e5832000 str r2,[r3]
50000108: ebffffd1 bl 50000054<delay>
5000010c: eaffffec b 500000c4<main+0x28>
50000110: 7f008800 svcvc 0x00008800
50000114: 7f008808 svcvc 0x00008808
50000118: 00001111 andeq r1,r0,r1,lslr1
5000011c: 50000124 andpl r0,r0,r4,lsr#2
Disassemblyofsection.data:
50000120<j>:
50000120: 12345678 eorsne r5,r4,#125829120 ;0x7800000
Disassemblyofsection.bss:
50000124<i>:
50000124: 00000000 andeq r0,r0,r0
50000128<k>:
50000128: 00000000 andeq r0,r0,r0
5000012c<g>:
5000012c: 00000000 andeq r0,r0,r0
Disassemblyofsection.comment:
00000000<.comment>:
0: 3a434347 bcc 10d0d24<_start-0x4ef2f2dc>
4: 74632820 strbtvc r2,[r3],#-2080 ;0x820
8: 312d676e teqcc sp,lr,ror#14
c: 312e382e teqcc lr,lr,lsr#16
10: 2941462d stmdbcs r1,{r0,r2,r3,r5,r9,sl,lr}^
14: 352e3420 strcc r3,[lr,#-1056]! ;0x420
18: Address0x00000018isoutofbounds.
首地址为0
Disassemblyofsection.ARM.attributes:
00000000<.ARM.attributes>:
0: 00003341 andeq r3,r0,r1,asr#6
4: 61656100 cmnvs r5,r0,lsl#2
8: 01006962 tsteq r0,r2,ror#18
c: 00000029 andeq r0,r0,r9,lsr#32
10: 4d524105 ldfmie f4,[r2,#-20] ;0xffffffec
14: 36373131 undefinedinstruction0x36373131
18: 2d465a4a vstrcs s11,[r6,#-296] ;0xfffffed8
1c: 09060053 stmdbeq r6,{r0,r1,r4,r6}
20: 01090108 tsteq r9,r8,lsl#2
24: 0412020a ldreq r0,[r2],#-522 ;0x20a
28: 01150114 tsteq r5,r4,lslr1
2c: 01180317 tsteq r8,r7,lslr3
30: 031b021a tsteq fp,#-1610612735 ;0xa0000001
led.elf:fileformatelf32-littlearm
Disassemblyofsection.text:
00000000<_start>:
0:e3a00207movr0,#1879048192;0x70000000
4:e3800013orrr0,r0,#19
8:ee0f0f92mcr15,0,r0,cr15,cr2,{4}
/*
Bltest的机器码eb00,0006
1110,1011,000000000000000000000110
--------------------------------------------------------------
1确定b/bl
剩余为偏移量
Branchinstructioncontainsasigned2'scomplement24bitoffset.Thisisshiftedlefttwobits,signextendedto32
bits,andaddedtothePC.
偏移量offset6<<2=6*2*2=24
Pc=pc+24
=（当前指令+8）+24
=（c+8）+24=(12+8)+24=44=0x2c
*/
c:eb000006Bltestldrpc,=test
10:e59ff018ldrpc,[pc,#24];30<test+0x4>
14:e59f0018ldrr0,[pc,#24];34<test+0x8>
18:e3a01000movr1,#0
1c:e5801000strr1,[r0]
20:e3a0da02movsp,#8192;0x2000
24:eb00001fbla8<main>
00000020<halt>:
20: eafffffe b 20<halt>
/*跳转到此位置*/
0000002c<test>:
2c:e1a0f00emovpc,lr
30:0000002candeqr0,r0,ip,lsr#32
34:07e00400strbeqr0,[r0,r0,lsl#8]!
38:00002541andeqr2,r0,r1,asr#10
3c:61656100cmnvsr5,r0,lsl#2
40:01006962tsteqr0,r2,ror#18
44:0000001bandeqr0,r0,fp,lslr0
48:4d524105ldfmief4,[r2,#-20];0xffffffec
4c:36373131undefinedinstruction0x36373131
50:2d465a4avstrcss11,[r6,#-296];0xfffffed8
54:09060053stmdbeqr6,{r0,r1,r4,r6}
58:01090108tsteqr9,r8,lsl#2
5c:0000020aandeqr0,r0,sl,lsl#4
00000054<delay>:
54: e52db004 push {fp} ;(strfp,[sp,#-4]!)
58: e28db000 add fp,sp,#0
5c: e24dd00c sub sp,sp,#12
60: e3a03a01 mov r3,#4096 ;0x1000
64: e50b3008 str r3,[fp,#-8]
68: e1a00000 nop ;(movr0,r0)
6c: e51b3008 ldr r3,[fp,#-8]
70: e3530000 cmp r3,#0
74: 03a02000 moveq r2,#0
78: 13a02001 movne r2,#1
7c: e6ef2072 uxtb r2,r2
80: e2433001 sub r3,r3,#1
84: e50b3008 str r3,[fp,#-8]
88: e3520000 cmp r2,#0
8c: 1afffff6 bne 6c<delay+0x18>
90: e28bd000 add sp,fp,#0
94: e8bd0800 pop {fp}
98: e12fff1e bx lr
0000009c<main>:
9c: e92d4800 push {fp,lr}
a0: e28db004 add fp,sp,#4
a4: e24dd008 sub sp,sp,#8
a8: e59f3060 ldr r3,[pc,#96] ;110<main+0x74>
ac: e50b3008 str r3,[fp,#-8]
b0: e59f305c ldr r3,[pc,#92] ;114<main+0x78>
b4: e50b300c str r3,[fp,#-12]
b8: e51b3008 ldr r3,[fp,#-8]
bc: e59f2054 ldr r2,[pc,#84] ;118<main+0x7c>
c0: e5832000 str r2,[r3]
c4: e59f3050 ldr r3,[pc,#80] ;11c<main+0x80>
c8: e5933000 ldr r3,[r3]
cc: e1a02003 mov r2,r3
d0: e51b300c ldr r3,[fp,#-12]
d4: e5832000 str r2,[r3]
d8: e59f303c ldr r3,[pc,#60] ;11c<main+0x80>
dc: e5933000 ldr r3,[r3]
e0: e2832001 add r2,r3,#1
e4: e59f3030 ldr r3,[pc,#48] ;11c<main+0x80>
e8: e5832000 str r2,[r3]
ec: e59f3028 ldr r3,[pc,#40] ;11c<main+0x80>
f0: e5933000 ldr r3,[r3]
f4: e3530010 cmp r3,#16
f8: 1a000002 bne 108<main+0x6c>
fc: e59f3018 ldr r3,[pc,#24] ;11c<main+0x80>
100: e3a02000 mov r2,#0
104: e5832000 str r2,[r3]
108: ebffffd1 bl 54<delay>
10c: eaffffec b c4<main+0x28>
110: 7f008800 svcvc 0x00008800
114: 7f008808 svcvc 0x00008808
118: 00001111 andeq r1,r0,r1,lslr1
11c: 00000124andeq r0,r0,r4,lsr#2
Disassemblyofsection.data:
00000120<j>:
120: 12345678 eorsne r5,r4,#125829120 ;0x7800000
Disassemblyofsection.bss:
00000124<i>:
124: 00000000 andeq r0,r0,r0
00000128<k>:
128: 00000000 andeq r0,r0,r0
0000012c<g>:
12c: 00000000 andeq r0,r0,r0
Disassemblyofsection.comment:
00000000<.comment>:
0: 3a434347 bcc 10d0d24<bss_end+0x10d0bf4>
4: 74632820 strbtvc r2,[r3],#-2080 ;0x820
8: 312d676e teqcc sp,lr,ror#14
c: 312e382e teqcc lr,lr,lsr#16
10: 2941462d stmdbcs r1,{r0,r2,r3,r5,r9,sl,lr}^
14: 352e3420 strcc r3,[lr,#-1056]! ;0x420
18: Address0x00000018isoutofbounds.
Disassemblyofsection.ARM.attributes:
00000000<.ARM.attributes>:
0: 00003341 andeq r3,r0,r1,asr#6
4: 61656100 cmnvs r5,r0,lsl#2
8: 01006962 tsteq r0,r2,ror#18
c: 00000029 andeq r0,r0,r9,lsr#32
10: 4d524105 ldfmie f4,[r2,#-20] ;0xffffffec
14: 36373131 undefinedinstruction0x36373131
18: 2d465a4a vstrcs s11,[r6,#-296] ;0xfffffed8
1c: 09060053 stmdbeq r6,{r0,r1,r4,r6}
20: 01090108 tsteq r9,r8,lsl#2
24: 0412020a ldreq r0,[r2],#-522 ;0x20a
28: 01150114 tsteq r5,r4,lslr1
2c: 01180317 tsteq r8,r7,lslr3
30: 031b021a tsteq fp,#-1610612735 ;0xa0000001