- 现在实现下面功能：
- 实现字符串拷贝，当程序开始执行时，先有_start标号进入汇编文件，然后跳入main函数，将字符串拷贝函数的定义放在汇编文件中，在c中调用。
- 目录结构：
strcpy.s
1: .global _start 2: .global mystrcpy 3: 4: _start: 5: B main 6: mystrcpy: 7: mov r2,#0 8: ldrb r2, [r0]; 9: strb r2, [r1] 10: cmp r2, #0 11: beq rr 12: add r0, #1 13: add r1, #1 14: b mystrcpy 15: rr: 16: moveq pc,lr 17:
strcpy.c
1: 2: char *source = "pengdonglin137@163.com";
3: 4: char dest[20] ="";
5: 6: extern void mystrcpy(char *src, char *dst);
7: 8: int main(void){
9: 10: mystrcpy(source, dest);11: while(1);
12: return 0;
13: }
Makefile
1: all: 2: arm-none-eabi-gcc -g -c strcpys.s -o mystrcpys.o // 3: arm-none-eabi-gcc -g -c strcpyc.c -o mystrcpyc.o 4: arm-none-eabi-ld -Ttext 0x20000 mystrcpys.o mystrcpyc.o -o mystrcpy.elf 5: arm-none-eabi-objdump -D mystrcpy.elf >p.dis //反汇编 6: clean: 7: rm -rf *.o *.elf *.dis 8:
S5PC100.init
target remote 127.0.0.1:3333 monitor reset halt
下面是反汇编：
1: 2: mystrcpy.elf: file format elf32-littlearm 3: 4: 5: Disassembly of section .text: 6: 7: 00020000 <_start>: 8: 20000: ea000008 b 20028 <main> //调到main函数，C语言中的函数名在汇编中就是一个标号 9: 10: 00020004 <mystrcpy>: 11: 20004: e3a02000 mov r2, #0 12: 20008: e5d02000 ldrb r2, [r0] 13: 2000c: e5c12000 strb r2, [r1] 14: 20010: e3520000 cmp r2, #0 15: 20014: 0a000002 beq 20024 <rr> 16: 20018: e2800001 add r0, r0, #1 17: 2001c: e2811001 add r1, r1, #1 18: 20020: eafffff7 b 20004 <mystrcpy> 19: 20: 00020024 <rr>: 21: 20024: 01a0f00e moveq pc, lr //将lr给pc，实现子程序的返回，lr在下面已经分析出来，是0x20044 22: 23: 00020028 <main>: 24: 20028: e92d4800 push {fp, lr} //main是非叶子函数，要保存lr 25: 2002c: e28db004 add fp, sp, #4 26: 20030: e59f3010 ldr r3, [pc, #16] ; 20048 <main+0x20> //执行该指令时，pc为0x20038,加16为0x20048,将0x20048单元内容给R3，即R3等于0x28068 27: 20034: e5933000 ldr r3, [r3] //将0x28068内容给r3,为0x20050 28: 20038: e1a00003 mov r0, r3 //r0为0x20050 29: 2003c: e59f1008 ldr r1, [pc, #8] ; 2004c <main+0x24> //pc为0x20044，加8，为0x2004c,r1为0x2806c 30: 20040: ebffffef bl 20004 <mystrcpy> //跳到0x20004（即函数mystrcpy的地址，就是汇编中的标号），pc为0x20048，pc存到lr，lr同时自减4，为0x20044 31: 20044: eafffffe b 20044 <main+0x1c> 32: 20048: 00028068 andeq r8, r2, r8, rrx 33: 2004c: 0002806c andeq r8, r2, ip, rrx 34: 35: Disassembly of section .rodata: 36: 37: 00020050 <.rodata>: 38: 20050: 676e6570 ; <UNDEFINED> instruction: 0x676e6570 //0x70 ‘p’ 0x65 ‘e’ 0x6e ‘n’ 0x67 ‘g’ 39: 20054: 676e6f64 strbvs r6, [lr, -r4, ror #30]! 40: 20058: 316e696c cmncc lr, ip, ror #18 41: 2005c: 31403733 cmpcc r0, r3, lsr r7 42: 20060: 632e3336 teqvs lr, #-671088640 ; 0xd8000000 43: 20064: 00006d6f andeq r6, r0, pc, ror #26 44: 45: Disassembly of section .data: 46: 47: 00028068 <__data_start>: 48: 28068: 00020050 andeq r0, r2, r0, asr r0 49: 50: Disassembly of section .bss: 51: 52: 0002806c <dest>: 53: ... 54: 55: Disassembly of section .comment: 56: 57: 00000000 <.comment>: 58: 0: 3a434347 bcc 10d0d24 <_stack+0x1050d24> 59: 4: 4e472820 cdpmi 8, 4, cr2, cr7, cr0, {1} 60: 8: 34202955 strtcc r2, [r0], #-2389 ; 0x955 61: c: 322e362e eorcc r3, lr, #48234496 ; 0x2e00000 62: ... 63: 64: Disassembly of section .debug_aranges: 65: 66: 00000000 <.debug_aranges>: 67: 0: 0000001c andeq r0, r0, ip, lsl r0 68: 4: 00000002 andeq r0, r0, r2 69: 8: 00040000 andeq r0, r4, r0 70: c: 00000000 andeq r0, r0, r0 71: 10: 00020000 andeq r0, r2, r0 72: 14: 00000028 andeq r0, r0, r8, lsr #32 73: ... 74: 20: 0000001c andeq r0, r0, ip, lsl r0 75: 24: 004d0002 subeq r0, sp, r2 76: 28: 00040000 andeq r0, r4, r0 77: 2c: 00000000 andeq r0, r0, r0 78: 30: 00020028 andeq r0, r2, r8, lsr #32 79: 34: 00000028 andeq r0, r0, r8, lsr #32 80: ... 81: 82: Disassembly of section .debug_info: 83: 84: 00000000 <.debug_info>: 85: 0: 00000049 andeq r0, r0, r9, asr #32 86: 4: 00000002 andeq r0, r0, r2 87: 8: 01040000 mrseq r0, (UNDEF: 4) 88: c: 00000000 andeq r0, r0, r0 89: 10: 00020000 andeq r0, r2, r0 90: 14: 00020028 andeq r0, r2, r8, lsr #32 91: 18: 63727473 cmnvs r2, #1929379840 ; 0x73000000 92: 1c: 2e737970 mrccs 9, 3, r7, cr3, cr0, {3} 93: 20: 3a440073 bcc 11001f4 <_stack+0x10801f4> 94: 24: 6c63655c cfstr64vs mvdx6, [r3], #-368 ; 0xfffffe90 95: 28: 65737069 ldrbvs r7, [r3, #-105]! ; 0x69 96: 2c: 6f72705f svcvs 0x0072705f 97: 30: 7463656a strbtvc r6, [r3], #-1386 ; 0x56a 98: 34: 796d5c73 stmdbvc sp!, {r0, r1, r4, r5, r6, sl, fp, ip, lr}^ 99: 38: 63727473 cmnvs r2, #1929379840 ; 0x73000000 100: 3c: 47007970 smlsdxmi r0, r0, r9, r7 101: 40: 4120554e teqmi r0, lr, asr #10 102: 44: 2e322053 mrccs 0, 1, r2, cr2, cr3, {2} 103: 48: 01003132 tsteq r0, r2, lsr r1 104: 4c: 0000a480 andeq sl, r0, r0, lsl #9 105: 50: 14000200 strne r0, [r0], #-512 ; 0x200 106: 54: 04000000 streq r0, [r0] 107: 58: 00000001 andeq r0, r0, r1 108: 5c: 00250100 eoreq r0, r5, r0, lsl #2 109: 60: 002f0000 eoreq r0, pc, r0 110: 64: 00280000 eoreq r0, r8, r0 111: 68: 00500002 subseq r0, r0, r2 112: 6c: 00400002 subeq r0, r0, r2 113: 70: 01020000 mrseq r0, (UNDEF: 2) 114: 74: 0000004c andeq r0, r0, ip, asr #32 115: 78: 3e010801 cdpcc 8, 0, cr0, cr1, cr1, {0} 116: 7c: 28000000 stmdacs r0, {} ; <UNPREDICTABLE> 117: 80: 50000200 andpl r0, r0, r0, lsl #4 118: 84: 00000200 andeq r0, r0, r0, lsl #4 119: 88: 03000000 movweq r0, #0 120: 8c: 6e690504 cdpvs 5, 6, cr0, cr9, cr4, {0} 121: 90: 0c040074 stceq 0, cr0, [r4], {116} ; 0x74 122: 94: 01000000 mrseq r0, (UNDEF: 0) 123: 98: 00005202 andeq r5, r0, r2, lsl #4 124: 9c: 05010100 streq r0, [r1, #-256] ; 0x100 125: a0: 00005804 andeq r5, r0, r4, lsl #16 126: a4: 08010600 stmdaeq r1, {r9, sl} 127: a8: 00000051 andeq r0, r0, r1, asr r0 128: ac: 00005807 andeq r5, r0, r7, lsl #16 129: b0: 00006f00 andeq r6, r0, r0, lsl #30 130: b4: 006f0800 rsbeq r0, pc, r0, lsl #16 131: b8: 00130000 andseq r0, r3, r0 132: bc: 13070406 movwne r0, #29702 ; 0x7406 133: c0: 04000000 streq r0, [r0] 134: c4: 00000020 andeq r0, r0, r0, lsr #32 135: c8: 005f0401 subseq r0, pc, r1, lsl #8 136: cc: 01010000 mrseq r0, (UNDEF: 1) 137: d0: 00000c09 andeq r0, r0, r9, lsl #24 138: d4: 52020100 andpl r0, r2, #0 139: d8: 01000000 mrseq r0, (UNDEF: 0) 140: dc: 80680305 rsbhi r0, r8, r5, lsl #6 141: e0: 20090002 andcs r0, r9, r2 142: e4: 01000000 mrseq r0, (UNDEF: 0) 143: e8: 00005f04 andeq r5, r0, r4, lsl #30 144: ec: 03050100 movweq r0, #20736 ; 0x5100 145: f0: 0002806c andeq r8, r2, ip, rrx 146: ... 147: 148: Disassembly of section .debug_abbrev: 149: 150: 00000000 <.debug_abbrev>: 151: 0: 10001101 andne r1, r0, r1, lsl #2 152: 4: 12011106 andne r1, r1, #-2147483647 ; 0x80000001 153: 8: 1b080301 blne 200c14 <_stack+0x180c14> 154: c: 13082508 movwne r2, #34056 ; 0x8508 155: 10: 00000005 andeq r0, r0, r5 156: 14: 25011101 strcs r1, [r1, #-257] ; 0x101 157: 18: 030b130e movweq r1, #45838 ; 0xb30e 158: 1c: 110e1b0e tstne lr, lr, lsl #22 159: 20: 10011201 andne r1, r1, r1, lsl #4 160: 24: 02000006 andeq r0, r0, #6 161: 28: 0c3f002e ldceq 0, cr0, [pc], #-184 ; ffffff78 <_stack+0xfff7ff78> 162: 2c: 0b3a0e03 bleq e83840 <_stack+0xe03840> 163: 30: 0c270b3b stceq 11, cr0, [r7], #-236 ; 0xffffff14 164: 34: 01111349 tsteq r1, r9, asr #6 165: 38: 06400112 ; <UNDEFINED> instruction: 0x06400112 166: 3c: 24030000 strcs r0, [r3] 167: 40: 3e0b0b00 vmlacc.f64 d0, d11, d0 168: 44: 0008030b andeq r0, r8, fp, lsl #6 169: 48: 00340400 eorseq r0, r4, r0, lsl #8 170: 4c: 0b3a0e03 bleq e83860 <_stack+0xe03860> 171: 50: 13490b3b movtne r0, #39739 ; 0x9b3b 172: 54: 0c3c0c3f ldceq 12, cr0, [ip], #-252 ; 0xffffff04 173: 58: 0f050000 svceq 0x00050000 174: 5c: 490b0b00 stmdbmi fp, {r8, r9, fp} 175: 60: 06000013 ; <UNDEFINED> instruction: 0x06000013 176: 64: 0b0b0024 bleq 2c00fc <_stack+0x2400fc> 177: 68: 0e030b3e vmoveq.16 d3[0], r0 178: 6c: 01070000 mrseq r0, (UNDEF: 7) 179: 70: 01134901 tsteq r3, r1, lsl #18 180: 74: 08000013 stmdaeq r0, {r0, r1, r4} 181: 78: 13490021 movtne r0, #36897 ; 0x9021 182: 7c: 00000b2f andeq r0, r0, pc, lsr #22 183: 80: 03003409 movweq r3, #1033 ; 0x409 184: 84: 3b0b3a0e blcc 2ce8c4 <_stack+0x24e8c4> 185: 88: 3f13490b svccc 0x0013490b 186: 8c: 000a020c andeq r0, sl, ip, lsl #4 187: ... 188: 189: Disassembly of section .debug_line: 190: 191: 00000000 <.debug_line>: 192: 0: 0000003c andeq r0, r0, ip, lsr r0 193: 4: 00200002 eoreq r0, r0, r2 194: 8: 01020000 mrseq r0, (UNDEF: 2) 195: c: 000d0efb strdeq r0, [sp], -fp 196: 10: 01010101 tsteq r1, r1, lsl #2 197: 14: 01000000 mrseq r0, (UNDEF: 0) 198: 18: 00010000 andeq r0, r1, r0 199: 1c: 63727473 cmnvs r2, #1929379840 ; 0x73000000 200: 20: 2e737970 mrccs 9, 3, r7, cr3, cr0, {3} 201: 24: 00000073 andeq r0, r0, r3, ror r0 202: 28: 05000000 streq r0, [r0] 203: 2c: 02000002 andeq r0, r0, #2 204: 30: 2f301600 svccs 0x00301600 205: 34: 2f2f2f2f svccs 0x002f2f2f 206: 38: 02302f2f eorseq r2, r0, #188 ; 0xbc 207: 3c: 01010002 tsteq r1, r2 208: 40: 00000039 andeq r0, r0, r9, lsr r0 209: 44: 00200002 eoreq r0, r0, r2 210: 48: 01020000 mrseq r0, (UNDEF: 2) 211: 4c: 000d0efb strdeq r0, [sp], -fp 212: 50: 01010101 tsteq r1, r1, lsl #2 213: 54: 01000000 mrseq r0, (UNDEF: 0) 214: 58: 00010000 andeq r0, r1, r0 215: 5c: 63727473 cmnvs r2, #1929379840 ; 0x73000000 216: 60: 2e637970 mcrcs 9, 3, r7, cr3, cr0, {3} 217: 64: 00000063 andeq r0, r0, r3, rrx 218: 68: 05000000 streq r0, [r0] 219: 6c: 02002802 andeq r2, r0, #131072 ; 0x20000 220: 70: 004c1900 subeq r1, ip, r0, lsl #18 221: 74: 9f010402 svcls 0x00010402 222: 78: 01000602 tsteq r0, r2, lsl #12223: 7c: Address 0x0000007c is out of bounds.
224: 225: 226: Disassembly of section .debug_frame: 227: 228: 00000000 <.debug_frame>: 229: 0: 0000000c andeq r0, r0, ip 230: 4: ffffffff ; <UNDEFINED> instruction: 0xffffffff 231: 8: 7c020001 stcvc 0, cr0, [r2], {1} 232: c: 000d0c0e andeq r0, sp, lr, lsl #24 233: 10: 00000018 andeq r0, r0, r8, lsl r0 234: 14: 00000000 andeq r0, r0, r0 235: 18: 00020028 andeq r0, r2, r8, lsr #32 236: 1c: 00000028 andeq r0, r0, r8, lsr #32 237: 20: 8e080e42 cdphi 14, 0, cr0, cr8, cr2, {2} 238: 24: 42028b01 andmi r8, r2, #1024 ; 0x400 239: 28: 00040b0c andeq r0, r4, ip, lsl #22 240: 241: Disassembly of section .debug_str: 242: 243: 00000000 <.debug_str>: 244: 0: 20554e47 subscs r4, r5, r7, asr #28 245: 4: 2e342043 cdpcs 0, 3, cr2, cr4, cr3, {2} 246: 8: 00322e36 eorseq r2, r2, r6, lsr lr 247: c: 72756f73 rsbsvc r6, r5, #460 ; 0x1cc 248: 10: 75006563 strvc r6, [r0, #-1379] ; 0x563 249: 14: 6769736e strbvs r7, [r9, -lr, ror #6]! 250: 18: 2064656e rsbcs r6, r4, lr, ror #10 251: 1c: 00746e69 rsbseq r6, r4, r9, ror #28 252: 20: 74736564 ldrbtvc r6, [r3], #-1380 ; 0x564 253: 24: 72747300 rsbsvc r7, r4, #0 254: 28: 63797063 cmnvs r9, #99 ; 0x63 255: 2c: 4400632e strmi r6, [r0], #-814 ; 0x32e 256: 30: 63655c3a cmnvs r5, #14848 ; 0x3a00 257: 34: 7370696c cmnvc r0, #1769472 ; 0x1b0000 258: 38: 72705f65 rsbsvc r5, r0, #404 ; 0x194 259: 3c: 63656a6f cmnvs r5, #454656 ; 0x6f000 260: 40: 6d5c7374 ldclvs 3, cr7, [ip, #-464] ; 0xfffffe30 261: 44: 72747379 rsbsvc r7, r4, #-469762047 ; 0xe4000001 262: 48: 00797063 rsbseq r7, r9, r3, rrx 263: 4c: 6e69616d powvsez f6, f1, #5.0 264: 50: 61686300 cmnvs r8, r0, lsl #6265: 54: Address 0x00000054 is out of bounds.
266: 267: 268: Disassembly of section .debug_loc: 269: 270: 00000000 <.debug_loc>: 271: 0: 00000000 andeq r0, r0, r0 272: 4: 00000004 andeq r0, r0, r4 273: 8: 007d0002 rsbseq r0, sp, r2 274: c: 00000004 andeq r0, r0, r4 275: 10: 00000008 andeq r0, r0, r8 276: 14: 087d0002 ldmdaeq sp!, {r1}^ 277: 18: 00000008 andeq r0, r0, r8 278: 1c: 00000028 andeq r0, r0, r8, lsr #32 279: 20: 047b0002 ldrbteq r0, [fp], #-2 280: ... 281: 282: Disassembly of section .ARM.attributes: 283: 284: 00000000 <_stack-0x80000>: 285: 0: 00002d41 andeq r2, r0, r1, asr #26 286: 4: 61656100 cmnvs r5, r0, lsl #2 287: 8: 01006962 tsteq r0, r2, ror #18 288: c: 00000023 andeq r0, r0, r3, lsr #32 289: 10: 4d524105 ldfmie f4, [r2, #-20] ; 0xffffffec 290: 14: 4d445437 cfstrdmi mvd5, [r4, #-220] ; 0xffffff24 291: 18: 02060049 andeq r0, r6, #73 ; 0x49 292: 1c: 01090108 tsteq r9, r8, lsl #2 293: 20: 01140412 tsteq r4, r2, lsl r4 294: 24: 03170115 tsteq r7, #1073741829 ; 0x40000005 295: 28: 011a0118 tsteq sl, r8, lsl r1296: 2c: Address 0x0000002c is out of bounds.
297: