prob3.c 핸드레이

prob3.c

Dump of assembler code for function main:
0x8048400 <main>:    push   %ebp //복귀주소 
0x8048401 <main+1>:    mov    %ebp,%esp
0x8048403 <main+3>:    sub    %esp,32 //32바이트 공간 할당 
 
0x8048406 <main+6>:    push   %edi //백업
0x8048407 <main+7>:    push   %esi //백업
0x8048408 <main+8>:    push   %ebx //백업
 
0x8048409 <main+9>:    mov    DWORD PTR [%ebp-4],0xa // a = 10 
0x8048410 <main+16>:    lea    %edi,[%ebp-28] // edi = ebp-28
0x8048413 <main+19>:    mov    %esi,0x8048510 //esi = "ABCDEFGHIJKLMNOP"
0x8048418 <main+24>:    cld    //direction flag = 0 
0x8048419 <main+25>:    mov    %ecx,0x4 //ecx = 0x4 아래 반복을 위함 
0x804841e <main+30>:    repz movs %es:(%edi),%ds:(%esi)//4바이트씩 처리
//repz(repe)  ->  cx가 0이 아닌동안, 비교가 같지 않은 동안 반복
//movs Source에서 Destination으로 데이터복사 
//ecx가 4이므로 총 4바이트씩 4번 16바이트를 처리 
 
0x8048420 <main+32>:    movs   %es:(%edi),%ds:(%esi) //?? 왜 한번에 안했지?? 
//ds(esi)에서 es(edi)로 데이터 복사 
 
 
0x8048421 <main+33>:    lea    %eax,[%ebp-11]
0x8048424 <main+36>:    push   3
0x8048426 <main+38>:    push   0
0x8048428 <main+40>:    push   %eax
0x8048429 <main+41>:    call   0x8048340 <memset> //memset([17],0,3) 
0x804842e <main+46>:    add    %esp,12
 
 
////////초기식///////////
0x8048431 <main+49>:    mov    DWORD PTR [%ebp-8],0x0 //ebp-8 = 0
/////////조건식////////////
0x8048438 <main+56>:    cmp    DWORD PTR [%ebp-8],15 //i와 15비교 
0x804843c <main+60>:    jle    0x8048440 <main+64> //왼쪽(0)이 작으면 아래 건너뜀 
0x804843e <main+62>:    jmp    0x80484a0 <main+160> //출력으로 점프
///////////////반복문 시작 ///////////////////// 
0x8048440 <main+64>:    mov    %eax,DWORD PTR [%ebp-8] //eax = i
0x8048443 <main+67>:    mov    %edx,%eax //edx = eax = i
0x8048445 <main+69>:    and    %edx,1 //edx = 홀수이면 1 짝수면 0 
0x8048448 <main+72>:    test   %edx,%edx //edx가 0인지 확인
0x804844a <main+74>:    jne    0x8048471 <main+113> //0이 아니면 점프
  
//짝수                                                                                                                                                                
0x804844c <main+76>:    lea    %eax,[%ebp-28] //eax = 문자열 주소 
0x804844f <main+79>:    mov    %edx,DWORD PTR [%ebp-8] //edx = i의 값 
0x8048452 <main+82>:    lea    %ecx,[%ebp-28] //ecx = 문자열 주소 
0x8048455 <main+85>:    mov    DWORD PTR [%ebp-32],%ecx //int tmp = 문자열주소 
0x8048458 <main+88>:    mov    %ebx,DWORD PTR [%ebp-8] //ebx = i값 
0x804845b <main+91>:    mov    %ecx,DWORD PTR [%ebp-32] //ecx = tmp의 값
0x804845e <main+94>:    mov    %cl,BYTE PTR [%ebx+%ecx] //cl = [문자열주소+i]의 문자 
0x8048461 <main+97>:    mov    BYTE PTR [%ebp-32],%cl //tmp = cl
0x8048464 <main+100>:    mov    %bl,BYTE PTR [%ebp-8] //bl = i의 값 
0x8048467 <main+103>:    mov    %cl,BYTE PTR [%ebp-32] //cl = tmp의 값
 
0x804846a <main+106>:    add    %cl,%bl //cl = cl+bl (tmp + i)
0x804846c <main+108>:    mov    BYTE PTR [%edx+%eax],%cl //[edx+eax] = cl
0x804846f <main+111>:    jmp    0x8048494 <main+148>
 
//홀수 
0x8048471 <main+113>:    lea    %eax,[%ebp-28] //eax = ebp-28
0x8048474 <main+116>:    mov    %edx,DWORD PTR [%ebp-8] //edx = [ebp-8]의 값 
0x8048477 <main+119>:    lea    %ecx,[%ebp-28] //ecx = ebp-28
0x804847a <main+122>:    mov    DWORD PTR [%ebp-32],%ecx //[ebp-32] = ebp-28
0x804847d <main+125>:    mov    %ebx,DWORD PTR [%ebp-8] //ebx = [ebp-8]의 값
0x8048480 <main+128>:    mov    %ecx,DWORD PTR [%ebp-32] //ecx = [ebp-32]의 값
0x8048483 <main+131>:    mov    %cl,BYTE PTR [%ebx+%ecx] //cl = [ebx+ecx]의 값
0x8048486 <main+134>:    mov    BYTE PTR [%ebp-32],%cl //[ebp-32] = cl
0x8048489 <main+137>:    mov    %bl,BYTE PTR [%ebp-8] //bl = [ebp-8]의 값
0x804848c <main+140>:    mov    %cl,BYTE PTR [%ebp-32] //cl = [ebp-32]의 값
0x804848f <main+143>:    sub    %cl,%bl //cl = cl+bl
0x8048491 <main+145>:    mov    BYTE PTR [%edx+%eax],%cl //[edx+eax] = cl
 
0x8048494 <main+148>:    inc    DWORD PTR [%ebp-8] //[ebp-8]++ -> 아마 for문 증가문 
0x8048497 <main+151>:    jmp    0x8048438 <main+56> //아마 반복문? 
//////////////반복문 끝//////// 
 
 
// 명령어파이프라인 -> 효율적 처리를 위함 
0x8048499 <main+153>:    lea    %esi,[%esi*1]
 
0x80484a0 <main+160>:    lea    %eax,[%ebp-28] //eax = ebp-28
0x80484a3 <main+163>:    push   %eax 
0x80484a4 <main+164>:    push   0x8048521 //"%s\n" 
0x80484a9 <main+169>:    call   0x8048330 <printf> // 
0x80484ae <main+174>:    add    %esp,8
 
 
0x80484b1 <main+177>:    lea    %esp,[%ebp-44]
0x80484b4 <main+180>:    pop    %ebx
0x80484b5 <main+181>:    pop    %esi
0x80484b6 <main+182>:    pop    %edi
0x80484b7 <main+183>:    leave  
0x80484b8 <main+184>:    ret
 
(gdb) x/s 0x8048510
0x8048510 <_IO_stdin_used+4>:     "ABCDEFGHIJKLMNOP"
 
(gdb) x/s 0x8048521
0x8048521 <_IO_stdin_used+21>:     "%s\n"

핸드레이

#include<stdio.h>
#include<string.h>
 
int main(){
    int i;
    int a=10;
    char arr[20]="ABCDEFGHIJKLMNOP";
    
    memset(&arr[17],0,3);
    
    for(i=0;i<=15;i++){
        if(i%2==0){
            arr[i]+=i;
        }else{
            arr[i]-=i;
        }
    }
    
    printf("%s",arr); 
    return 0;
}