[Layer7] 2026년 5월 13일 리버싱 1차시 과제

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}

imnyang@mizuki:workspaces/temp/layer7 > gcc -E main.c -o main.i
imnyang@mizuki:workspaces/temp/layer7 > cat main.i
# 0 "main.c"
# 0 "<built-in>"
# 0 "<command-line>"
# 1 "/nix/store/fbbw928argckfii0j322346ihmllg7a7-glibc-2.42-61-dev/include/stdc-predef.h" 1 3 4
# 0 "<command-line>" 2
# 1 "main.c"
# 1 "/nix/store/fbbw928argckfii0j322346ihmllg7a7-glibc-2.42-61-dev/include/stdio.h" 1 3 4
# 28 "/nix/store/fbbw928argckfii0j322346ihmllg7a7-glibc-2.42-61-dev/include/stdio.h" 3 4
# 1 "/nix/store/fbbw928argckfii0j322346ihmllg7a7-glibc-2.42-61-dev/include/bits/libc-header-start.h" 1 3 4
# 33 "/nix/store/fbbw928argckfii0j322346ihmllg7a7-glibc-2.42-61-dev/include/bits/libc-header-start.h" 3 4
...

imnyang@mizuki:workspaces/temp/layer7 > gcc -S main.i -o main.s
imnyang@mizuki:workspaces/temp/layer7 > bat main.s
─────┬─────────────────────────────────────────────────────────────────────────────────────────────────────
     │ File: main.s
─────┼─────────────────────────────────────────────────────────────────────────────────────────────────────
   1 │     .file   "main.c"
   2 │     .text
   3 │     .section    .rodata
   4 │ .LC0:
   5 │     .string "Hello, World!"
   6 │     .text
   7 │     .globl  main
   8 │     .type   main, @function
   9 │ main:
  10 │ .LFB0:
  11 │     .cfi_startproc
  12 │     pushq   %rbp
  13 │     .cfi_def_cfa_offset 16
  14 │     .cfi_offset 6, -16
  15 │     movq    %rsp, %rbp
  16 │     .cfi_def_cfa_register 6
  17 │     leaq    .LC0(%rip), %rax
  18 │     movq    %rax, %rdi
  19 │     movl    $0, %eax
  20 │     call    printf@PLT
  21 │     movl    $0, %eax
  22 │     popq    %rbp
  23 │     .cfi_def_cfa 7, 8
  24 │     ret
  25 │     .cfi_endproc
  26 │ .LFE0:
  27 │     .size   main, .-main
  28 │     .ident  "GCC: (GNU) 15.2.0"
  29 │     .section    .note.GNU-stack,"",@progbits
─────┴─────────────────────────────────────────────────────────────────────────────────────────────────────

imnyang@mizuki:workspaces/temp/layer7 > gcc -c main.s -o main.o
imnyang@mizuki:workspaces/temp/layer7 > bat main.o | head -n10
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                                                                       x�t

imnyang@mizuki:workspaces/temp/layer7 > gcc main.o -o main
imnyang@mizuki:workspaces/temp/layer7 > bat main | head -n10
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section .data
    msg db 'Hello, World!', 0

section .text
    global _start

_start:
    mov rax, 4
    mov rdi, 1
    mov rsi, msg
    mov rdx, 14
    syscall

    mov rax, 60
    mov rdi, 0
    syscall

mov rax, 3

48 C7 C0 03 00 00 00

section .data
    newline db 10

section .bss
    num1 resb 2
    num2 resb 2
    result resb 2

section .text
    global _start

_start:
    mov rax, 0
    mov rdi, 0
    mov rsi, num1
    mov rdx, 2
    syscall ; 첫번째 입력

    mov rax, 0
    mov rdi, 0
    mov rsi, num2
    mov rdx, 2
    syscall; 두번째 숫자 입력

    mov r8b, [num1]
    sub r8b, '0'      ; r8b(num1)를 숫자로 변환
    mov r9b, [num2]
    sub r9b, '0'      ; r9b(num2)를 숫자로 변환

    mov al, r8b       ; r8b(num1)를 al로 복사
    add al, r9b       ; r8b(num1) + r9b(num2)
    call _print

    mov al, r8b       ; r8b(num1)를 al로 복사
    sub al, r9b       ; r8b(num1) - r9b(num2)
    call _print

    mov al, r8b       ; r8b(num1)를 al로 복사
    mul r9b           ; r8b * r9b
    call _print

    movzx ax, r8b     ; r8b(num1)를 ax로 확장 (ah를 0으로 자동 초기화)
    div r9b           ; ax / r9b 수행
    call _print

    ; 종료
    mov rax, 60
    xor rdi, rdi
    syscall

_print:
    add al, '0'
    mov [result], al

    mov rax, 1
    mov rdi, 1
    mov rsi, result
    mov rdx, 1
    syscall         ; 결과 출력

    mov rax, 1
    mov rdi, 1
    mov rsi, newline
    mov rdx, 1
    syscall         ; 줄바꿈 출력

    ret             ; 함수 종료