C语言与64位汇编对应关系

小咪咪 2022-09-11 07:17 187阅读 0赞

#include <stdio.h>
    
    int global;
    int func_op(void) {
         return 0; }
    
    void func(void)
    {
        
    	unsigned long long val64 = 0;
    
    	val64 = 0xffffeeeeddddcccc;  // 7
    	global = 0x5555;  // 8
    }
    #define MAX_WORD 16
    
    int main(void)
    {
        
    	unsigned int i = 0;
    	char words[MAX_WORD] = "Hello World";
    	char word;
    
    	int (*func_pointer)(void) = &func_op;
    
    	i = 0xabcd;  // 1
    
    	if (i != 0x1234)  // 2
    		i = 0;  // 3
    
    	while (i == 0)  // 4
    	{
        
    		i++;  // 5
    	}
    
    	func();  // 6
    	i = func_pointer();  // 9
    
    	for (i = 0; i < MAX_WORD - 1; i++)  // 10
    		word = words[i];  // 11
    
    	return 0;  // 12
    }

$ gcc -Wall -o0 assemble.c -o assemble
    ⨯
    assemble.c: In function ‘func’:
    assemble.c:8:21: warning: variable ‘val64’ set but not used [-Wunused-but-set-variable]
        8 |  unsigned long long val64 = 0;
          |                     ^~~~~
    assemble.c: In function ‘main’:
    assemble.c:19:7: warning: variable ‘word’ set but not used [-Wunused-but-set-variable]
       19 |  char word;
          |       ^~~~

![1][]

$ objdump -d --no-show-raw-insn assemble
    # --no-show-raw-insn 使其不输出机器语言
    
    assemble:     file format elf64-x86-64
    
    
    Disassembly of section .init:
    
    ......
    
    0000000000001130 <func>:
        1130:       push   %rbp
        1131:       mov    %rsp,%rbp
        1134:       movq   $0x0,-0x8(%rbp)
        113c:       movabs $0xffffeeeeddddcccc,%rax  # val64 = 0xffffeeeeddddcccc;  // 7
        1146:       mov    %rax,-0x8(%rbp)
        114a:       movl   $0x5555,0x2ed8(%rip)        # 402c <global>  global = 0x5555;  // 8
        1154:       nop
        1155:       pop    %rbp
        1156:       ret    
    
    0000000000001157 <main>:
        1157:       push   %rbp
        1158:       mov    %rsp,%rbp  # 初始化栈，对应()
        115b:       sub    $0x30,%rsp
        115f:       movl   $0x0,-0x4(%rbp)
        1166:       movabs $0x6f57206f6c6c6548,%rax
        1170:       mov    $0x646c72,%edx
        1175:       mov    %rax,-0x30(%rbp)
        1179:       mov    %rdx,-0x28(%rbp)
        117d:       lea    -0x5f(%rip),%rax        # 1125 <func_op>
        1184:       mov    %rax,-0x10(%rbp)
        # 设置变量的值
        1188:       movl   $0xabcd,-0x4(%rbp)  # i = 0xabcd;  // 1
        
        # if比较
        118f:       cmpl   $0x1234,-0x4(%rbp)  # if (i != 0x1234)  // 2
        1196:       je     11a5 <main+0x4e>  # 如果相等
        1198:       movl   $0x0,-0x4(%rbp)  # i = 0;  // 3
        119f:       jmp    11a5 <main+0x4e>  # 跳转  // 2
        
        # while
        11a1:       addl   $0x1,-0x4(%rbp)  # i++;  // 5
        11a5:       cmpl   $0x0,-0x4(%rbp)
        11a9:       je     11a1 <main+0x4a>
        
        # 函数调用call
        11ab:       call   1130 <func>  # func();  // 6
        11b0:       mov    -0x10(%rbp),%rax
        # 函数指针调用
        11b4:       call   *%rax  # i = func_pointer();  // 9
        11b6:       mov    %eax,-0x4(%rbp)
    
        # for
        11b9:       movl   $0x0,-0x4(%rbp)  # word = words[i];  // 11
        11c0:       jmp    11d1 <main+0x7a>
        11c2:       mov    -0x4(%rbp),%eax
        # 数组操作：movzbl
        11c5:       movzbl -0x30(%rbp,%rax,1),%eax
        11ca:       mov    %al,-0x11(%rbp)
        11cd:       addl   $0x1,-0x4(%rbp)
        11d1:       cmpl   $0xe,-0x4(%rbp)
        
        11d5:       jbe    11c2 <main+0x6b>
        # 返回值设置，返回值放到eax
        11d7:       mov    $0x0,%eax  # return 0;  // 12
        11dc:       leave  
        11dd:       ret    
        11de:       xchg   %ax,%ax
    
    ......

[1]: /images/20220828/ac0d9822e63a4ba4a860d50f116f823e.png