Assembly language (8) x86 inline assembly

1 One-line assembly

#include <stdio.h>
#include <stdlib.h>

int main()
{
    
	int nNum = 0;
	_asm mov nNum, 100
	printf("%d\n", nNum);
	system("pause");
	return 0;
}

2 multi-line assembly

2.1 库函数

#include <stdio.h>
#include <stdlib.h>

int main()
{
    
	char * szFormat = "%d\n";
	int nNum = 0;
	_asm {
    
		mov nNum, 100
		push nNum
		mov eax, szFormat
		push eax
		call printf
		add esp, 8

	}
	
	system("pause");
	return 0;
}

2.2 自写函数

#include <stdio.h>
#include <stdlib.h>

int MyAdd(int a, int b)
{
    
	return a + b;
}

int main()
{
    
	char * szFormat = "%d\n";
	int nNum = 0;
	_asm {
    
		push 1
		push 2
		call MyAdd
		add esp, 8
		mov esi,eax
		push esi
		mov eax, szFormat
		push eax
		call printf
		add esp, 8
	}
	
	system("pause");
	return 0;
}

3 The interaction of the custom function with the main function

使用esi可以,使用ecx就不行,Cause the custom function is initialized at the beginning of the run,改变了ecx的值.

#include <stdio.h>
#include <stdlib.h>

int MyAdd(int a, int b)
{
    
	int nNum = 0;
	_asm mov nNum, edx
	if (nNum != 12313)
	{
    
		_asm jmp x1
	}
	else
	{
    
		_asm jmp esi
	}
x1:
	return a + b;
}

int main()
{
    
	char * szFormat = "%d\n";
	int nNum = 0;
	_asm {
    
		mov edx, 12313
		mov esi, thisx
	}
thisx:
	system("pause");
	return 0;
}

4 The stack implements the interaction between the main function and the custom function

#include <stdio.h>
#include <stdlib.h>

int MyAdd(int a, int b)
{
    
	int nNum = 0;
	_asm mov nNum, ebp - 4
	if (nNum != 12313)
	{
    
		_asm jmp x1
	}
	else
	{
    
		_asm jmp ebp - 8
	}
x1:
	return a + b;
}

int main()
{
    
	char * szFormat = "%d\n";
	int nNum = 0;
	_asm {
    
		push 12313
		push thisx
		call MyAdd
	}
thisx:
	system("pause");
	return 0;
}

5 数组遍历

#include <stdio.h>
#include <stdlib.h>

int main()
{
    
	int arr[] = {
     1,2,3,4,5,3,3,1,1,1,0 };
	char * szFormat = "%d\n";
	_asm {
    
		xor esi,esi
		jmp lookX
	lookM:
		inc esi
	lookX:
		mov edi, [arr + esi * 4]
		push edi
		mov eax, szFormat
		push eax
		call printf
		add esp, 8
		cmp edi, 0
		jne lookM  //若不相等则跳转
	}
	system("pause");
	return 0;
}

6 Iterates by the length of the array

#include <stdio.h>
#include <stdlib.h>

int main()
{
    
	int arr[] = {
     0,1,2,3,4,5 };
	char * szFormat = "%d\n";
	_asm {
    
		mov edi, 5h
		xor esi,esi
		jmp look1
	look:
		inc esi
	look1:
		push [arr + esi * 4]
		mov eax, szFormat
		push eax
		call printf
		add esp, 8
		cmp esi, edi
		jne look
	}
	system("pause");
	return 0;
}