SB lab22 ex3

displace.c

#include <stdio.h>

typedef int (*FuncPtr)(int);

unsigned char codigo[] = {
 	0x55,
 	0x48, 0x89, 0xe5,
 	0x48, 0x83, 0xec, 0x10,
 	0x89, 0x7d, 0xfc,
 	0x8b, 0x45, 0xfc,
 	0x89, 0xc7,
 	0xe8, 0x00, 0x00, 0x00, 0x00,
 	0xc9,
 	0xc3
};

int sum(int v) { return v+2; }

int mul(int v) { return 2*v; }

int main(){

 int i;
 FuncPtr f;

 long addsum = (long)&sum;
 long addprox = (long)&codigo[21];

 long disp = addsum - addprox;

 //printf("%ld\n", disp);

 //---------------------------------------
 // Deslocamento de “sum” aqui
 //---------------------------------------
 // Chama a função

 int *ptr = (int*)&codigo[17];
 *ptr = (int)disp;
 //printf("%d\n", *ptr);


 f = (FuncPtr)codigo;
 i = f(10);
 printf("%d\n", i);

 //---------------------------------------
 // Deslocamento de “mul” aqui
 //---------------------------------------
 // Chama a função
 //f = (FuncPtr)codigo;
 //i = f(10);
 //printf("%d\n", i);

 return 0;
}