unsigned char block[50] = {0};

/* ...code to fill block with machine instructions here... */

/* try to execute the block with an assembly call */
__asm__ (
	"mov %0, %%eax;\
	call *%%eax;"
	:			/* no output */
	: "r" (block)		/* input variable, replaces %0 in above code */
	: "eax"			/* tell gcc eax may have changed */
);

int pagesize = getpagesize();
void* target = (block - ((long)block % pagesize)));
mprotect(target, 100, (PROT_READ | PROT_WRITE | PROT_EXEC));

int main() {
	typedef int (*fadd)(int, int);

	/* code for function:    int add(int a, int b) { return a+b; } */
	byte block[] = {
			0x55,                      //push   %ebp
			0x89, 0xe5,                //mov    %esp,%ebp
			0x8b, 0x45, 0x0c,          //mov    0xc(%ebp),%eax
			0x03, 0x45, 0x08,          //add    0x8(%ebp),%eax
			0xc9,                      //leave  
			0xc3,                      //ret    
			0x90,                      //nop    
			0x8d, 0x74, 0x26, 0x00     //lea    0x0(%esi),%esi
	};
	int pagesize;
	int i;
	
	pagesize = getpagesize();
	if (mprotect((block - ((long)block % pagesize)), 16, PROT_EXEC) == -1) {
		perror("mprotect()");
		return 0;
	}

	fadd fptr = block;
	i = (*fptr)(1, 2);
	printf("fptr = %i\n", i);	
	
	return 0;