Demonstrates we can now support limited JIT compilation on recent versions of iOS (assuming Apple approves entitlements at some future point)

main.m

//
//	main.m
//	ProtectTest
//	Demonstrates newer versions of iOS now support PROT_EXEC pages, for just-in-time compilation.
//
//      Must be compiled with Thumb disabled
//
//	Created by Stuart Carnie on 3/4/11.
//	Copyright 2011 Manomio LLC. All rights reserved.
//
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/mman.h>

#include <limits.h>	   /* for PAGESIZE */
#ifndef PAGESIZE
#define PAGESIZE 4096
#endif

typedef int (*inc_t)(int a);
inc_t _inc = NULL;

int
main(void)
{
	uint32_t code[] = {
		0xe2800001, // add	r0, r0, #1
		0xe12fff1e, // bx	lr
	};
	
	uint32_t *p;
	
	/* Allocate a buffer; it will have the default
	 protection of PROT_READ|PROT_WRITE. */
	p = malloc(1024+PAGESIZE-1);
	if (!p) {
		perror("Couldn't malloc(1024)");
		exit(errno);
	}
	
	/* Align to a multiple of PAGESIZE, assumed to be a power of two */
	p = (uint32_t *)(((int) p + PAGESIZE-1) & ~(PAGESIZE-1));
	
	// copy instructions to function
	p[0] = code[0];
	p[1] = code[1];
	
	/* Mark the buffer read / execute. */
	if (mprotect(p, 1024, PROT_READ | PROT_EXEC)) {
		perror("Couldn't mprotect");
		exit(errno);
	}
	
	_inc = (inc_t)p;
	int a = 1;
	a = _inc(a);
	printf("%d\n", a);	// as expected, echos 2
	
	exit(0);
}

@vpeca You need a get-task-allow entitlement (injected by Xcode automatically) and get ptrace to trace you in some way. Either this can be done by attaching via LLDB, as Xcode does, or you can do it programmatically with ptrace(PT_TRACE_ME, 0, NULL, 0).