#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>

#define MAX 2

int main ()
{
    char *p[MAX];
    int sz[MAX] = {0x2000, 0x1000};
    int keep = 0x1000;
    int offset = 0x42;
    int magic = 0x33;
    int i;
    int pid;
    int rv;

    for(i=0; i<MAX; i++)
    {
        p[i] = (char *) mmap (0, sz[i], PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
        printf ("mmap() = %p\n", p[i]);
    }

#define KEEPLO
#ifdef KEEPLO
    /* keep lower chunk -> segv */
    rv = munmap (p[0]+keep, sz[0]-keep);
#else
    /* keep upper chunk -> ok */
    rv = munmap (p[0], keep);
#endif

    printf ("munmap() = %d\n",rv);

    i = 1;
    p[i][offset] = magic;

    pid = fork ();

    switch (pid)
    {
    case (-1):
        printf ("fork() failed\n");
        break;
    case (0):
        printf ("child touching %p\n", &(p[i][offset]));
        printf ("child M[%p] = 0x%x\n", &(p[i][offset]), p[i][offset]);
        break;
    default:
        printf ("parent touching %p\n", &(p[i][offset]));
        printf ("parent M[%p] = 0x%x\n", &(p[i][offset]), p[i][offset]);
        break;
    }

    return 0;
}