#define _GNU_SOURCE
#include <sys/mman.h>
#include <assert.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>

#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif

static void my_segv(int sig)
{
    printf ("Test FAILED\n");
    _exit (EXIT_FAILURE);
}

int main(void)
{
    const char *file = "mrtst2.c";
    char *addr, *addr2, *addr3;
    int fd;

    fd = open (file, O_RDONLY);
    if (fd == -1)
        return EXIT_FAILURE;
    addr = mmap (NULL, PAGE_SIZE * 2, PROT_READ, MAP_PRIVATE, fd, 0);
    close(fd);
    if (addr == MAP_FAILED) {
        perror("mmap()");
        return EXIT_FAILURE;
    }
    addr2 = mmap (NULL, PAGE_SIZE * 2, PROT_READ | PROT_WRITE,
                  MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
    if (addr2 == MAP_FAILED) {
        perror("mmap()");
        return EXIT_FAILURE;
    }
    /* split VMA to fail mremap() */
    mprotect (addr, PAGE_SIZE, PROT_READ | PROT_WRITE);
    /* VMAs won't be merged, bug */
    mprotect (addr, PAGE_SIZE, PROT_READ);
    /* make sure dest is here and writable */
    addr2[0] = 3;
    /* expose the bug */
    addr3 = mremap (addr, PAGE_SIZE * 2, PAGE_SIZE * 2,
                    MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_DONTUNMAP,
                    addr2);
    if (addr3 == addr2) {
        printf ("Even VMAs merged? Excellent!\n");
        return 0;
    }
    assert (addr3 == MAP_FAILED);
    signal (SIGSEGV, my_segv);
    /* see if dest address unmapped */
    addr2[0] = 5;
    assert (addr2[0] == 5);
    printf ("Test PASSED\n");
    return 0;
}