#define _XOPEN_SOURCE            500
#define NT_FILE_BACKED_PAGE_SIZE 4096

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

static int test_file_backed_mmap(int size)
{
	int     fd;
	int     exsize;
	void *  addr;
	char *  test;
	char *  cap;
	char    name[12];

	/* create test file of desired size */
	sprintf(name,"%d.tmp",size);

	if ((fd = creat(name,0755)) < 0)
		return -1;

	if (ftruncate(fd,size))
		return -1;

	close(fd);

	/* write 'W' to all bytes of test file */
	if ((fd = open(name,O_RDWR,0)) < 0)
		return -1;

	if ((addr = mmap(0,size,PROT_WRITE,MAP_SHARED,fd,0)) == MAP_FAILED)
		return -1;

	close(fd);

	test = (char *)addr;
	cap  = (char *)addr + size;

	for (; test<cap; test++)
		*test = 'W';

	munmap(addr,size);

	/* map file for read access */
	if ((fd = open(name,O_RDONLY,0)) < 0)
		return -1;

	if ((addr = mmap(0,size,PROT_READ,MAP_PRIVATE,fd,0)) == MAP_FAILED)
		return -1;

	close(fd);

	/* test */
	exsize = size + NT_FILE_BACKED_PAGE_SIZE;
	exsize &= ~(NT_FILE_BACKED_PAGE_SIZE - 1);

	test = (char *)addr + size;
	cap  = (char *)addr + exsize;

	for (; test<cap; test++)
		if (*test)
			return -1;

	/* clean-up */
	munmap(addr,size);
	unlink(name);

	return 0;

}

int main(void)
{
	int i;

	for (i=1; i<65536; i++)
		if (i % NT_FILE_BACKED_PAGE_SIZE)
			if (test_file_backed_mmap(i))
				return 2;

	return 0;
}