/*
 *  smiffy by Davide Libenzi (MAP_NOZERO pages sniffer)
 *  Copyright (C) 2007  Davide Libenzi
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 *
 *
 *  Smiffy continuosly creates mmap(MAP_NOZERO) anonymous mappings, and
 *  verifies that the pages it recevies are ZERO pages. For the test to
 *  be valid,  smiffy  should be run under a user that has no other
 *  task running and that owns no files in the system. Better create a
 *  dummy user and run  smiffy  under such user.
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/resource.h>

#ifndef MAP_NOZERO
#define MAP_NOZERO	0x04000000
#endif

#define DEFAULT_SIZE_PAGES	128

static unsigned int pgsize;

static int page_check(void *page) {
	unsigned long *p, *top;

	p = page;
	top = page + pgsize;
	/*
	 * Write-fault the page before, otherwise you get ZERO_PAGE plus
	 * copy_page() behaviour ...
	 */
	*p++ = 1;
	for (; p < top; p++)
		if (*p)
			return 0;

	return 1;
}

static int test_mmap(unsigned int size) {
	unsigned int nzcount;
	char *addr, *p, *top;

	size = ((size + pgsize - 1) / pgsize) * pgsize;
	addr = mmap(NULL, size, PROT_READ | PROT_WRITE,
		    MAP_ANONYMOUS | MAP_PRIVATE | MAP_NOZERO, -1, 0);
	if (addr == MAP_FAILED) {
		perror("mmap");
		return -1;
	}
	for (p = addr, top = addr + size, nzcount = 0; p < top; p += pgsize) {
		if (!page_check(p))
			nzcount++;
	}
	munmap(addr, size);
	if (nzcount)
		fprintf(stderr, "mapping had %u non-zero pages\n", nzcount);

	return 0;
}

int main(int ac, char **av) {
	int i, sltimeo = 1000000, nice = 0;
	unsigned int size;

	pgsize = sysconf(_SC_PAGESIZE);
	size = pgsize * DEFAULT_SIZE_PAGES;
	while ((i = getopt(ac, av, "s:p:N:h")) != -1) {
		switch (i) {
		case 's':
			size = atoi(optarg) * pgsize;
			break;
		case 'p':
			sltimeo = atoi(optarg);
			break;
		case 'N':
			nice = atoi(optarg);
			break;
		case 'h':

			break;
		}
	}
	if (setpriority(PRIO_PROCESS, 0, nice))
		perror("setpriority");
	for (;;) {
		test_mmap(size);
		usleep(sltimeo);
	}

	return 0;
}