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/*
* Author: Tyler Hicks <tyhicks@canonical.com>
*
* Copyright (C) 2012 Canonical, Ltd.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#define MEM_LEN (4096*8)
#define MEM_CHUNK (4096)
int main(int argc, char **argv)
{
void *mem;
int i, fd, rc;
if (argc != 2) {
fprintf(stderr, "Usage: %s FILE_PATH\n", argv[0]);
return EINVAL;
}
fd = open(argv[1], O_RDWR | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
if (fd < 0) {
perror("open");
return errno;
}
rc = ftruncate(fd, MEM_LEN);
if (rc < 0) {
perror("ftruncate");
return errno;
}
mem = mmap(NULL, MEM_LEN, PROT_WRITE, MAP_SHARED, fd, 0);
if (mem == MAP_FAILED) {
perror("mmap");
return errno;
}
/**
* This is the crux of the problem: close() before pages are dirtied
* and munmap() is called.
*/
close(fd);
for (i = 0; i < MEM_LEN; i += MEM_CHUNK)
memset(((char *)mem) + i, 0xFF, MEM_CHUNK);
rc = munmap(mem, MEM_LEN);
if (rc < 0) {
perror("munmap");
return errno;
}
return 0;
}
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