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/* $OpenBSD: mmap_noreplace.c,v 1.1 2014/06/19 19:34:22 matthew Exp $ */
/*
* Copyright (c) 2014 Google Inc.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/mman.h>
#include <assert.h>
#include <string.h>
#include <unistd.h>
#define CHECK(a) assert(a)
#define CHECK_EQ(a, b) assert((a) == (b))
#define CHECK_NE(a, b) assert((a) != (b))
#define CHECK_GE(a, b) assert((a) >= (b))
int
ismemset(void *b, int c, size_t n)
{
unsigned char *p = b;
size_t i;
for (i = 0; i < n; i++)
if (p[i] != c)
return (0);
return (1);
}
int
main()
{
char *p;
long pagesize;
pagesize = sysconf(_SC_PAGESIZE);
CHECK_GE(pagesize, 1);
/* Allocate three pages of anonymous memory. */
p = mmap(NULL, 3 * pagesize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
CHECK_NE(MAP_FAILED, p);
/* Initialize memory to all 1 bytes. */
memset(p, 1, 3 * pagesize);
CHECK(ismemset(p, 1, 3 * pagesize));
/* Map new anonymous memory over the second page. */
CHECK_EQ(p + pagesize, mmap(p + pagesize, pagesize,
PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON|MAP_FIXED, -1, 0));
/* Verify the second page is zero'd out, and the others are unscathed. */
CHECK(ismemset(p, 1, pagesize));
CHECK(ismemset(p + pagesize, 0, pagesize));
CHECK(ismemset(p + 2 * pagesize, 1, pagesize));
/* Re-initialized memory. */
memset(p, 1, 3 * pagesize);
CHECK(ismemset(p, 1, 3 * pagesize));
/* Try to map over second page with __MAP_NOREPLACE; should fail. */
CHECK_EQ(MAP_FAILED, mmap(p, pagesize, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANON|MAP_FIXED|__MAP_NOREPLACE, -1, 0));
/* Verify the pages are still set. */
CHECK(ismemset(p, 1, 3 * pagesize));
return (0);
}
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