1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <errno.h>
30#include <sys/mman.h>
31#include <unistd.h>
32
33#include "private/ErrnoRestorer.h"
34
35// mmap2(2) is like mmap(2), but the offset is in 4096-byte blocks, not bytes.
36extern "C" void*  __mmap2(void*, size_t, int, int, int, size_t);
37
38#define MMAP2_SHIFT 12 // 2**12 == 4096
39
40static bool kernel_has_MADV_MERGEABLE = true;
41
42void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) {
43  if (offset < 0 || (offset & ((1UL << MMAP2_SHIFT)-1)) != 0) {
44    errno = EINVAL;
45    return MAP_FAILED;
46  }
47
48  bool is_private_anonymous = (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) != 0;
49  void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT);
50
51  if (result != MAP_FAILED && kernel_has_MADV_MERGEABLE && is_private_anonymous) {
52    ErrnoRestorer errno_restorer;
53    int rc = madvise(result, size, MADV_MERGEABLE);
54    if (rc == -1 && errno == EINVAL) {
55      kernel_has_MADV_MERGEABLE = false;
56    }
57  }
58
59  return result;
60}
61
62void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
63  return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset));
64}
65