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 <stdint.h>
31#include <sys/mman.h>
32#include <unistd.h>
33
34#include "private/bionic_macros.h"
35#include "private/ErrnoRestorer.h"
36
37// mmap2(2) is like mmap(2), but the offset is in 4096-byte blocks, not bytes.
38extern "C" void*  __mmap2(void*, size_t, int, int, int, size_t);
39
40#define MMAP2_SHIFT 12 // 2**12 == 4096
41
42static bool kernel_has_MADV_MERGEABLE = true;
43
44void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) {
45  if (offset < 0 || (offset & ((1UL << MMAP2_SHIFT)-1)) != 0) {
46    errno = EINVAL;
47    return MAP_FAILED;
48  }
49
50  // prevent allocations large enough for `end - start` to overflow
51  size_t rounded = BIONIC_ALIGN(size, PAGE_SIZE);
52  if (rounded < size || rounded > PTRDIFF_MAX) {
53    errno = ENOMEM;
54    return MAP_FAILED;
55  }
56
57  bool is_private_anonymous =
58      (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) == (MAP_PRIVATE | MAP_ANONYMOUS);
59  bool is_stack_or_grows_down = (flags & (MAP_STACK | MAP_GROWSDOWN)) != 0;
60
61  void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT);
62
63  if (result != MAP_FAILED && kernel_has_MADV_MERGEABLE &&
64      is_private_anonymous && !is_stack_or_grows_down) {
65    ErrnoRestorer errno_restorer;
66    int rc = madvise(result, size, MADV_MERGEABLE);
67    if (rc == -1 && errno == EINVAL) {
68      kernel_has_MADV_MERGEABLE = false;
69    }
70  }
71
72  return result;
73}
74
75void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
76  return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset));
77}
78