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#undef _FORTIFY_SOURCE
30#include <errno.h>
31#include <malloc.h>
32#include <string.h>
33#include <unistd.h>
34
35extern "C" int __getcwd(char* buf, size_t size);
36
37char* getcwd(char* buf, size_t size) {
38  // You can't specify size 0 unless you're asking us to allocate for you.
39  if (buf != NULL && size == 0) {
40    errno = EINVAL;
41    return NULL;
42  }
43
44  // Allocate a buffer if necessary.
45  char* allocated_buf = NULL;
46  size_t allocated_size = size;
47  if (buf == NULL) {
48    if (size == 0) {
49      // The Linux kernel won't return more than a page, so translate size 0 to 4KiB.
50      // TODO: if we need to support paths longer than that, we'll have to walk the tree ourselves.
51      allocated_size = getpagesize();
52    }
53    buf = allocated_buf = static_cast<char*>(malloc(allocated_size));
54    if (buf == NULL) {
55      // malloc should set errno, but valgrind's malloc wrapper doesn't.
56      errno = ENOMEM;
57      return NULL;
58    }
59  }
60
61  // Ask the kernel to fill our buffer.
62  int rc = __getcwd(buf, allocated_size);
63  if (rc == -1) {
64    free(allocated_buf);
65    // __getcwd set errno.
66    return NULL;
67  }
68
69  // If we allocated a whole page, only return as large an allocation as necessary.
70  if (allocated_buf != NULL) {
71    if (size == 0) {
72      buf = strdup(allocated_buf);
73      free(allocated_buf);
74    } else {
75      buf = allocated_buf;
76    }
77  }
78
79  return buf;
80}
81