1/* Determine current working directory. Linux version.
2 Copyright (C) 1997-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20#include <assert.h>
21#include <errno.h>
22#include <limits.h>
23#include <stdlib.h>
24#include <unistd.h>
25#include <sys/param.h>
26
27#include <sysdep.h>
28#include <sys/syscall.h>
29
30
31/* If we compile the file for use in ld.so we don't need the feature
32 that getcwd() allocates the buffers itself. */
33#if IS_IN (rtld)
34# define NO_ALLOCATION 1
35#endif
36
37
38/* The "proc" filesystem provides an easy method to retrieve the value.
39 For each process, the corresponding directory contains a symbolic link
40 named `cwd'. Reading the content of this link immediate gives us the
41 information. But we have to take care for systems which do not have
42 the proc filesystem mounted. Use the POSIX implementation in this case. */
43
44/* Get the code for the generic version. */
45#define GETCWD_RETURN_TYPE static char *
46#include <sysdeps/posix/getcwd.c>
47
48char *
49__getcwd (char *buf, size_t size)
50{
51 char *path;
52 char *result;
53
54#ifndef NO_ALLOCATION
55 size_t alloc_size = size;
56 if (size == 0)
57 {
58 if (buf != NULL)
59 {
60 __set_errno (EINVAL);
61 return NULL;
62 }
63
64 alloc_size = MAX (PATH_MAX, __getpagesize ());
65 }
66
67 if (buf == NULL)
68 {
69 path = malloc (alloc_size);
70 if (path == NULL)
71 return NULL;
72 }
73 else
74#else
75# define alloc_size size
76#endif
77 path = buf;
78
79 int retval;
80
81 retval = INLINE_SYSCALL (getcwd, 2, path, alloc_size);
82 if (retval > 0 && path[0] == '/')
83 {
84#ifndef NO_ALLOCATION
85 if (buf == NULL && size == 0)
86 /* Ensure that the buffer is only as large as necessary. */
87 buf = realloc (path, (size_t) retval);
88
89 if (buf == NULL)
90 /* Either buf was NULL all along, or `realloc' failed but
91 we still have the original string. */
92 buf = path;
93#endif
94
95 return buf;
96 }
97
98 /* The system call either cannot handle paths longer than a page
99 or can succeed without returning an absolute path. Just use the
100 generic implementation right away. */
101 if (retval >= 0 || errno == ENAMETOOLONG)
102 {
103#ifndef NO_ALLOCATION
104 if (buf == NULL && size == 0)
105 {
106 free (path);
107 path = NULL;
108 }
109#endif
110
111 result = __getcwd_generic (path, size);
112
113#ifndef NO_ALLOCATION
114 if (result == NULL && buf == NULL && size != 0)
115 free (path);
116#endif
117
118 return result;
119 }
120
121 /* It should never happen that the `getcwd' syscall failed because
122 the buffer is too small if we allocated the buffer ourselves
123 large enough. */
124 assert (errno != ERANGE || buf != NULL || size != 0);
125
126#ifndef NO_ALLOCATION
127 if (buf == NULL)
128 free (path);
129#endif
130
131 return NULL;
132}
133libc_hidden_def (__getcwd)
134weak_alias (__getcwd, getcwd)
135