1/* Copyright (C) 1991-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <dirent.h>
19#include <fcntl.h>
20#include <errno.h>
21#include <stdio.h> /* For BUFSIZ. */
22#include <sys/param.h> /* For MIN and MAX. */
23
24#include <not-cancel.h>
25
26/* The st_blksize value of the directory is used as a hint for the
27 size of the buffer which receives struct dirent values from the
28 kernel. st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the
29 file system provides a bogus value. */
30#define MAX_DIR_BUFFER_SIZE 1048576U
31
32enum {
33 opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC
34};
35
36static bool
37invalid_name (const char *name)
38{
39 if (__glibc_unlikely (name[0] == '\0'))
40 {
41 /* POSIX.1-1990 says an empty name gets ENOENT;
42 but `open' might like it fine. */
43 __set_errno (ENOENT);
44 return true;
45 }
46 return false;
47}
48
49static DIR *
50opendir_tail (int fd)
51{
52 if (__glibc_unlikely (fd < 0))
53 return NULL;
54
55 /* Now make sure this really is a directory and nothing changed since the
56 `stat' call. The S_ISDIR check is superfluous if O_DIRECTORY works,
57 but it's cheap and we need the stat call for st_blksize anyway. */
58 struct stat64 statbuf;
59 if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &statbuf) < 0))
60 goto lose;
61 if (__glibc_unlikely (! S_ISDIR (statbuf.st_mode)))
62 {
63 __set_errno (ENOTDIR);
64 lose:
65 __close_nocancel_nostatus (fd);
66 return NULL;
67 }
68
69 return __alloc_dir (fd, true, 0, &statbuf);
70}
71
72
73#if IS_IN (libc)
74DIR *
75__opendirat (int dfd, const char *name)
76{
77 if (__glibc_unlikely (invalid_name (name)))
78 return NULL;
79
80 return opendir_tail (__openat_nocancel (dfd, name, opendir_oflags));
81}
82#endif
83
84
85/* Open a directory stream on NAME. */
86DIR *
87__opendir (const char *name)
88{
89 if (__glibc_unlikely (invalid_name (name)))
90 return NULL;
91
92 return opendir_tail (__open_nocancel (name, opendir_oflags));
93}
94weak_alias (__opendir, opendir)
95
96DIR *
97__alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp)
98{
99 /* We have to set the close-on-exit flag if the user provided the
100 file descriptor. */
101 if (!close_fd
102 && __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0))
103 goto lose;
104
105 const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64)
106 ? sizeof (struct dirent64) : 4 * BUFSIZ);
107 const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64)
108 ? sizeof (struct dirent64) : BUFSIZ);
109 size_t allocation = default_allocation;
110#ifdef _STATBUF_ST_BLKSIZE
111 /* Increase allocation if requested, but not if the value appears to
112 be bogus. */
113 if (statp != NULL)
114 allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation),
115 MAX_DIR_BUFFER_SIZE);
116#endif
117
118 DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
119 if (dirp == NULL)
120 {
121 allocation = small_allocation;
122 dirp = (DIR *) malloc (sizeof (DIR) + allocation);
123
124 if (dirp == NULL)
125 lose:
126 {
127 if (close_fd)
128 {
129 int save_errno = errno;
130 __close_nocancel_nostatus (fd);
131 __set_errno (save_errno);
132 }
133 return NULL;
134 }
135 }
136
137 dirp->fd = fd;
138#if IS_IN (libc)
139 __libc_lock_init (dirp->lock);
140#endif
141 dirp->allocation = allocation;
142 dirp->size = 0;
143 dirp->offset = 0;
144 dirp->filepos = 0;
145 dirp->errcode = 0;
146
147 return dirp;
148}
149