opendir.c revision 178256 
1/*-
2 * Copyright (c) 1983, 1993
3 *	The Regents of the University of California.  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 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#if defined(LIBC_SCCS) && !defined(lint)
31static char sccsid[] = "@(#)opendir.c	8.8 (Berkeley) 5/1/95";
32#endif /* LIBC_SCCS and not lint */
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD: head/lib/libc/gen/opendir.c 178256 2008-04-16 18:59:36Z delphij $");
35
36#include "namespace.h"
37#include <sys/param.h>
38#include <sys/mount.h>
39#include <sys/stat.h>
40
41#include <dirent.h>
42#include <errno.h>
43#include <fcntl.h>
44#include <stdlib.h>
45#include <string.h>
46#include <unistd.h>
47#include "un-namespace.h"
48
49#include "telldir.h"
50
51static DIR * __opendir_common(int, const char *, int);
52
53/*
54 * Open a directory.
55 */
56DIR *
57opendir(const char *name)
58{
59
60	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
61}
62
63/*
64 * Open a directory with existing file descriptor.
65 */
66DIR *
67fdopendir(int fd)
68{
69
70	return (__opendir_common(fd, NULL, DTF_HIDEW|DTF_NODUP));
71}
72
73DIR *
74__opendir2(const char *name, int flags)
75{
76	int fd;
77	struct stat statb;
78
79	/*
80	 * stat() before _open() because opening of special files may be
81	 * harmful.
82	 */
83	if (stat(name, &statb) != 0)
84		return (NULL);
85	if (!S_ISDIR(statb.st_mode)) {
86		errno = ENOTDIR;
87		return (NULL);
88	}
89	if ((fd = _open(name, O_RDONLY | O_NONBLOCK)) == -1)
90		return (NULL);
91
92	return __opendir_common(fd, name, flags);
93}
94
95/*
96 * Common routine for opendir(3), __opendir2(3) and fdopendir(3).
97 */
98static DIR *
99__opendir_common(int fd, const char *name, int flags)
100{
101	DIR *dirp;
102	int incr;
103	int saved_errno;
104	int unionstack;
105	struct stat statb;
106
107	dirp = NULL;
108	/* _fstat() the open handler because the file may have changed.  */
109	if (_fstat(fd, &statb) != 0)
110		goto fail;
111	if (!S_ISDIR(statb.st_mode)) {
112		errno = ENOTDIR;
113		goto fail;
114	}
115	if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
116	    (dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
117		goto fail;
118
119	dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
120	LIST_INIT(&dirp->dd_td->td_locq);
121	dirp->dd_td->td_loccnt = 0;
122
123	/*
124	 * Use the system page size if that is a multiple of DIRBLKSIZ.
125	 * Hopefully this can be a big win someday by allowing page
126	 * trades to user space to be done by _getdirentries().
127	 */
128	incr = getpagesize();
129	if ((incr % DIRBLKSIZ) != 0)
130		incr = DIRBLKSIZ;
131
132	/*
133	 * Determine whether this directory is the top of a union stack.
134	 */
135	if (flags & DTF_NODUP) {
136		struct statfs sfb;
137
138		if (_fstatfs(fd, &sfb) < 0)
139			goto fail;
140		unionstack = !strcmp(sfb.f_fstypename, "unionfs")
141		    || (sfb.f_flags & MNT_UNION);
142	} else {
143		unionstack = 0;
144	}
145
146	if (unionstack) {
147		int len = 0;
148		int space = 0;
149		char *buf = 0;
150		char *ddptr = 0;
151		char *ddeptr;
152		int n;
153		struct dirent **dpv;
154
155		/*
156		 * The strategy here is to read all the directory
157		 * entries into a buffer, sort the buffer, and
158		 * remove duplicate entries by setting the inode
159		 * number to zero.
160		 */
161
162		do {
163			/*
164			 * Always make at least DIRBLKSIZ bytes
165			 * available to _getdirentries
166			 */
167			if (space < DIRBLKSIZ) {
168				space += incr;
169				len += incr;
170				buf = reallocf(buf, len);
171				if (buf == NULL)
172					goto fail;
173				ddptr = buf + (len - space);
174			}
175
176			n = _getdirentries(fd, ddptr, space, &dirp->dd_seek);
177			if (n > 0) {
178				ddptr += n;
179				space -= n;
180			}
181		} while (n > 0);
182
183		ddeptr = ddptr;
184		flags |= __DTF_READALL;
185
186		/*
187		 * Re-open the directory.
188		 * This has the effect of rewinding back to the
189		 * top of the union stack and is needed by
190		 * programs which plan to fchdir to a descriptor
191		 * which has also been read -- see fts.c.
192		 */
193		if (flags & DTF_REWIND) {
194			(void)_close(fd);
195			if ((fd = _open(name, O_RDONLY)) == -1) {
196				saved_errno = errno;
197				free(buf);
198				free(dirp);
199				errno = saved_errno;
200				return (NULL);
201			}
202		}
203
204		/*
205		 * There is now a buffer full of (possibly) duplicate
206		 * names.
207		 */
208		dirp->dd_buf = buf;
209
210		/*
211		 * Go round this loop twice...
212		 *
213		 * Scan through the buffer, counting entries.
214		 * On the second pass, save pointers to each one.
215		 * Then sort the pointers and remove duplicate names.
216		 */
217		for (dpv = 0;;) {
218			n = 0;
219			ddptr = buf;
220			while (ddptr < ddeptr) {
221				struct dirent *dp;
222
223				dp = (struct dirent *) ddptr;
224				if ((long)dp & 03L)
225					break;
226				if ((dp->d_reclen <= 0) ||
227				    (dp->d_reclen > (ddeptr + 1 - ddptr)))
228					break;
229				ddptr += dp->d_reclen;
230				if (dp->d_fileno) {
231					if (dpv)
232						dpv[n] = dp;
233					n++;
234				}
235			}
236
237			if (dpv) {
238				struct dirent *xp;
239
240				/*
241				 * This sort must be stable.
242				 */
243				mergesort(dpv, n, sizeof(*dpv), alphasort);
244
245				dpv[n] = NULL;
246				xp = NULL;
247
248				/*
249				 * Scan through the buffer in sort order,
250				 * zapping the inode number of any
251				 * duplicate names.
252				 */
253				for (n = 0; dpv[n]; n++) {
254					struct dirent *dp = dpv[n];
255
256					if ((xp == NULL) ||
257					    strcmp(dp->d_name, xp->d_name)) {
258						xp = dp;
259					} else {
260						dp->d_fileno = 0;
261					}
262					if (dp->d_type == DT_WHT &&
263					    (flags & DTF_HIDEW))
264						dp->d_fileno = 0;
265				}
266
267				free(dpv);
268				break;
269			} else {
270				dpv = malloc((n+1) * sizeof(struct dirent *));
271				if (dpv == NULL)
272					break;
273			}
274		}
275
276		dirp->dd_len = len;
277		dirp->dd_size = ddptr - dirp->dd_buf;
278	} else {
279		dirp->dd_len = incr;
280		dirp->dd_size = 0;
281		dirp->dd_buf = malloc(dirp->dd_len);
282		if (dirp->dd_buf == NULL)
283			goto fail;
284		dirp->dd_seek = 0;
285		flags &= ~DTF_REWIND;
286	}
287
288	dirp->dd_loc = 0;
289	dirp->dd_fd = fd;
290	dirp->dd_flags = flags;
291	dirp->dd_lock = NULL;
292
293	/*
294	 * Set up seek point for rewinddir.
295	 */
296	dirp->dd_rewind = telldir(dirp);
297
298	return (dirp);
299
300fail:
301	saved_errno = errno;
302	free(dirp);
303	(void)_close(fd);
304	errno = saved_errno;
305	return (NULL);
306}
307