opendir.c revision 232385 
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 232385 2012-03-02 10:03:38Z ru $");
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	struct stat statb;
70
71	/* Check that fd is associated with a directory. */
72	if (_fstat(fd, &statb) != 0)
73		return (NULL);
74	if (!S_ISDIR(statb.st_mode)) {
75		errno = ENOTDIR;
76		return (NULL);
77	}
78	if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
79		return (NULL);
80	return (__opendir_common(fd, NULL, DTF_HIDEW|DTF_NODUP));
81}
82
83DIR *
84__opendir2(const char *name, int flags)
85{
86	int fd;
87	DIR *dir;
88	int saved_errno;
89
90	if ((fd = _open(name,
91	    O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC)) == -1)
92		return (NULL);
93
94	dir = __opendir_common(fd, name, flags);
95	if (dir == NULL) {
96		saved_errno = errno;
97		_close(fd);
98		errno = saved_errno;
99	}
100	return (dir);
101}
102
103static int
104opendir_compar(const void *p1, const void *p2)
105{
106
107	return (strcmp((*(const struct dirent **)p1)->d_name,
108	    (*(const struct dirent **)p2)->d_name));
109}
110
111/*
112 * Common routine for opendir(3), __opendir2(3) and fdopendir(3).
113 */
114static DIR *
115__opendir_common(int fd, const char *name, int flags)
116{
117	DIR *dirp;
118	int incr;
119	int saved_errno;
120	int unionstack;
121	int fd2;
122
123	if ((dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
124		return (NULL);
125
126	dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
127	LIST_INIT(&dirp->dd_td->td_locq);
128	dirp->dd_td->td_loccnt = 0;
129
130	/*
131	 * Use the system page size if that is a multiple of DIRBLKSIZ.
132	 * Hopefully this can be a big win someday by allowing page
133	 * trades to user space to be done by _getdirentries().
134	 */
135	incr = getpagesize();
136	if ((incr % DIRBLKSIZ) != 0)
137		incr = DIRBLKSIZ;
138
139	/*
140	 * Determine whether this directory is the top of a union stack.
141	 */
142	if (flags & DTF_NODUP) {
143		struct statfs sfb;
144
145		if (_fstatfs(fd, &sfb) < 0)
146			goto fail;
147		unionstack = !strcmp(sfb.f_fstypename, "unionfs")
148		    || (sfb.f_flags & MNT_UNION);
149	} else {
150		unionstack = 0;
151	}
152
153	if (unionstack) {
154		int len = 0;
155		int space = 0;
156		char *buf = 0;
157		char *ddptr = 0;
158		char *ddeptr;
159		int n;
160		struct dirent **dpv;
161
162		/*
163		 * The strategy here is to read all the directory
164		 * entries into a buffer, sort the buffer, and
165		 * remove duplicate entries by setting the inode
166		 * number to zero.
167		 */
168
169		do {
170			/*
171			 * Always make at least DIRBLKSIZ bytes
172			 * available to _getdirentries
173			 */
174			if (space < DIRBLKSIZ) {
175				space += incr;
176				len += incr;
177				buf = reallocf(buf, len);
178				if (buf == NULL)
179					goto fail;
180				ddptr = buf + (len - space);
181			}
182
183			n = _getdirentries(fd, ddptr, space, &dirp->dd_seek);
184			if (n > 0) {
185				ddptr += n;
186				space -= n;
187			}
188		} while (n > 0);
189
190		ddeptr = ddptr;
191		flags |= __DTF_READALL;
192
193		/*
194		 * Re-open the directory.
195		 * This has the effect of rewinding back to the
196		 * top of the union stack and is needed by
197		 * programs which plan to fchdir to a descriptor
198		 * which has also been read -- see fts.c.
199		 */
200		if (flags & DTF_REWIND) {
201			if ((fd2 = _open(name, O_RDONLY | O_DIRECTORY)) == -1) {
202				saved_errno = errno;
203				free(buf);
204				free(dirp);
205				errno = saved_errno;
206				return (NULL);
207			}
208			(void)_dup2(fd2, fd);
209			_close(fd2);
210		}
211
212		/*
213		 * There is now a buffer full of (possibly) duplicate
214		 * names.
215		 */
216		dirp->dd_buf = buf;
217
218		/*
219		 * Go round this loop twice...
220		 *
221		 * Scan through the buffer, counting entries.
222		 * On the second pass, save pointers to each one.
223		 * Then sort the pointers and remove duplicate names.
224		 */
225		for (dpv = 0;;) {
226			n = 0;
227			ddptr = buf;
228			while (ddptr < ddeptr) {
229				struct dirent *dp;
230
231				dp = (struct dirent *) ddptr;
232				if ((long)dp & 03L)
233					break;
234				if ((dp->d_reclen <= 0) ||
235				    (dp->d_reclen > (ddeptr + 1 - ddptr)))
236					break;
237				ddptr += dp->d_reclen;
238				if (dp->d_fileno) {
239					if (dpv)
240						dpv[n] = dp;
241					n++;
242				}
243			}
244
245			if (dpv) {
246				struct dirent *xp;
247
248				/*
249				 * This sort must be stable.
250				 */
251				mergesort(dpv, n, sizeof(*dpv),
252				    opendir_compar);
253
254				dpv[n] = NULL;
255				xp = NULL;
256
257				/*
258				 * Scan through the buffer in sort order,
259				 * zapping the inode number of any
260				 * duplicate names.
261				 */
262				for (n = 0; dpv[n]; n++) {
263					struct dirent *dp = dpv[n];
264
265					if ((xp == NULL) ||
266					    strcmp(dp->d_name, xp->d_name)) {
267						xp = dp;
268					} else {
269						dp->d_fileno = 0;
270					}
271					if (dp->d_type == DT_WHT &&
272					    (flags & DTF_HIDEW))
273						dp->d_fileno = 0;
274				}
275
276				free(dpv);
277				break;
278			} else {
279				dpv = malloc((n+1) * sizeof(struct dirent *));
280				if (dpv == NULL)
281					break;
282			}
283		}
284
285		dirp->dd_len = len;
286		dirp->dd_size = ddptr - dirp->dd_buf;
287	} else {
288		dirp->dd_len = incr;
289		dirp->dd_size = 0;
290		dirp->dd_buf = malloc(dirp->dd_len);
291		if (dirp->dd_buf == NULL)
292			goto fail;
293		dirp->dd_seek = 0;
294		flags &= ~DTF_REWIND;
295	}
296
297	dirp->dd_loc = 0;
298	dirp->dd_fd = fd;
299	dirp->dd_flags = flags;
300	dirp->dd_lock = NULL;
301
302	/*
303	 * Set up seek point for rewinddir.
304	 */
305	dirp->dd_rewind = telldir(dirp);
306
307	return (dirp);
308
309fail:
310	saved_errno = errno;
311	free(dirp);
312	errno = saved_errno;
313	return (NULL);
314}
315