1 /* $NetBSD: opendir.c,v 1.33 2008/01/10 09:49:04 elad Exp $ */ 2 3 /* 4 * Copyright (c) 1983, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 #if defined(LIBC_SCCS) && !defined(lint) 34 #if 0 35 static char sccsid[] = "@(#)opendir.c 8.7 (Berkeley) 12/10/94"; 36 #else 37 __RCSID("$NetBSD: opendir.c,v 1.33 2008/01/10 09:49:04 elad Exp $"); 38 #endif 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include "namespace.h" 42 #include "reentrant.h" 43 #include "extern.h" 44 #include <sys/param.h> 45 #include <sys/mount.h> 46 #include <sys/stat.h> 47 48 #include <assert.h> 49 #include <dirent.h> 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <stdlib.h> 53 #include <string.h> 54 #include <unistd.h> 55 56 #include "dirent_private.h" 57 58 #define MAXITERATIONS 100 59 60 /* 61 * Open a directory. 62 */ 63 DIR * 64 opendir(const char *name) 65 { 66 67 _DIAGASSERT(name != NULL); 68 69 return (__opendir2(name, DTF_HIDEW|DTF_NODUP)); 70 } 71 72 DIR * 73 __opendir2(const char *name, int flags) 74 { 75 DIR *dirp = NULL; 76 int fd; 77 int serrno; 78 struct stat sb; 79 int pagesz; 80 int incr; 81 int unionstack, nfsdir; 82 struct statvfs sfb; 83 84 _DIAGASSERT(name != NULL); 85 86 if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1 || 87 fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) 88 goto error; 89 if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) { 90 errno = ENOTDIR; 91 goto error; 92 } 93 if ((dirp = (DIR *)malloc(sizeof(DIR))) == NULL) 94 goto error; 95 dirp->dd_buf = NULL; 96 97 /* 98 * If the machine's page size is an exact multiple of DIRBLKSIZ, 99 * use a buffer that is cluster boundary aligned. 100 * Hopefully this can be a big win someday by allowing page trades 101 * to user space to be done by getdirentries() 102 */ 103 if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0) 104 incr = pagesz; 105 else 106 incr = DIRBLKSIZ; 107 108 /* 109 * Determine whether this directory is the top of a union stack. 110 */ 111 112 if (fstatvfs1(fd, &sfb, ST_NOWAIT) < 0) 113 goto error; 114 115 if (flags & DTF_NODUP) 116 unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION, 117 sizeof(sfb.f_fstypename))) || (sfb.f_flag & MNT_UNION); 118 else 119 unionstack = 0; 120 121 nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, sizeof(sfb.f_fstypename))); 122 123 if (unionstack || nfsdir) { 124 size_t len; 125 size_t space; 126 char *buf, *nbuf; 127 char *ddptr; 128 char *ddeptr; 129 int n; 130 struct dirent **dpv; 131 int i; 132 133 /* 134 * The strategy here for directories on top of a union stack 135 * is to read all the directory entries into a buffer, sort 136 * the buffer, and remove duplicate entries by setting the 137 * inode number to zero. 138 * 139 * For directories on an NFS mounted filesystem, we try 140 * to get a consistent snapshot by trying until we have 141 * successfully read all of the directory without errors 142 * (i.e. 'bad cookie' errors from the server because 143 * the directory was modified). These errors should not 144 * happen often, but need to be dealt with. 145 */ 146 i = 0; 147 retry: 148 len = 0; 149 space = 0; 150 buf = 0; 151 ddptr = 0; 152 153 do { 154 /* 155 * Always make at least DIRBLKSIZ bytes 156 * available to getdirentries 157 */ 158 if (space < DIRBLKSIZ) { 159 space += incr; 160 len += incr; 161 nbuf = realloc(buf, len); 162 if (nbuf == NULL) { 163 dirp->dd_buf = buf; 164 goto error; 165 } 166 buf = nbuf; 167 ddptr = buf + (len - space); 168 } 169 170 dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR); 171 n = getdents(fd, ddptr, space); 172 /* 173 * For NFS: EINVAL means a bad cookie error 174 * from the server. Keep trying to get a 175 * consistent view, in this case this means 176 * starting all over again. 177 */ 178 if (n == -1 && errno == EINVAL && nfsdir) { 179 free(buf); 180 lseek(fd, (off_t)0, SEEK_SET); 181 if (++i > MAXITERATIONS) 182 goto error; 183 goto retry; 184 } 185 if (n > 0) { 186 ddptr += n; 187 space -= n; 188 } 189 } while (n > 0); 190 191 ddeptr = ddptr; 192 flags |= __DTF_READALL; 193 194 /* 195 * Re-open the directory. 196 * This has the effect of rewinding back to the 197 * top of the union stack and is needed by 198 * programs which plan to fchdir to a descriptor 199 * which has also been read -- see fts.c. 200 */ 201 if (flags & DTF_REWIND) { 202 (void) close(fd); 203 if ((fd = open(name, O_RDONLY)) == -1 || 204 fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { 205 dirp->dd_buf = buf; 206 goto error; 207 } 208 } 209 210 /* 211 * There is now a buffer full of (possibly) duplicate 212 * names. 213 */ 214 dirp->dd_buf = buf; 215 216 /* 217 * Go round this loop twice... 218 * 219 * Scan through the buffer, counting entries. 220 * On the second pass, save pointers to each one. 221 * Then sort the pointers and remove duplicate names. 222 */ 223 if (!nfsdir) { 224 for (dpv = 0;;) { 225 for (n = 0, ddptr = buf; ddptr < ddeptr;) { 226 struct dirent *dp; 227 228 dp = (struct dirent *)(void *)ddptr; 229 if ((long)dp & _DIRENT_ALIGN(dp)) 230 break; 231 /* 232 * d_reclen is unsigned, 233 * so no need to compare <= 0 234 */ 235 if (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, (size_t)n, sizeof(*dpv), 252 alphasort); 253 254 dpv[n] = NULL; 255 xp = NULL; 256 257 /* 258 * Scan through the buffer in sort 259 * order, zapping the inode number 260 * of any 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, 267 xp->d_name)) 268 xp = dp; 269 else 270 dp->d_fileno = 0; 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) * 280 sizeof(struct dirent *)); 281 if (dpv == NULL) 282 break; 283 } 284 } 285 } 286 287 dirp->dd_len = len; 288 dirp->dd_size = ddptr - dirp->dd_buf; 289 } else { 290 dirp->dd_len = incr; 291 dirp->dd_buf = malloc((size_t)dirp->dd_len); 292 if (dirp->dd_buf == NULL) 293 goto error; 294 dirp->dd_seek = 0; 295 flags &= ~DTF_REWIND; 296 } 297 298 dirp->dd_loc = 0; 299 dirp->dd_fd = fd; 300 dirp->dd_flags = flags; 301 302 /* 303 * Set up seek point for rewinddir. 304 */ 305 #ifdef _REENTRANT 306 if (__isthreaded) { 307 if ((dirp->dd_lock = malloc(sizeof(mutex_t))) == NULL) 308 goto error; 309 mutex_init((mutex_t *)dirp->dd_lock, NULL); 310 } 311 #endif 312 dirp->dd_internal = NULL; 313 (void)_telldir_unlocked(dirp); 314 return (dirp); 315 error: 316 serrno = errno; 317 if (dirp && dirp->dd_buf) 318 free(dirp->dd_buf); 319 if (dirp) 320 free(dirp); 321 if (fd != -1) 322 (void)close(fd); 323 errno = serrno; 324 return NULL; 325 } 326