1 /* $NetBSD: opendir.c,v 1.36 2010/09/16 02:38:50 yamt 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 1.36 2010/09/16 02:38:50 yamt Exp $"); 38 #endif 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include "namespace.h" 42 #include "reentrant.h" 43 #include "extern.h" 44 45 #include <sys/param.h> 46 #include <sys/mount.h> 47 #include <sys/stat.h> 48 49 #include <assert.h> 50 #include <dirent.h> 51 #include <errno.h> 52 #include <fcntl.h> 53 #include <stdlib.h> 54 #include <string.h> 55 #include <unistd.h> 56 57 #include "dirent_private.h" 58 59 #define MAXITERATIONS 100 60 61 static DIR *__opendir_common(int, const char *, int); 62 63 __weak_alias(fdopendir,_fdopendir) 64 65 /* 66 * Open a directory. 67 */ 68 DIR * 69 opendir(const char *name) 70 { 71 72 _DIAGASSERT(name != NULL); 73 74 return (__opendir2(name, DTF_HIDEW|DTF_NODUP)); 75 } 76 77 DIR * 78 __opendir2(const char *name, int flags) 79 { 80 int fd; 81 82 if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1) 83 return NULL; 84 return __opendir_common(fd, name, flags); 85 } 86 87 #ifndef __LIBC12_SOURCE__ 88 DIR * 89 _fdopendir(int fd) 90 { 91 92 return __opendir_common(fd, NULL, DTF_HIDEW|DTF_NODUP); 93 } 94 #endif 95 96 static DIR * 97 __opendir_common(int fd, const char *name, int flags) 98 { 99 DIR *dirp = NULL; 100 int serrno; 101 struct stat sb; 102 int pagesz; 103 int incr; 104 int unionstack, nfsdir; 105 struct statvfs sfb; 106 107 if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) 108 goto error; 109 if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) { 110 errno = ENOTDIR; 111 goto error; 112 } 113 if ((dirp = (DIR *)malloc(sizeof(DIR))) == NULL) 114 goto error; 115 dirp->dd_buf = NULL; 116 117 /* 118 * If the machine's page size is an exact multiple of DIRBLKSIZ, 119 * use a buffer that is cluster boundary aligned. 120 * Hopefully this can be a big win someday by allowing page trades 121 * to user space to be done by getdents() 122 */ 123 if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0) 124 incr = pagesz; 125 else 126 incr = DIRBLKSIZ; 127 128 /* 129 * Determine whether this directory is the top of a union stack. 130 */ 131 132 if (fstatvfs1(fd, &sfb, ST_NOWAIT) < 0) 133 goto error; 134 135 if (flags & DTF_NODUP) 136 unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION, 137 sizeof(sfb.f_fstypename))) || (sfb.f_flag & MNT_UNION); 138 else 139 unionstack = 0; 140 141 nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, 142 sizeof(sfb.f_fstypename))); 143 144 if (unionstack || nfsdir) { 145 size_t len; 146 size_t space; 147 char *buf, *nbuf; 148 char *ddptr; 149 char *ddeptr; 150 int n; 151 struct dirent **dpv; 152 int i; 153 154 /* 155 * The strategy here for directories on top of a union stack 156 * is to read all the directory entries into a buffer, sort 157 * the buffer, and remove duplicate entries by setting the 158 * inode number to zero. 159 * 160 * For directories on an NFS mounted filesystem, we try 161 * to get a consistent snapshot by trying until we have 162 * successfully read all of the directory without errors 163 * (i.e. 'bad cookie' errors from the server because 164 * the directory was modified). These errors should not 165 * happen often, but need to be dealt with. 166 */ 167 i = 0; 168 retry: 169 len = 0; 170 space = 0; 171 buf = 0; 172 ddptr = 0; 173 174 do { 175 /* 176 * Always make at least DIRBLKSIZ bytes 177 * available to getdents 178 */ 179 if (space < DIRBLKSIZ) { 180 space += incr; 181 len += incr; 182 nbuf = realloc(buf, len); 183 if (nbuf == NULL) { 184 dirp->dd_buf = buf; 185 goto error; 186 } 187 buf = nbuf; 188 ddptr = buf + (len - space); 189 } 190 191 dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR); 192 n = getdents(fd, ddptr, space); 193 /* 194 * For NFS: EINVAL means a bad cookie error 195 * from the server. Keep trying to get a 196 * consistent view, in this case this means 197 * starting all over again. 198 */ 199 if (n == -1 && errno == EINVAL && nfsdir) { 200 free(buf); 201 lseek(fd, (off_t)0, SEEK_SET); 202 if (++i > MAXITERATIONS) 203 goto error; 204 goto retry; 205 } 206 if (n > 0) { 207 ddptr += n; 208 space -= n; 209 } 210 } while (n > 0); 211 212 ddeptr = ddptr; 213 flags |= __DTF_READALL; 214 215 /* 216 * Re-open the directory. 217 * This has the effect of rewinding back to the 218 * top of the union stack and is needed by 219 * programs which plan to fchdir to a descriptor 220 * which has also been read -- see fts.c. 221 */ 222 if (flags & DTF_REWIND) { 223 (void) close(fd); 224 if ((fd = open(name, O_RDONLY)) == -1 || 225 fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { 226 dirp->dd_buf = buf; 227 goto error; 228 } 229 } 230 231 /* 232 * There is now a buffer full of (possibly) duplicate 233 * names. 234 */ 235 dirp->dd_buf = buf; 236 237 /* 238 * Go round this loop twice... 239 * 240 * Scan through the buffer, counting entries. 241 * On the second pass, save pointers to each one. 242 * Then sort the pointers and remove duplicate names. 243 */ 244 if (!nfsdir) { 245 for (dpv = 0;;) { 246 for (n = 0, ddptr = buf; ddptr < ddeptr;) { 247 struct dirent *dp; 248 249 dp = (struct dirent *)(void *)ddptr; 250 if ((long)dp & _DIRENT_ALIGN(dp)) 251 break; 252 /* 253 * d_reclen is unsigned, 254 * so no need to compare <= 0 255 */ 256 if (dp->d_reclen > (ddeptr + 1 - ddptr)) 257 break; 258 ddptr += dp->d_reclen; 259 if (dp->d_fileno) { 260 if (dpv) 261 dpv[n] = dp; 262 n++; 263 } 264 } 265 266 if (dpv) { 267 struct dirent *xp; 268 269 /* 270 * This sort must be stable. 271 */ 272 mergesort(dpv, (size_t)n, sizeof(*dpv), 273 alphasort); 274 275 dpv[n] = NULL; 276 xp = NULL; 277 278 /* 279 * Scan through the buffer in sort 280 * order, zapping the inode number 281 * of any duplicate names. 282 */ 283 for (n = 0; dpv[n]; n++) { 284 struct dirent *dp = dpv[n]; 285 286 if ((xp == NULL) || 287 strcmp(dp->d_name, 288 xp->d_name)) 289 xp = dp; 290 else 291 dp->d_fileno = 0; 292 if (dp->d_type == DT_WHT && 293 (flags & DTF_HIDEW)) 294 dp->d_fileno = 0; 295 } 296 297 free(dpv); 298 break; 299 } else { 300 dpv = malloc((n + 1) * 301 sizeof(struct dirent *)); 302 if (dpv == NULL) 303 break; 304 } 305 } 306 } 307 308 dirp->dd_len = len; 309 dirp->dd_size = ddptr - dirp->dd_buf; 310 } else { 311 dirp->dd_len = incr; 312 dirp->dd_buf = malloc((size_t)dirp->dd_len); 313 if (dirp->dd_buf == NULL) 314 goto error; 315 dirp->dd_seek = 0; 316 flags &= ~DTF_REWIND; 317 } 318 319 dirp->dd_loc = 0; 320 dirp->dd_fd = fd; 321 dirp->dd_flags = flags; 322 323 /* 324 * Set up seek point for rewinddir. 325 */ 326 #ifdef _REENTRANT 327 if (__isthreaded) { 328 if ((dirp->dd_lock = malloc(sizeof(mutex_t))) == NULL) 329 goto error; 330 mutex_init((mutex_t *)dirp->dd_lock, NULL); 331 } 332 #endif 333 dirp->dd_internal = NULL; 334 (void)_telldir_unlocked(dirp); 335 return (dirp); 336 error: 337 serrno = errno; 338 if (dirp && dirp->dd_buf) 339 free(dirp->dd_buf); 340 if (dirp) 341 free(dirp); 342 if (fd != -1) 343 (void)close(fd); 344 errno = serrno; 345 return NULL; 346 } 347