1 /* $NetBSD: opendir.c,v 1.25 2004/04/21 01:05:32 christos 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 1.25 2004/04/21 01:05:32 christos Exp $"); 38 #endif 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include "namespace.h" 42 #include "reentrant.h" 43 #include <sys/param.h> 44 #include <sys/mount.h> 45 #include <sys/stat.h> 46 47 #include <assert.h> 48 #include <dirent.h> 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 55 #ifdef __weak_alias 56 __weak_alias(opendir,_opendir) 57 #endif 58 59 /* 60 * Open a directory. 61 */ 62 DIR * 63 opendir(name) 64 const char *name; 65 { 66 67 _DIAGASSERT(name != NULL); 68 69 return (__opendir2(name, DTF_HIDEW|DTF_NODUP)); 70 } 71 72 DIR * 73 __opendir2(name, flags) 74 const char *name; 75 int flags; 76 { 77 DIR *dirp = NULL; 78 int fd; 79 int serrno; 80 struct stat sb; 81 int pagesz; 82 int incr; 83 int unionstack, nfsdir; 84 struct statvfs sfb; 85 86 _DIAGASSERT(name != NULL); 87 88 if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1) 89 return (NULL); 90 if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) { 91 close(fd); 92 errno = ENOTDIR; 93 return (NULL); 94 } 95 if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 || 96 (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) { 97 goto error; 98 } 99 dirp->dd_buf = NULL; 100 101 /* 102 * If the machine's page size is an exact multiple of DIRBLKSIZ, 103 * use a buffer that is cluster boundary aligned. 104 * Hopefully this can be a big win someday by allowing page trades 105 * to user space to be done by getdirentries() 106 */ 107 if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0) 108 incr = pagesz; 109 else 110 incr = DIRBLKSIZ; 111 112 /* 113 * Determine whether this directory is the top of a union stack. 114 */ 115 116 if (fstatvfs1(fd, &sfb, ST_NOWAIT) < 0) 117 goto error; 118 119 if (flags & DTF_NODUP) 120 unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION, 121 MFSNAMELEN)) || (sfb.f_flag & MNT_UNION); 122 else 123 unionstack = 0; 124 125 nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, MFSNAMELEN)); 126 127 if (unionstack || nfsdir) { 128 size_t len; 129 size_t space; 130 char *buf, *nbuf; 131 char *ddptr; 132 char *ddeptr; 133 int n; 134 struct dirent **dpv; 135 136 /* 137 * The strategy here for directories on top of a union stack 138 * is to read all the directory entries into a buffer, sort 139 * the buffer, and remove duplicate entries by setting the 140 * inode number to zero. 141 * 142 * For directories on an NFS mounted filesystem, we try 143 * to get a consistent snapshot by trying until we have 144 * successfully read all of the directory without errors 145 * (i.e. 'bad cookie' errors from the server because 146 * the directory was modified). These errors should not 147 * happen often, but need to be dealt with. 148 */ 149 retry: 150 len = 0; 151 space = 0; 152 buf = 0; 153 ddptr = 0; 154 155 do { 156 /* 157 * Always make at least DIRBLKSIZ bytes 158 * available to getdirentries 159 */ 160 if (space < DIRBLKSIZ) { 161 space += incr; 162 len += incr; 163 nbuf = realloc(buf, len); 164 if (nbuf == NULL) { 165 dirp->dd_buf = buf; 166 goto error; 167 } 168 buf = nbuf; 169 ddptr = buf + (len - space); 170 } 171 172 dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR); 173 n = getdents(fd, ddptr, space); 174 /* 175 * For NFS: EINVAL means a bad cookie error 176 * from the server. Keep trying to get a 177 * consistent view, in this case this means 178 * starting all over again. 179 */ 180 if (n == -1 && errno == EINVAL && nfsdir) { 181 free(buf); 182 lseek(fd, (off_t)0, SEEK_SET); 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 dirp->dd_buf = buf; 205 goto error; 206 } 207 } 208 209 /* 210 * There is now a buffer full of (possibly) duplicate 211 * names. 212 */ 213 dirp->dd_buf = buf; 214 215 /* 216 * Go round this loop twice... 217 * 218 * Scan through the buffer, counting entries. 219 * On the second pass, save pointers to each one. 220 * Then sort the pointers and remove duplicate names. 221 */ 222 if (!nfsdir) { 223 for (dpv = 0;;) { 224 for (n = 0, ddptr = buf; ddptr < ddeptr;) { 225 struct dirent *dp; 226 227 dp = (struct dirent *)(void *)ddptr; 228 if ((long)dp & 03) 229 break; 230 /* 231 * d_reclen is unsigned, 232 * so no need to compare <= 0 233 */ 234 if (dp->d_reclen > (ddeptr + 1 - ddptr)) 235 break; 236 ddptr += dp->d_reclen; 237 if (dp->d_fileno) { 238 if (dpv) 239 dpv[n] = dp; 240 n++; 241 } 242 } 243 244 if (dpv) { 245 struct dirent *xp; 246 247 /* 248 * This sort must be stable. 249 */ 250 mergesort(dpv, (size_t)n, sizeof(*dpv), 251 alphasort); 252 253 dpv[n] = NULL; 254 xp = NULL; 255 256 /* 257 * Scan through the buffer in sort 258 * order, zapping the inode number 259 * of any duplicate names. 260 */ 261 for (n = 0; dpv[n]; n++) { 262 struct dirent *dp = dpv[n]; 263 264 if ((xp == NULL) || 265 strcmp(dp->d_name, 266 xp->d_name)) 267 xp = dp; 268 else 269 dp->d_fileno = 0; 270 if (dp->d_type == DT_WHT && 271 (flags & DTF_HIDEW)) 272 dp->d_fileno = 0; 273 } 274 275 free(dpv); 276 break; 277 } else { 278 dpv = malloc((n + 1) * 279 sizeof(struct dirent *)); 280 if (dpv == NULL) 281 break; 282 } 283 } 284 } 285 286 dirp->dd_len = len; 287 dirp->dd_size = ddptr - dirp->dd_buf; 288 } else { 289 dirp->dd_len = incr; 290 dirp->dd_buf = malloc((size_t)dirp->dd_len); 291 if (dirp->dd_buf == NULL) 292 goto error; 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; 300 301 /* 302 * Set up seek point for rewinddir. 303 */ 304 #ifdef _REENTRANT 305 if (__isthreaded) { 306 if ((dirp->dd_lock = malloc(sizeof(mutex_t))) == NULL) 307 goto error; 308 mutex_init((mutex_t *)dirp->dd_lock, NULL); 309 } 310 #endif 311 dirp->dd_rewind = telldir(dirp); 312 return (dirp); 313 error: 314 serrno = errno; 315 if (dirp && dirp->dd_buf) 316 free(dirp->dd_buf); 317 if (dirp) 318 free(dirp); 319 if (fd != -1) 320 (void)close(fd); 321 errno = serrno; 322 return NULL; 323 } 324