lib/libc/gen/opendir.c

   1 /*      $NetBSD: opendir.c,v 1.33.12.1 2009/01/04 17:02:19 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 1.33.12.1 2009/01/04 17:02:19 christos 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         _DIAGASSERT(name != NULL);
 108
 109         if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
 110                 goto error;
 111         if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) {
 112                 errno = ENOTDIR;
 113                 goto error;
 114         }
 115         if ((dirp = (DIR *)malloc(sizeof(DIR))) == NULL)
 116                 goto error;
 117         dirp->dd_buf = NULL;
 118
 119         /*
 120          * If the machine's page size is an exact multiple of DIRBLKSIZ,
 121          * use a buffer that is cluster boundary aligned.
 122          * Hopefully this can be a big win someday by allowing page trades
 123          * to user space to be done by getdirentries()
 124          */
 125         if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0)
 126                 incr = pagesz;
 127         else
 128                 incr = DIRBLKSIZ;
 129
 130         /*
 131          * Determine whether this directory is the top of a union stack.
 132          */
 133
 134         if (fstatvfs1(fd, &sfb, ST_NOWAIT) < 0)
 135                 goto error;
 136
 137         if (flags & DTF_NODUP)
 138                 unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION,
 139                     sizeof(sfb.f_fstypename))) || (sfb.f_flag & MNT_UNION);
 140         else
 141                 unionstack = 0;
 142
 143         nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, sizeof(sfb.f_fstypename)));
 144
 145         if (unionstack || nfsdir) {
 146                 size_t len;
 147                 size_t space;
 148                 char *buf, *nbuf;
 149                 char *ddptr;
 150                 char *ddeptr;
 151                 int n;
 152                 struct dirent **dpv;
 153                 int i;
 154
 155                 /*
 156                  * The strategy here for directories on top of a union stack
 157                  * is to read all the directory entries into a buffer, sort
 158                  * the buffer, and remove duplicate entries by setting the
 159                  * inode number to zero.
 160                  *
 161                  * For directories on an NFS mounted filesystem, we try
 162                  * to get a consistent snapshot by trying until we have
 163                  * successfully read all of the directory without errors
 164                  * (i.e. 'bad cookie' errors from the server because
 165                  * the directory was modified). These errors should not
 166                  * happen often, but need to be dealt with.
 167                  */
 168                 i = 0;
 169 retry:
 170                 len = 0;
 171                 space = 0;
 172                 buf = 0;
 173                 ddptr = 0;
 174
 175                 do {
 176                         /*
 177                          * Always make at least DIRBLKSIZ bytes
 178                          * available to getdirentries
 179                          */
 180                         if (space < DIRBLKSIZ) {
 181                                 space += incr;
 182                                 len += incr;
 183                                 nbuf = realloc(buf, len);
 184                                 if (nbuf == NULL) {
 185                                         dirp->dd_buf = buf;
 186                                         goto error;
 187                                 }
 188                                 buf = nbuf;
 189                                 ddptr = buf + (len - space);
 190                         }
 191
 192                         dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR);
 193                         n = getdents(fd, ddptr, space);
 194                         /*
 195                          * For NFS: EINVAL means a bad cookie error
 196                          * from the server. Keep trying to get a
 197                          * consistent view, in this case this means
 198                          * starting all over again.
 199                          */
 200                         if (n == -1 && errno == EINVAL && nfsdir) {
 201                                 free(buf);
 202                                 lseek(fd, (off_t)0, SEEK_SET);
 203                                 if (++i > MAXITERATIONS)
 204                                         goto error;
 205                                 goto retry;
 206                         }
 207                         if (n > 0) {
 208                                 ddptr += n;
 209                                 space -= n;
 210                         }
 211                 } while (n > 0);
 212
 213                 ddeptr = ddptr;
 214                 flags |= __DTF_READALL;
 215
 216                 /*
 217                  * Re-open the directory.
 218                  * This has the effect of rewinding back to the
 219                  * top of the union stack and is needed by
 220                  * programs which plan to fchdir to a descriptor
 221                  * which has also been read -- see fts.c.
 222                  */
 223                 if (flags & DTF_REWIND) {
 224                         (void) close(fd);
 225                         if ((fd = open(name, O_RDONLY)) == -1 ||
 226                             fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
 227                                 dirp->dd_buf = buf;
 228                                 goto error;
 229                         }
 230                 }
 231
 232                 /*
 233                  * There is now a buffer full of (possibly) duplicate
 234                  * names.
 235                  */
 236                 dirp->dd_buf = buf;
 237
 238                 /*
 239                  * Go round this loop twice...
 240                  *
 241                  * Scan through the buffer, counting entries.
 242                  * On the second pass, save pointers to each one.
 243                  * Then sort the pointers and remove duplicate names.
 244                  */
 245                 if (!nfsdir) {
 246                         for (dpv = 0;;) {
 247                                 for (n = 0, ddptr = buf; ddptr < ddeptr;) {
 248                                         struct dirent *dp;
 249
 250                                         dp = (struct dirent *)(void *)ddptr;
 251                                         if ((long)dp & _DIRENT_ALIGN(dp))
 252                                                 break;
 253                                         /*
 254                                          * d_reclen is unsigned,
 255                                          * so no need to compare <= 0
 256                                          */
 257                                         if (dp->d_reclen > (ddeptr + 1 - ddptr))
 258                                                 break;
 259                                         ddptr += dp->d_reclen;
 260                                         if (dp->d_fileno) {
 261                                                 if (dpv)
 262                                                         dpv[n] = dp;
 263                                                 n++;
 264                                         }
 265                                 }
 266
 267                                 if (dpv) {
 268                                         struct dirent *xp;
 269
 270                                         /*
 271                                          * This sort must be stable.
 272                                          */
 273                                         mergesort(dpv, (size_t)n, sizeof(*dpv),
 274                                             alphasort);
 275
 276                                         dpv[n] = NULL;
 277                                         xp = NULL;
 278
 279                                         /*
 280                                          * Scan through the buffer in sort
 281                                          * order, zapping the inode number
 282                                          * of any duplicate names.
 283                                          */
 284                                         for (n = 0; dpv[n]; n++) {
 285                                                 struct dirent *dp = dpv[n];
 286
 287                                                 if ((xp == NULL) ||
 288                                                     strcmp(dp->d_name,
 289                                                       xp->d_name))
 290                                                         xp = dp;
 291                                                 else
 292                                                         dp->d_fileno = 0;
 293                                                 if (dp->d_type == DT_WHT &&
 294                                                     (flags & DTF_HIDEW))
 295                                                         dp->d_fileno = 0;
 296                                         }
 297
 298                                         free(dpv);
 299                                         break;
 300                                 } else {
 301                                         dpv = malloc((n + 1) *
 302                                             sizeof(struct dirent *));
 303                                         if (dpv == NULL)
 304                                                 break;
 305                                 }
 306                         }
 307                 }
 308
 309                 dirp->dd_len = len;
 310                 dirp->dd_size = ddptr - dirp->dd_buf;
 311         } else {
 312                 dirp->dd_len = incr;
 313                 dirp->dd_buf = malloc((size_t)dirp->dd_len);
 314                 if (dirp->dd_buf == NULL)
 315                         goto error;
 316                 dirp->dd_seek = 0;
 317                 flags &= ~DTF_REWIND;
 318         }
 319
 320         dirp->dd_loc = 0;
 321         dirp->dd_fd = fd;
 322         dirp->dd_flags = flags;
 323
 324         /*
 325          * Set up seek point for rewinddir.
 326          */
 327 #ifdef _REENTRANT
 328         if (__isthreaded) {
 329                 if ((dirp->dd_lock = malloc(sizeof(mutex_t))) == NULL)
 330                         goto error;
 331                 mutex_init((mutex_t *)dirp->dd_lock, NULL);
 332         }
 333 #endif
 334         dirp->dd_internal = NULL;
 335         (void)_telldir_unlocked(dirp);
 336         return (dirp);
 337 error:
 338         serrno = errno;
 339         if (dirp && dirp->dd_buf)
 340                 free(dirp->dd_buf);
 341         if (dirp)
 342                 free(dirp);
 343         if (fd != -1)
 344                 (void)close(fd);
 345         errno = serrno;
 346         return NULL;
 347 }