gen/FreeBSD/opendir.c

   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)
  31 static 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: src/lib/libc/gen/opendir.c,v 1.24 2008/04/16 18:40:52 delphij Exp $");
  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 /*
  51  * Open a directory.
  52  */
  53 DIR *
  54 opendir(const char *name)
  55 {
  56
  57         return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
  58 }
  59
  60 DIR *
  61 __opendir2(const char *name, int flags)
  62 {
  63         DIR *dirp;
  64         int fd;
  65         int incr;
  66         int saved_errno;
  67         int unionstack;
  68         struct stat statb;
  69
  70         /*
  71          * stat() before _open() because opening of special files may be
  72          * harmful.  _fstat() after open because the file may have changed.
  73          */
  74         if (stat(name, &statb) != 0)
  75                 return (NULL);
  76         if (!S_ISDIR(statb.st_mode)) {
  77                 errno = ENOTDIR;
  78                 return (NULL);
  79         }
  80         if ((fd = _open(name, O_RDONLY | O_NONBLOCK)) == -1)
  81                 return (NULL);
  82         dirp = NULL;
  83         if (_fstat(fd, &statb) != 0)
  84                 goto fail;
  85         if (!S_ISDIR(statb.st_mode)) {
  86                 errno = ENOTDIR;
  87                 goto fail;
  88         }
  89         if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
  90             (dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
  91                 goto fail;
  92
  93         dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
  94         LIST_INIT(&dirp->dd_td->td_locq);
  95         dirp->dd_td->td_loccnt = 0;
  96
  97         /*
  98          * Use the system page size if that is a multiple of DIRBLKSIZ.
  99          * Hopefully this can be a big win someday by allowing page
 100          * trades to user space to be done by _getdirentries().
 101          */
 102         incr = getpagesize();
 103         if ((incr % DIRBLKSIZ) != 0)
 104                 incr = DIRBLKSIZ;
 105
 106         /*
 107          * Determine whether this directory is the top of a union stack.
 108          */
 109         if (flags & DTF_NODUP) {
 110                 struct statfs sfb;
 111
 112                 if (_fstatfs(fd, &sfb) < 0)
 113                         goto fail;
 114                 unionstack = !strcmp(sfb.f_fstypename, "unionfs")
 115                     || (sfb.f_flags & MNT_UNION);
 116         } else {
 117                 unionstack = 0;
 118         }
 119
 120         if (unionstack) {
 121                 int len = 0;
 122                 int space = 0;
 123                 char *buf = 0;
 124                 char *ddptr = 0;
 125                 char *ddeptr;
 126                 int n;
 127                 struct dirent **dpv;
 128
 129                 /*
 130                  * The strategy here is to read all the directory
 131                  * entries into a buffer, sort the buffer, and
 132                  * remove duplicate entries by setting the inode
 133                  * number to zero.
 134                  */
 135
 136                 do {
 137                         /*
 138                          * Always make at least DIRBLKSIZ bytes
 139                          * available to _getdirentries
 140                          */
 141                         if (space < DIRBLKSIZ) {
 142                                 space += incr;
 143                                 len += incr;
 144                                 buf = reallocf(buf, len);
 145                                 if (buf == NULL)
 146                                         goto fail;
 147                                 ddptr = buf + (len - space);
 148                         }
 149
 150                         n = _getdirentries(fd, ddptr, space, &dirp->dd_seek);
 151                         if (n > 0) {
 152                                 ddptr += n;
 153                                 space -= n;
 154                         }
 155                 } while (n > 0);
 156
 157                 ddeptr = ddptr;
 158                 flags |= __DTF_READALL;
 159
 160                 /*
 161                  * Re-open the directory.
 162                  * This has the effect of rewinding back to the
 163                  * top of the union stack and is needed by
 164                  * programs which plan to fchdir to a descriptor
 165                  * which has also been read -- see fts.c.
 166                  */
 167                 if (flags & DTF_REWIND) {
 168                         (void)_close(fd);
 169                         if ((fd = _open(name, O_RDONLY)) == -1) {
 170                                 saved_errno = errno;
 171                                 free(buf);
 172                                 free(dirp);
 173                                 errno = saved_errno;
 174                                 return (NULL);
 175                         }
 176                 }
 177
 178                 /*
 179                  * There is now a buffer full of (possibly) duplicate
 180                  * names.
 181                  */
 182                 dirp->dd_buf = buf;
 183
 184                 /*
 185                  * Go round this loop twice...
 186                  *
 187                  * Scan through the buffer, counting entries.
 188                  * On the second pass, save pointers to each one.
 189                  * Then sort the pointers and remove duplicate names.
 190                  */
 191                 for (dpv = 0;;) {
 192                         n = 0;
 193                         ddptr = buf;
 194                         while (ddptr < ddeptr) {
 195                                 struct dirent *dp;
 196
 197                                 dp = (struct dirent *) ddptr;
 198                                 if ((long)dp & 03L)
 199                                         break;
 200                                 if ((dp->d_reclen <= 0) ||
 201                                     (dp->d_reclen > (ddeptr + 1 - ddptr)))
 202                                         break;
 203                                 ddptr += dp->d_reclen;
 204                                 if (dp->d_fileno) {
 205                                         if (dpv)
 206                                                 dpv[n] = dp;
 207                                         n++;
 208                                 }
 209                         }
 210
 211                         if (dpv) {
 212                                 struct dirent *xp;
 213
 214                                 /*
 215                                  * This sort must be stable.
 216                                  */
 217                                 mergesort(dpv, n, sizeof(*dpv), alphasort);
 218
 219                                 dpv[n] = NULL;
 220                                 xp = NULL;
 221
 222                                 /*
 223                                  * Scan through the buffer in sort order,
 224                                  * zapping the inode number of any
 225                                  * duplicate names.
 226                                  */
 227                                 for (n = 0; dpv[n]; n++) {
 228                                         struct dirent *dp = dpv[n];
 229
 230                                         if ((xp == NULL) ||
 231                                             strcmp(dp->d_name, xp->d_name)) {
 232                                                 xp = dp;
 233                                         } else {
 234                                                 dp->d_fileno = 0;
 235                                         }
 236                                         if (dp->d_type == DT_WHT &&
 237                                             (flags & DTF_HIDEW))
 238                                                 dp->d_fileno = 0;
 239                                 }
 240
 241                                 free(dpv);
 242                                 break;
 243                         } else {
 244                                 dpv = malloc((n+1) * sizeof(struct dirent *));
 245                                 if (dpv == NULL)
 246                                         break;
 247                         }
 248                 }
 249
 250                 dirp->dd_len = len;
 251                 dirp->dd_size = ddptr - dirp->dd_buf;
 252         } else {
 253                 dirp->dd_len = incr;
 254                 dirp->dd_size = 0;
 255                 dirp->dd_buf = malloc(dirp->dd_len);
 256                 if (dirp->dd_buf == NULL)
 257                         goto fail;
 258                 dirp->dd_seek = 0;
 259                 flags &= ~DTF_REWIND;
 260         }
 261
 262         dirp->dd_loc = 0;
 263         dirp->dd_fd = fd;
 264         dirp->dd_flags = flags;
 265         dirp->dd_lock = NULL;
 266
 267         /*
 268          * Set up seek point for rewinddir.
 269          */
 270         dirp->dd_rewind = telldir(dirp);
 271
 272         return (dirp);
 273
 274 fail:
 275         saved_errno = errno;
 276         free(dirp);
 277         (void)_close(fd);
 278         errno = saved_errno;
 279         return (NULL);
 280 }