openbsd-compat/getcwd.c

   1 /* OPENBSD ORIGINAL: lib/libc/gen/getcwd.c */
   2
   3 /*
   4  * Copyright (c) 1989, 1991, 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 "includes.h"
  33
  34 #if !defined(HAVE_GETCWD)
  35
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 static char rcsid[] = "$OpenBSD: getcwd.c,v 1.9 2003/06/11 21:03:10 deraadt Exp $";
  38 #endif /* LIBC_SCCS and not lint */
  39
  40 #include <sys/param.h>
  41 #include <sys/stat.h>
  42 #include <errno.h>
  43 #include <dirent.h>
  44 #include <sys/dir.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48 #include "includes.h"
  49
  50 #define ISDOT(dp) \
  51         (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
  52             (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
  53
  54 char *
  55 getcwd(char *pt, size_t size)
  56 {
  57         register struct dirent *dp;
  58         register DIR *dir = NULL;
  59         register dev_t dev;
  60         register ino_t ino;
  61         register int first;
  62         register char *bpt, *bup;
  63         struct stat s;
  64         dev_t root_dev;
  65         ino_t root_ino;
  66         size_t ptsize, upsize;
  67         int save_errno;
  68         char *ept, *eup, *up;
  69
  70         /*
  71          * If no buffer specified by the user, allocate one as necessary.
  72          * If a buffer is specified, the size has to be non-zero.  The path
  73          * is built from the end of the buffer backwards.
  74          */
  75         if (pt) {
  76                 ptsize = 0;
  77                 if (!size) {
  78                         errno = EINVAL;
  79                         return (NULL);
  80                 }
  81                 ept = pt + size;
  82         } else {
  83                 if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
  84                         return (NULL);
  85                 ept = pt + ptsize;
  86         }
  87         bpt = ept - 1;
  88         *bpt = '\0';
  89
  90         /*
  91          * Allocate bytes (1024 - malloc space) for the string of "../"'s.
  92          * Should always be enough (it's 340 levels).  If it's not, allocate
  93          * as necessary.  Special * case the first stat, it's ".", not "..".
  94          */
  95         if ((up = malloc(upsize = 1024 - 4)) == NULL)
  96                 goto err;
  97         eup = up + MAXPATHLEN;
  98         bup = up;
  99         up[0] = '.';
 100         up[1] = '\0';
 101
 102         /* Save root values, so know when to stop. */
 103         if (stat("/", &s))
 104                 goto err;
 105         root_dev = s.st_dev;
 106         root_ino = s.st_ino;
 107
 108         errno = 0;                      /* XXX readdir has no error return. */
 109
 110         for (first = 1;; first = 0) {
 111                 /* Stat the current level. */
 112                 if (lstat(up, &s))
 113                         goto err;
 114
 115                 /* Save current node values. */
 116                 ino = s.st_ino;
 117                 dev = s.st_dev;
 118
 119                 /* Check for reaching root. */
 120                 if (root_dev == dev && root_ino == ino) {
 121                         *--bpt = '/';
 122                         /*
 123                          * It's unclear that it's a requirement to copy the
 124                          * path to the beginning of the buffer, but it's always
 125                          * been that way and stuff would probably break.
 126                          */
 127                         memmove(pt, bpt, ept - bpt);
 128                         free(up);
 129                         return (pt);
 130                 }
 131
 132                 /*
 133                  * Build pointer to the parent directory, allocating memory
 134                  * as necessary.  Max length is 3 for "../", the largest
 135                  * possible component name, plus a trailing NUL.
 136                  */
 137                 if (bup + 3  + MAXNAMLEN + 1 >= eup) {
 138                         char *nup;
 139
 140                         if ((nup = realloc(up, upsize *= 2)) == NULL)
 141                                 goto err;
 142                         up = nup;
 143                         bup = up;
 144                         eup = up + upsize;
 145                 }
 146                 *bup++ = '.';
 147                 *bup++ = '.';
 148                 *bup = '\0';
 149
 150                 /* Open and stat parent directory.
 151                  * RACE?? - replaced fstat(dirfd(dir), &s) w/ lstat(up,&s)
 152                  */
 153                 if (!(dir = opendir(up)) || lstat(up,&s))
 154                         goto err;
 155
 156                 /* Add trailing slash for next directory. */
 157                 *bup++ = '/';
 158
 159                 /*
 160                  * If it's a mount point, have to stat each element because
 161                  * the inode number in the directory is for the entry in the
 162                  * parent directory, not the inode number of the mounted file.
 163                  */
 164                 save_errno = 0;
 165                 if (s.st_dev == dev) {
 166                         for (;;) {
 167                                 if (!(dp = readdir(dir)))
 168                                         goto notfound;
 169                                 if (dp->d_fileno == ino)
 170                                         break;
 171                         }
 172                 } else
 173                         for (;;) {
 174                                 if (!(dp = readdir(dir)))
 175                                         goto notfound;
 176                                 if (ISDOT(dp))
 177                                         continue;
 178                                 memmove(bup, dp->d_name, dp->d_namlen + 1);
 179
 180                                 /* Save the first error for later. */
 181                                 if (lstat(up, &s)) {
 182                                         if (!save_errno)
 183                                                 save_errno = errno;
 184                                         errno = 0;
 185                                         continue;
 186                                 }
 187                                 if (s.st_dev == dev && s.st_ino == ino)
 188                                         break;
 189                         }
 190
 191                 /*
 192                  * Check for length of the current name, preceding slash,
 193                  * leading slash.
 194                  */
 195                 if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
 196                         size_t len, off;
 197                         char *npt;
 198
 199                         if (!ptsize) {
 200                                 errno = ERANGE;
 201                                 goto err;
 202                         }
 203                         off = bpt - pt;
 204                         len = ept - bpt;
 205                         if ((npt = realloc(pt, ptsize *= 2)) == NULL)
 206                                 goto err;
 207                         pt = npt;
 208                         bpt = pt + off;
 209                         ept = pt + ptsize;
 210                         memmove(ept - len, bpt, len);
 211                         bpt = ept - len;
 212                 }
 213                 if (!first)
 214                         *--bpt = '/';
 215                 bpt -= dp->d_namlen;
 216                 memmove(bpt, dp->d_name, dp->d_namlen);
 217                 (void)closedir(dir);
 218
 219                 /* Truncate any file name. */
 220                 *bup = '\0';
 221         }
 222
 223 notfound:
 224         /*
 225          * If readdir set errno, use it, not any saved error; otherwise,
 226          * didn't find the current directory in its parent directory, set
 227          * errno to ENOENT.
 228          */
 229         if (!errno)
 230                 errno = save_errno ? save_errno : ENOENT;
 231         /* FALLTHROUGH */
 232 err:
 233         if (ptsize)
 234                 free(pt);
 235         if (up)
 236                 free(up);
 237         if (dir)
 238                 (void)closedir(dir);
 239         return (NULL);
 240 }
 241
 242 #endif /* !defined(HAVE_GETCWD) */