gen/getcwd-fbsd.c

   1 /*
   2  * Copyright (c) 1989, 1991, 1993, 1995
   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  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 static char sccsid[] = "@(#)getcwd.c    8.5 (Berkeley) 2/7/95";
  36 #endif /* LIBC_SCCS and not lint */
  37 #include <sys/cdefs.h>
  38 __FBSDID("$FreeBSD: src/lib/libc/gen/getcwd.c,v 1.25 2003/10/29 10:45:01 tjr Exp $");
  39
  40 #include "namespace.h"
  41 #include <sys/param.h>
  42 #include <sys/stat.h>
  43
  44 #include <dirent.h>
  45 #include <errno.h>
  46 #include <fcntl.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include <string.h>
  50 #include <unistd.h>
  51 #include "un-namespace.h"
  52
  53 #define ISDOT(dp) \
  54         (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
  55             (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
  56
  57 /*
  58  * If __getcwd() ever becomes a syscall, we can remove this workaround.
  59  * The problem here is that fcntl() assumes a buffer of size MAXPATHLEN,
  60  * if size is less than MAXPATHLEN, we need to use a temporary buffer
  61  * and see if it fits.  We also have to assume that open() or fcntl()
  62  * don't fail with errno=ERANGE.
  63  */
  64 static inline int
  65 __getcwd(char *buf, size_t size)
  66 {
  67         int fd, err, save;
  68         struct stat dot, pt;
  69         char *b;
  70
  71         if ((fd = open(".", O_RDONLY)) < 0)
  72                 return -1;
  73         if (fstat(fd, &dot) < 0) {
  74                 save = errno;
  75                 close(fd);
  76                 errno = save;
  77                 return -1;
  78         }
  79         /* check that the device and inode are non-zero, otherwise punt */
  80         if (dot.st_dev == 0 || dot.st_ino == 0) {
  81                 close(fd);
  82                 errno = EINVAL;
  83                 return -1;
  84         }
  85         if (size < MAXPATHLEN) {
  86                 /* the hard case; allocate a buffer of size MAXPATHLEN to use */
  87                 b = (char *)alloca(MAXPATHLEN);
  88                 if (b == NULL) {
  89                         close(fd);
  90                         errno = ENOMEM; /* make sure it isn't ERANGE */
  91                         return -1;
  92                 }
  93         } else
  94                 b = buf;
  95
  96         err = fcntl(fd, F_GETPATH, b);
  97         if (err) {
  98                 save = errno;
  99                 close(fd);
 100                 errno = save;
 101                 return err;
 102         }
 103         close(fd);
 104         /*
 105          * now double-check that the path returned by fcntl() has the same
 106          * device and inode number as '.'.
 107          */
 108         if (stat(b, &pt) < 0)
 109                 return -1;
 110         /*
 111          * Since dot.st_dev and dot.st_ino are non-zero, we don't need to
 112          * separately test for pt.st_dev and pt.st_ino being non-zero, because
 113          * they have to match
 114          */
 115         if (dot.st_dev != pt.st_dev || dot.st_ino != pt.st_ino) {
 116                 errno = EINVAL;
 117                 return -1;
 118         }
 119         /*
 120          * For the case where we allocated a buffer, check that it can fit
 121          * in the real buffer, and copy it over.
 122          */
 123         if (size < MAXPATHLEN) {
 124                 if (strlen(b) >= size) {
 125                         errno = ERANGE;
 126                         return -1;
 127                 }
 128                 strcpy(buf, b);
 129         }
 130         return 0;
 131 }
 132
 133 __private_extern__ char *
 134 __private_getcwd(pt, size, usegetpath)
 135         char *pt;
 136         size_t size;
 137         int usegetpath;
 138 {
 139         struct dirent *dp;
 140         DIR *dir = NULL;
 141         dev_t dev;
 142         ino_t ino;
 143         int first;
 144         char *bpt, *bup;
 145         struct stat s;
 146         dev_t root_dev;
 147         ino_t root_ino;
 148         size_t ptsize, upsize;
 149         int save_errno;
 150         char *ept, *eup, *up, c;
 151
 152         /*
 153          * If no buffer specified by the user, allocate one as necessary.
 154          * If a buffer is specified, the size has to be non-zero.  The path
 155          * is built from the end of the buffer backwards.
 156          */
 157         if (pt) {
 158                 ptsize = 0;
 159                 if (!size) {
 160                         errno = EINVAL;
 161                         return (NULL);
 162                 }
 163                 if (size == 1) {
 164                         errno = ERANGE;
 165                         return (NULL);
 166                 }
 167                 ept = pt + size;
 168         } else {
 169                 if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
 170                         return (NULL);
 171                 ept = pt + ptsize;
 172         }
 173         if (usegetpath) {
 174                 if (__getcwd(pt, ept - pt) == 0) {
 175                         return (pt);
 176                 } else if (errno == ERANGE) /* failed because buffer too small */
 177                         return NULL;
 178         }
 179         bpt = ept - 1;
 180         *bpt = '\0';
 181
 182         /*
 183          * Allocate bytes MAXPATHLEN) for the string of "../"'s.
 184          * Should always be enough (it's 340 levels).  If it's not, allocate
 185          * as necessary.  Special case the first stat, it's ".", not "..".
 186          */
 187         if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
 188                 goto err;
 189         eup = up + MAXPATHLEN;
 190         bup = up;
 191         up[0] = '.';
 192         up[1] = '\0';
 193
 194         /* Save root values, so know when to stop. */
 195         if (stat("/", &s))
 196                 goto err;
 197         root_dev = s.st_dev;
 198         root_ino = s.st_ino;
 199
 200         errno = 0;                      /* XXX readdir has no error return. */
 201
 202         for (first = 1;; first = 0) {
 203                 /* Stat the current level. */
 204                 if (lstat(up, &s))
 205                         goto err;
 206
 207                 /* Save current node values. */
 208                 ino = s.st_ino;
 209                 dev = s.st_dev;
 210
 211                 /* Check for reaching root. */
 212                 if (root_dev == dev && root_ino == ino) {
 213                         *--bpt = '/';
 214                         /*
 215                          * It's unclear that it's a requirement to copy the
 216                          * path to the beginning of the buffer, but it's always
 217                          * been that way and stuff would probably break.
 218                          */
 219                         bcopy(bpt, pt, ept - bpt);
 220                         free(up);
 221                         return (pt);
 222                 }
 223
 224                 /*
 225                  * Build pointer to the parent directory, allocating memory
 226                  * as necessary.  Max length is 3 for "../", the largest
 227                  * possible component name, plus a trailing NUL.
 228                  */
 229                 if (bup + 3  + MAXNAMLEN + 1 >= eup) {
 230                         if ((up = reallocf(up, upsize *= 2)) == NULL)
 231                                 goto err;
 232                         bup = up;
 233                         eup = up + upsize;
 234                 }
 235                 *bup++ = '.';
 236                 *bup++ = '.';
 237                 *bup = '\0';
 238
 239                 /* Open and stat parent directory. */
 240                 if (!(dir = opendir(up)) || _fstat(dirfd(dir), &s))
 241                         goto err;
 242
 243                 /* Add trailing slash for next directory. */
 244                 *bup++ = '/';
 245                 *bup = '\0';
 246
 247                 /*
 248                  * If it's a mount point, have to stat each element because
 249                  * the inode number in the directory is for the entry in the
 250                  * parent directory, not the inode number of the mounted file.
 251                  */
 252                 save_errno = 0;
 253                 if (s.st_dev == dev) {
 254                         for (;;) {
 255                                 if (!(dp = readdir(dir)))
 256                                         goto notfound;
 257                                 if (dp->d_fileno == ino)
 258                                         break;
 259                         }
 260                 } else
 261                         for (;;) {
 262                                 if (!(dp = readdir(dir)))
 263                                         goto notfound;
 264                                 if (ISDOT(dp))
 265                                         continue;
 266                                 bcopy(dp->d_name, bup, dp->d_namlen + 1);
 267
 268                                 /* Save the first error for later. */
 269                                 if (lstat(up, &s)) {
 270                                         if (!save_errno)
 271                                                 save_errno = errno;
 272                                         errno = 0;
 273                                         continue;
 274                                 }
 275                                 if (s.st_dev == dev && s.st_ino == ino)
 276                                         break;
 277                         }
 278
 279                 /*
 280                  * Check for length of the current name, preceding slash,
 281                  * leading slash.
 282                  */
 283                 if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
 284                         size_t len, off;
 285
 286                         if (!ptsize) {
 287                                 errno = ERANGE;
 288                                 goto err;
 289                         }
 290                         off = bpt - pt;
 291                         len = ept - bpt;
 292                         if ((pt = reallocf(pt, ptsize *= 2)) == NULL)
 293                                 goto err;
 294                         bpt = pt + off;
 295                         ept = pt + ptsize;
 296                         bcopy(bpt, ept - len, len);
 297                         bpt = ept - len;
 298                 }
 299                 if (!first)
 300                         *--bpt = '/';
 301                 bpt -= dp->d_namlen;
 302                 bcopy(dp->d_name, bpt, dp->d_namlen);
 303                 (void) closedir(dir);
 304                 dir = NULL;
 305
 306                 /* Truncate any file name. */
 307                 *bup = '\0';
 308         }
 309
 310 notfound:
 311         /*
 312          * If readdir set errno, use it, not any saved error; otherwise,
 313          * didn't find the current directory in its parent directory, set
 314          * errno to ENOENT.
 315          */
 316         if (!errno)
 317                 errno = save_errno ? save_errno : ENOENT;
 318         /* FALLTHROUGH */
 319 err:
 320         save_errno = errno;
 321
 322         if (ptsize)
 323                 free(pt);
 324         if (dir)
 325                 (void) closedir(dir);
 326         free(up);
 327
 328         errno = save_errno;
 329         return (NULL);
 330 }
 331
 332 char *
 333 getcwd(pt, size)
 334         char *pt;
 335         size_t size;
 336 {
 337         return __private_getcwd(pt, size, 1);
 338 }