gen/FreeBSD/getcwd.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  * 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[] = "@(#)getcwd.c    8.5 (Berkeley) 2/7/95";
  32 #endif /* LIBC_SCCS and not lint */
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD: src/lib/libc/gen/getcwd.c,v 1.29 2007/01/09 00:27:53 imp Exp $");
  35
  36 #include "namespace.h"
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39
  40 #include <dirent.h>
  41 #include <errno.h>
  42 #include <fcntl.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46 #include <unistd.h>
  47 #include "un-namespace.h"
  48
  49 #define ISDOT(dp) \
  50         (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
  51             (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
  52
  53 /*
  54  * If __getcwd() ever becomes a syscall, we can remove this workaround.
  55  * The problem here is that fcntl() assumes a buffer of size MAXPATHLEN,
  56  * if size is less than MAXPATHLEN, we need to use a temporary buffer
  57  * and see if it fits.  We also have to assume that open() or fcntl()
  58  * don't fail with errno=ERANGE.
  59  */
  60 static inline int
  61 __getcwd(char *buf, size_t size)
  62 {
  63         int fd, err, save;
  64         struct stat dot, pt;
  65         char *b;
  66
  67         if ((fd = open(".", O_RDONLY)) < 0)
  68                 return -1;
  69         if (fstat(fd, &dot) < 0) {
  70                 save = errno;
  71                 close(fd);
  72                 errno = save;
  73                 return -1;
  74         }
  75         /* check that the device and inode are non-zero, otherwise punt */
  76         if (dot.st_dev == 0 || dot.st_ino == 0) {
  77                 close(fd);
  78                 errno = EINVAL;
  79                 return -1;
  80         }
  81         if (size < MAXPATHLEN) {
  82                 /* the hard case; allocate a buffer of size MAXPATHLEN to use */
  83                 b = (char *)alloca(MAXPATHLEN);
  84                 if (b == NULL) {
  85                         close(fd);
  86                         errno = ENOMEM; /* make sure it isn't ERANGE */
  87                         return -1;
  88                 }
  89         } else
  90                 b = buf;
  91
  92         err = fcntl(fd, F_GETPATH, b);
  93         if (err) {
  94                 save = errno;
  95                 close(fd);
  96                 errno = save;
  97                 return err;
  98         }
  99         close(fd);
 100         /*
 101          * now double-check that the path returned by fcntl() has the same
 102          * device and inode number as '.'.
 103          */
 104         if (stat(b, &pt) < 0)
 105                 return -1;
 106         /*
 107          * Since dot.st_dev and dot.st_ino are non-zero, we don't need to
 108          * separately test for pt.st_dev and pt.st_ino being non-zero, because
 109          * they have to match
 110          */
 111         if (dot.st_dev != pt.st_dev || dot.st_ino != pt.st_ino) {
 112                 errno = EINVAL;
 113                 return -1;
 114         }
 115         /*
 116          * For the case where we allocated a buffer, check that it can fit
 117          * in the real buffer, and copy it over.
 118          */
 119         if (size < MAXPATHLEN) {
 120                 if (strlen(b) >= size) {
 121                         errno = ERANGE;
 122                         return -1;
 123                 }
 124                 strcpy(buf, b);
 125         }
 126         return 0;
 127 }
 128
 129 __private_extern__ char *
 130 __private_getcwd(pt, size, usegetpath)
 131         char *pt;
 132         size_t size;
 133         int usegetpath;
 134 {
 135         struct dirent *dp;
 136         DIR *dir = NULL;
 137         dev_t dev;
 138         ino_t ino;
 139         int first;
 140         char *bpt, *bup;
 141         struct stat s;
 142         dev_t root_dev;
 143         ino_t root_ino;
 144         size_t ptsize, upsize;
 145         int save_errno;
 146         char *ept, *eup, *up;
 147
 148         /*
 149          * If no buffer specified by the user, allocate one as necessary.
 150          * If a buffer is specified, the size has to be non-zero.  The path
 151          * is built from the end of the buffer backwards.
 152          */
 153         if (pt) {
 154                 ptsize = 0;
 155                 if (!size) {
 156                         errno = EINVAL;
 157                         return (NULL);
 158                 }
 159                 if (size == 1) {
 160                         errno = ERANGE;
 161                         return (NULL);
 162                 }
 163                 ept = pt + size;
 164         } else {
 165                 if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
 166                         return (NULL);
 167                 ept = pt + ptsize;
 168         }
 169         if (usegetpath) {
 170                 if (__getcwd(pt, ept - pt) == 0) {
 171                         return (pt);
 172                 } else if (errno == ERANGE) /* failed because buffer too small */
 173                         return NULL;
 174         }
 175         bpt = ept - 1;
 176         *bpt = '\0';
 177
 178         /*
 179          * Allocate MAXPATHLEN bytes for the string of "../"'s.
 180          * Should always be enough.  If it's not, allocate
 181          * as necessary.  Special case the first stat, it's ".", not "..".
 182          */
 183         if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
 184                 goto err;
 185         eup = up + MAXPATHLEN;
 186         bup = up;
 187         up[0] = '.';
 188         up[1] = '\0';
 189
 190         /* Save root values, so know when to stop. */
 191         if (stat("/", &s))
 192                 goto err;
 193         root_dev = s.st_dev;
 194         root_ino = s.st_ino;
 195
 196         errno = 0;                      /* XXX readdir has no error return. */
 197
 198         for (first = 1;; first = 0) {
 199                 /* Stat the current level. */
 200                 if (lstat(up, &s))
 201                         goto err;
 202
 203                 /* Save current node values. */
 204                 ino = s.st_ino;
 205                 dev = s.st_dev;
 206
 207                 /* Check for reaching root. */
 208                 if (root_dev == dev && root_ino == ino) {
 209                         *--bpt = '/';
 210                         /*
 211                          * It's unclear that it's a requirement to copy the
 212                          * path to the beginning of the buffer, but it's always
 213                          * been that way and stuff would probably break.
 214                          */
 215                         bcopy(bpt, pt, ept - bpt);
 216                         free(up);
 217                         return (pt);
 218                 }
 219
 220                 /*
 221                  * Build pointer to the parent directory, allocating memory
 222                  * as necessary.  Max length is 3 for "../", the largest
 223                  * possible component name, plus a trailing NUL.
 224                  */
 225                 while (bup + 3  + MAXNAMLEN + 1 >= eup) {
 226                         if ((up = reallocf(up, upsize *= 2)) == NULL)
 227                                 goto err;
 228                         bup = up;
 229                         eup = up + upsize;
 230                 }
 231                 *bup++ = '.';
 232                 *bup++ = '.';
 233                 *bup = '\0';
 234
 235                 /* Open and stat parent directory. */
 236                 if (!(dir = opendir(up)) || _fstat(dirfd(dir), &s))
 237                         goto err;
 238
 239                 /* Add trailing slash for next directory. */
 240                 *bup++ = '/';
 241                 *bup = '\0';
 242
 243                 /*
 244                  * If it's a mount point, have to stat each element because
 245                  * the inode number in the directory is for the entry in the
 246                  * parent directory, not the inode number of the mounted file.
 247                  */
 248                 save_errno = 0;
 249                 if (s.st_dev == dev) {
 250                         for (;;) {
 251                                 if (!(dp = readdir(dir)))
 252                                         goto notfound;
 253                                 if (dp->d_fileno == ino)
 254                                         break;
 255                         }
 256                 } else
 257                         for (;;) {
 258                                 if (!(dp = readdir(dir)))
 259                                         goto notfound;
 260                                 if (ISDOT(dp))
 261                                         continue;
 262                                 bcopy(dp->d_name, bup, dp->d_namlen + 1);
 263
 264                                 /* Save the first error for later. */
 265                                 if (lstat(up, &s)) {
 266                                         if (!save_errno)
 267                                                 save_errno = errno;
 268                                         errno = 0;
 269                                         continue;
 270                                 }
 271                                 if (s.st_dev == dev && s.st_ino == ino)
 272                                         break;
 273                         }
 274
 275                 /*
 276                  * Check for length of the current name, preceding slash,
 277                  * leading slash.
 278                  */
 279                 while (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
 280                         size_t len, off;
 281
 282                         if (!ptsize) {
 283                                 errno = ERANGE;
 284                                 goto err;
 285                         }
 286                         off = bpt - pt;
 287                         len = ept - bpt;
 288                         if ((pt = reallocf(pt, ptsize *= 2)) == NULL)
 289                                 goto err;
 290                         bpt = pt + off;
 291                         ept = pt + ptsize;
 292                         bcopy(bpt, ept - len, len);
 293                         bpt = ept - len;
 294                 }
 295                 if (!first)
 296                         *--bpt = '/';
 297                 bpt -= dp->d_namlen;
 298                 bcopy(dp->d_name, bpt, dp->d_namlen);
 299                 (void) closedir(dir);
 300                 dir = NULL;
 301
 302                 /* Truncate any file name. */
 303                 *bup = '\0';
 304         }
 305
 306 notfound:
 307         /*
 308          * If readdir set errno, use it, not any saved error; otherwise,
 309          * didn't find the current directory in its parent directory, set
 310          * errno to ENOENT.
 311          */
 312         if (!errno)
 313                 errno = save_errno ? save_errno : ENOENT;
 314         /* FALLTHROUGH */
 315 err:
 316         save_errno = errno;
 317
 318         if (ptsize)
 319                 free(pt);
 320         if (dir)
 321                 (void) closedir(dir);
 322         free(up);
 323
 324         errno = save_errno;
 325         return (NULL);
 326 }
 327
 328 char *
 329 getcwd(pt, size)
 330         char *pt;
 331         size_t size;
 332 {
 333         return __private_getcwd(pt, size, 1);
 334 }