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 #pragma clang diagnostic push
  31 #pragma clang diagnostic ignored "-Wstrict-prototypes"
  32
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)getcwd.c    8.5 (Berkeley) 2/7/95";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/gen/getcwd.c,v 1.29 2007/01/09 00:27:53 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <sys/param.h>
  41 #include <sys/stat.h>
  42
  43 #include <dirent.h>
  44 #include <errno.h>
  45 #include <fcntl.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <string.h>
  49 #include <unistd.h>
  50 #include "un-namespace.h"
  51
  52 #define ISDOT(dp) \
  53         (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
  54             (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
  55
  56 /*
  57  * If __getcwd() ever becomes a syscall, we can remove this workaround.
  58  * The problem here is that fcntl() assumes a buffer of size MAXPATHLEN,
  59  * if size is less than MAXPATHLEN, we need to use a temporary buffer
  60  * and see if it fits.  We also have to assume that open() or fcntl()
  61  * don't fail with errno=ERANGE.
  62  */
  63 static inline int
  64 __getcwd(char *buf, size_t size)
  65 {
  66         int fd, err, save;
  67         struct stat dot, pt;
  68         char *b;
  69
  70         if ((fd = open(".", O_RDONLY)) < 0)
  71                 return -1;
  72         if (fstat(fd, &dot) < 0) {
  73                 save = errno;
  74                 close(fd);
  75                 errno = save;
  76                 return -1;
  77         }
  78         /* check that the device and inode are non-zero, otherwise punt */
  79         if (dot.st_dev == 0 || dot.st_ino == 0) {
  80                 close(fd);
  81                 errno = EINVAL;
  82                 return -1;
  83         }
  84         if (size < MAXPATHLEN) {
  85                 /* the hard case; allocate a buffer of size MAXPATHLEN to use */
  86                 b = (char *)alloca(MAXPATHLEN);
  87                 if (b == NULL) {
  88                         close(fd);
  89                         errno = ENOMEM; /* make sure it isn't ERANGE */
  90                         return -1;
  91                 }
  92         } else
  93                 b = buf;
  94
  95         err = fcntl(fd, F_GETPATH, b);
  96         if (err) {
  97                 save = errno;
  98                 close(fd);
  99                 errno = save;
 100                 return err;
 101         }
 102         close(fd);
 103         /*
 104          * now double-check that the path returned by fcntl() has the same
 105          * device and inode number as '.'.
 106          */
 107         if (stat(b, &pt) < 0)
 108                 return -1;
 109         /*
 110          * Since dot.st_dev and dot.st_ino are non-zero, we don't need to
 111          * separately test for pt.st_dev and pt.st_ino being non-zero, because
 112          * they have to match
 113          */
 114         if (dot.st_dev != pt.st_dev || dot.st_ino != pt.st_ino) {
 115                 errno = EINVAL;
 116                 return -1;
 117         }
 118         /*
 119          * For the case where we allocated a buffer, check that it can fit
 120          * in the real buffer, and copy it over.
 121          */
 122         if (size < MAXPATHLEN) {
 123                 if (strlen(b) >= size) {
 124                         errno = ERANGE;
 125                         return -1;
 126                 }
 127                 strcpy(buf, b);
 128         }
 129         return 0;
 130 }
 131
 132 __private_extern__ char *
 133 __private_getcwd(pt, size, usegetpath)
 134         char *pt;
 135         size_t size;
 136         int usegetpath;
 137 {
 138         struct dirent *dp;
 139         DIR *dir = NULL;
 140         dev_t dev;
 141         ino_t ino;
 142         int first;
 143         char *bpt, *bup;
 144         struct stat s;
 145         dev_t root_dev;
 146         ino_t root_ino;
 147         size_t ptsize, upsize;
 148         int save_errno;
 149         char *ept, *eup, *up;
 150
 151         /*
 152          * If no buffer specified by the user, allocate one as necessary.
 153          * If a buffer is specified, the size has to be non-zero.  The path
 154          * is built from the end of the buffer backwards.
 155          */
 156         if (pt) {
 157                 ptsize = 0;
 158                 if (!size) {
 159                         errno = EINVAL;
 160                         return (NULL);
 161                 }
 162                 if (size == 1) {
 163                         errno = ERANGE;
 164                         return (NULL);
 165                 }
 166                 ept = pt + size;
 167         } else {
 168                 if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
 169                         return (NULL);
 170                 ept = pt + ptsize;
 171         }
 172         if (usegetpath) {
 173                 if (__getcwd(pt, ept - pt) == 0) {
 174                         return (pt);
 175                 } else if (errno == ERANGE) /* failed because buffer too small */
 176                         return NULL;
 177         }
 178         bpt = ept - 1;
 179         *bpt = '\0';
 180
 181         /*
 182          * Allocate MAXPATHLEN bytes for the string of "../"'s.
 183          * Should always be enough.  If it's not, allocate
 184          * as necessary.  Special case the first stat, it's ".", not "..".
 185          */
 186         if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
 187                 goto err;
 188         eup = up + MAXPATHLEN;
 189         bup = up;
 190         up[0] = '.';
 191         up[1] = '\0';
 192
 193         /* Save root values, so know when to stop. */
 194         if (stat("/", &s))
 195                 goto err;
 196         root_dev = s.st_dev;
 197         root_ino = s.st_ino;
 198
 199         errno = 0;                      /* XXX readdir has no error return. */
 200
 201         for (first = 1;; first = 0) {
 202                 /* Stat the current level. */
 203                 if (lstat(up, &s))
 204                         goto err;
 205
 206                 /* Save current node values. */
 207                 ino = s.st_ino;
 208                 dev = s.st_dev;
 209
 210                 /* Check for reaching root. */
 211                 if (root_dev == dev && root_ino == ino) {
 212                         *--bpt = '/';
 213                         /*
 214                          * It's unclear that it's a requirement to copy the
 215                          * path to the beginning of the buffer, but it's always
 216                          * been that way and stuff would probably break.
 217                          */
 218                         bcopy(bpt, pt, ept - bpt);
 219                         free(up);
 220                         return (pt);
 221                 }
 222
 223                 /*
 224                  * Build pointer to the parent directory, allocating memory
 225                  * as necessary.  Max length is 3 for "../", the largest
 226                  * possible component name, plus a trailing NUL.
 227                  */
 228                 while (bup + 3  + MAXNAMLEN + 1 >= eup) {
 229                         if ((up = reallocf(up, upsize *= 2)) == NULL)
 230                                 goto err;
 231                         bup = up;
 232                         eup = up + upsize;
 233                 }
 234                 *bup++ = '.';
 235                 *bup++ = '.';
 236                 *bup = '\0';
 237
 238                 /* Open and stat parent directory. */
 239                 if (!(dir = opendir(up)) || _fstat(dirfd(dir), &s))
 240                         goto err;
 241
 242                 /* Add trailing slash for next directory. */
 243                 *bup++ = '/';
 244                 *bup = '\0';
 245
 246                 /*
 247                  * If it's a mount point, have to stat each element because
 248                  * the inode number in the directory is for the entry in the
 249                  * parent directory, not the inode number of the mounted file.
 250                  */
 251                 save_errno = 0;
 252                 if (s.st_dev == dev) {
 253                         for (;;) {
 254                                 if (!(dp = readdir(dir)))
 255                                         goto notfound;
 256                                 if (dp->d_fileno == ino)
 257                                         break;
 258                         }
 259                 } else
 260                         for (;;) {
 261                                 if (!(dp = readdir(dir)))
 262                                         goto notfound;
 263                                 if (ISDOT(dp))
 264                                         continue;
 265                                 bcopy(dp->d_name, bup, dp->d_namlen + 1);
 266
 267                                 /* Save the first error for later. */
 268                                 if (lstat(up, &s)) {
 269                                         if (!save_errno)
 270                                                 save_errno = errno;
 271                                         errno = 0;
 272                                         continue;
 273                                 }
 274                                 if (s.st_dev == dev && s.st_ino == ino)
 275                                         break;
 276                         }
 277
 278                 /*
 279                  * Check for length of the current name, preceding slash,
 280                  * leading slash.
 281                  */
 282                 while (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
 283                         size_t len, off;
 284
 285                         if (!ptsize) {
 286                                 errno = ERANGE;
 287                                 goto err;
 288                         }
 289                         off = bpt - pt;
 290                         len = ept - bpt;
 291                         if ((pt = reallocf(pt, ptsize *= 2)) == NULL)
 292                                 goto err;
 293                         bpt = pt + off;
 294                         ept = pt + ptsize;
 295                         bcopy(bpt, ept - len, len);
 296                         bpt = ept - len;
 297                 }
 298                 if (!first)
 299                         *--bpt = '/';
 300                 bpt -= dp->d_namlen;
 301                 bcopy(dp->d_name, bpt, dp->d_namlen);
 302                 (void) closedir(dir);
 303                 dir = NULL;
 304
 305                 /* Truncate any file name. */
 306                 *bup = '\0';
 307         }
 308
 309 notfound:
 310         /*
 311          * If readdir set errno, use it, not any saved error; otherwise,
 312          * didn't find the current directory in its parent directory, set
 313          * errno to ENOENT.
 314          */
 315         if (!errno)
 316                 errno = save_errno ? save_errno : ENOENT;
 317         /* FALLTHROUGH */
 318 err:
 319         save_errno = errno;
 320
 321         if (ptsize)
 322                 free(pt);
 323         if (dir)
 324                 (void) closedir(dir);
 325         free(up);
 326
 327         errno = save_errno;
 328         return (NULL);
 329 }
 330
 331 char *
 332 getcwd(pt, size)
 333         char *pt;
 334         size_t size;
 335 {
 336         return __private_getcwd(pt, size, 1);
 337 }
 338 #pragma clang diagnostic pop