kernel/syscall/getcwd.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #pragma ident   "%Z%%M% %I%     %E% SMI"
  28
  29 #include <sys/copyops.h>
  30 #include <sys/errno.h>
  31 #include <sys/kmem.h>
  32 #include <sys/param.h>
  33 #include <sys/pathname.h>
  34 #include <sys/sysmacros.h>
  35 #include <sys/systm.h>
  36 #include <sys/types.h>
  37 #include <sys/vnode.h>
  38
  39 int
  40 getcwd(char *buf, size_t buflen)
  41 {
  42         int err;
  43         char *kbuf;
  44         size_t kbuflen;
  45
  46         /*
  47          * The user should be able to specify any size buffer, but we don't want
  48          * to arbitrarily allocate huge kernel buffers just because the user
  49          * requests it.  So we'll start with MAXPATHLEN (which should hold any
  50          * normal path), and only increase it if we fail with ERANGE.
  51          */
  52         kbuflen = MIN(buflen, MAXPATHLEN);
  53
  54         for (;;) {
  55                 kbuf = kmem_alloc(kbuflen, KM_SLEEP);
  56
  57                 if (((err = dogetcwd(kbuf, kbuflen)) == 0) &&
  58                     (copyout(kbuf, buf, strlen(kbuf) + 1) != 0))
  59                         err = EFAULT;
  60
  61                 kmem_free(kbuf, kbuflen);
  62
  63                 if (err == ENAMETOOLONG) {
  64                         /*
  65                          * If the user's buffer really was too small, give up.
  66                          * For some reason, getcwd() uses ERANGE for this case.
  67                          */
  68                         if (kbuflen == buflen) {
  69                                 err = ERANGE;
  70                                 break;
  71                         }
  72                         kbuflen = MIN(kbuflen * 2, buflen);
  73                 } else {
  74                         break;
  75                 }
  76         }
  77
  78         return ((err != 0) ? set_errno(err) : 0);
  79 }