sysdeps/mach/hurd/readlinkat.c

   1 /* Copyright (C) 1991-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If
  16    not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <unistd.h>
  19 #include <hurd.h>
  20 #include <hurd/paths.h>
  21 #include <hurd/fd.h>
  22 #include <fcntl.h>
  23 #include <string.h>
  24
  25 /* Read the contents of the symbolic link FILE_NAME relative to FD into no more
  26    than LEN bytes of BUF.  The contents are not null-terminated.
  27    Returns the number of characters read, or -1 for errors.  */
  28 ssize_t
  29 readlinkat (fd, file_name, buf, len)
  30      int fd;
  31      const char *file_name;
  32      char *buf;
  33      size_t len;
  34 {
  35   error_t err;
  36   file_t file;
  37   struct stat64 st;
  38
  39   file = __file_name_lookup_at (fd, 0, file_name, O_READ | O_NOLINK, 0);
  40   if (file == MACH_PORT_NULL)
  41     return -1;
  42
  43   err = __io_stat (file, &st);
  44   if (! err)
  45     if (S_ISLNK (st.st_mode))
  46       {
  47         char *rbuf = buf;
  48
  49         err = __io_read (file, &rbuf, &len, 0, len);
  50         if (!err && rbuf != buf)
  51           {
  52             memcpy (buf, rbuf, len);
  53             __vm_deallocate (__mach_task_self (), (vm_address_t)rbuf, len);
  54           }
  55       }
  56     else
  57       err = EINVAL;
  58
  59   __mach_port_deallocate (__mach_task_self (), file);
  60
  61   return err ? __hurd_fail (err) : len;
  62 }
  63 libc_hidden_def (readlinkat)