sysdeps/mach/hurd/readlinkat.c

   1 /* Copyright (C) 1991-2023 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 <https://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 (int fd, const char *file_name, char *buf, size_t len)
  30 {
  31   error_t err;
  32   file_t file_stat;
  33   struct stat64 st;
  34
  35   file_stat = __file_name_lookup_at (fd, 0, file_name, O_NOLINK, 0);
  36   if (file_stat == MACH_PORT_NULL)
  37     return -1;
  38
  39   err = __io_stat (file_stat, &st);
  40   if (! err)
  41     if (S_ISLNK (st.st_mode))
  42       {
  43         enum retry_type doretry;
  44         char retryname[1024];
  45         file_t file;
  46         char *rbuf = buf;
  47
  48         err = __dir_lookup (file_stat, "", O_READ | O_NOLINK, 0, &doretry, retryname, &file);
  49         if (! err && (doretry != FS_RETRY_NORMAL || retryname[0] != '\0'))
  50           err = EGRATUITOUS;
  51         if (! err)
  52           {
  53             err = __io_read (file, &rbuf, &len, 0, len);
  54             if (!err && rbuf != buf)
  55               {
  56                 memcpy (buf, rbuf, len);
  57                 __vm_deallocate (__mach_task_self (), (vm_address_t)rbuf, len);
  58               }
  59
  60             __mach_port_deallocate (__mach_task_self (), file);
  61           }
  62       }
  63     else
  64       err = EINVAL;
  65
  66   __mach_port_deallocate (__mach_task_self (), file_stat);
  67
  68   return err ? __hurd_fail (err) : len;
  69 }
  70 weak_alias (__readlinkat, readlinkat)
  71 libc_hidden_def (readlinkat)