libc/stdlib/grantpt.c

   1 /* Copyright (C) 1998, 1999 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 Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    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    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <limits.h>
  19 #include <stdlib.h>
  20
  21 /* If __ASSUME_DEVPTS__ is defined, grantpt() reduces to a stub since we
  22    assume that the devfs/devpts filesystem automatically manages the
  23    permissions. */
  24 #if !defined __ASSUME_DEVPTS__
  25 #include <sys/statfs.h>
  26
  27 /* Constant that identifies the `devpts' filesystem.  */
  28 #define DEVPTS_SUPER_MAGIC      0x1cd1
  29 /* Constant that identifies the `devfs' filesystem.  */
  30 #define DEVFS_SUPER_MAGIC       0x1373
  31
  32 /* Prototype for function that changes ownership and access permission
  33    for slave pseudo terminals that do not live on a `devpts'
  34    filesystem.  */
  35 static int __unix_grantpt (int fd);
  36
  37 /* Prototype for private function that gets the name of the slave
  38    pseudo terminal in a safe way.  */
  39 static int pts_name (int fd, char **pts, size_t buf_len);
  40 extern __typeof(statfs) __libc_statfs;
  41
  42 /* Change the ownership and access permission of the slave pseudo
  43    terminal associated with the master pseudo terminal specified
  44    by FD.  */
  45 int grantpt (int fd)
  46 {
  47   struct statfs fsbuf;
  48   char _buf[PATH_MAX];
  49   char *buf = _buf;
  50
  51   if (pts_name (fd, &buf, sizeof (_buf)))
  52     return -1;
  53
  54   if (__libc_statfs (buf, &fsbuf) < 0)
  55     return -1;
  56
  57   /* If the slave pseudo terminal lives on a `devpts' filesystem, the
  58      ownership and access permission are already set.  */
  59   if (fsbuf.f_type != DEVPTS_SUPER_MAGIC && fsbuf.f_type != DEVFS_SUPER_MAGIC)
  60     return __unix_grantpt (fd);
  61
  62   return 0;
  63 }
  64
  65 # define grantpt __unix_grantpt
  66 # include "unix_grantpt.c"
  67
  68 #else
  69
  70 int grantpt (attribute_unused int fd)
  71 {
  72   return 0;
  73 }
  74
  75 #endif