libc/stdlib/ptsname.c

   1 /* Copyright (C) 1998, 2000, 2001, 2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <stdio.h>
  20 #include <errno.h>
  21 #include <paths.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/ioctl.h>
  25 #include <sys/stat.h>
  26 #include <sys/sysmacros.h>
  27 #include <termios.h>
  28 #include <unistd.h>
  29 #include <bits/uClibc_uintmaxtostr.h>
  30
  31
  32 #if !defined __UNIX98PTY_ONLY__
  33
  34 /* Check if DEV corresponds to a master pseudo terminal device.  */
  35 #define MASTER_P(Dev)                                                         \
  36   (major ((Dev)) == 2                                                         \
  37    || (major ((Dev)) == 4 && minor ((Dev)) >= 128 && minor ((Dev)) < 192)     \
  38    || (major ((Dev)) >= 128 && major ((Dev)) < 136))
  39
  40 /* Check if DEV corresponds to a slave pseudo terminal device.  */
  41 #define SLAVE_P(Dev)                                                          \
  42   (major ((Dev)) == 3                                                         \
  43    || (major ((Dev)) == 4 && minor ((Dev)) >= 192 && minor ((Dev)) < 256)     \
  44    || (major ((Dev)) >= 136 && major ((Dev)) < 144))
  45
  46 /* Note that major number 4 corresponds to the old BSD style pseudo
  47    terminal devices.  As of Linux 2.1.115 these are no longer
  48    supported.  They have been replaced by major numbers 2 (masters)
  49    and 3 (slaves).  */
  50
  51 /* The are declared in getpt.c.  */
  52 extern const char __libc_ptyname1[] attribute_hidden;
  53 extern const char __libc_ptyname2[] attribute_hidden;
  54
  55 #endif
  56
  57 /* Directory where we can find the slave pty nodes.  */
  58 #define _PATH_DEVPTS "/dev/pts/"
  59
  60 /* Store at most BUFLEN characters of the pathname of the slave pseudo
  61    terminal associated with the master FD is open on in BUF.
  62    Return 0 on success, otherwise an error number.  */
  63 int ptsname_r (int fd, char *buf, size_t buflen)
  64 {
  65   int save_errno = errno;
  66 #if !defined __UNIX98PTY_ONLY__
  67   struct stat st;
  68 #endif
  69   int ptyno;
  70
  71   if (buf == NULL)
  72     {
  73       errno = EINVAL;
  74       return EINVAL;
  75     }
  76
  77 #if !defined __UNIX98PTY_ONLY__
  78   if (!isatty (fd))
  79     {
  80       errno = ENOTTY;
  81       return ENOTTY;
  82     }
  83 #elif !defined TIOCGPTN
  84 # error "__UNIX98PTY_ONLY__ enabled but TIOCGPTN ioctl not supported by your kernel."
  85 #endif
  86 #ifdef TIOCGPTN
  87   if (ioctl (fd, TIOCGPTN, &ptyno) == 0)
  88     {
  89       /* Buffer we use to print the number in. */
  90       char numbuf[__BUFLEN_INT10TOSTR];
  91       static const char devpts[] = _PATH_DEVPTS;
  92       char *p;
  93
  94       p = _int10tostr(&numbuf[sizeof numbuf - 1], ptyno);
  95
  96       if (buflen < sizeof(devpts) + (size_t)(&numbuf[sizeof(numbuf) - 1] - p))
  97         {
  98           errno = ERANGE;
  99           return ERANGE;
 100         }
 101
 102       strcpy (buf, devpts);
 103       strcat (buf, p);
 104       /* Note: Don't bother with stat on the slave name and checking the
 105          driver's major device number - the ioctl above succeeded so
 106          we know the fd was a Unix'98 master and the /dev/pts/ prefix
 107          is set by definition.  If the name isn't really a slave PTY,
 108          the system is misconfigured anyway - something else will fail
 109          later.
 110          */
 111       errno = save_errno;
 112       return 0;
 113     }
 114 #endif
 115 #if defined __UNIX98PTY_ONLY__
 116   else
 117     {
 118       /* If the ioctl fails it wasn't a Unix 98 master PTY */
 119       errno = ENOTTY;
 120       return ENOTTY;
 121     }
 122 #else
 123 # if defined TIOCGPTN
 124   else if (errno == EINVAL)
 125 # endif
 126     {
 127       char *p;
 128
 129       if (buflen < strlen (_PATH_TTY) + 3)
 130         {
 131           errno = ERANGE;
 132           return ERANGE;
 133         }
 134
 135       if (fstat (fd, &st) < 0)
 136         return errno;
 137
 138       /* Check if FD really is a master pseudo terminal.  */
 139       if (! MASTER_P (st.st_rdev))
 140         {
 141           errno = ENOTTY;
 142           return ENOTTY;
 143         }
 144
 145       ptyno = minor (st.st_rdev);
 146       /* This is for the old BSD pseudo terminals.  As of Linux
 147          2.1.115 these are no longer supported.  */
 148       if (major (st.st_rdev) == 4)
 149         ptyno -= 128;
 150
 151       if (ptyno / 16 >= strlen (__libc_ptyname1))
 152         {
 153           errno = ENOTTY;
 154           return ENOTTY;
 155         }
 156
 157       strcpy (buf, _PATH_TTY);
 158       p = buf + strlen (buf);
 159       p[0] = __libc_ptyname1[ptyno / 16];
 160       p[1] = __libc_ptyname2[ptyno % 16];
 161       p[2] = '\0';
 162     }
 163
 164   if (stat(buf, &st) < 0)
 165     return errno;
 166
 167   /* Check if the name we're about to return really corresponds to a
 168      slave pseudo terminal.  */
 169   if (! S_ISCHR (st.st_mode) || ! SLAVE_P (st.st_rdev))
 170     {
 171       /* This really is a configuration problem.  */
 172       errno = ENOTTY;
 173       return ENOTTY;
 174     }
 175 #endif
 176
 177   errno = save_errno;
 178   return 0;
 179 }
 180 libc_hidden_def(ptsname_r)
 181
 182 /* Return the pathname of the pseudo terminal slave assoicated with
 183    the master FD is open on, or NULL on errors.
 184    The returned storage is good until the next call to this function.  */
 185 char *
 186 ptsname (int fd)
 187 {
 188   static char buffer[sizeof (_PATH_DEVPTS) + 20];
 189
 190   return ptsname_r (fd, buffer, sizeof (buffer)) != 0 ? NULL : buffer;
 191 }