sysdeps/unix/sysv/linux/ptsname.c

   1 /* Copyright (C) 1998-2018 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 <errno.h>
  20 #include <paths.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/ioctl.h>
  24 #include <sys/stat.h>
  25 #include <sys/sysmacros.h>
  26 #include <termios.h>
  27 #include <unistd.h>
  28
  29 #include <_itoa.h>
  30
  31 /* Check if DEV corresponds to a master pseudo terminal device.  */
  32 #define MASTER_P(Dev)                                                   \
  33   (__gnu_dev_major ((Dev)) == 2                                         \
  34    || (__gnu_dev_major ((Dev)) == 4                                     \
  35        && __gnu_dev_minor ((Dev)) >= 128 && __gnu_dev_minor ((Dev)) < 192) \
  36    || (__gnu_dev_major ((Dev)) >= 128 && __gnu_dev_major ((Dev)) < 136))
  37
  38 /* Check if DEV corresponds to a slave pseudo terminal device.  */
  39 #define SLAVE_P(Dev)                                                    \
  40   (__gnu_dev_major ((Dev)) == 3                                         \
  41    || (__gnu_dev_major ((Dev)) == 4                                     \
  42        && __gnu_dev_minor ((Dev)) >= 192 && __gnu_dev_minor ((Dev)) < 256) \
  43    || (__gnu_dev_major ((Dev)) >= 136 && __gnu_dev_major ((Dev)) < 144))
  44
  45 /* Note that major number 4 corresponds to the old BSD style pseudo
  46    terminal devices.  As of Linux 2.1.115 these are no longer
  47    supported.  They have been replaced by major numbers 2 (masters)
  48    and 3 (slaves).  */
  49
  50 /* Directory where we can find the slave pty nodes.  */
  51 #define _PATH_DEVPTS "/dev/pts/"
  52
  53 /* The are declared in getpt.c.  */
  54 extern const char __libc_ptyname1[] attribute_hidden;
  55 extern const char __libc_ptyname2[] attribute_hidden;
  56
  57 /* Static buffer for `ptsname'.  */
  58 static char buffer[sizeof (_PATH_DEVPTS) + 20];
  59
  60
  61 /* Return the pathname of the pseudo terminal slave associated with
  62    the master FD is open on, or NULL on errors.
  63    The returned storage is good until the next call to this function.  */
  64 char *
  65 ptsname (int fd)
  66 {
  67   return __ptsname_r (fd, buffer, sizeof (buffer)) != 0 ? NULL : buffer;
  68 }
  69
  70
  71 int
  72 __ptsname_internal (int fd, char *buf, size_t buflen, struct stat64 *stp)
  73 {
  74   int save_errno = errno;
  75   unsigned int ptyno;
  76
  77   if (!__isatty (fd))
  78     {
  79       __set_errno (ENOTTY);
  80       return ENOTTY;
  81     }
  82
  83 #ifdef TIOCGPTN
  84   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
  85     {
  86       /* Buffer we use to print the number in.  For a maximum size for
  87          `int' of 8 bytes we never need more than 20 digits.  */
  88       char numbuf[21];
  89       const char *devpts = _PATH_DEVPTS;
  90       const size_t devptslen = strlen (_PATH_DEVPTS);
  91       char *p;
  92
  93       numbuf[sizeof (numbuf) - 1] = '\0';
  94       p = _itoa_word (ptyno, &numbuf[sizeof (numbuf) - 1], 10, 0);
  95
  96       if (buflen < devptslen + (&numbuf[sizeof (numbuf)] - p))
  97         {
  98           __set_errno (ERANGE);
  99           return ERANGE;
 100         }
 101
 102       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
 103     }
 104   else if (errno != EINVAL)
 105     return errno;
 106   else
 107 #endif
 108     {
 109       char *p;
 110
 111       if (buflen < strlen (_PATH_TTY) + 3)
 112         {
 113           __set_errno (ERANGE);
 114           return ERANGE;
 115         }
 116
 117       if (__fxstat64 (_STAT_VER, fd, stp) < 0)
 118         return errno;
 119
 120       /* Check if FD really is a master pseudo terminal.  */
 121       if (! MASTER_P (stp->st_rdev))
 122         {
 123           __set_errno (ENOTTY);
 124           return ENOTTY;
 125         }
 126
 127       ptyno = __gnu_dev_minor (stp->st_rdev);
 128
 129       if (ptyno / 16 >= strlen (__libc_ptyname1))
 130         {
 131           __set_errno (ENOTTY);
 132           return ENOTTY;
 133         }
 134
 135       p = __stpcpy (buf, _PATH_TTY);
 136       p[0] = __libc_ptyname1[ptyno / 16];
 137       p[1] = __libc_ptyname2[ptyno % 16];
 138       p[2] = '\0';
 139     }
 140
 141   if (__xstat64 (_STAT_VER, buf, stp) < 0)
 142     return errno;
 143
 144   /* Check if the name we're about to return really corresponds to a
 145      slave pseudo terminal.  */
 146   if (! S_ISCHR (stp->st_mode) || ! SLAVE_P (stp->st_rdev))
 147     {
 148       /* This really is a configuration problem.  */
 149       __set_errno (ENOTTY);
 150       return ENOTTY;
 151     }
 152
 153   __set_errno (save_errno);
 154   return 0;
 155 }
 156
 157
 158 /* Store at most BUFLEN characters of the pathname of the slave pseudo
 159    terminal associated with the master FD is open on in BUF.
 160    Return 0 on success, otherwise an error number.  */
 161 int
 162 __ptsname_r (int fd, char *buf, size_t buflen)
 163 {
 164   struct stat64 st;
 165   return __ptsname_internal (fd, buf, buflen, &st);
 166 }
 167 weak_alias (__ptsname_r, ptsname_r)