sysdeps/unix/sysv/linux/ptsname.c

   1 /* Copyright (C) 1998-2017 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   (major ((Dev)) == 2                                                         \
  34    || (major ((Dev)) == 4 && minor ((Dev)) >= 128 && minor ((Dev)) < 192)     \
  35    || (major ((Dev)) >= 128 && major ((Dev)) < 136))
  36
  37 /* Check if DEV corresponds to a slave pseudo terminal device.  */
  38 #define SLAVE_P(Dev)                                                          \
  39   (major ((Dev)) == 3                                                         \
  40    || (major ((Dev)) == 4 && minor ((Dev)) >= 192 && minor ((Dev)) < 256)     \
  41    || (major ((Dev)) >= 136 && major ((Dev)) < 144))
  42
  43 /* Note that major number 4 corresponds to the old BSD style pseudo
  44    terminal devices.  As of Linux 2.1.115 these are no longer
  45    supported.  They have been replaced by major numbers 2 (masters)
  46    and 3 (slaves).  */
  47
  48 /* Directory where we can find the slave pty nodes.  */
  49 #define _PATH_DEVPTS "/dev/pts/"
  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 /* Static buffer for `ptsname'.  */
  56 static char buffer[sizeof (_PATH_DEVPTS) + 20];
  57
  58
  59 /* Return the pathname of the pseudo terminal slave associated with
  60    the master FD is open on, or NULL on errors.
  61    The returned storage is good until the next call to this function.  */
  62 char *
  63 ptsname (int fd)
  64 {
  65   return __ptsname_r (fd, buffer, sizeof (buffer)) != 0 ? NULL : buffer;
  66 }
  67
  68
  69 int
  70 __ptsname_internal (int fd, char *buf, size_t buflen, struct stat64 *stp)
  71 {
  72   int save_errno = errno;
  73   unsigned int ptyno;
  74
  75   if (!__isatty (fd))
  76     {
  77       __set_errno (ENOTTY);
  78       return ENOTTY;
  79     }
  80
  81 #ifdef TIOCGPTN
  82   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
  83     {
  84       /* Buffer we use to print the number in.  For a maximum size for
  85          `int' of 8 bytes we never need more than 20 digits.  */
  86       char numbuf[21];
  87       const char *devpts = _PATH_DEVPTS;
  88       const size_t devptslen = strlen (_PATH_DEVPTS);
  89       char *p;
  90
  91       numbuf[sizeof (numbuf) - 1] = '\0';
  92       p = _itoa_word (ptyno, &numbuf[sizeof (numbuf) - 1], 10, 0);
  93
  94       if (buflen < devptslen + (&numbuf[sizeof (numbuf)] - p))
  95         {
  96           __set_errno (ERANGE);
  97           return ERANGE;
  98         }
  99
 100       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
 101     }
 102   else if (errno != EINVAL)
 103     return errno;
 104   else
 105 #endif
 106     {
 107       char *p;
 108
 109       if (buflen < strlen (_PATH_TTY) + 3)
 110         {
 111           __set_errno (ERANGE);
 112           return ERANGE;
 113         }
 114
 115       if (__fxstat64 (_STAT_VER, fd, stp) < 0)
 116         return errno;
 117
 118       /* Check if FD really is a master pseudo terminal.  */
 119       if (! MASTER_P (stp->st_rdev))
 120         {
 121           __set_errno (ENOTTY);
 122           return ENOTTY;
 123         }
 124
 125       ptyno = minor (stp->st_rdev);
 126
 127       if (ptyno / 16 >= strlen (__libc_ptyname1))
 128         {
 129           __set_errno (ENOTTY);
 130           return ENOTTY;
 131         }
 132
 133       p = __stpcpy (buf, _PATH_TTY);
 134       p[0] = __libc_ptyname1[ptyno / 16];
 135       p[1] = __libc_ptyname2[ptyno % 16];
 136       p[2] = '\0';
 137     }
 138
 139   if (__xstat64 (_STAT_VER, buf, stp) < 0)
 140     return errno;
 141
 142   /* Check if the name we're about to return really corresponds to a
 143      slave pseudo terminal.  */
 144   if (! S_ISCHR (stp->st_mode) || ! SLAVE_P (stp->st_rdev))
 145     {
 146       /* This really is a configuration problem.  */
 147       __set_errno (ENOTTY);
 148       return ENOTTY;
 149     }
 150
 151   __set_errno (save_errno);
 152   return 0;
 153 }
 154
 155
 156 /* Store at most BUFLEN characters of the pathname of the slave pseudo
 157    terminal associated with the master FD is open on in BUF.
 158    Return 0 on success, otherwise an error number.  */
 159 int
 160 __ptsname_r (int fd, char *buf, size_t buflen)
 161 {
 162   struct stat64 st;
 163   return __ptsname_internal (fd, buf, buflen, &st);
 164 }
 165 weak_alias (__ptsname_r, ptsname_r)