sysdeps/unix/sysv/linux/ptsname.c

   1 /* Copyright (C) 1998-2015 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  They have been replaced by major numbers 2 (masters)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 (buf == NULL)
  76     {
  77       __set_errno (EINVAL);
  78       return EINVAL;
  79     }
  80
  81   if (!__isatty (fd))
  82     {
  83       __set_errno (ENOTTY);
  84       return ENOTTY;
  85     }
  86
  87 #ifdef TIOCGPTN
  88   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
  89     {
  90       /* Buffer we use to print the number in.  For a maximum size for
  91          `int' of 8 bytes we never need more than 20 digits.  */
  92       char numbuf[21];
  93       const char *devpts = _PATH_DEVPTS;
  94       const size_t devptslen = strlen (_PATH_DEVPTS);
  95       char *p;
  96
  97       numbuf[sizeof (numbuf) - 1] = '\0';
  98       p = _itoa_word (ptyno, &numbuf[sizeof (numbuf) - 1], 10, 0);
  99
 100       if (buflen < devptslen + (&numbuf[sizeof (numbuf)] - p))
 101         {
 102           __set_errno (ERANGE);
 103           return ERANGE;
 104         }
 105
 106       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
 107     }
 108   else if (errno != EINVAL)
 109     return errno;
 110   else
 111 #endif
 112     {
 113       char *p;
 114
 115       if (buflen < strlen (_PATH_TTY) + 3)
 116         {
 117           __set_errno (ERANGE);
 118           return ERANGE;
 119         }
 120
 121       if (__fxstat64 (_STAT_VER, fd, stp) < 0)
 122         return errno;
 123
 124       /* Check if FD really is a master pseudo terminal.  */
 125       if (! MASTER_P (stp->st_rdev))
 126         {
 127           __set_errno (ENOTTY);
 128           return ENOTTY;
 129         }
 130
 131       ptyno = minor (stp->st_rdev);
 132
 133       if (ptyno / 16 >= strlen (__libc_ptyname1))
 134         {
 135           __set_errno (ENOTTY);
 136           return ENOTTY;
 137         }
 138
 139       p = __stpcpy (buf, _PATH_TTY);
 140       p[0] = __libc_ptyname1[ptyno / 16];
 141       p[1] = __libc_ptyname2[ptyno % 16];
 142       p[2] = '\0';
 143     }
 144
 145   if (__xstat64 (_STAT_VER, buf, stp) < 0)
 146     return errno;
 147
 148   /* Check if the name we're about to return really corresponds to a
 149      slave pseudo terminal.  */
 150   if (! S_ISCHR (stp->st_mode) || ! SLAVE_P (stp->st_rdev))
 151     {
 152       /* This really is a configuration problem.  */
 153       __set_errno (ENOTTY);
 154       return ENOTTY;
 155     }
 156
 157   __set_errno (save_errno);
 158   return 0;
 159 }
 160
 161
 162 /* Store at most BUFLEN characters of the pathname of the slave pseudo
 163    terminal associated with the master FD is open on in BUF.
 164    Return 0 on success, otherwise an error number.  */
 165 int
 166 __ptsname_r (int fd, char *buf, size_t buflen)
 167 {
 168   struct stat64 st;
 169   return __ptsname_internal (fd, buf, buflen, &st);
 170 }
 171 weak_alias (__ptsname_r, ptsname_r)