sysdeps/unix/sysv/linux/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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  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
  30 #include <stdio-common/_itoa.h>
  31
  32 /* Check if DEV corresponds to a master pseudo terminal device.  */
  33 #define MASTER_P(Dev)                                                         \
  34   (major ((Dev)) == 2                                                         \
  35    || (major ((Dev)) == 4 && minor ((Dev)) >= 128 && minor ((Dev)) < 192)     \
  36    || (major ((Dev)) >= 128 && major ((Dev)) < 136))
  37
  38 /* Check if DEV corresponds to a slave pseudo terminal device.  */
  39 #define SLAVE_P(Dev)                                                          \
  40   (major ((Dev)) == 3                                                         \
  41    || (major ((Dev)) == 4 && minor ((Dev)) >= 192 && minor ((Dev)) < 256)     \
  42    || (major ((Dev)) >= 136 && major ((Dev)) < 144))
  43
  44 /* Note that major number 4 corresponds to the old BSD style pseudo
  45    terminal devices.  As of Linux 2.1.115 these are no longer
  46    supported.  They have been replaced by major numbers 2 (masters)
  47    and 3 (slaves).  */
  48
  49 /* Directory where we can find the slave pty nodes.  */
  50 #define _PATH_DEVPTS "/dev/pts/"
  51
  52 /* The are declared in getpt.c.  */
  53 extern const char __libc_ptyname1[] attribute_hidden;
  54 extern const char __libc_ptyname2[] attribute_hidden;
  55
  56 /* Static buffer for `ptsname'.  */
  57 static char buffer[sizeof (_PATH_DEVPTS) + 20];
  58
  59
  60 /* Return the pathname of the pseudo terminal slave assoicated with
  61    the master FD is open on, or NULL on errors.
  62    The returned storage is good until the next call to this function.  */
  63 char *
  64 ptsname (int fd)
  65 {
  66   return __ptsname_r (fd, buffer, sizeof (buffer)) != 0 ? NULL : buffer;
  67 }
  68
  69
  70 /* Store at most BUFLEN characters of the pathname of the slave pseudo
  71    terminal associated with the master FD is open on in BUF.
  72    Return 0 on success, otherwise an error number.  */
  73 int
  74 __ptsname_r (int fd, char *buf, size_t buflen)
  75 {
  76   int save_errno = errno;
  77   struct stat64 st;
  78   unsigned int ptyno;
  79
  80   if (buf == NULL)
  81     {
  82       __set_errno (EINVAL);
  83       return EINVAL;
  84     }
  85
  86   if (!__isatty (fd))
  87     {
  88       __set_errno (ENOTTY);
  89       return ENOTTY;
  90     }
  91
  92 #ifdef TIOCGPTN
  93   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
  94     {
  95       /* Buffer we use to print the number in.  For a maximum size for
  96          `int' of 8 bytes we never need more than 20 digits.  */
  97       char numbuf[21];
  98       const char *devpts = _PATH_DEVPTS;
  99       const size_t devptslen = strlen (_PATH_DEVPTS);
 100       char *p;
 101
 102       numbuf[sizeof (numbuf) - 1] = '\0';
 103       p = _itoa_word (ptyno, &numbuf[sizeof (numbuf) - 1], 10, 0);
 104
 105       if (buflen < devptslen + (&numbuf[sizeof (numbuf)] - p))
 106         {
 107           __set_errno (ERANGE);
 108           return ERANGE;
 109         }
 110
 111       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
 112     }
 113   else if (errno == EINVAL)
 114 #endif
 115     {
 116       char *p;
 117
 118       if (buflen < strlen (_PATH_TTY) + 3)
 119         {
 120           __set_errno (ERANGE);
 121           return ERANGE;
 122         }
 123
 124       if (__fxstat64 (_STAT_VER, fd, &st) < 0)
 125         return errno;
 126
 127       /* Check if FD really is a master pseudo terminal.  */
 128       if (! MASTER_P (st.st_rdev))
 129         {
 130           __set_errno (ENOTTY);
 131           return ENOTTY;
 132         }
 133
 134       ptyno = minor (st.st_rdev);
 135       /* This is for the old BSD pseudo terminals.  As of Linux
 136          2.1.115 these are no longer supported.  */
 137       if (major (st.st_rdev) == 4)
 138         ptyno -= 128;
 139
 140       if (ptyno / 16 >= strlen (__libc_ptyname1))
 141         {
 142           __set_errno (ENOTTY);
 143           return ENOTTY;
 144         }
 145
 146       p = __stpcpy (buf, _PATH_TTY);
 147       p[0] = __libc_ptyname1[ptyno / 16];
 148       p[1] = __libc_ptyname2[ptyno % 16];
 149       p[2] = '\0';
 150     }
 151
 152   if (__xstat64 (_STAT_VER, buf, &st) < 0)
 153     return errno;
 154
 155   /* Check if the name we're about to return really corresponds to a
 156      slave pseudo terminal.  */
 157   if (! S_ISCHR (st.st_mode) || ! SLAVE_P (st.st_rdev))
 158     {
 159       /* This really is a configuration problem.  */
 160       __set_errno (ENOTTY);
 161       return ENOTTY;
 162     }
 163
 164   __set_errno (save_errno);
 165   return 0;
 166 }
 167 weak_alias (__ptsname_r, ptsname_r)