sysdeps/unix/sysv/linux/ptsname.c

   1 /* Copyright (C) 1998, 2000, 2001, 2002, 2009 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  They have been replaced by major numbers 2 (masters)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 int
  71 __ptsname_internal (int fd, char *buf, size_t buflen, struct stat64 *stp)
  72 {
  73   int save_errno = errno;
  74   unsigned int ptyno;
  75
  76   if (buf == NULL)
  77     {
  78       __set_errno (EINVAL);
  79       return EINVAL;
  80     }
  81
  82   if (!__isatty (fd))
  83     {
  84       __set_errno (ENOTTY);
  85       return ENOTTY;
  86     }
  87
  88 #ifdef TIOCGPTN
  89   if (__ioctl (fd, TIOCGPTN, &ptyno) == 0)
  90     {
  91       /* Buffer we use to print the number in.  For a maximum size for
  92          `int' of 8 bytes we never need more than 20 digits.  */
  93       char numbuf[21];
  94       const char *devpts = _PATH_DEVPTS;
  95       const size_t devptslen = strlen (_PATH_DEVPTS);
  96       char *p;
  97
  98       numbuf[sizeof (numbuf) - 1] = '\0';
  99       p = _itoa_word (ptyno, &numbuf[sizeof (numbuf) - 1], 10, 0);
 100
 101       if (buflen < devptslen + (&numbuf[sizeof (numbuf)] - p))
 102         {
 103           __set_errno (ERANGE);
 104           return ERANGE;
 105         }
 106
 107       memcpy (__stpcpy (buf, devpts), p, &numbuf[sizeof (numbuf)] - p);
 108     }
 109   else if (errno == EINVAL)
 110 #endif
 111     {
 112       char *p;
 113
 114       if (buflen < strlen (_PATH_TTY) + 3)
 115         {
 116           __set_errno (ERANGE);
 117           return ERANGE;
 118         }
 119
 120       if (__fxstat64 (_STAT_VER, fd, stp) < 0)
 121         return errno;
 122
 123       /* Check if FD really is a master pseudo terminal.  */
 124       if (! MASTER_P (stp->st_rdev))
 125         {
 126           __set_errno (ENOTTY);
 127           return ENOTTY;
 128         }
 129
 130       ptyno = minor (stp->st_rdev);
 131 #if __LINUX_KERNEL_VERSION < 131443
 132       /* This is for the old BSD pseudo terminals.  As of Linux
 133          2.1.115 these are no longer supported.  */
 134       if (major (stp->st_rdev) == 4)
 135         ptyno -= 128;
 136 #endif
 137
 138       if (ptyno / 16 >= strlen (__libc_ptyname1))
 139         {
 140           __set_errno (ENOTTY);
 141           return ENOTTY;
 142         }
 143
 144       p = __stpcpy (buf, _PATH_TTY);
 145       p[0] = __libc_ptyname1[ptyno / 16];
 146       p[1] = __libc_ptyname2[ptyno % 16];
 147       p[2] = '\0';
 148     }
 149
 150   if (__xstat64 (_STAT_VER, buf, stp) < 0)
 151     return errno;
 152
 153   /* Check if the name we're about to return really corresponds to a
 154      slave pseudo terminal.  */
 155   if (! S_ISCHR (stp->st_mode) || ! SLAVE_P (stp->st_rdev))
 156     {
 157       /* This really is a configuration problem.  */
 158       __set_errno (ENOTTY);
 159       return ENOTTY;
 160     }
 161
 162   __set_errno (save_errno);
 163   return 0;
 164 }
 165
 166
 167 /* Store at most BUFLEN characters of the pathname of the slave pseudo
 168    terminal associated with the master FD is open on in BUF.
 169    Return 0 on success, otherwise an error number.  */
 170 int
 171 __ptsname_r (int fd, char *buf, size_t buflen)
 172 {
 173   struct stat64 st;
 174   return __ptsname_internal (fd, buf, buflen, &st);
 175 }
 176 weak_alias (__ptsname_r, ptsname_r)