sysdeps/unix/sysv/linux/ttyname.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <limits.h>
  20 #include <stddef.h>
  21 #include <dirent.h>
  22 #include <sys/types.h>
  23 #include <sys/stat.h>
  24 #include <termios.h>
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28
  29 #include <_itoa.h>
  30
  31 #include "ttyname.h"
  32
  33 #if 0
  34 /* Is this used anywhere?  It is not exported.  */
  35 char *__ttyname;
  36 #endif
  37
  38 static char *getttyname (const char *dev, dev_t mydev,
  39                          ino64_t myino, int save, int *dostat)
  40      internal_function;
  41
  42
  43 libc_freeres_ptr (static char *getttyname_name);
  44
  45 static char *
  46 internal_function attribute_compat_text_section
  47 getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
  48 {
  49   static size_t namelen;
  50   struct stat64 st;
  51   DIR *dirstream;
  52   struct dirent64 *d;
  53   size_t devlen = strlen (dev) + 1;
  54
  55   dirstream = __opendir (dev);
  56   if (dirstream == NULL)
  57     {
  58       *dostat = -1;
  59       return NULL;
  60     }
  61
  62   /* Prepare for the loop.  If we already have a buffer copy the directory
  63      name we look at into it.  */
  64   if (devlen < namelen)
  65     *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
  66
  67   while ((d = __readdir64 (dirstream)) != NULL)
  68     if ((d->d_fileno == myino || *dostat)
  69         && strcmp (d->d_name, "stdin")
  70         && strcmp (d->d_name, "stdout")
  71         && strcmp (d->d_name, "stderr"))
  72       {
  73         size_t dlen = _D_ALLOC_NAMLEN (d);
  74         if (devlen + dlen > namelen)
  75           {
  76             free (getttyname_name);
  77             namelen = 2 * (devlen + dlen); /* Big enough.  */
  78             getttyname_name = malloc (namelen);
  79             if (! getttyname_name)
  80               {
  81                 *dostat = -1;
  82                 /* Perhaps it helps to free the directory stream buffer.  */
  83                 (void) __closedir (dirstream);
  84                 return NULL;
  85               }
  86             *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
  87           }
  88         memcpy (&getttyname_name[devlen], d->d_name, dlen);
  89         if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0
  90 #ifdef _STATBUF_ST_RDEV
  91             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  92 #else
  93             && d->d_fileno == myino && st.st_dev == mydev
  94 #endif
  95            )
  96           {
  97             (void) __closedir (dirstream);
  98 #if 0
  99             __ttyname = getttyname_name;
 100 #endif
 101             __set_errno (save);
 102             return getttyname_name;
 103           }
 104       }
 105
 106   (void) __closedir (dirstream);
 107   __set_errno (save);
 108   return NULL;
 109 }
 110
 111
 112 /* Static buffer in `ttyname'.  */
 113 libc_freeres_ptr (static char *ttyname_buf);
 114
 115
 116 /* Return the pathname of the terminal FD is open on, or NULL on errors.
 117    The returned storage is good only until the next call to this function.  */
 118 char *
 119 ttyname (int fd)
 120 {
 121   static size_t buflen;
 122   char procname[30];
 123   struct stat64 st, st1;
 124   int dostat = 0;
 125   char *name;
 126   int save = errno;
 127   struct termios term;
 128
 129   /* isatty check, tcgetattr is used because it sets the correct
 130      errno (EBADF resp. ENOTTY) on error.  */
 131   if (__glibc_unlikely (__tcgetattr (fd, &term) < 0))
 132     return NULL;
 133
 134   if (__fxstat64 (_STAT_VER, fd, &st) < 0)
 135     return NULL;
 136
 137   /* We try using the /proc filesystem.  */
 138   *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';
 139
 140   if (buflen == 0)
 141     {
 142       buflen = 4095;
 143       ttyname_buf = (char *) malloc (buflen + 1);
 144       if (ttyname_buf == NULL)
 145         {
 146           buflen = 0;
 147           return NULL;
 148         }
 149     }
 150
 151   ssize_t len = __readlink (procname, ttyname_buf, buflen);
 152   if (__glibc_likely (len != -1))
 153     {
 154       if ((size_t) len >= buflen)
 155         return NULL;
 156
 157 #define UNREACHABLE_LEN strlen ("(unreachable)")
 158       if (len > UNREACHABLE_LEN
 159           && memcmp (ttyname_buf, "(unreachable)", UNREACHABLE_LEN) == 0)
 160         {
 161           memmove (ttyname_buf, ttyname_buf + UNREACHABLE_LEN,
 162                    len - UNREACHABLE_LEN);
 163           len -= UNREACHABLE_LEN;
 164         }
 165
 166       /* readlink need not terminate the string.  */
 167       ttyname_buf[len] = '\0';
 168
 169       /* Verify readlink result, fall back on iterating through devices.  */
 170       if (ttyname_buf[0] == '/'
 171           && __xstat64 (_STAT_VER, ttyname_buf, &st1) == 0
 172 #ifdef _STATBUF_ST_RDEV
 173           && S_ISCHR (st1.st_mode)
 174           && st1.st_rdev == st.st_rdev
 175 #endif
 176           && st1.st_ino == st.st_ino
 177           && st1.st_dev == st.st_dev)
 178         return ttyname_buf;
 179
 180       /* If the link doesn't exist, then it points to a device in another
 181          namespace. */
 182       if (is_pty (&st))
 183         {
 184           __set_errno (ENODEV);
 185           return NULL;
 186         }
 187     }
 188
 189   if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
 190     {
 191 #ifdef _STATBUF_ST_RDEV
 192       name = getttyname ("/dev/pts", st.st_rdev, st.st_ino, save, &dostat);
 193 #else
 194       name = getttyname ("/dev/pts", st.st_dev, st.st_ino, save, &dostat);
 195 #endif
 196     }
 197   else
 198     {
 199       __set_errno (save);
 200       name = NULL;
 201     }
 202
 203   if (!name && dostat != -1)
 204     {
 205 #ifdef _STATBUF_ST_RDEV
 206       name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
 207 #else
 208       name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
 209 #endif
 210     }
 211
 212   if (!name && dostat != -1)
 213     {
 214       dostat = 1;
 215 #ifdef _STATBUF_ST_RDEV
 216       name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
 217 #else
 218       name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
 219 #endif
 220     }
 221
 222   return name;
 223 }