sysdeps/unix/sysv/linux/ttyname.c

   1 /* Copyright (C) 1991-2015 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 #if 0
  32 /* Is this used anywhere?  It is not exported.  */
  33 char *__ttyname;
  34 #endif
  35
  36 static char *getttyname (const char *dev, dev_t mydev,
  37                          ino64_t myino, int save, int *dostat)
  38      internal_function;
  39
  40
  41 libc_freeres_ptr (static char *getttyname_name);
  42
  43 static char *
  44 internal_function attribute_compat_text_section
  45 getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
  46 {
  47   static size_t namelen;
  48   struct stat64 st;
  49   DIR *dirstream;
  50   struct dirent64 *d;
  51   size_t devlen = strlen (dev) + 1;
  52
  53   dirstream = __opendir (dev);
  54   if (dirstream == NULL)
  55     {
  56       *dostat = -1;
  57       return NULL;
  58     }
  59
  60   /* Prepare for the loop.  If we already have a buffer copy the directory
  61      name we look at into it.  */
  62   if (devlen < namelen)
  63     *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
  64
  65   while ((d = __readdir64 (dirstream)) != NULL)
  66     if ((d->d_fileno == myino || *dostat)
  67         && strcmp (d->d_name, "stdin")
  68         && strcmp (d->d_name, "stdout")
  69         && strcmp (d->d_name, "stderr"))
  70       {
  71         size_t dlen = _D_ALLOC_NAMLEN (d);
  72         if (devlen + dlen > namelen)
  73           {
  74             free (getttyname_name);
  75             namelen = 2 * (devlen + dlen); /* Big enough.  */
  76             getttyname_name = malloc (namelen);
  77             if (! getttyname_name)
  78               {
  79                 *dostat = -1;
  80                 /* Perhaps it helps to free the directory stream buffer.  */
  81                 (void) __closedir (dirstream);
  82                 return NULL;
  83               }
  84             *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
  85           }
  86         memcpy (&getttyname_name[devlen], d->d_name, dlen);
  87         if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0
  88 #ifdef _STATBUF_ST_RDEV
  89             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  90 #else
  91             && d->d_fileno == myino && st.st_dev == mydev
  92 #endif
  93            )
  94           {
  95             (void) __closedir (dirstream);
  96 #if 0
  97             __ttyname = getttyname_name;
  98 #endif
  99             __set_errno (save);
 100             return getttyname_name;
 101           }
 102       }
 103
 104   (void) __closedir (dirstream);
 105   __set_errno (save);
 106   return NULL;
 107 }
 108
 109
 110 /* Static buffer in `ttyname'.  */
 111 libc_freeres_ptr (static char *ttyname_buf);
 112
 113
 114 /* Return the pathname of the terminal FD is open on, or NULL on errors.
 115    The returned storage is good only until the next call to this function.  */
 116 char *
 117 ttyname (int fd)
 118 {
 119   static size_t buflen;
 120   char procname[30];
 121   struct stat64 st, st1;
 122   int dostat = 0;
 123   char *name;
 124   int save = errno;
 125   struct termios term;
 126
 127   /* isatty check, tcgetattr is used because it sets the correct
 128      errno (EBADF resp. ENOTTY) on error.  */
 129   if (__glibc_unlikely (__tcgetattr (fd, &term) < 0))
 130     return NULL;
 131
 132   if (__fxstat64 (_STAT_VER, fd, &st) < 0)
 133     return NULL;
 134
 135   /* We try using the /proc filesystem.  */
 136   *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';
 137
 138   if (buflen == 0)
 139     {
 140       buflen = 4095;
 141       ttyname_buf = (char *) malloc (buflen + 1);
 142       if (ttyname_buf == NULL)
 143         {
 144           buflen = 0;
 145           return NULL;
 146         }
 147     }
 148
 149   ssize_t len = __readlink (procname, ttyname_buf, buflen);
 150   if (__glibc_likely (len != -1))
 151     {
 152       if ((size_t) len >= buflen)
 153         return NULL;
 154
 155 #define UNREACHABLE_LEN strlen ("(unreachable)")
 156       if (len > UNREACHABLE_LEN
 157           && memcmp (ttyname_buf, "(unreachable)", UNREACHABLE_LEN) == 0)
 158         {
 159           memmove (ttyname_buf, ttyname_buf + UNREACHABLE_LEN,
 160                    len - UNREACHABLE_LEN);
 161           len -= UNREACHABLE_LEN;
 162         }
 163
 164       /* readlink need not terminate the string.  */
 165       ttyname_buf[len] = '\0';
 166
 167       /* Verify readlink result, fall back on iterating through devices.  */
 168       if (ttyname_buf[0] == '/'
 169           && __xstat64 (_STAT_VER, ttyname_buf, &st1) == 0
 170 #ifdef _STATBUF_ST_RDEV
 171           && S_ISCHR (st1.st_mode)
 172           && st1.st_rdev == st.st_rdev
 173 #else
 174           && st1.st_ino == st.st_ino
 175           && st1.st_dev == st.st_dev
 176 #endif
 177           )
 178         return ttyname_buf;
 179     }
 180
 181   if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
 182     {
 183 #ifdef _STATBUF_ST_RDEV
 184       name = getttyname ("/dev/pts", st.st_rdev, st.st_ino, save, &dostat);
 185 #else
 186       name = getttyname ("/dev/pts", st.st_dev, st.st_ino, save, &dostat);
 187 #endif
 188     }
 189   else
 190     {
 191       __set_errno (save);
 192       name = NULL;
 193     }
 194
 195   if (!name && dostat != -1)
 196     {
 197 #ifdef _STATBUF_ST_RDEV
 198       name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
 199 #else
 200       name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
 201 #endif
 202     }
 203
 204   if (!name && dostat != -1)
 205     {
 206       dostat = 1;
 207 #ifdef _STATBUF_ST_RDEV
 208       name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
 209 #else
 210       name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
 211 #endif
 212     }
 213
 214   return name;
 215 }