sysdeps/unix/sysv/linux/ttyname_r.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 static int getttyname_r (char *buf, size_t buflen,
  34                          dev_t mydev, ino64_t myino, int save,
  35                          int *dostat);
  36
  37 static int
  38 attribute_compat_text_section
  39 getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
  40               int save, int *dostat)
  41 {
  42   struct stat64 st;
  43   DIR *dirstream;
  44   struct dirent64 *d;
  45   size_t devlen = strlen (buf);
  46
  47   dirstream = __opendir (buf);
  48   if (dirstream == NULL)
  49     {
  50       *dostat = -1;
  51       return errno;
  52     }
  53
  54   while ((d = __readdir64 (dirstream)) != NULL)
  55     if ((d->d_fileno == myino || *dostat)
  56         && strcmp (d->d_name, "stdin")
  57         && strcmp (d->d_name, "stdout")
  58         && strcmp (d->d_name, "stderr"))
  59       {
  60         char *cp;
  61         size_t needed = _D_EXACT_NAMLEN (d) + 1;
  62
  63         if (needed > buflen)
  64           {
  65             *dostat = -1;
  66             (void) __closedir (dirstream);
  67             __set_errno (ERANGE);
  68             return ERANGE;
  69           }
  70
  71         cp = __stpncpy (buf + devlen, d->d_name, needed);
  72         cp[0] = '\0';
  73
  74         if (__xstat64 (_STAT_VER, buf, &st) == 0
  75 #ifdef _STATBUF_ST_RDEV
  76             && S_ISCHR (st.st_mode) && st.st_rdev == mydev
  77 #else
  78             && d->d_fileno == myino && st.st_dev == mydev
  79 #endif
  80            )
  81           {
  82             (void) __closedir (dirstream);
  83             __set_errno (save);
  84             return 0;
  85           }
  86       }
  87
  88   (void) __closedir (dirstream);
  89   __set_errno (save);
  90   /* It is not clear what to return in this case.  `isatty' says FD
  91      refers to a TTY but no entry in /dev has this inode.  */
  92   return ENOTTY;
  93 }
  94
  95 /* Store at most BUFLEN character of the pathname of the terminal FD is
  96    open on in BUF.  Return 0 on success,  otherwise an error number.  */
  97 int
  98 __ttyname_r (int fd, char *buf, size_t buflen)
  99 {
 100   char procname[30];
 101   struct stat64 st, st1;
 102   int dostat = 0;
 103   int save = errno;
 104
 105   /* Test for the absolute minimal size.  This makes life easier inside
 106      the loop.  */
 107   if (!buf)
 108     {
 109       __set_errno (EINVAL);
 110       return EINVAL;
 111     }
 112
 113   if (buflen < sizeof ("/dev/pts/"))
 114     {
 115       __set_errno (ERANGE);
 116       return ERANGE;
 117     }
 118
 119   /* isatty check, tcgetattr is used because it sets the correct
 120      errno (EBADF resp. ENOTTY) on error.  */
 121   struct termios term;
 122   if (__glibc_unlikely (__tcgetattr (fd, &term) < 0))
 123     return errno;
 124
 125   if (__fxstat64 (_STAT_VER, fd, &st) < 0)
 126     return errno;
 127
 128   /* We try using the /proc filesystem.  */
 129   *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0';
 130
 131   ssize_t ret = __readlink (procname, buf, buflen - 1);
 132   if (__glibc_unlikely (ret == -1 && errno == ENAMETOOLONG))
 133     {
 134       __set_errno (ERANGE);
 135       return ERANGE;
 136     }
 137
 138   if (__glibc_likely (ret != -1))
 139     {
 140 #define UNREACHABLE_LEN strlen ("(unreachable)")
 141       if (ret > UNREACHABLE_LEN
 142           && memcmp (buf, "(unreachable)", UNREACHABLE_LEN) == 0)
 143         {
 144           memmove (buf, buf + UNREACHABLE_LEN, ret - UNREACHABLE_LEN);
 145           ret -= UNREACHABLE_LEN;
 146         }
 147
 148       /* readlink need not terminate the string.  */
 149       buf[ret] = '\0';
 150
 151       /* Verify readlink result, fall back on iterating through devices.  */
 152       if (buf[0] == '/'
 153           && __xstat64 (_STAT_VER, buf, &st1) == 0
 154 #ifdef _STATBUF_ST_RDEV
 155           && S_ISCHR (st1.st_mode)
 156           && st1.st_rdev == st.st_rdev
 157 #endif
 158           && st1.st_ino == st.st_ino
 159           && st1.st_dev == st.st_dev)
 160         return 0;
 161
 162       /* If the link doesn't exist, then it points to a device in another
 163        * namespace.
 164        */
 165       if (is_pty (&st))
 166         {
 167           __set_errno (ENODEV);
 168           return ENODEV;
 169         }
 170     }
 171
 172   /* Prepare the result buffer.  */
 173   memcpy (buf, "/dev/pts/", sizeof ("/dev/pts/"));
 174   buflen -= sizeof ("/dev/pts/") - 1;
 175
 176   if (__xstat64 (_STAT_VER, buf, &st1) == 0 && S_ISDIR (st1.st_mode))
 177     {
 178 #ifdef _STATBUF_ST_RDEV
 179       ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
 180                           &dostat);
 181 #else
 182       ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
 183                           &dostat);
 184 #endif
 185     }
 186   else
 187     {
 188       __set_errno (save);
 189       ret = ENOENT;
 190     }
 191
 192   if (ret && dostat != -1)
 193     {
 194       buf[sizeof ("/dev/") - 1] = '\0';
 195       buflen += sizeof ("pts/") - 1;
 196 #ifdef _STATBUF_ST_RDEV
 197       ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
 198                           &dostat);
 199 #else
 200       ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
 201                           &dostat);
 202 #endif
 203     }
 204
 205   if (ret && dostat != -1)
 206     {
 207       buf[sizeof ("/dev/") - 1] = '\0';
 208       dostat = 1;
 209 #ifdef _STATBUF_ST_RDEV
 210       ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino,
 211                           save, &dostat);
 212 #else
 213       ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino,
 214                           save, &dostat);
 215 #endif
 216     }
 217
 218   return ret;
 219 }
 220
 221 weak_alias (__ttyname_r, ttyname_r)