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. */
35char *__ttyname;
36#endif
37
38static char *getttyname (const char *dev, dev_t mydev,
39 ino64_t myino, int save, int *dostat)
40 internal_function;
41
42
43libc_freeres_ptr (static char *getttyname_name);
44
45static char *
46internal_function attribute_compat_text_section
47getttyname (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'. */
113libc_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. */
118char *
119ttyname (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}
224