ptsname.c revision 331722 
1/*-
2 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Portions of this software were developed under sponsorship from Snow
6 * B.V., the Netherlands.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#include <sys/cdefs.h>
31#ifndef lint
32__FBSDID("$FreeBSD: stable/11/lib/libc/stdlib/ptsname.c 331722 2018-03-29 02:50:57Z eadler $");
33#endif /* not lint */
34
35#include "namespace.h"
36#include <sys/param.h>
37#include <sys/ioctl.h>
38
39#include <errno.h>
40#include <paths.h>
41#include <stdlib.h>
42#include "un-namespace.h"
43
44/*
45 * __isptmaster():  return whether the file descriptor refers to a
46 *                  pseudo-terminal master device.
47 */
48static int
49__isptmaster(int fildes)
50{
51
52	if (_ioctl(fildes, TIOCPTMASTER) == 0)
53		return (0);
54
55	if (errno != EBADF)
56		errno = EINVAL;
57
58	return (-1);
59}
60
61/*
62 * In our implementation, grantpt() and unlockpt() don't actually have
63 * any use, because PTY's are created on the fly and already have proper
64 * permissions upon creation.
65 *
66 * Just make sure `fildes' actually points to a real PTY master device.
67 */
68__strong_reference(__isptmaster, grantpt);
69__strong_reference(__isptmaster, unlockpt);
70
71/*
72 * ptsname():  return the pathname of the slave pseudo-terminal device
73 *             associated with the specified master.
74 */
75char *
76ptsname(int fildes)
77{
78	static char pt_slave[sizeof _PATH_DEV + SPECNAMELEN] = _PATH_DEV;
79	char *ret = NULL;
80
81	/* Make sure fildes points to a master device. */
82	if (__isptmaster(fildes) != 0)
83		goto done;
84
85	if (fdevname_r(fildes, pt_slave + (sizeof _PATH_DEV - 1),
86	    sizeof pt_slave - (sizeof _PATH_DEV - 1)) != NULL)
87		ret = pt_slave;
88
89done:
90	return (ret);
91}
92