xref: /freebsd/lib/libc/stdlib/ptsname.c (revision bb15ca603fa442c72dde3f3cb8b46db6970e3950)
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("$FreeBSD$");
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  */
48 static 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  */
75 char *
76 ptsname(int fildes)
77 {
78 	static char pt_slave[sizeof _PATH_DEV + SPECNAMELEN] = _PATH_DEV;
79 	char *ret = NULL;
80 	int sverrno = errno;
81 
82 	/* Make sure fildes points to a master device. */
83 	if (__isptmaster(fildes) != 0)
84 		goto done;
85 
86 	if (fdevname_r(fildes, pt_slave + (sizeof _PATH_DEV - 1),
87 	    sizeof pt_slave - (sizeof _PATH_DEV - 1)) != NULL)
88 		ret = pt_slave;
89 
90 done:	/* Make sure ptsname() does not overwrite errno. */
91 	errno = sverrno;
92 	return (ret);
93 }
94