xref: /freebsd/sys/kern/tty_tty.c (revision 66fd12cf4896eb08ad8e7a2627537f84ead84dd3)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2003 Poul-Henning Kamp.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25  * SUCH DAMAGE.
26  */
27 
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD$");
30 
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/eventhandler.h>
34 #include <sys/conf.h>
35 #include <sys/kernel.h>
36 #include <sys/proc.h>
37 #include <sys/sx.h>
38 #include <sys/vnode.h>
39 
40 #include <fs/devfs/devfs.h>
41 #include <fs/devfs/devfs_int.h>
42 
43 static	d_open_t	cttyopen;
44 
45 static struct cdevsw ctty_cdevsw = {
46 	.d_version =	D_VERSION,
47 	.d_open =	cttyopen,
48 	.d_name =	"ctty",
49 };
50 
51 static struct cdev *ctty;
52 
53 static	int
54 cttyopen(struct cdev *dev, int flag, int mode, struct thread *td)
55 {
56 
57 	return (ENXIO);
58 }
59 
60 static void
61 ctty_clone(void *arg, struct ucred *cred, char *name, int namelen,
62     struct cdev **dev)
63 {
64 	struct proc *p;
65 
66 	if (*dev != NULL)
67 		return;
68 	if (strcmp(name, "tty"))
69 		return;
70 	p = curproc;
71 	sx_slock(&proctree_lock);
72 	dev_lock();
73 	if (!(p->p_flag & P_CONTROLT))
74 		*dev = ctty;
75 	else if (p->p_session->s_ttyvp == NULL)
76 		*dev = ctty;
77 	else if (p->p_session->s_ttyvp->v_type == VBAD ||
78 	    p->p_session->s_ttyvp->v_rdev == NULL) {
79 		/* e.g. s_ttyvp was revoked */
80 		*dev = ctty;
81 	} else
82 		*dev = p->p_session->s_ttyvp->v_rdev;
83 	dev_refl(*dev);
84 	dev_unlock();
85 	sx_sunlock(&proctree_lock);
86 }
87 
88 static void
89 ctty_drvinit(void *unused)
90 {
91 
92 	EVENTHANDLER_REGISTER(dev_clone, ctty_clone, 0, 1000);
93 	ctty = make_dev_credf(MAKEDEV_ETERNAL, &ctty_cdevsw, 0, NULL, UID_ROOT,
94 	    GID_WHEEL, 0666, "ctty");
95 }
96 
97 SYSINIT(cttydev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,ctty_drvinit,NULL);
98