xref: /freebsd/sys/kern/tty_tty.c (revision 2b15cb3d0922bd70ea592f0da9b4a5b167f4d53f)
1 /*-
2  * Copyright (c) 2003 Poul-Henning Kamp.  All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23  * SUCH DAMAGE.
24  */
25 
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
28 
29 #include <sys/param.h>
30 #include <sys/systm.h>
31 #include <sys/conf.h>
32 #include <sys/kernel.h>
33 #include <sys/proc.h>
34 #include <sys/sx.h>
35 #include <sys/vnode.h>
36 
37 #include <fs/devfs/devfs.h>
38 #include <fs/devfs/devfs_int.h>
39 
40 static	d_open_t	cttyopen;
41 
42 static struct cdevsw ctty_cdevsw = {
43 	.d_version =	D_VERSION,
44 	.d_open =	cttyopen,
45 	.d_name =	"ctty",
46 };
47 
48 static struct cdev *ctty;
49 
50 static	int
51 cttyopen(struct cdev *dev, int flag, int mode, struct thread *td)
52 {
53 
54 	return (ENXIO);
55 }
56 
57 static void
58 ctty_clone(void *arg, struct ucred *cred, char *name, int namelen,
59     struct cdev **dev)
60 {
61 
62 	if (*dev != NULL)
63 		return;
64 	if (strcmp(name, "tty"))
65 		return;
66 	sx_sunlock(&clone_drain_lock);
67 	sx_slock(&proctree_lock);
68 	sx_slock(&clone_drain_lock);
69 	dev_lock();
70 	if (!(curthread->td_proc->p_flag & P_CONTROLT))
71 		*dev = ctty;
72 	else if (curthread->td_proc->p_session->s_ttyvp == NULL)
73 		*dev = ctty;
74 	else if (curthread->td_proc->p_session->s_ttyvp->v_type == VBAD ||
75 	    curthread->td_proc->p_session->s_ttyvp->v_rdev == NULL) {
76 		/* e.g. s_ttyvp was revoked */
77 		*dev = ctty;
78 	} else
79 		*dev = curthread->td_proc->p_session->s_ttyvp->v_rdev;
80 	dev_refl(*dev);
81 	dev_unlock();
82 	sx_sunlock(&proctree_lock);
83 }
84 
85 static void
86 ctty_drvinit(void *unused)
87 {
88 
89 	EVENTHANDLER_REGISTER(dev_clone, ctty_clone, 0, 1000);
90 	ctty = make_dev_credf(MAKEDEV_ETERNAL, &ctty_cdevsw, 0, NULL, UID_ROOT,
91 	    GID_WHEEL, 0666, "ctty");
92 }
93 
94 SYSINIT(cttydev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,ctty_drvinit,NULL);
95