pty.c revision 187680 
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__FBSDID("$FreeBSD: head/sys/kern/tty_pty.c 187680 2009-01-25 08:27:11Z ed $");
32
33#include <sys/param.h>
34#include <sys/conf.h>
35#include <sys/eventhandler.h>
36#include <sys/fcntl.h>
37#include <sys/kernel.h>
38#include <sys/proc.h>
39#include <sys/sysctl.h>
40#include <sys/systm.h>
41#include <sys/tty.h>
42
43/*
44 * This driver implements a BSD-style compatibility naming scheme for
45 * the pts(4) driver. We just call into pts(4) to create the actual PTY.
46 * To make sure we don't use the same PTY multiple times, we abuse
47 * si_drv1 inside the cdev to mark whether the PTY is in use.
48 */
49
50static unsigned int pty_warningcnt = 10;
51SYSCTL_UINT(_kern, OID_AUTO, tty_pty_warningcnt, CTLFLAG_RW,
52	&pty_warningcnt, 0,
53	"Warnings that will be triggered upon PTY allocation");
54
55static int
56ptydev_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
57{
58	int error;
59	char name[6]; /* "ttyXX" */
60
61	if (!atomic_cmpset_ptr((uintptr_t *)&dev->si_drv1, 0, 1))
62		return (EBUSY);
63
64	/* Generate device name and create PTY. */
65	strcpy(name, devtoname(dev));
66	name[0] = 't';
67
68	error = pts_alloc_external(fflags & (FREAD|FWRITE), td, fp, dev, name);
69	if (error != 0) {
70		destroy_dev_sched(dev);
71		return (error);
72	}
73
74	/* Raise a warning when a legacy PTY has been allocated. */
75	if (pty_warningcnt > 0) {
76		pty_warningcnt--;
77		printf("pid %d (%s) is using legacy pty devices%s\n",
78		    td->td_proc->p_pid, td->td_name,
79		    pty_warningcnt ? "" : " - not logging anymore");
80	}
81
82	return (0);
83}
84
85static struct cdevsw ptydev_cdevsw = {
86	.d_version	= D_VERSION,
87	.d_fdopen	= ptydev_fdopen,
88	.d_name		= "ptydev",
89};
90
91static void
92pty_clone(void *arg, struct ucred *cr, char *name, int namelen,
93    struct cdev **dev)
94{
95
96	/* Cloning is already satisfied. */
97	if (*dev != NULL)
98		return;
99
100	/* Only catch /dev/ptyXX. */
101	if (namelen != 5 || bcmp(name, "pty", 3) != 0)
102		return;
103
104	/* Only catch /dev/pty[l-sL-S]X. */
105	if (!(name[3] >= 'l' && name[3] <= 's') &&
106	    !(name[3] >= 'L' && name[3] <= 'S'))
107		return;
108
109	/* Only catch /dev/pty[l-sL-S][0-9a-v]. */
110	if (!(name[4] >= '0' && name[4] <= '9') &&
111	    !(name[4] >= 'a' && name[4] <= 'v'))
112		return;
113
114	/* Create the controller device node. */
115	*dev = make_dev_credf(MAKEDEV_REF, &ptydev_cdevsw, 0,
116	    NULL, UID_ROOT, GID_WHEEL, 0666, name);
117}
118
119static void
120pty_init(void *unused)
121{
122
123	EVENTHANDLER_REGISTER(dev_clone, pty_clone, 0, 1000);
124}
125
126SYSINIT(pty, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, pty_init, NULL);
127