pty.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__FBSDID("$FreeBSD: stable/11/sys/dev/pty/pty.c 331722 2018-03-29 02:50:57Z eadler $");
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/module.h>
39#include <sys/proc.h>
40#include <sys/sysctl.h>
41#include <sys/syslog.h>
42#include <sys/systm.h>
43#include <sys/tty.h>
44
45/*
46 * This driver implements a BSD-style compatibility naming scheme for
47 * the pts(4) driver. We just call into pts(4) to create the actual PTY.
48 * To make sure we don't use the same PTY multiple times, we abuse
49 * si_drv1 inside the cdev to mark whether the PTY is in use.
50 *
51 * It also implements a /dev/ptmx device node, which is useful for Linux
52 * binary emulation.
53 */
54
55static unsigned pty_warningcnt = 1;
56SYSCTL_UINT(_kern, OID_AUTO, tty_pty_warningcnt, CTLFLAG_RW,
57    &pty_warningcnt, 0,
58    "Warnings that will be triggered upon legacy PTY allocation");
59
60static int
61ptydev_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
62{
63	int error;
64	char name[6]; /* "ttyXX" */
65
66	if (!atomic_cmpset_ptr((uintptr_t *)&dev->si_drv1, 0, 1))
67		return (EBUSY);
68
69	/* Generate device name and create PTY. */
70	strlcpy(name, devtoname(dev), sizeof(name));
71	name[0] = 't';
72
73	error = pts_alloc_external(fflags & (FREAD|FWRITE), td, fp, dev, name);
74	if (error != 0) {
75		destroy_dev_sched(dev);
76		return (error);
77	}
78
79	/* Raise a warning when a legacy PTY has been allocated. */
80	counted_warning(&pty_warningcnt, "is using legacy pty devices");
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	struct make_dev_args mda;
96	int error;
97
98	/* Cloning is already satisfied. */
99	if (*dev != NULL)
100		return;
101
102	/* Only catch /dev/ptyXX. */
103	if (namelen != 5 || bcmp(name, "pty", 3) != 0)
104		return;
105
106	/* Only catch /dev/pty[l-sL-S]X. */
107	if (!(name[3] >= 'l' && name[3] <= 's') &&
108	    !(name[3] >= 'L' && name[3] <= 'S'))
109		return;
110
111	/* Only catch /dev/pty[l-sL-S][0-9a-v]. */
112	if (!(name[4] >= '0' && name[4] <= '9') &&
113	    !(name[4] >= 'a' && name[4] <= 'v'))
114		return;
115
116	/* Create the controller device node. */
117	make_dev_args_init(&mda);
118	mda.mda_flags =  MAKEDEV_CHECKNAME | MAKEDEV_REF;
119	mda.mda_devsw = &ptydev_cdevsw;
120	mda.mda_uid = UID_ROOT;
121	mda.mda_gid = GID_WHEEL;
122	mda.mda_mode = 0666;
123	error = make_dev_s(&mda, dev, "%s", name);
124	if (error != 0)
125		*dev = NULL;
126}
127
128static int
129ptmx_fdopen(struct cdev *dev __unused, int fflags, struct thread *td,
130    struct file *fp)
131{
132
133	return (pts_alloc(fflags & (FREAD|FWRITE), td, fp));
134}
135
136static struct cdevsw ptmx_cdevsw = {
137	.d_version	= D_VERSION,
138	.d_fdopen	= ptmx_fdopen,
139	.d_name		= "ptmx",
140};
141
142static int
143pty_modevent(module_t mod, int type, void *data)
144{
145
146	switch(type) {
147	case MOD_LOAD:
148		EVENTHANDLER_REGISTER(dev_clone, pty_clone, 0, 1000);
149		make_dev_credf(MAKEDEV_ETERNAL_KLD, &ptmx_cdevsw, 0, NULL,
150		    UID_ROOT, GID_WHEEL, 0666, "ptmx");
151		break;
152	case MOD_SHUTDOWN:
153		break;
154	case MOD_UNLOAD:
155		/* XXX: No unloading support yet. */
156		return (EBUSY);
157	default:
158		return (EOPNOTSUPP);
159	}
160
161	return (0);
162}
163
164DEV_MODULE(pty, pty_modevent, NULL);
165