null.c revision 221853 
1/*-
2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
3 * Copyright (c) 2001-2004 Mark R. V. Murray
4 * 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 *    in this position and unchanged.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: head/sys/dev/null/null.c 221853 2011-05-13 18:48:00Z mdf $");
31
32#include <sys/param.h>
33#include <sys/systm.h>
34#include <sys/conf.h>
35#include <sys/uio.h>
36#include <sys/kernel.h>
37#include <sys/malloc.h>
38#include <sys/module.h>
39#include <sys/priv.h>
40#include <sys/disk.h>
41#include <sys/bus.h>
42#include <machine/bus.h>
43
44/* For use with destroy_dev(9). */
45static struct cdev *null_dev;
46static struct cdev *zero_dev;
47
48static d_write_t null_write;
49static d_ioctl_t null_ioctl;
50static d_read_t zero_read;
51
52static struct cdevsw null_cdevsw = {
53	.d_version =	D_VERSION,
54	.d_read =	(d_read_t *)nullop,
55	.d_write =	null_write,
56	.d_ioctl =	null_ioctl,
57	.d_name =	"null",
58};
59
60static struct cdevsw zero_cdevsw = {
61	.d_version =	D_VERSION,
62	.d_read =	zero_read,
63	.d_write =	null_write,
64	.d_name =	"zero",
65	.d_flags =	D_MMAP_ANON,
66};
67
68/* ARGSUSED */
69static int
70null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
71{
72	uio->uio_resid = 0;
73
74	return (0);
75}
76
77/* ARGSUSED */
78static int
79null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
80    int flags __unused, struct thread *td)
81{
82	int error;
83
84	if (cmd != DIOCSKERNELDUMP)
85		return (ENOIOCTL);
86	error = priv_check(td, PRIV_SETDUMPER);
87	if (error)
88		return (error);
89	return (set_dumper(NULL));
90}
91
92/* ARGSUSED */
93static int
94zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
95{
96	void *zbuf;
97	ssize_t len;
98	int error = 0;
99
100	KASSERT(uio->uio_rw == UIO_READ,
101	    ("Can't be in %s for write", __func__));
102	zbuf = __DECONST(void *, zero_region);
103	while (uio->uio_resid > 0 && error == 0) {
104		len = uio->uio_resid;
105		if (len > ZERO_REGION_SIZE)
106			len = ZERO_REGION_SIZE;
107		error = uiomove(zbuf, len, uio);
108	}
109
110	return (error);
111}
112
113/* ARGSUSED */
114static int
115null_modevent(module_t mod __unused, int type, void *data __unused)
116{
117	switch(type) {
118	case MOD_LOAD:
119		if (bootverbose)
120			printf("null: <null device, zero device>\n");
121		null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
122		    NULL, UID_ROOT, GID_WHEEL, 0666, "null");
123		zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
124		    NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
125		break;
126
127	case MOD_UNLOAD:
128		destroy_dev(null_dev);
129		destroy_dev(zero_dev);
130		break;
131
132	case MOD_SHUTDOWN:
133		break;
134
135	default:
136		return (EOPNOTSUPP);
137	}
138
139	return (0);
140}
141
142DEV_MODULE(null, null_modevent, NULL);
143MODULE_VERSION(null, 1);
144