null.c revision 331722 
1/*-
2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
3 * Copyright (c) 2001-2004 Mark R. V. Murray
4 * Copyright (c) 2014 Eitan Adler
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer
12 *    in this position and unchanged.
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 AUTHORS ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD: stable/11/sys/dev/null/null.c 331722 2018-03-29 02:50:57Z eadler $");
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/conf.h>
36#include <sys/uio.h>
37#include <sys/kernel.h>
38#include <sys/malloc.h>
39#include <sys/module.h>
40#include <sys/disk.h>
41#include <sys/bus.h>
42#include <sys/filio.h>
43
44#include <machine/bus.h>
45#include <machine/vmparam.h>
46
47/* For use with destroy_dev(9). */
48static struct cdev *full_dev;
49static struct cdev *null_dev;
50static struct cdev *zero_dev;
51
52static d_write_t full_write;
53static d_write_t null_write;
54static d_ioctl_t null_ioctl;
55static d_ioctl_t zero_ioctl;
56static d_read_t zero_read;
57
58static struct cdevsw full_cdevsw = {
59	.d_version =	D_VERSION,
60	.d_read =	zero_read,
61	.d_write =	full_write,
62	.d_ioctl =	zero_ioctl,
63	.d_name =	"full",
64};
65
66static struct cdevsw null_cdevsw = {
67	.d_version =	D_VERSION,
68	.d_read =	(d_read_t *)nullop,
69	.d_write =	null_write,
70	.d_ioctl =	null_ioctl,
71	.d_name =	"null",
72};
73
74static struct cdevsw zero_cdevsw = {
75	.d_version =	D_VERSION,
76	.d_read =	zero_read,
77	.d_write =	null_write,
78	.d_ioctl =	zero_ioctl,
79	.d_name =	"zero",
80	.d_flags =	D_MMAP_ANON,
81};
82
83
84
85/* ARGSUSED */
86static int
87full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused)
88{
89
90	return (ENOSPC);
91}
92
93/* ARGSUSED */
94static int
95null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
96{
97	uio->uio_resid = 0;
98
99	return (0);
100}
101
102/* ARGSUSED */
103static int
104null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
105    int flags __unused, struct thread *td)
106{
107	int error;
108	error = 0;
109
110	switch (cmd) {
111	case DIOCSKERNELDUMP:
112		error = set_dumper(NULL, NULL, td);
113		break;
114	case FIONBIO:
115		break;
116	case FIOASYNC:
117		if (*(int *)data != 0)
118			error = EINVAL;
119		break;
120	default:
121		error = ENOIOCTL;
122	}
123	return (error);
124}
125
126/* ARGSUSED */
127static int
128zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
129	   int flags __unused, struct thread *td)
130{
131	int error;
132	error = 0;
133
134	switch (cmd) {
135	case FIONBIO:
136		break;
137	case FIOASYNC:
138		if (*(int *)data != 0)
139			error = EINVAL;
140		break;
141	default:
142		error = ENOIOCTL;
143	}
144	return (error);
145}
146
147
148/* ARGSUSED */
149static int
150zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
151{
152	void *zbuf;
153	ssize_t len;
154	int error = 0;
155
156	KASSERT(uio->uio_rw == UIO_READ,
157	    ("Can't be in %s for write", __func__));
158	zbuf = __DECONST(void *, zero_region);
159	while (uio->uio_resid > 0 && error == 0) {
160		len = uio->uio_resid;
161		if (len > ZERO_REGION_SIZE)
162			len = ZERO_REGION_SIZE;
163		error = uiomove(zbuf, len, uio);
164	}
165
166	return (error);
167}
168
169/* ARGSUSED */
170static int
171null_modevent(module_t mod __unused, int type, void *data __unused)
172{
173	switch(type) {
174	case MOD_LOAD:
175		if (bootverbose)
176			printf("null: <full device, null device, zero device>\n");
177		full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0,
178		    NULL, UID_ROOT, GID_WHEEL, 0666, "full");
179		null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
180		    NULL, UID_ROOT, GID_WHEEL, 0666, "null");
181		zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
182		    NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
183		break;
184
185	case MOD_UNLOAD:
186		destroy_dev(full_dev);
187		destroy_dev(null_dev);
188		destroy_dev(zero_dev);
189		break;
190
191	case MOD_SHUTDOWN:
192		break;
193
194	default:
195		return (EOPNOTSUPP);
196	}
197
198	return (0);
199}
200
201DEV_MODULE(null, null_modevent, NULL);
202MODULE_VERSION(null, 1);
203