null.c revision 116794 
1/*-
2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer
10 *    in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/dev/null/null.c 116794 2003-06-24 19:50:48Z phk $
27 */
28
29#include <sys/param.h>
30#include <sys/systm.h>
31#include <sys/conf.h>
32#include <sys/uio.h>
33#include <sys/kernel.h>
34#include <sys/malloc.h>
35#include <sys/module.h>
36#include <sys/disk.h>
37#include <sys/bus.h>
38#include <machine/bus.h>
39
40/* For use with destroy_dev(9). */
41static dev_t null_dev;
42static dev_t zero_dev;
43
44static d_write_t null_write;
45static d_ioctl_t null_ioctl;
46static d_read_t zero_read;
47static d_read_t null_read;
48
49#define CDEV_MAJOR	2
50#define NULL_MINOR	2
51#define ZERO_MINOR	12
52
53static struct cdevsw null_cdevsw = {
54	.d_open =	nullopen,
55	.d_close =	nullclose,
56	.d_read =	null_read,
57	.d_write =	null_write,
58	.d_ioctl =	null_ioctl,
59	.d_name =	"null",
60	.d_maj =	CDEV_MAJOR,
61	.d_flags =	D_NOGIANT,
62};
63
64static struct cdevsw zero_cdevsw = {
65	.d_open =	nullopen,
66	.d_close =	nullclose,
67	.d_read =	zero_read,
68	.d_write =	null_write,
69	.d_name =	"zero",
70	.d_maj =	CDEV_MAJOR,
71	.d_flags =	D_MMAP_ANON | D_NOGIANT,
72};
73
74static void *zbuf;
75
76static int
77null_read(dev_t dev __unused, struct uio *uio, int flags __unused)
78{
79
80	return 0;
81}
82
83/* ARGSUSED */
84static int
85null_write(dev_t dev __unused, struct uio *uio, int flags __unused)
86{
87	uio->uio_resid = 0;
88	return 0;
89}
90
91static int
92null_ioctl(dev_t dev, u_long cmd, caddr_t data, int flags, struct thread *td)
93{
94	int error;
95
96	if (cmd != DIOCSKERNELDUMP)
97		return (noioctl(dev, cmd, data, flags, td));
98	error = suser(td);
99	if (error)
100		return (error);
101	return (set_dumper(NULL));
102}
103
104/* ARGSUSED */
105static int
106zero_read(dev_t dev __unused, struct uio *uio, int flags __unused)
107{
108	int c;
109	int error = 0;
110
111	while (uio->uio_resid > 0 && error == 0) {
112		c = uio->uio_resid < PAGE_SIZE ? uio->uio_resid : PAGE_SIZE;
113		error = uiomove(zbuf, c, uio);
114	}
115	return error;
116}
117
118/* ARGSUSED */
119static int
120null_modevent(module_t mod __unused, int type, void *data __unused)
121{
122	switch(type) {
123	case MOD_LOAD:
124		if (bootverbose)
125			printf("null: <null device, zero device>\n");
126		zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
127		zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT,
128			GID_WHEEL, 0666, "zero");
129		null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT,
130			GID_WHEEL, 0666, "null");
131		return 0;
132
133	case MOD_UNLOAD:
134		destroy_dev(null_dev);
135		destroy_dev(zero_dev);
136		free(zbuf, M_TEMP);
137		return 0;
138
139	case MOD_SHUTDOWN:
140		return 0;
141
142	default:
143		return EOPNOTSUPP;
144	}
145}
146
147DEV_MODULE(null, null_modevent, NULL);
148