xref: /freebsd/sys/dev/null/null.c (revision d8a0fe102c0cfdfcd5b818f850eff09d8536c9bc)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
5  * Copyright (c) 2001-2004 Mark R. V. Murray
6  * Copyright (c) 2014 Eitan Adler
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer
14  *    in this position and unchanged.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  *
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include "opt_compat.h"
36 
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/conf.h>
40 #include <sys/uio.h>
41 #include <sys/kernel.h>
42 #include <sys/malloc.h>
43 #include <sys/module.h>
44 #include <sys/disk.h>
45 #include <sys/bus.h>
46 #include <sys/filio.h>
47 
48 #include <machine/bus.h>
49 #include <machine/vmparam.h>
50 
51 /* For use with destroy_dev(9). */
52 static struct cdev *full_dev;
53 static struct cdev *null_dev;
54 static struct cdev *zero_dev;
55 
56 static d_write_t full_write;
57 static d_write_t null_write;
58 static d_ioctl_t null_ioctl;
59 static d_ioctl_t zero_ioctl;
60 static d_read_t zero_read;
61 
62 static struct cdevsw full_cdevsw = {
63 	.d_version =	D_VERSION,
64 	.d_read =	zero_read,
65 	.d_write =	full_write,
66 	.d_ioctl =	zero_ioctl,
67 	.d_name =	"full",
68 };
69 
70 static struct cdevsw null_cdevsw = {
71 	.d_version =	D_VERSION,
72 	.d_read =	(d_read_t *)nullop,
73 	.d_write =	null_write,
74 	.d_ioctl =	null_ioctl,
75 	.d_name =	"null",
76 };
77 
78 static struct cdevsw zero_cdevsw = {
79 	.d_version =	D_VERSION,
80 	.d_read =	zero_read,
81 	.d_write =	null_write,
82 	.d_ioctl =	zero_ioctl,
83 	.d_name =	"zero",
84 	.d_flags =	D_MMAP_ANON,
85 };
86 
87 
88 
89 /* ARGSUSED */
90 static int
91 full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused)
92 {
93 
94 	return (ENOSPC);
95 }
96 
97 /* ARGSUSED */
98 static int
99 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
100 {
101 	uio->uio_resid = 0;
102 
103 	return (0);
104 }
105 
106 /* ARGSUSED */
107 static int
108 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
109     int flags __unused, struct thread *td)
110 {
111 	int error;
112 	error = 0;
113 
114 	switch (cmd) {
115 #ifdef COMPAT_FREEBSD11
116 	case DIOCSKERNELDUMP_FREEBSD11:
117 #endif
118 	case DIOCSKERNELDUMP:
119 		error = set_dumper(NULL, NULL, td, 0, 0, NULL, 0, NULL);
120 		break;
121 	case FIONBIO:
122 		break;
123 	case FIOASYNC:
124 		if (*(int *)data != 0)
125 			error = EINVAL;
126 		break;
127 	default:
128 		error = ENOIOCTL;
129 	}
130 	return (error);
131 }
132 
133 /* ARGSUSED */
134 static int
135 zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
136 	   int flags __unused, struct thread *td)
137 {
138 	int error;
139 	error = 0;
140 
141 	switch (cmd) {
142 	case FIONBIO:
143 		break;
144 	case FIOASYNC:
145 		if (*(int *)data != 0)
146 			error = EINVAL;
147 		break;
148 	default:
149 		error = ENOIOCTL;
150 	}
151 	return (error);
152 }
153 
154 
155 /* ARGSUSED */
156 static int
157 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
158 {
159 	void *zbuf;
160 	ssize_t len;
161 	int error = 0;
162 
163 	KASSERT(uio->uio_rw == UIO_READ,
164 	    ("Can't be in %s for write", __func__));
165 	zbuf = __DECONST(void *, zero_region);
166 	while (uio->uio_resid > 0 && error == 0) {
167 		len = uio->uio_resid;
168 		if (len > ZERO_REGION_SIZE)
169 			len = ZERO_REGION_SIZE;
170 		error = uiomove(zbuf, len, uio);
171 	}
172 
173 	return (error);
174 }
175 
176 /* ARGSUSED */
177 static int
178 null_modevent(module_t mod __unused, int type, void *data __unused)
179 {
180 	switch(type) {
181 	case MOD_LOAD:
182 		if (bootverbose)
183 			printf("null: <full device, null device, zero device>\n");
184 		full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0,
185 		    NULL, UID_ROOT, GID_WHEEL, 0666, "full");
186 		null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
187 		    NULL, UID_ROOT, GID_WHEEL, 0666, "null");
188 		zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
189 		    NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
190 		break;
191 
192 	case MOD_UNLOAD:
193 		destroy_dev(full_dev);
194 		destroy_dev(null_dev);
195 		destroy_dev(zero_dev);
196 		break;
197 
198 	case MOD_SHUTDOWN:
199 		break;
200 
201 	default:
202 		return (EOPNOTSUPP);
203 	}
204 
205 	return (0);
206 }
207 
208 DEV_MODULE(null, null_modevent, NULL);
209 MODULE_VERSION(null, 1);
210