xref: /freebsd/sys/dev/null/null.c (revision cc3f4b99653c34ae64f8a1fddea370abefef680e)
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("$FreeBSD$");
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/priv.h>
41 #include <sys/disk.h>
42 #include <sys/bus.h>
43 #include <sys/filio.h>
44 
45 #include <machine/bus.h>
46 #include <machine/vmparam.h>
47 
48 /* For use with destroy_dev(9). */
49 static struct cdev *full_dev;
50 static struct cdev *null_dev;
51 static struct cdev *zero_dev;
52 
53 static d_write_t full_write;
54 static d_write_t null_write;
55 static d_ioctl_t null_ioctl;
56 static d_ioctl_t zero_ioctl;
57 static d_read_t zero_read;
58 
59 static struct cdevsw full_cdevsw = {
60 	.d_version =	D_VERSION,
61 	.d_read =	zero_read,
62 	.d_write =	full_write,
63 	.d_ioctl =	zero_ioctl,
64 	.d_name =	"full",
65 };
66 
67 static struct cdevsw null_cdevsw = {
68 	.d_version =	D_VERSION,
69 	.d_read =	(d_read_t *)nullop,
70 	.d_write =	null_write,
71 	.d_ioctl =	null_ioctl,
72 	.d_name =	"null",
73 };
74 
75 static struct cdevsw zero_cdevsw = {
76 	.d_version =	D_VERSION,
77 	.d_read =	zero_read,
78 	.d_write =	null_write,
79 	.d_ioctl =	zero_ioctl,
80 	.d_name =	"zero",
81 	.d_flags =	D_MMAP_ANON,
82 };
83 
84 
85 
86 /* ARGSUSED */
87 static int
88 full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused)
89 {
90 
91 	return (ENOSPC);
92 }
93 
94 /* ARGSUSED */
95 static int
96 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
97 {
98 	uio->uio_resid = 0;
99 
100 	return (0);
101 }
102 
103 /* ARGSUSED */
104 static int
105 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
106     int flags __unused, struct thread *td)
107 {
108 	int error;
109 	error = 0;
110 
111 	switch (cmd) {
112 	case DIOCSKERNELDUMP:
113 		error = priv_check(td, PRIV_SETDUMPER);
114 		if (error == 0)
115 			error = set_dumper(NULL, NULL);
116 		break;
117 	case FIONBIO:
118 		break;
119 	case FIOASYNC:
120 		if (*(int *)data != 0)
121 			error = EINVAL;
122 		break;
123 	default:
124 		error = ENOIOCTL;
125 	}
126 	return (error);
127 }
128 
129 /* ARGSUSED */
130 static int
131 zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
132 	   int flags __unused, struct thread *td)
133 {
134 	int error;
135 	error = 0;
136 
137 	switch (cmd) {
138 	case FIONBIO:
139 		break;
140 	case FIOASYNC:
141 		if (*(int *)data != 0)
142 			error = EINVAL;
143 		break;
144 	default:
145 		error = ENOIOCTL;
146 	}
147 	return (error);
148 }
149 
150 
151 /* ARGSUSED */
152 static int
153 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
154 {
155 	void *zbuf;
156 	ssize_t len;
157 	int error = 0;
158 
159 	KASSERT(uio->uio_rw == UIO_READ,
160 	    ("Can't be in %s for write", __func__));
161 	zbuf = __DECONST(void *, zero_region);
162 	while (uio->uio_resid > 0 && error == 0) {
163 		len = uio->uio_resid;
164 		if (len > ZERO_REGION_SIZE)
165 			len = ZERO_REGION_SIZE;
166 		error = uiomove(zbuf, len, uio);
167 	}
168 
169 	return (error);
170 }
171 
172 /* ARGSUSED */
173 static int
174 null_modevent(module_t mod __unused, int type, void *data __unused)
175 {
176 	switch(type) {
177 	case MOD_LOAD:
178 		if (bootverbose)
179 			printf("null: <full device, null device, zero device>\n");
180 		full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0,
181 		    NULL, UID_ROOT, GID_WHEEL, 0666, "full");
182 		null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
183 		    NULL, UID_ROOT, GID_WHEEL, 0666, "null");
184 		zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
185 		    NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
186 		break;
187 
188 	case MOD_UNLOAD:
189 		destroy_dev(full_dev);
190 		destroy_dev(null_dev);
191 		destroy_dev(zero_dev);
192 		break;
193 
194 	case MOD_SHUTDOWN:
195 		break;
196 
197 	default:
198 		return (EOPNOTSUPP);
199 	}
200 
201 	return (0);
202 }
203 
204 DEV_MODULE(null, null_modevent, NULL);
205 MODULE_VERSION(null, 1);
206