FreeBSD/Linux Kernel Cross Reference
sys/dev/null/null.c
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 <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/conf.h>
38 #include <sys/uio.h>
39 #include <sys/kernel.h>
40 #include <sys/malloc.h>
41 #include <sys/module.h>
42 #include <sys/disk.h>
43 #include <sys/bus.h>
44 #include <sys/filio.h>
45
46 #include <machine/bus.h>
47 #include <machine/vmparam.h>
48
49 /* For use with destroy_dev(9). */
50 static struct cdev *full_dev;
51 static struct cdev *null_dev;
52 static struct cdev *zero_dev;
53
54 static d_write_t full_write;
55 static d_write_t null_write;
56 static d_ioctl_t null_ioctl;
57 static d_ioctl_t zero_ioctl;
58 static d_read_t zero_read;
59
60 static struct cdevsw full_cdevsw = {
61 .d_version = D_VERSION,
62 .d_read = zero_read,
63 .d_write = full_write,
64 .d_ioctl = zero_ioctl,
65 .d_name = "full",
66 };
67
68 static struct cdevsw null_cdevsw = {
69 .d_version = D_VERSION,
70 .d_read = (d_read_t *)nullop,
71 .d_write = null_write,
72 .d_ioctl = null_ioctl,
73 .d_name = "null",
74 };
75
76 static struct cdevsw zero_cdevsw = {
77 .d_version = D_VERSION,
78 .d_read = zero_read,
79 .d_write = null_write,
80 .d_ioctl = zero_ioctl,
81 .d_name = "zero",
82 .d_flags = D_MMAP_ANON,
83 };
84
85 /* ARGSUSED */
86 static int
87 full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused)
88 {
89
90 return (ENOSPC);
91 }
92
93 /* ARGSUSED */
94 static int
95 null_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 */
103 static int
104 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
105 int flags __unused, struct thread *td)
106 {
107 struct diocskerneldump_arg kda;
108 int error;
109
110 error = 0;
111 switch (cmd) {
112 case DIOCSKERNELDUMP:
113 bzero(&kda, sizeof(kda));
114 kda.kda_index = KDA_REMOVE_ALL;
115 error = dumper_remove(NULL, &kda);
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 /* ARGSUSED */
151 static int
152 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
153 {
154 void *zbuf;
155 ssize_t len;
156 int error = 0;
157
158 KASSERT(uio->uio_rw == UIO_READ,
159 ("Can't be in %s for write", __func__));
160 zbuf = __DECONST(void *, zero_region);
161 while (uio->uio_resid > 0 && error == 0) {
162 len = uio->uio_resid;
163 if (len > ZERO_REGION_SIZE)
164 len = ZERO_REGION_SIZE;
165 error = uiomove(zbuf, len, uio);
166 }
167
168 return (error);
169 }
170
171 /* ARGSUSED */
172 static int
173 null_modevent(module_t mod __unused, int type, void *data __unused)
174 {
175 switch(type) {
176 case MOD_LOAD:
177 if (bootverbose)
178 printf("null: <full device, null device, zero device>\n");
179 full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0,
180 NULL, UID_ROOT, GID_WHEEL, 0666, "full");
181 null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
182 NULL, UID_ROOT, GID_WHEEL, 0666, "null");
183 zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
184 NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
185 break;
186
187 case MOD_UNLOAD:
188 destroy_dev(full_dev);
189 destroy_dev(null_dev);
190 destroy_dev(zero_dev);
191 break;
192
193 case MOD_SHUTDOWN:
194 break;
195
196 default:
197 return (EOPNOTSUPP);
198 }
199
200 return (0);
201 }
202
203 DEV_MODULE(null, null_modevent, NULL);
204 MODULE_VERSION(null, 1);
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