FreeBSD/Linux Kernel Cross Reference
sys/dev/null/null.c
1 /*-
2 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen
3 * Copyright (c) 2001-2004 Mark R. V. Murray
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer
11 * in this position and unchanged.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD: releng/6.4/sys/dev/null/null.c 142707 2005-02-27 22:01:09Z phk $");
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/conf.h>
35 #include <sys/uio.h>
36 #include <sys/kernel.h>
37 #include <sys/malloc.h>
38 #include <sys/module.h>
39 #include <sys/disk.h>
40 #include <sys/bus.h>
41 #include <machine/bus.h>
42
43 /* For use with destroy_dev(9). */
44 static struct cdev *null_dev;
45 static struct cdev *zero_dev;
46
47 static d_write_t null_write;
48 static d_ioctl_t null_ioctl;
49 static d_read_t zero_read;
50
51 #define NULL_MINOR 2
52 #define ZERO_MINOR 12
53
54 static struct cdevsw null_cdevsw = {
55 .d_version = D_VERSION,
56 .d_read = (d_read_t *)nullop,
57 .d_write = null_write,
58 .d_ioctl = null_ioctl,
59 .d_name = "null",
60 };
61
62 static struct cdevsw zero_cdevsw = {
63 .d_version = D_VERSION,
64 .d_read = zero_read,
65 .d_write = null_write,
66 .d_name = "zero",
67 .d_flags = D_MMAP_ANON,
68 };
69
70 static void *zbuf;
71
72 /* ARGSUSED */
73 static int
74 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
75 {
76 uio->uio_resid = 0;
77
78 return (0);
79 }
80
81 /* ARGSUSED */
82 static int
83 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
84 int flags __unused, struct thread *td)
85 {
86 int error;
87
88 if (cmd != DIOCSKERNELDUMP)
89 return (ENOIOCTL);
90 error = suser(td);
91 if (error)
92 return (error);
93 return (set_dumper(NULL));
94 }
95
96 /* ARGSUSED */
97 static int
98 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
99 {
100 int error = 0;
101
102 while (uio->uio_resid > 0 && error == 0)
103 error = uiomove(zbuf, MIN(uio->uio_resid, PAGE_SIZE), uio);
104
105 return (error);
106 }
107
108 /* ARGSUSED */
109 static int
110 null_modevent(module_t mod __unused, int type, void *data __unused)
111 {
112 switch(type) {
113 case MOD_LOAD:
114 if (bootverbose)
115 printf("null: <null device, zero device>\n");
116 zbuf = (void *)malloc(PAGE_SIZE, M_TEMP, M_WAITOK | M_ZERO);
117 null_dev = make_dev(&null_cdevsw, NULL_MINOR, UID_ROOT,
118 GID_WHEEL, 0666, "null");
119 zero_dev = make_dev(&zero_cdevsw, ZERO_MINOR, UID_ROOT,
120 GID_WHEEL, 0666, "zero");
121 break;
122
123 case MOD_UNLOAD:
124 destroy_dev(null_dev);
125 destroy_dev(zero_dev);
126 free(zbuf, M_TEMP);
127 break;
128
129 case MOD_SHUTDOWN:
130 break;
131
132 default:
133 return (EOPNOTSUPP);
134 }
135
136 return (0);
137 }
138
139 DEV_MODULE(null, null_modevent, NULL);
140 MODULE_VERSION(null, 1);
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