xref: /freebsd/sys/dev/null/null.c (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
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("$FreeBSD$");
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/priv.h>
40 #include <sys/disk.h>
41 #include <sys/bus.h>
42 #include <sys/filio.h>
43 
44 #include <machine/bus.h>
45 #include <machine/vmparam.h>
46 
47 /* For use with destroy_dev(9). */
48 static struct cdev *null_dev;
49 static struct cdev *zero_dev;
50 
51 static d_write_t null_write;
52 static d_ioctl_t null_ioctl;
53 static d_ioctl_t zero_ioctl;
54 static d_read_t zero_read;
55 
56 static struct cdevsw null_cdevsw = {
57 	.d_version =	D_VERSION,
58 	.d_read =	(d_read_t *)nullop,
59 	.d_write =	null_write,
60 	.d_ioctl =	null_ioctl,
61 	.d_name =	"null",
62 };
63 
64 static struct cdevsw zero_cdevsw = {
65 	.d_version =	D_VERSION,
66 	.d_read =	zero_read,
67 	.d_write =	null_write,
68 	.d_ioctl =	zero_ioctl,
69 	.d_name =	"zero",
70 	.d_flags =	D_MMAP_ANON,
71 };
72 
73 /* ARGSUSED */
74 static int
75 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused)
76 {
77 	uio->uio_resid = 0;
78 
79 	return (0);
80 }
81 
82 /* ARGSUSED */
83 static int
84 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
85     int flags __unused, struct thread *td)
86 {
87 	int error;
88 	error = 0;
89 
90 	switch (cmd) {
91 	case DIOCSKERNELDUMP:
92 		error = priv_check(td, PRIV_SETDUMPER);
93 		if (error == 0)
94 			error = set_dumper(NULL, NULL);
95 		break;
96 	case FIONBIO:
97 		break;
98 	case FIOASYNC:
99 		if (*(int *)data != 0)
100 			error = EINVAL;
101 		break;
102 	default:
103 		error = ENOIOCTL;
104 	}
105 	return (error);
106 }
107 
108 /* ARGSUSED */
109 static int
110 zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused,
111 	   int flags __unused, struct thread *td)
112 {
113 	int error;
114 	error = 0;
115 
116 	switch (cmd) {
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 
130 /* ARGSUSED */
131 static int
132 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused)
133 {
134 	void *zbuf;
135 	ssize_t len;
136 	int error = 0;
137 
138 	KASSERT(uio->uio_rw == UIO_READ,
139 	    ("Can't be in %s for write", __func__));
140 	zbuf = __DECONST(void *, zero_region);
141 	while (uio->uio_resid > 0 && error == 0) {
142 		len = uio->uio_resid;
143 		if (len > ZERO_REGION_SIZE)
144 			len = ZERO_REGION_SIZE;
145 		error = uiomove(zbuf, len, uio);
146 	}
147 
148 	return (error);
149 }
150 
151 /* ARGSUSED */
152 static int
153 null_modevent(module_t mod __unused, int type, void *data __unused)
154 {
155 	switch(type) {
156 	case MOD_LOAD:
157 		if (bootverbose)
158 			printf("null: <null device, zero device>\n");
159 		null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0,
160 		    NULL, UID_ROOT, GID_WHEEL, 0666, "null");
161 		zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0,
162 		    NULL, UID_ROOT, GID_WHEEL, 0666, "zero");
163 		break;
164 
165 	case MOD_UNLOAD:
166 		destroy_dev(null_dev);
167 		destroy_dev(zero_dev);
168 		break;
169 
170 	case MOD_SHUTDOWN:
171 		break;
172 
173 	default:
174 		return (EOPNOTSUPP);
175 	}
176 
177 	return (0);
178 }
179 
180 DEV_MODULE(null, null_modevent, NULL);
181 MODULE_VERSION(null, 1);
182