1 /* $NetBSD: mapper.c,v 1.4 2020/09/06 02:18:53 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2019 The NetBSD Foundation, Inc.
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 * 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __KERNEL_RCSID(0, "$NetBSD: mapper.c,v 1.4 2020/09/06 02:18:53 riastradh Exp $");
31
32 #include <sys/param.h>
33 #include <sys/conf.h>
34 #include <sys/device.h>
35 #include <sys/kernel.h>
36 #include <sys/kmem.h>
37 #include <sys/module.h>
38 #include <sys/systm.h>
39
40 #include <uvm/uvm_extern.h>
41
42 /*
43 * Creating a device /dev/mapper for demonstration.
44 * To use this device you need to do:
45 * mknod /dev/mapper c 351 0
46 *
47 */
48
49 dev_type_open(mapper_open);
50 dev_type_close(mapper_close);
51 dev_type_mmap(mapper_mmap);
52
53 static struct cdevsw mapper_cdevsw = {
54 .d_open = mapper_open,
55 .d_close = mapper_close,
56 .d_read = noread,
57 .d_write = nowrite,
58 .d_ioctl = noioctl,
59 .d_stop = nostop,
60 .d_tty = notty,
61 .d_poll = nopoll,
62 .d_mmap = mapper_mmap,
63 .d_kqfilter = nokqfilter,
64 .d_discard = nodiscard,
65 .d_flag = D_OTHER
66 };
67
68 struct mapper_softc {
69 int refcnt;
70 char *buffer;
71 };
72
73 static struct mapper_softc sc;
74
75 int
mapper_open(dev_t self __unused,int flag __unused,int mode __unused,struct lwp * l __unused)76 mapper_open(dev_t self __unused, int flag __unused, int mode __unused,
77 struct lwp *l __unused)
78 {
79 if (sc.refcnt > 0)
80 return EBUSY;
81 ++sc.refcnt;
82 sc.buffer = kmem_zalloc(PAGE_SIZE, KM_SLEEP);
83 snprintf(sc.buffer, PAGE_SIZE, "Hey There!");
84 return 0;
85 }
86
87 int
mapper_close(dev_t self __unused,int flag __unused,int mode __unused,struct lwp * l __unused)88 mapper_close(dev_t self __unused, int flag __unused, int mode __unused,
89 struct lwp *l __unused)
90 {
91 kmem_free(sc.buffer, PAGE_SIZE);
92 --sc.refcnt;
93 return 0;
94 }
95
96 /*
97 * Here, pmap_extract() is used to extract the mapping from the specified
98 * physical map for the provided virtual address, where pmap_kernel() points
99 * to the kernel pmap.
100 */
101
102 paddr_t
mapper_mmap(dev_t dev,off_t off,int prot)103 mapper_mmap(dev_t dev, off_t off, int prot)
104 {
105 paddr_t pa;
106
107 if (off & PAGE_MASK)
108 return (paddr_t)-1;
109 if (prot != VM_PROT_READ)
110 return (paddr_t)-1;
111 if (pmap_extract(pmap_kernel(), (vaddr_t)sc.buffer, &pa))
112 return (paddr_t)atop(pa);
113
114 return (paddr_t)-1;
115 }
116
117 MODULE(MODULE_CLASS_MISC, mapper, NULL);
118
119 static int
mapper_modcmd(modcmd_t cmd,void * arg __unused)120 mapper_modcmd(modcmd_t cmd, void *arg __unused)
121 {
122 /* The major should be verified and changed if needed to avoid
123 * conflicts with other devices. */
124 int cmajor = 351, bmajor = -1;
125
126 switch (cmd) {
127 case MODULE_CMD_INIT:
128 if (devsw_attach("mapper", NULL, &bmajor, &mapper_cdevsw,
129 &cmajor))
130 return ENXIO;
131 return 0;
132 case MODULE_CMD_FINI:
133 if (sc.refcnt > 0)
134 return EBUSY;
135 devsw_detach(NULL, &mapper_cdevsw);
136 return 0;
137 default:
138 return ENOTTY;
139 }
140 return 0;
141 }
142