1 /* $NetBSD: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $ */
2
3 /*-
4 * Copyright (c) 2018 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: sysctl.c,v 1.2 2021/03/23 13:19:09 simonb Exp $");
31
32 #include <sys/param.h>
33 #include <sys/module.h>
34 #include <sys/sysctl.h>
35
36 /*
37 * Check if sysctl -A contains an entry
38 * example_subroot1.sysctl_example=0
39 * to test this module
40 *
41 */
42
43 MODULE(MODULE_CLASS_MISC, sysctl, NULL);
44
45 static int sysctl_example;
46
47 static struct sysctllog *example_sysctl_log;
48
49 static void sysctl_example_setup(struct sysctllog **);
50
51
52 /*
53 * sysctl_example_setup :
54 * It first creates a subtree by adding a node to the tree.
55 * This node is named as example_subroot1.
56 *
57 * It then creates a node in subtree for the example variable which
58 * is an integer and is defined in this file itself.
59 *
60 * ROOT
61 * |
62 * -------
63 * |
64 * examples_subroot1
65 * |
66 * |
67 * sysctl_example (INT)
68 *
69 */
70
71 static void
sysctl_example_setup(struct sysctllog ** clog)72 sysctl_example_setup(struct sysctllog **clog)
73 {
74 const struct sysctlnode *rnode;
75
76 sysctl_createv(clog, 0, NULL, &rnode,
77 CTLFLAG_PERMANENT,
78 CTLTYPE_NODE, "example_subroot1",
79 NULL,
80 NULL, 0,
81 NULL, 0,
82 CTL_CREATE, CTL_EOL);
83
84 sysctl_createv(clog, 0, &rnode, NULL,
85 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
86 CTLTYPE_INT, "sysctl_example",
87 SYSCTL_DESCR("An example for sysctl_example"),
88 NULL, 0,
89 &sysctl_example, 0,
90 CTL_CREATE, CTL_EOL);
91 }
92
93 /*
94 * The sysctl_example modcmd has two functions.
95 * 1. Call the sysctl_example_setup function to create a sysctl
96 * handle when the module is loaded in the kernel.
97 * 2. Remove the sysctl entry from the kernel once the module
98 * is unloaded.
99 */
100
101
102 static int
sysctl_modcmd(modcmd_t cmd,void * arg)103 sysctl_modcmd(modcmd_t cmd, void *arg)
104 {
105 switch(cmd) {
106 case MODULE_CMD_INIT:
107 printf("sysctl module inserted\n");
108 sysctl_example_setup(&example_sysctl_log);
109 break;
110 case MODULE_CMD_FINI:
111 printf("sysctl module unloaded\n");
112 sysctl_teardown(&example_sysctl_log);
113 break;
114 default:
115 return ENOTTY;
116 }
117 return 0;
118 }
119