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Add new example kernel module: sysctl

sysctl - demonstrates adding a sysctl handle dynamically.

Patch by <Siddharth Muralee>
Polishing by myself.
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krytarowski committed Apr 13, 2018
1 parent f3373b9 commit 4f8914d81cb741471ebd168640c70576fe1ab67e
@@ -1,4 +1,4 @@
# $NetBSD: Makefile,v 1.2 2017/04/15 18:22:35 kamil Exp $
# $NetBSD: Makefile,v 1.3 2018/04/13 01:20:27 kamil Exp $
.include <bsd.own.mk>
@@ -8,5 +8,6 @@ SUBDIR+= luareadhappy # Needs an additional Lua script
SUBDIR+= ping # Needs an additional helper program
SUBDIR+= properties
SUBDIR+= readhappy
SUBDIR+= sysctl
.include <bsd.subdir.mk>
@@ -1,17 +1,18 @@
$NetBSD: README,v 1.4 2017/04/23 23:39:42 sevan Exp $
$NetBSD: README,v 1.5 2018/04/13 01:20:27 kamil Exp $
Kernel Developer's Manual
DESCRIPTION
The kernel example dynamic modules.
This directory contains the following example modules:
This directory contains the following example modules
* hello - the simplest `hello world' module
* properties - handle incoming properties during the module load
* readhappy - basic implementation of read(9) with happy numbers
* ping - basic ioctl(9)
* luahello - the simplest `hello world' Lua module
* luareadhappy - demonstrates calling Lua code from C
* sysctl - demonstrates adding a sysctl handle dynamically
To build the examples you need a local copy of NetBSD sources. You also
need the comp set with toolchain. To build the module just enter a
@@ -56,5 +57,8 @@ HISTORY
ping, luahello and luareadhappy) first appeared in NetBSD 8.0; they were
written by Kamil Rytarowski.
The sysctl module first appeared in NetBSD 9.0 and was authored by
Siddharth Muralee.
AUTHORS
This document was written by Kamil Rytarowski.
@@ -0,0 +1,10 @@
# $NetBSD: Makefile,v 1.1 2018/04/13 01:20:28 kamil Exp $
.include "../Makefile.inc"
#S?= /usr/src/sys
KMOD= sysctl
SRCS= sysctl.c
.include <bsd.kmodule.mk>
@@ -0,0 +1,118 @@
/* $NetBSD: sysctl.c,v 1.1 2018/04/13 01:20:28 kamil Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sysctl.c,v 1.1 2018/04/13 01:20:28 kamil Exp $");
#include <sys/param.h>
#include <sys/module.h>
#include <sys/sysctl.h>
/*
* Check if sysctl -A contains an entry
* example_subroot1.sysctl_example=0
* to test this module
*
*/
MODULE(MODULE_CLASS_MISC, sysctl, NULL);
static int sysctl_example;
static struct sysctllog *example_sysctl_log;
static void sysctl_example_setup(struct sysctllog **);
/*
* sysctl_example_setup :
* It first creates a subtree by adding a node to the tree.
* This node is named as example_subroot1.
*
* It then creates a node in subtree for the example variable which
* is an integer and is defined in this file itself.
*
* ROOT
* |
* -------
* |
* examples_subroot1
* |
* |
* sysctl_example (INT)
*
*/
static void
sysctl_example_setup(struct sysctllog **clog)
{
const struct sysctlnode *rnode;
sysctl_createv(clog, 0, NULL, &rnode,
CTLFLAG_PERMANENT,
CTLTYPE_NODE, "example_subroot1",
NULL,
NULL, 0,
NULL, 0,
CTL_CREATE, CTL_EOL);
sysctl_createv(clog, 0, &rnode, NULL,
CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
CTLTYPE_INT, "sysctl_example",
SYSCTL_DESCR("An example for sysctl_example"),
NULL, 0,
&sysctl_example, 0,
CTL_CREATE, CTL_EOL);
}
/*
* The sysctl_example modcmd has two functions.
* 1. Call the sysctl_example_setup function to create a sysctl
* handle when the module is loaded in the kernel.
* 2. Remove the sysctl entry from the kernel once the module
* is unloaded.
*/
static int
sysctl_modcmd(modcmd_t cmd, void *arg)
{
switch(cmd) {
case MODULE_CMD_INIT:
printf("sysctl module inserted");
sysctl_example_setup(&example_sysctl_log);
break;
case MODULE_CMD_FINI:
printf("sysctl module unloaded");
sysctl_teardown(&example_sysctl_log);
break;
default:
return ENOTTY;
}
return 0;
}

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