lib/test_sysctl.c

/*
 * proc sysctl test driver
 *
 * Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or at your option any
 * later version; or, when distributed separately from the Linux kernel or
 * when incorporated into other software packages, subject to the following
 * license:
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of copyleft-next (version 0.3.1 or later) as published
 * at http://copyleft-next.org/.
 */

/*
 * This module provides an interface to the the proc sysctl interfaces.  This
 * driver requires CONFIG_PROC_SYSCTL. It will not normally be loaded by the
 * system unless explicitly requested by name. You can also build this driver
 * into your kernel.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/async.h>
#include <linux/delay.h>
#include <linux/vmalloc.h>

static int i_zero;
static int i_one_hundred = 100;

struct test_sysctl_data {
	int int_0001;
	int int_0002;

	char string_0001[65];
};

static struct test_sysctl_data test_data = {
	.int_0001 = 60,
	.int_0002 = 1,

	.string_0001 = "(none)",
};

/* These are all under /proc/sys/debug/test_sysctl/ */
static struct ctl_table test_table[] = {
	{
		.procname	= "int_0001",
		.data		= &test_data.int_0001,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_minmax,
		.extra1		= &i_zero,
		.extra2         = &i_one_hundred,
	},
	{
		.procname	= "int_0002",
		.data		= &test_data.int_0002,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "string_0001",
		.data		= &test_data.string_0001,
		.maxlen		= sizeof(test_data.string_0001),
		.mode		= 0644,
		.proc_handler	= proc_dostring,
	},
	{ }
};

static struct ctl_table test_sysctl_table[] = {
	{
		.procname	= "test_sysctl",
		.maxlen		= 0,
		.mode		= 0555,
		.child		= test_table,
	},
	{ }
};

static struct ctl_table test_sysctl_root_table[] = {
	{
		.procname	= "debug",
		.maxlen		= 0,
		.mode		= 0555,
		.child		= test_sysctl_table,
	},
	{ }
};

static struct ctl_table_header *test_sysctl_header;

static int __init test_sysctl_init(void)
{
	test_sysctl_header = register_sysctl_table(test_sysctl_root_table);
	if (!test_sysctl_header)
		return -ENOMEM;
	return 0;
}
late_initcall(test_sysctl_init);

static void __exit test_sysctl_exit(void)
{
	if (test_sysctl_header)
		unregister_sysctl_table(test_sysctl_header);
}

module_exit(test_sysctl_exit);

MODULE_AUTHOR("Luis R. Rodriguez <mcgrof@kernel.org>");
MODULE_LICENSE("GPL");