/*
   * 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;

  	int int_0003[4];

  	unsigned int uint_0001;

  	char string_0001[65];

  
  #define SYSCTL_TEST_BITMAP_SIZE	65536
  	unsigned long *bitmap_0001;

  };
  
  static struct test_sysctl_data test_data = {
  	.int_0001 = 60,

  	.int_0002 = 1,

  	.int_0003[0] = 0,
  	.int_0003[1] = 1,
  	.int_0003[2] = 2,
  	.int_0003[3] = 3,

  	.uint_0001 = 314,

  	.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	= "int_0003",
  		.data		= &test_data.int_0003,
  		.maxlen		= sizeof(test_data.int_0003),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec,
  	},
  	{

  		.procname	= "uint_0001",
  		.data		= &test_data.uint_0001,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_douintvec,
  	},
  	{

  		.procname	= "string_0001",
  		.data		= &test_data.string_0001,
  		.maxlen		= sizeof(test_data.string_0001),
  		.mode		= 0644,
  		.proc_handler	= proc_dostring,
  	},

  	{
  		.procname	= "bitmap_0001",
  		.data		= &test_data.bitmap_0001,
  		.maxlen		= SYSCTL_TEST_BITMAP_SIZE,
  		.mode		= 0644,
  		.proc_handler	= proc_do_large_bitmap,
  	},

  	{ }
  };
  
  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_data.bitmap_0001 = kzalloc(SYSCTL_TEST_BITMAP_SIZE/8, GFP_KERNEL);
  	if (!test_data.bitmap_0001)
  		return -ENOMEM;

  	test_sysctl_header = register_sysctl_table(test_sysctl_root_table);

  	if (!test_sysctl_header) {
  		kfree(test_data.bitmap_0001);

  		return -ENOMEM;

  	}

  	return 0;
  }
  late_initcall(test_sysctl_init);
  
  static void __exit test_sysctl_exit(void)
  {

  	kfree(test_data.bitmap_0001);

  	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");