/*
   *  Copyright (C) 2007
   *
   *  Author: Eric Biederman <ebiederm@xmision.com>
   *
   *  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, version 2 of the
   *  License.
   */

  #include <linux/export.h>

  #include <linux/uts.h>
  #include <linux/utsname.h>

  #include <linux/sysctl.h>

  #include <linux/wait.h>

  
  static void *get_uts(ctl_table *table, int write)
  {
  	char *which = table->data;

  	struct uts_namespace *uts_ns;
  
  	uts_ns = current->nsproxy->uts_ns;
  	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;

  	if (!write)
  		down_read(&uts_sem);
  	else
  		down_write(&uts_sem);
  	return which;
  }
  
  static void put_uts(ctl_table *table, int write, void *which)
  {
  	if (!write)
  		up_read(&uts_sem);
  	else
  		up_write(&uts_sem);
  }

  #ifdef CONFIG_PROC_SYSCTL

  /*
   *	Special case of dostring for the UTS structure. This has locks
   *	to observe. Should this be in kernel/sys.c ????
   */

  static int proc_do_uts_string(ctl_table *table, int write,

  		  void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	struct ctl_table uts_table;
  	int r;
  	memcpy(&uts_table, table, sizeof(uts_table));
  	uts_table.data = get_uts(table, write);

  	r = proc_dostring(&uts_table,write,buffer,lenp, ppos);

  	put_uts(table, write, uts_table.data);

  
  	if (write)
  		proc_sys_poll_notify(table->poll);

  	return r;
  }
  #else
  #define proc_do_uts_string NULL
  #endif

  static DEFINE_CTL_TABLE_POLL(hostname_poll);
  static DEFINE_CTL_TABLE_POLL(domainname_poll);

  static struct ctl_table uts_kern_table[] = {
  	{

  		.procname	= "ostype",
  		.data		= init_uts_ns.name.sysname,
  		.maxlen		= sizeof(init_uts_ns.name.sysname),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "osrelease",
  		.data		= init_uts_ns.name.release,
  		.maxlen		= sizeof(init_uts_ns.name.release),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "version",
  		.data		= init_uts_ns.name.version,
  		.maxlen		= sizeof(init_uts_ns.name.version),
  		.mode		= 0444,
  		.proc_handler	= proc_do_uts_string,

  	},
  	{

  		.procname	= "hostname",
  		.data		= init_uts_ns.name.nodename,
  		.maxlen		= sizeof(init_uts_ns.name.nodename),
  		.mode		= 0644,
  		.proc_handler	= proc_do_uts_string,

  		.poll		= &hostname_poll,

  	},
  	{

  		.procname	= "domainname",
  		.data		= init_uts_ns.name.domainname,
  		.maxlen		= sizeof(init_uts_ns.name.domainname),
  		.mode		= 0644,
  		.proc_handler	= proc_do_uts_string,

  		.poll		= &domainname_poll,

  	},
  	{}
  };
  
  static struct ctl_table uts_root_table[] = {
  	{

  		.procname	= "kernel",
  		.mode		= 0555,
  		.child		= uts_kern_table,
  	},
  	{}
  };

  #ifdef CONFIG_PROC_SYSCTL
  /*
   * Notify userspace about a change in a certain entry of uts_kern_table,
   * identified by the parameter proc.
   */
  void uts_proc_notify(enum uts_proc proc)
  {
  	struct ctl_table *table = &uts_kern_table[proc];
  
  	proc_sys_poll_notify(table->poll);
  }
  #endif

  static int __init utsname_sysctl_init(void)
  {

  	register_sysctl_table(uts_root_table);

  	return 0;
  }
  
  __initcall(utsname_sysctl_init);