/*
   *  Copyright (C) 2004 IBM Corporation
   *
   *  Author: Serge Hallyn <serue@us.ibm.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/module.h>
  #include <linux/uts.h>
  #include <linux/utsname.h>

  #include <linux/err.h>

  #include <linux/slab.h>

  static struct uts_namespace *create_uts_ns(void)
  {
  	struct uts_namespace *uts_ns;
  
  	uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  	if (uts_ns)
  		kref_init(&uts_ns->kref);
  	return uts_ns;
  }

  /*

   * Clone a new ns copying an original utsname, setting refcount to 1
   * @old_ns: namespace to clone
   * Return NULL on error (failure to kmalloc), new ns otherwise
   */
  static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  {
  	struct uts_namespace *ns;

  	ns = create_uts_ns();

  	if (!ns)
  		return ERR_PTR(-ENOMEM);

  	down_read(&uts_sem);

  	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));

  	up_read(&uts_sem);

  	return ns;
  }
  
  /*

   * Copy task tsk's utsname namespace, or clone it if flags
   * specifies CLONE_NEWUTS.  In latter case, changes to the
   * utsname of this process won't be seen by parent, and vice
   * versa.
   */

  struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)

  {

  	struct uts_namespace *new_ns;

  	BUG_ON(!old_ns);

  	get_uts_ns(old_ns);

  	if (!(flags & CLONE_NEWUTS))

  		return old_ns;

  
  	new_ns = clone_uts_ns(old_ns);

  	put_uts_ns(old_ns);

  	return new_ns;

  }
  
  void free_uts_ns(struct kref *kref)
  {
  	struct uts_namespace *ns;
  
  	ns = container_of(kref, struct uts_namespace, kref);
  	kfree(ns);
  }