/* uaccess.c: userspace access functions
   *
   * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.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; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/mm.h>

  #include <linux/module.h>

  #include <asm/uaccess.h>
  
  /*****************************************************************************/
  /*
   * copy a null terminated string from userspace
   */

  long strncpy_from_user(char *dst, const char __user *src, long count)

  {
  	unsigned long max;
  	char *p, ch;
  	long err = -EFAULT;

  	BUG_ON(count < 0);

  
  	p = dst;
  
  #ifndef CONFIG_MMU
  	if ((unsigned long) src < memory_start)
  		goto error;
  #endif
  
  	if ((unsigned long) src >= get_addr_limit())
  		goto error;
  
  	max = get_addr_limit() - (unsigned long) src;
  	if ((unsigned long) count > max) {
  		memset(dst + max, 0, count - max);
  		count = max;
  	}
  
  	err = 0;
  	for (; count > 0; count--, p++, src++) {
  		__get_user_asm(err, ch, src, "ub", "=r");
  		if (err < 0)
  			goto error;
  		if (!ch)
  			break;
  		*p = ch;
  	}
  
  	err = p - dst; /* return length excluding NUL */
  
   error:
  	if (count > 0)
  		memset(p, 0, count); /* clear remainder of buffer [security] */
  
  	return err;

  } /* end strncpy_from_user() */

  EXPORT_SYMBOL(strncpy_from_user);

  /*****************************************************************************/
  /*
   * Return the size of a string (including the ending 0)
   *
   * Return 0 on exception, a value greater than N if too long
   */

  long strnlen_user(const char __user *src, long count)

  {

  	const char __user *p;

  	long err = 0;
  	char ch;

  	BUG_ON(count < 0);

  
  #ifndef CONFIG_MMU
  	if ((unsigned long) src < memory_start)
  		return 0;
  #endif
  
  	if ((unsigned long) src >= get_addr_limit())
  		return 0;
  
  	for (p = src; count > 0; count--, p++) {
  		__get_user_asm(err, ch, p, "ub", "=r");
  		if (err < 0)
  			return 0;
  		if (!ch)
  			break;
  	}
  
  	return p - src + 1; /* return length including NUL */

  } /* end strnlen_user() */

  
  EXPORT_SYMBOL(strnlen_user);