/*
   * Constant-time equality testing of memory regions.
   *
   * Authors:
   *
   *   James Yonan <james@openvpn.net>
   *   Daniel Borkmann <dborkman@redhat.com>
   *
   * This file is provided under a dual BSD/GPLv2 license.  When using or
   * redistributing this file, you may do so under either license.
   *
   * GPL LICENSE SUMMARY
   *
   * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of version 2 of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   * The full GNU General Public License is included in this distribution
   * in the file called LICENSE.GPL.
   *
   * BSD LICENSE
   *
   * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   *   * Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   *   * Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in
   *     the documentation and/or other materials provided with the
   *     distribution.
   *   * Neither the name of OpenVPN Technologies nor the names of its
   *     contributors may be used to endorse or promote products derived
   *     from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include <crypto/algapi.h>
  
  #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
  
  /* Generic path for arbitrary size */
  static inline unsigned long
  __crypto_memneq_generic(const void *a, const void *b, size_t size)
  {
  	unsigned long neq = 0;
  
  #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
  	while (size >= sizeof(unsigned long)) {
  		neq |= *(unsigned long *)a ^ *(unsigned long *)b;

  		OPTIMIZER_HIDE_VAR(neq);

  		a += sizeof(unsigned long);
  		b += sizeof(unsigned long);
  		size -= sizeof(unsigned long);
  	}
  #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
  	while (size > 0) {
  		neq |= *(unsigned char *)a ^ *(unsigned char *)b;

  		OPTIMIZER_HIDE_VAR(neq);

  		a += 1;
  		b += 1;
  		size -= 1;
  	}
  	return neq;
  }
  
  /* Loop-free fast-path for frequently used 16-byte size */
  static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
  {

  	unsigned long neq = 0;

  #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS

  	if (sizeof(unsigned long) == 8) {
  		neq |= *(unsigned long *)(a)   ^ *(unsigned long *)(b);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8);
  		OPTIMIZER_HIDE_VAR(neq);
  	} else if (sizeof(unsigned int) == 4) {
  		neq |= *(unsigned int *)(a)    ^ *(unsigned int *)(b);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned int *)(a+4)  ^ *(unsigned int *)(b+4);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned int *)(a+8)  ^ *(unsigned int *)(b+8);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12);
  		OPTIMIZER_HIDE_VAR(neq);

  	} else

  #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */

  	{

  		neq |= *(unsigned char *)(a)    ^ *(unsigned char *)(b);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+1)  ^ *(unsigned char *)(b+1);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+2)  ^ *(unsigned char *)(b+2);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+3)  ^ *(unsigned char *)(b+3);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+4)  ^ *(unsigned char *)(b+4);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+5)  ^ *(unsigned char *)(b+5);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+6)  ^ *(unsigned char *)(b+6);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+7)  ^ *(unsigned char *)(b+7);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+8)  ^ *(unsigned char *)(b+8);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+9)  ^ *(unsigned char *)(b+9);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
  		OPTIMIZER_HIDE_VAR(neq);
  		neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15);
  		OPTIMIZER_HIDE_VAR(neq);
  	}
  
  	return neq;

  }
  
  /* Compare two areas of memory without leaking timing information,
   * and with special optimizations for common sizes.  Users should
   * not call this function directly, but should instead use
   * crypto_memneq defined in crypto/algapi.h.
   */
  noinline unsigned long __crypto_memneq(const void *a, const void *b,
  				       size_t size)
  {
  	switch (size) {
  	case 16:
  		return __crypto_memneq_16(a, b);
  	default:
  		return __crypto_memneq_generic(a, b, size);
  	}
  }
  EXPORT_SYMBOL(__crypto_memneq);
  
  #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */