LibertyBSD_kernel/sys/lib/libkern/arch/i386/memmove.S

/*	$OpenBSD: memmove.S,v 1.7 2014/11/29 18:51:23 tedu Exp $	*/

/*-
 * Copyright (c) 1993, 1994, 1995 Charles M. Hannum.  All rights reserved.
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the University 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 REGENTS 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 REGENTS 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 <machine/param.h>
#include <machine/asm.h>

/*
 * Emulate bcopy() by swapping the first two arguments, and jumping
 * into memmove(), which handles overlapping regions.
 */
ENTRY(bcopy)
	pushl	%esi
	pushl	%edi
	movl	12(%esp),%esi
	movl	16(%esp),%edi
	jmp	docopy

/*
 * memmove(caddr_t dst, caddr_t src, size_t len);
 * Copy len bytes, coping with overlapping space.
 */
ENTRY(memmove)
	pushl	%esi
	pushl	%edi
	movl	12(%esp),%edi
	movl	16(%esp),%esi
docopy:
	movl	20(%esp),%ecx
	movl	%edi,%eax
	subl	%esi,%eax
	cmpl	%ecx,%eax		# overlapping?
	jb	1f
	jmp	docopyf			# nope
/*
 * memcpy() doesn't worry about overlap and always copies forward
 */
ENTRY(memcpy)
	pushl	%esi
	pushl	%edi
	movl	12(%esp),%edi
	movl	16(%esp),%esi
	movl	20(%esp),%ecx
docopyf:
	movl	%edi,%eax		# setup return value for memcpy/memmove
	shrl	$2,%ecx			# copy by 32-bit words
	rep
	movsl
	movl	20(%esp),%ecx
	andl	$3,%ecx			# any bytes left?
	rep
	movsb
	popl	%edi
	popl	%esi
	ret

	_ALIGN_TEXT
1:	movl	%edi,%eax		# setup return value for memmove
	addl	%ecx,%edi		# copy backward
	addl	%ecx,%esi
	std
	andl	$3,%ecx			# any fractional bytes?
	decl	%edi
	decl	%esi
	rep
	movsb
	movl	20(%esp),%ecx		# copy remainder by 32-bit words
	shrl	$2,%ecx
	subl	$3,%esi
	subl	$3,%edi
	rep
	movsl
	popl	%edi
	popl	%esi
	cld
	ret