bzero.S revision 22993 
1/*
2 * Copyright (c) 1993 Winning Strategies, Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *      This product includes software developed by Winning Strategies, Inc.
16 * 4. The name of the author may not be used to endorse or promote products
17 *    derived from this software withough specific prior written permission
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 *	$Id$
31 */
32
33#if defined(LIBC_RCS) && !defined(lint)
34	.text
35        .asciz "$Id$"
36#endif /* LIBC_RCS and not lint */
37
38#include "DEFS.h"
39
40/*
41 * bzero (void *b, size_t len)
42 *	write len zero bytes to the string b.
43 *
44 * Written by:
45 *	J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
46 */
47
48ENTRY(bzero)
49	pushl	%edi
50	pushl	%ebx
51	movl	12(%esp),%edi
52	movl	16(%esp),%ecx
53
54	cld				/* set fill direction forward */
55	xorl	%eax,%eax		/* set fill data to 0 */
56
57	/*
58	 * if the string is too short, it's really not worth the overhead
59	 * of aligning to word boundries, etc.  So we jump to a plain
60	 * unaligned set.
61	 */
62	cmpl	$0x0f,%ecx
63	jle	L1
64
65	movl	%edi,%edx		/* compute misalignment */
66	negl	%edx
67	andl	$3,%edx
68	movl	%ecx,%ebx
69	subl	%edx,%ebx
70
71	movl	%edx,%ecx		/* zero until word aligned */
72	rep
73	stosb
74
75	movl	%ebx,%ecx		/* zero by words */
76	shrl	$2,%ecx
77	rep
78	stosl
79
80	movl	%ebx,%ecx
81	andl	$3,%ecx			/* zero remainder by bytes */
82L1:	rep
83	stosb
84
85	popl	%ebx
86	popl	%edi
87	ret
88