bzero.S revision 184548
1193326Sed/* 2193326Sed * Copyright (c) 1993 Winning Strategies, Inc. 3193326Sed * All rights reserved. 4193326Sed * 5193326Sed * Redistribution and use in source and binary forms, with or without 6193326Sed * modification, are permitted provided that the following conditions 7193326Sed * are met: 8193326Sed * 1. Redistributions of source code must retain the above copyright 9193326Sed * notice, this list of conditions and the following disclaimer. 10198092Srdivacky * 2. Redistributions in binary form must reproduce the above copyright 11193326Sed * notice, this list of conditions and the following disclaimer in the 12193326Sed * documentation and/or other materials provided with the distribution. 13193326Sed * 3. All advertising materials mentioning features or use of this software 14193326Sed * must display the following acknowledgement: 15193326Sed * This product includes software developed by Winning Strategies, Inc. 16193326Sed * 4. The name of the author may not be used to endorse or promote products 17193326Sed * derived from this software without specific prior written permission 18193326Sed * 19249423Sdim * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20193326Sed * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21193326Sed * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22193326Sed * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23198092Srdivacky * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24193326Sed * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25193326Sed * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26193326Sed * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27193326Sed * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28193326Sed * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29193326Sed */ 30193326Sed 31198092Srdivacky#include <machine/asm.h> 32193326Sed__FBSDID("$FreeBSD: head/lib/libc/i386/string/bzero.S 184548 2008-11-02 01:28:47Z peter $"); 33198092Srdivacky 34193326Sed/* 35193326Sed * bzero (void *b, size_t len) 36193326Sed * write len zero bytes to the string b. 37193326Sed * 38198092Srdivacky * Written by: 39193326Sed * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. 40193326Sed */ 41193326Sed 42193326SedENTRY(bzero) 43198092Srdivacky pushl %edi 44193326Sed pushl %ebx 45193326Sed movl 12(%esp),%edi 46193326Sed movl 16(%esp),%ecx 47198092Srdivacky 48193326Sed cld /* set fill direction forward */ 49193326Sed xorl %eax,%eax /* set fill data to 0 */ 50193326Sed 51193326Sed /* 52193326Sed * if the string is too short, it's really not worth the overhead 53193326Sed * of aligning to word boundries, etc. So we jump to a plain 54193326Sed * unaligned set. 55193326Sed */ 56193326Sed cmpl $0x0f,%ecx 57193326Sed jle L1 58198092Srdivacky 59193326Sed movl %edi,%edx /* compute misalignment */ 60198092Srdivacky negl %edx 61193326Sed andl $3,%edx 62193326Sed movl %ecx,%ebx 63198092Srdivacky subl %edx,%ebx 64193326Sed 65198092Srdivacky movl %edx,%ecx /* zero until word aligned */ 66193326Sed rep 67193326Sed stosb 68193326Sed 69193326Sed movl %ebx,%ecx /* zero by words */ 70198092Srdivacky shrl $2,%ecx 71193326Sed rep 72193326Sed stosl 73193326Sed 74198092Srdivacky movl %ebx,%ecx 75193326Sed andl $3,%ecx /* zero remainder by bytes */ 76193326SedL1: rep 77193326Sed stosb 78193326Sed 79193326Sed popl %ebx 80198092Srdivacky popl %edi 81193326Sed ret 82193326SedEND(bzero) 83193326Sed