osfmk/i386/commpage/bzero_scalar.s

   1 /*
   2  * Copyright (c) 2003-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1993 Winning Strategies, Inc.
  24  * All rights reserved.
  25  *
  26  * Redistribution and use in source and binary forms, with or without
  27  * modification, are permitted provided that the following conditions
  28  * are met:
  29  * 1. Redistributions of source code must retain the above copyright
  30  *    notice, this list of conditions and the following disclaimer.
  31  * 2. Redistributions in binary form must reproduce the above copyright
  32  *    notice, this list of conditions and the following disclaimer in the
  33  *    documentation and/or other materials provided with the distribution.
  34  * 3. All advertising materials mentioning features or use of this software
  35  *    must display the following acknowledgement:
  36  *      This product includes software developed by Winning Strategies, Inc.
  37  * 4. The name of the author may not be used to endorse or promote products
  38  *    derived from this software withough specific prior written permission
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  41  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  42  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  43  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  44  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  45  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  46  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  47  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  48  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  49  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  50  *
  51  */
  52
  53 #include <sys/appleapiopts.h>
  54 #include <machine/cpu_capabilities.h>
  55 #include <machine/commpage.h>
  56
  57 /*
  58  * bzero (void *b, size_t len)
  59  *      write len zero bytes to the string b.
  60  *
  61  * Written by:
  62  *      J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
  63  */
  64
  65 .text
  66 .align 5, 0x90
  67 Lbzero_scalar:
  68         pushl   %ebp                    /* set up a frame for backtraces */
  69         movl    %esp,%ebp
  70         pushl   %edi
  71         pushl   %ebx
  72         movl    8(%ebp),%edi
  73         movl    12(%ebp),%ecx
  74
  75         cld                             /* set fill direction forward */
  76         xorl    %eax,%eax               /* set fill data to 0 */
  77
  78         /*
  79          * if the string is too short, it's really not worth the overhead
  80          * of aligning to word boundries, etc.  So we jump to a plain
  81          * unaligned set.
  82          */
  83         cmpl    $0x0f,%ecx
  84         jbe     L1
  85
  86         movl    %edi,%edx               /* compute misalignment */
  87         negl    %edx
  88         andl    $3,%edx
  89         movl    %ecx,%ebx
  90         subl    %edx,%ebx
  91
  92         movl    %edx,%ecx               /* zero until word aligned */
  93         rep
  94         stosb
  95
  96         movl    %ebx,%ecx               /* zero by words */
  97         shrl    $2,%ecx
  98         rep
  99         stosl
 100
 101         movl    %ebx,%ecx
 102         andl    $3,%ecx                 /* zero remainder by bytes */
 103 L1:     rep
 104         stosb
 105
 106         popl    %ebx
 107         popl    %edi
 108         popl    %ebp
 109         ret
 110
 111         COMMPAGE_DESCRIPTOR(bzero_scalar,_COMM_PAGE_BZERO,0,kHasSSE2)