libkern/ppc/OSAtomic.s

   1 /*
   2  * Copyright (c) 2000 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) 1997-1998 Apple Computer, Inc.
  24  *
  25  *
  26  * HISTORY
  27  *
  28  * sdouglas  22 Oct 97 - first checked in from DriverServices
  29  * sdouglas  28 Jul 98 - start IOKit
  30  */
  31
  32 #include <architecture/ppc/asm_help.h>
  33
  34 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  35 ;
  36 ; ENTRY         functionName
  37 ;
  38 ; Assembly directives to begin an exported function.
  39 ;
  40 ; Takes: functionName - name of the exported function
  41 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  42
  43 .macro ENTRY
  44     .text
  45     .align      2
  46     .globl      $0
  47 $0:
  48 .endmacro
  49
  50 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  51
  52 /*
  53 int OSCompareAndSwap( UInt32 oldVal, UInt32 newVal, UInt32 * addr )
  54 This is now an alias to hw_compare_and_store, see xnu/libkern/Makefile
  55 */
  56
  57 /*
  58 Note:  We can not use the hw_atomic routines provided by osfmk/ppc as
  59 the return the result of the addition not the original value.
  60 */
  61 /*
  62 SInt32  OSDecrementAtomic(SInt32 * value)
  63 */
  64     ENTRY       _OSDecrementAtomic
  65     mr          r4, r3
  66     li          r3, -1
  67     b           _OSAddAtomic
  68
  69 /*
  70 SInt32  OSIncrementAtomic(SInt32 * value)
  71 */
  72
  73     .align      5
  74
  75     ENTRY       _OSIncrementAtomic
  76     mr          r4, r3
  77     li          r3, 1
  78
  79 /*
  80 SInt32  OSAddAtomic(SInt32 amount, SInt32 * value)
  81 */
  82
  83     ENTRY       _OSAddAtomic
  84
  85     mr          r5,r3           /* Save the increment */
  86 .L_AAretry:
  87     lwarx       r3, 0, r4       /* Grab the area value */
  88     add         r6, r3, r5      /* Add the value */
  89     stwcx.      r6, 0, r4       /* Try to save the new value */
  90     bne-        .L_AAretry      /* Didn't get it, try again... */
  91     blr                         /* Return the original value */