mach/sbrk.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /*
  24  *      File:   sbrk.c
  25  *
  26  *      Unix compatibility for sbrk system call.
  27  *
  28  * HISTORY
  29  * 09-Mar-90  Gregg Kellogg (gk) at NeXT.
  30  *      include <kern/mach_interface.h> instead of <kern/mach.h>
  31  *
  32  * 14-Feb-89  Avadis Tevanian (avie) at NeXT.
  33  *      Total rewrite using a fixed area of VM from break region.
  34  */
  35
  36 #include <mach/mach.h>          /* for vm_allocate, vm_offset_t */
  37 #include <mach/vm_statistics.h>
  38 #include <sys/types.h>          /* for caddr_t */
  39
  40 static int sbrk_needs_init = TRUE;
  41 static vm_size_t sbrk_region_size = 4*1024*1024; /* Well, what should it be? */
  42 static vm_address_t sbrk_curbrk;
  43
  44 caddr_t sbrk(size)
  45         int     size;
  46 {
  47         kern_return_t   ret;
  48
  49         if (sbrk_needs_init) {
  50                 sbrk_needs_init = FALSE;
  51                 /*
  52                  *      Allocate a big region to simulate break region.
  53                  */
  54                 ret =  vm_allocate(mach_task_self(), &sbrk_curbrk, sbrk_region_size,
  55                                   VM_MAKE_TAG(VM_MEMORY_SBRK)|TRUE);
  56                 if (ret != KERN_SUCCESS)
  57                         return((caddr_t)-1);
  58         }
  59
  60         if (size <= 0)
  61                 return((caddr_t)sbrk_curbrk);
  62         else if (size > sbrk_region_size)
  63                 return((caddr_t)-1);
  64         sbrk_curbrk += size;
  65         sbrk_region_size -= size;
  66         return((caddr_t)(sbrk_curbrk - size));
  67 }
  68
  69 caddr_t brk(x)
  70         caddr_t x;
  71 {
  72         return((caddr_t)-1);
  73 }
  74