libgloss/mep/sbrk.c

   1 /*
   2  * Copyright (c) 2003  Red Hat, Inc. All rights reserved.
   3  *
   4  * This copyrighted material is made available to anyone wishing to use, modify,
   5  * copy, or redistribute it subject to the terms and conditions of the BSD
   6  * License.  This program is distributed in the hope that it will be useful,
   7  * but WITHOUT ANY WARRANTY expressed or implied, including the implied
   8  * warranties of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  A copy
   9  * of this license is available at http://www.opensource.org/licenses. Any
  10  * Red Hat trademarks that are incorporated in the source code or documentation
  11  * are not subject to the BSD License and may only be used or replicated with
  12  * the express permission of Red Hat, Inc.
  13  */
  14
  15 #include <errno.h>
  16
  17 extern int __heap __far;      /* beginning of heap */
  18 extern int __heap_end __far;  /* if at address 0, use stack pointer as limit */
  19
  20 static char *the_break = (char *)(& __heap);
  21
  22 int
  23 is_addr_0 (int address)
  24 {
  25   return address ? 0 : 1;
  26 }
  27
  28 void *
  29 sbrk(int inc)
  30 {
  31   char *current_heap_limit = (char *) (& __heap_end);
  32
  33   /* is_addr_0 avoids optimizing out this block.  */
  34   if (is_addr_0 ((int) current_heap_limit))
  35     {
  36       int something;
  37       int margin = 4096;
  38       current_heap_limit = (char *) (& something) - margin;
  39     }
  40
  41   if ((the_break + inc) < current_heap_limit)
  42     {
  43       void *rv = (void *) the_break;
  44       the_break += inc;
  45       return rv;
  46     }
  47   else
  48     {
  49       errno = ENOMEM;
  50       return (void *) -1;
  51     }
  52 }
  53
  54 int
  55 brk (void *ptr)
  56 {
  57   the_break = ptr;
  58   return 0;
  59 }