rom/exec/allocabs.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Allocate memory at address
   6     Lang: english
   7 */
   8
   9 #include <aros/debug.h>
  10 #include <exec/alerts.h>
  11 #include <exec/execbase.h>
  12 #include <exec/memory.h>
  13 #include <exec/memheaderext.h>
  14 #include <proto/exec.h>
  15
  16 #include "exec_intern.h"
  17 #include "memory.h"
  18 #include "mungwall.h"
  19
  20 /*****************************************************************************
  21
  22     NAME */
  23
  24         AROS_LH2(APTR, AllocAbs,
  25
  26 /*  SYNOPSIS */
  27         AROS_LHA(ULONG, byteSize, D0),
  28         AROS_LHA(APTR,  location, A1),
  29
  30 /*  LOCATION */
  31         struct ExecBase *, SysBase, 34, Exec)
  32
  33 /*  FUNCTION
  34         Allocate some memory from the system memory pool at a given address.
  35
  36     INPUTS
  37         byteSize - Number of bytes you want to get
  38         location - Where you want to get the memory
  39
  40     RESULT
  41         A pointer to some memory including the requested bytes or NULL if
  42         the memory couldn't be allocated
  43
  44     NOTES
  45
  46     EXAMPLE
  47
  48     BUGS
  49
  50     SEE ALSO
  51         FreeMem()
  52
  53     INTERNALS
  54         This function may trash memory right after the allocation if it builds
  55         a new MemChunk there. Additionally it will trash additional area before
  56         and after the allocated space if mungwall is turned on. The additional
  57         space will be used for mungwall service data.
  58
  59         We can't just disable mungwalling for this function because in this case
  60         FreeMem() on AllocAbs()ed region will crash (FreeMem() will expect mungwall
  61         header attached to the chunk and there's no way to tell which function was
  62         used to allocate it.
  63
  64 ******************************************************************************/
  65 {
  66     AROS_LIBFUNC_INIT
  67
  68     IPTR origSize = byteSize;
  69     APTR ret = NULL;
  70
  71     /* Zero bytes requested? May return everything ;-). */
  72     if(!byteSize)
  73         return NULL;
  74
  75     /* Make room for mungwall if needed */
  76     if (PrivExecBase(SysBase)->IntFlags & EXECF_MungWall)
  77     {
  78         location -= MUNGWALL_BLOCK_SHIFT;
  79         byteSize += MUNGWALL_TOTAL_SIZE;
  80     }
  81
  82     ret = InternalAllocAbs(location, byteSize, SysBase);
  83
  84     D(bug("[AllocAbs] Location: requested 0x%p, actual 0x%p\n", location, ret));
  85     D(bug("[AllocAbs] Length: requested %u, actual %u\n", origSize, origSize + location - ret));
  86     /*
  87      * Starting address may have been adjusted, in this case 'ret' will
  88      * differ from 'location', and allocation length was in fact increased
  89      * by this difference.
  90      * We also specify MEMF_CLEAR because we do not want to destroy original
  91      * memory contents.
  92      */
  93     return MungWall_Build(ret, NULL, origSize + location - ret, MEMF_CLEAR, "AllocAbs", __builtin_return_address(0), SysBase);
  94
  95     AROS_LIBFUNC_EXIT
  96 } /* AllocAbs */