arch/.unmaintained/m68k-native/exec/preparecontext.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5 #include <exec/types.h>
   6 #include <aros/libcall.h>
   7
   8 #error "PrepareContext() has been changed. Additional tagList param, etc."
   9 #error "This one here needs to be rewritten!"
  10
  11 /*****************************************************************************
  12
  13     NAME */
  14
  15         AROS_LH3I(APTR, PrepareContext,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(APTR, stackPointer, A0),
  19         AROS_LHA(APTR, entryPoint,   A1),
  20         AROS_LHA(APTR, fallBack,     A2),
  21
  22 /*  LOCATION */
  23         struct ExecBase *, SysBase, 9, Exec)
  24
  25 /*  FUNCTION
  26         Allocates the space required to hold a new set of registers on the
  27         Stack given by stackPointer and clears the area except for pc which
  28         is set to the address given by entryPoint.
  29
  30     INPUTS
  31         stackPointer - Pointer to a scpecific stack
  32         entryPoint   - Address of the function to call when the new context
  33                        becomes active.
  34         fallBack     - Address to be called when the entryPoint function ended
  35                        with an rts.
  36
  37     RESULT
  38         The new Stackpointer with the underlying context.
  39
  40     NOTES
  41         This function is for internal use by exec only.
  42
  43         This function is processor dependant.
  44
  45     EXAMPLE
  46
  47     BUGS
  48
  49     SEE ALSO
  50         SwitchTasks()
  51
  52     INTERNALS
  53
  54     HISTORY
  55
  56 ******************************************************************************/
  57 {
  58     AROS_LIBFUNC_INIT
  59     UBYTE *sp=(UBYTE *)stackPointer;
  60     int i;
  61
  62     /*
  63         mc68000 version. As long as no FPU is in use this works for the
  64         other mc680xx brands as well.
  65     */
  66
  67     /* Push fallback address */
  68     sp-=sizeof(APTR);
  69     *(APTR *)sp=fallBack;
  70
  71     /* Now push the context. First a5. */
  72     sp-=sizeof(LONG);
  73     *(LONG *)sp=0;
  74
  75     /* Then a reverse rte (ccr & pc). */
  76     sp-=sizeof(WORD);
  77     *(WORD *)sp=0;
  78     sp-=sizeof(APTR);
  79     *(APTR *)sp=entryPoint;
  80
  81     /* Push 14 registers */
  82     for(i=0;i<14;i++)
  83     {
  84         sp-=sizeof(LONG);
  85         *(LONG *)sp=0;
  86     }
  87
  88     return sp;
  89     AROS_LIBFUNC_EXIT
  90 }