arch/m68k-all/exec/preparecontext.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: PrepareContext() - Prepare a task context for dispatch, m68k version
   6     Lang: english
   7 */
   8
   9 #include <exec/execbase.h>
  10 #include <exec/memory.h>
  11 #include <utility/tagitem.h>
  12 #include <aros/m68k/cpucontext.h>
  13 #include <proto/kernel.h>
  14
  15 #include "exec_intern.h"
  16 #include "exec_util.h"
  17
  18 #define _PUSH(sp, val) *--sp = (IPTR)val
  19
  20 BOOL PrepareContext(struct Task *task, APTR entryPoint, APTR fallBack,
  21                     const struct TagItem *tagList, struct ExecBase *SysBase)
  22 {
  23     IPTR args[8] = {0};
  24     WORD numargs = 0;
  25     IPTR *sp = task->tc_SPReg;
  26     struct ExceptionContext *ctx;
  27
  28     if (!(task->tc_Flags & TF_ETASK))
  29         return FALSE;
  30
  31     ctx = KrnCreateContext();
  32     task->tc_UnionETask.tc_ETask->et_RegFrame = ctx;
  33     if (!ctx)
  34         return FALSE;
  35
  36     while(tagList)
  37     {
  38         switch(tagList->ti_Tag)
  39         {
  40             case TAG_MORE:
  41                 tagList = (const struct TagItem *)tagList->ti_Data;
  42                 continue;
  43
  44             case TAG_SKIP:
  45                 tagList += tagList->ti_Data;
  46                 break;
  47
  48             case TAG_DONE:
  49                 tagList = NULL;
  50                 break;
  51
  52 #define HANDLEARG(x)                                    \
  53             case TASKTAG_ARG ## x:                      \
  54                 args[x - 1] = (IPTR)tagList->ti_Data;   \
  55                 if (x > numargs) numargs = x;           \
  56                 break;
  57
  58             HANDLEARG(1)
  59             HANDLEARG(2)
  60             HANDLEARG(3)
  61             HANDLEARG(4)
  62             HANDLEARG(5)
  63             HANDLEARG(6)
  64             HANDLEARG(7)
  65             HANDLEARG(8)
  66         }
  67
  68         if (tagList) tagList++;
  69     }
  70
  71     /*
  72         There is not much to do here, or at least that is how it
  73         appears. Most of the work is done in the kernel_cpu.h macros.
  74     */
  75
  76     if (numargs)
  77     {
  78         /* On m68k C function gets all param on stack */
  79         while(numargs--)
  80         {
  81             _PUSH(sp, args[numargs]);
  82         }
  83     }
  84
  85     /* First we push the return address */
  86     _PUSH(sp, fallBack);
  87
  88     /* Then set up the frame to be used by Dispatch() */
  89     ctx->pc   = (IPTR)entryPoint;
  90     ctx->a[7] = (IPTR)sp;
  91     ctx->sr   = 0x0000;
  92
  93     /* We return the new stack pointer back to the caller. */
  94     task->tc_SPReg = sp;
  95
  96     return TRUE;
  97 } /* PrepareContext() */