arch/i386-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, i386 version
   6     Lang: english
   7 */
   8
   9 #include <exec/types.h>
  10 #include <exec/execbase.h>
  11 #include <exec/memory.h>
  12 #include <utility/tagitem.h>
  13 #include <proto/alib.h>
  14 #include <proto/kernel.h>
  15 #include <aros/i386/cpucontext.h>
  16
  17 #include "exec_intern.h"
  18 #include "exec_util.h"
  19
  20 #define _PUSH(sp, val) *--sp = (IPTR)val
  21
  22 BOOL PrepareContext(struct Task *task, APTR entryPoint, APTR fallBack,
  23                     const struct TagItem *tagList, struct ExecBase *SysBase)
  24 {
  25     IPTR args[8] = {0};
  26     WORD numargs = 0;
  27     IPTR *sp = task->tc_SPReg;
  28     struct TagItem *t;
  29     struct ExceptionContext *ctx;
  30
  31     if (!(task->tc_Flags & TF_ETASK) )
  32         return FALSE;
  33
  34     ctx = KrnCreateContext();
  35     task->tc_UnionETask.tc_ETask->et_RegFrame = ctx;
  36     if (!ctx)
  37         return FALSE;
  38
  39     while((t = LibNextTagItem((struct TagItem **)&tagList)))
  40     {
  41         switch(t->ti_Tag)
  42         {
  43
  44 #define HANDLEARG(x)                      \
  45         case TASKTAG_ARG ## x:            \
  46             args[x - 1] = t->ti_Data;     \
  47             if (x > numargs) numargs = x; \
  48             break;
  49
  50         HANDLEARG(1)
  51         HANDLEARG(2)
  52         HANDLEARG(3)
  53         HANDLEARG(4)
  54         HANDLEARG(5)
  55         HANDLEARG(6)
  56         HANDLEARG(7)
  57         HANDLEARG(8)
  58         }
  59     }
  60
  61     /*
  62         There is not much to do here, or at least that is how it
  63         appears. Most of the work is done in the kernel_cpu.h macros.
  64     */
  65
  66     if (numargs)
  67     {
  68         /* On i386 C function gets all param on stack */
  69         while(numargs--)
  70         {
  71             _PUSH(sp, args[numargs]);
  72         }
  73     }
  74
  75     /* First we push the return address */
  76     _PUSH(sp, fallBack);
  77
  78     /* Then set up the frame to be used by Dispatch() */
  79     ctx->ebp = 0;
  80     ctx->eip = (IPTR)entryPoint;
  81     ctx->esp = (IPTR)sp;
  82
  83     /* We return the new stack pointer back to the caller. */
  84     task->tc_SPReg = sp;
  85
  86     return TRUE;
  87 } /* PrepareContext() */