arch/m68k-amiga/exec/preparecontext.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include <exec/types.h>
   7 #include <aros/libcall.h>
   8 #include <exec/execbase.h>
   9 #include <exec/tasks.h>
  10 #include <exec/memory.h>
  11 #include <exec/ptrace.h>
  12 #include "etask.h"
  13 #include "exec_util.h"
  14
  15 /*****************************************************************************
  16
  17     NAME */
  18
  19         AROS_LH4(BOOL, PrepareContext,
  20
  21 /*  SYNOPSIS */
  22         AROS_LHA(VOLATILE struct Task *, task,       A0),
  23         AROS_LHA(APTR,                   entryPoint, A1),
  24         AROS_LHA(APTR,                   fallBack,   A2),
  25         AROS_LHA(struct TagItem *,       tagList,    A3),
  26
  27 /*  LOCATION */
  28         struct ExecBase *, SysBase, 6, Exec)
  29
  30 /*  FUNCTION
  31         Allocates the space required to hold a new set of registers on the
  32         Stack given by stackPointer and clears the area except for pc which
  33         is set to the address given by entryPoint.
  34
  35     INPUTS
  36         task         - Pointer to the new task
  37         entryPoint   - Address of the function to call when the new context
  38                        becomes active.
  39         fallBack     - Address to be called when the entryPoint function ended
  40                        with an rts.
  41         tagList      -
  42
  43     RESULT
  44         The new Stackpointer with the underlying context.
  45
  46     NOTES
  47         This function is for internal use by exec only.
  48
  49         This function is processor dependant.
  50
  51     EXAMPLE
  52
  53     BUGS
  54
  55     SEE ALSO
  56         SwitchTasks()
  57
  58     INTERNALS
  59
  60     HISTORY
  61
  62 ******************************************************************************/
  63 {
  64         AROS_LIBFUNC_INIT
  65
  66         struct pt_regs *regs;
  67
  68         UBYTE *sp = (UBYTE *)task->tc_SPReg;
  69
  70         /* Push fallBack address */
  71         sp -= sizeof(APTR);
  72         *(APTR *)sp = fallBack;
  73
  74         if (!(task->tc_Flags & TF_ETASK)) {
  75           *(ULONG *)0x0bad0001=0;
  76           return FALSE;
  77         }
  78
  79         GetIntETask (task)->iet_Context = AllocTaskMem ((struct Task *)task
  80             , SIZEOF_ALL_REGISTERS
  81             , MEMF_PUBLIC|MEMF_CLEAR
  82         );
  83
  84         if (!(regs  = (struct pt_regs *)GetIntETask(task)->iet_Context)) {
  85           *(ULONG *)0x0bad0003=0;
  86           return FALSE;
  87         }
  88
  89         regs->usp = (IPTR)sp;
  90         regs->pc  = (ULONG)entryPoint;
  91
  92         task->tc_SPReg = sp;
  93
  94         return TRUE;
  95         AROS_LIBFUNC_EXIT
  96 }