****************************************************************************
*
*    $RCSfile: STACKCHK.asm $
* Description: Runtime support for the Oberon-A compiler
*
*  Created by: fjc (Frank Copeland)
*   $Revision: 1.2 $
*     $Author: fjc $
*       $Date: 1994/08/08 16:31:56 $
*
* Copyright © 1994, Frank Copeland.
* This file is part of the Oberon-A Library.
* See Oberon-A.doc for conditions of use and distribution.
*
* Log entries are at the end of the file.
*
****************************************************************************
*
* This file contains the MC68000 source code for part of the runtime
* support library of the Oberon-A compiler.  It contains the code to
* implement stack checking on procedure entry.
*
* Other parts of the runtime system may be found in the other files in
* this directory.  The object files resulting from assembling these
* files are concatenated to create OberonSys.lib.
*
* This code is by definition *not* re-entrant and is not suitable for
* creating shared-code libraries.
*
****************************************************************************

;---------------------------------------------------------------------
;    Program unit hunk name
;    !! DO NOT CHANGE UNLESS YOU KNOW WHAT YOU ARE DOING !!

     TTL OberonSys

;---------------------------------------------------------------------
;    Imports

     INCLUDE   "OberonSys.i"

ABSEXECBASE    EQU  4
ThisTask       EQU  276
tc_SPLower     EQU  58

;---------------------------------------------------------------------
; PROCEDURE OberonSys_STACKCHK
;   ( size {D0} : LONGINT )
;
; A call to this procedure is generated by the compiler when it
; generates the code for entry to a procedure.
;
; The procedure assumes that 1500 bytes must remain free on the stack,
; to allow for the parameters of procedures called in the body of the
; procedure, and the extra stack required by dos.library functions.
; This limit is the same as the constant OCG.ParLimit. If that
; constant changes, this code must be modified and re-assembled.
;
; OberonSys_STACKCHK trashes the A0 register.
;---------------------------------------------------------------------

     SECTION OberonSys,CODE

     XDEF      OberonSys_STACKCHK

OberonSys_STACKCHK:

        MOVE.L  A0,-(A7)            ; (* Save register *)
        MOVE.L  ABSEXECBASE,A0      ; IF SysBase.ThisTask.tc_SPLower
        MOVE.L  ThisTask(A0),A0
        MOVE.L  tc_SPLower(A0),A0
        ADD.L   D0,A0               ;   + size + OCG.ParLimit
        ADD.W   #1500,A0
        CMP.L   A7,A0               ;   > A7 THEN
        BLS.S   1$
        TRAP    #OS_StackChk        ;   TRAP #StackChk
1$
        MOVE.L  (A7)+,A0            ; (* Restore register *)
        RTS                         ; END

;---------------------------------------------------------------------

     END  ; OberonSys

****************************************************************************
*
* $Log: STACKCHK.asm $
;; Revision 1.2  1994/08/08  16:31:56  fjc
;; Release 1.4
;;
;; Revision 1.1  1994/07/24  18:31:36  fjc
;; Initial revision
;;
****************************************************************************