arch/arm-raspidzy/exec/superstate.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: SuperState() - Switch the processor into a higher plane.
   6     Lang: english
   7 */
   8
   9 /*****************************************************************************
  10
  11     NAME */
  12 #include <proto/exec.h>
  13
  14         AROS_LH0(APTR, SuperState,
  15
  16 /*  LOCATION */
  17         struct ExecBase *, SysBase, 25, Exec)
  18
  19 /*  FUNCTION
  20         Enter supervisor mode (like Supervisor()), but return on the user
  21         stack. This will mean that the user stack variables are still there.
  22         A call to UserState() will end this mode.
  23
  24     INPUTS
  25         None.
  26
  27     RESULT
  28         The old supervisor stack. This must be passed to UserState(). If the
  29         processor was already in supervisor mode, then this function will
  30         return NULL. In that case do NOT call UserState().
  31
  32     NOTES
  33         This is not a good function to use, it has limited scope, and will
  34         probably be even less useful in the future.
  35
  36     EXAMPLE
  37
  38     BUGS
  39         You can easily cause your system to cease operating normally.
  40
  41     SEE ALSO
  42         Supervisor(), UserState()
  43
  44     INTERNALS
  45         For extra details see Supervisor().
  46
  47 ******************************************************************************/
  48 {
  49     AROS_LIBFUNC_INIT
  50
  51     asm("cps #0x13\n"); /* switch to SVC (supervisor) mode */
  52
  53     /* We have to return something. NULL is an invalid address for a
  54        stack, so it could be used to say that this function does
  55        nothing.
  56     */
  57     return NULL;
  58
  59     AROS_LIBFUNC_EXIT
  60 } /* SuperState() */