arch/ppc-sam440/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 #include <asm/amcc440.h>
  14
  15         AROS_LH0(APTR, SuperState,
  16
  17 /*  LOCATION */
  18         struct ExecBase *, SysBase, 25, Exec)
  19
  20 /*  FUNCTION
  21         Enter supervisor mode (like Supervisor()), but return on the user
  22         stack. This will mean that the user stack variables are still there.
  23         A call to UserState() will end this mode.
  24
  25     INPUTS
  26         None.
  27
  28     RESULT
  29         The old supervisor stack. This must be passed to UserState(). If the
  30         processor was already in supervisor mode, then this function will
  31         return NULL. In that case do NOT call UserState().
  32
  33     NOTES
  34         This is not a good function to use, it has limited scope, and will
  35         probably be even less useful in the future.
  36
  37     EXAMPLE
  38
  39     BUGS
  40         You can easily cause your system to cease operating normally.
  41
  42     SEE ALSO
  43         Supervisor(), UserState()
  44
  45     INTERNALS
  46         For extra details see Supervisor().
  47
  48 ******************************************************************************/
  49 {
  50     AROS_LIBFUNC_INIT
  51
  52     asm volatile("li %%r3,%0; sc"::"i"(6 /*SC_SUPERSTATE*/):"memory","r3");
  53
  54     /* We have to return something. NULL is an invalid address for a
  55        stack, so it could be used to say that this function does
  56        nothing.
  57     */
  58     return NULL;
  59
  60     AROS_LIBFUNC_EXIT
  61 } /* SuperState() */