arch/.unmaintained/ppc-native/exec/superstate.s

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 /*****************************************************************************
   7
   8     NAME
   9
  10         AROS_LH0(APTR, SuperState,
  11
  12     SYNOPSIS
  13
  14     LOCATION
  15         struct ExecBase *, SysBase, 25, Exec)
  16
  17     FUNCTION
  18         Enter supervisor mode (like Supervisor()), but return on the normal
  19         user stack, so that user stack variables are still there. A call
  20         to Userstate() will end this mode.
  21
  22     INPUTS
  23
  24     RESULT
  25         Old supervisor stack. NULL if called from supervisor mode.
  26
  27     NOTES
  28         The user stack must be big enough to hold all possible nestings
  29         of interrupts.
  30
  31     EXAMPLE
  32
  33     BUGS
  34
  35     SEE ALSO
  36         UserState(), Supervisor()
  37
  38     INTERNALS
  39
  40     HISTORY
  41
  42 ******************************************************************************/
  43
  44         #include "machine.i"
  45
  46         .text
  47         .balign 4
  48         .globl  AROS_SLIB_ENTRY(SuperState,Exec)
  49         .type   AROS_SLIB_ENTRY(SuperState,Exec),@function
  50 AROS_SLIB_ENTRY(SuperState,Exec):
  51         push    scr
  52         mflr    scr
  53         push    scr
  54         /* cause a trap */
  55 .global _Superstate_trp:
  56         mfmsr   r0
  57         /* no trap? We are in usermode, so restore lr */
  58         pop     scr
  59         mtlr    scr
  60         pop     scr
  61         /* return 0, because we are in supervisor mode */
  62         li      ret,0
  63         /* return from this subroutine */
  64         blr