arch/.unmaintained/dummy/superstate.c

   1 |*****************************************************************************
   2 |
   3 |   NAME
   4 |
   5 |       __AROS_LH0(APTR, SuperState,
   6 |
   7 |   SYNOPSIS
   8 |
   9 |   LOCATION
  10 |       struct ExecBase *, SysBase, 25, Exec)
  11 |
  12 |   FUNCTION
  13 |       Enter supervisor mode (like Supervisor()), but return on the normal
  14 |       user stack, so that user stack variables are still there. A call
  15 |       to Userstate() will end this mode.
  16 |
  17 |   INPUTS
  18 |
  19 |   RESULT
  20 |       Old supervisor stack. NULL if called from supervisor mode.
  21 |
  22 |   NOTES
  23 |       The user stack must be big enough to hold all possible nestings
  24 |       of interrupts.
  25 |
  26 |   EXAMPLE
  27 |
  28 |   BUGS
  29 |
  30 |   SEE ALSO
  31 |       UserState(), Supervisor()
  32 |
  33 |   INTERNALS
  34 |
  35 |   HISTORY
  36 |
  37 |******************************************************************************
  38
  39         Supervisor  =   -0x1e
  40
  41         .globl  _Exec_SuperState
  42 _Exec_SuperState:
  43         | Goto supervisor mode. Preserve a5 in d0 (faster than stack space)
  44         movel   a5,d0
  45         leal    super,a5
  46
  47         | Do not change user stack - use jmp
  48         jmp     a6@(Supervisor)
  49 super:
  50         | Restore a5
  51         movel   d0,a5
  52
  53         | Check if called from supervisor mode
  54         btst    #5,sp@
  55         jeq     fromuser
  56
  57         | Called from supervisor mode. Just return NULL.
  58         moveql  #0,d0
  59         rte
  60
  61 fromuser:
  62         | Called from user mode. Restore sp and return supervisor sp.
  63         movel   sp,d0
  64         movel   usp,sp
  65
  66         | usp already points to the returnaddress for the SuperState() call.
  67         rts
  68