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

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Supervisor() - Execute some code in a privileged environment.
   6     Lang: english
   7 */
   8
   9 /*****************************************************************************
  10
  11     NAME
  12
  13         AROS_LH1(void, Supervisor,
  14
  15     SYNOPSIS
  16         AROS_LHA(ULONG_FUNC, userFunction, A5),
  17
  18     LOCATION
  19         struct ExecBase *, SysBase, 5, Exec)
  20
  21     FUNCTION
  22         Supervisor will allow a short privileged instruction sequence to
  23         be called from user mode. This has very few uses, and it is probably
  24         better to use any system supplied method to do anything.
  25
  26         The function supplied will be called as if it was a system interrupt,
  27         notably this means that you must *NOT* make any system calls or
  28         use any system data structures, and on certain systems you must
  29         use special methods to leave the code.
  30
  31         The code will not be passed any parameters.
  32
  33     INPUTS
  34         userFunc    -   The address of the code you want called in supervisor
  35                         mode.
  36
  37     RESULT
  38         The code will be called.
  39
  40     NOTES
  41         This function has completely different effects on different
  42         processors and architectures.
  43
  44         Currently defined effects are:
  45
  46         Kernel                      Effect
  47         -------------------------------------------------------------------
  48         i386 (under emulation)      Runs the function in supervisor mode.
  49                                     The function MUST end with an IRET
  50                                     instruction. Just like on m68k.
  51                                     Nothing is passed via stack.
  52         m68k (native)               Runs the process in supervisor mode.
  53                                     The process must end with an RTE
  54                                     instruction. It should save any
  55                                     registers which is uses.
  56         m68k (under emulation)
  57         ppc (native)                Runs the function in supervisor mode.
  58                                     There is no supervisor stack. The
  59                                     function must return with RFS
  60
  61     EXAMPLE
  62
  63     BUGS
  64         You can very easily make the system unusable with this function.
  65         In fact it is recommended that you do not use it at all.
  66
  67     SEE ALSO
  68         SuperState(), UserState()
  69
  70     INTERNALS
  71         You can do what you want with this function, even ignoring it if
  72         you don't think it makes any sense. But it could be quite useful
  73         to make it run something under different protection levels.
  74
  75         You should trust that the programmer know what they are doing :-)
  76
  77     HISTORY
  78
  79 ******************************************************************************/
  80         /* try to cause a trap */
  81 .global _Supervisor_trp:
  82         mfmsr   r0
  83         /* no exception? we are in supervisor mode so continue */
  84         ljmp    arg0