arch/i386-pc/exec/supervisor.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Supervisor() - Execute some code in a priviledged environment.
   6     Lang: english
   7 */
   8
   9 /*****************************************************************************
  10
  11     NAME */
  12 #include <proto/exec.h>
  13
  14         AROS_LH1(ULONG, Supervisor,
  15
  16 /*  SYNOPSIS */
  17         AROS_LHA(ULONG_FUNC, userFunction, A5),
  18
  19 /*  LOCATION */
  20         struct ExecBase *, SysBase, 5, Exec)
  21
  22 /*  FUNCTION
  23         Supervisor will allow a short priviledged instruction sequence to
  24         be called from user mode. This has very few uses, and it is probably
  25         better to use any system supplied method to do anything.
  26
  27         The function supplied will be called as if it was a system interrupt,
  28         notably this means that you must *NOT* make any system calls or
  29         use any system data structures, and on certain systems you must
  30         use special methods to leave the code.
  31
  32         The code will not be passed any parameters.
  33
  34     INPUTS
  35         userFunc    -   The address of the code you want called in supervisor
  36                         mode.
  37
  38     RESULT
  39         The code will be called.
  40
  41     NOTES
  42         This function has completely different effects on different
  43         processors and architectures.
  44
  45         Currently defined effects are:
  46
  47         Kernel                      Effect
  48         -------------------------------------------------------------------
  49         i386 (under emulation)      None
  50         m68k (native)               Runs the process in supervisor mode.
  51                                     The process must end with an RTE
  52                                     instruction. It should save any
  53                                     registers which is uses.
  54         m68k (under emulation)
  55
  56     EXAMPLE
  57
  58     BUGS
  59         You can very easily make the system unusable with this function.
  60         In fact it is recommended that you do not use it at all.
  61
  62     SEE ALSO
  63         SuperState(), UserState()
  64
  65     INTERNALS
  66         You can do what you want with this function, even ignoring it if
  67         you don't think it makes any sense. But it could be quite useful
  68         to make it run something under different protection levels.
  69
  70         You should trust that the programmer know what they are doing :-)
  71
  72     HISTORY
  73
  74 ******************************************************************************/
  75 {
  76     AROS_LIBFUNC_INIT
  77     ULONG retval;
  78
  79     __asm__ __volatile__ (
  80         "movl $-2,%%eax\n\t"
  81         "int $0x80"
  82         :"=a"(retval)
  83         :"d"(userFunction)
  84         );
  85
  86     return retval;
  87     AROS_LIBFUNC_EXIT
  88 } /* Supervisor() */