gcc/ada/s-stache.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --                 S Y S T E M . S T A C K _ C H E C K I N G                --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --                             $Revision: 1.6 $
  10 --                                                                          --
  11 --           Copyright (C) 1999-2001 Free Software Foundation, Inc.         --
  12 --                                                                          --
  13 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- As a special exception,  if other files  instantiate  generics from this --
  25 -- unit, or you link  this unit with other files  to produce an executable, --
  26 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  27 -- covered  by the  GNU  General  Public  License.  This exception does not --
  28 -- however invalidate  any other reasons why  the executable file  might be --
  29 -- covered by the  GNU Public License.                                      --
  30 --                                                                          --
  31 -- GNARL was developed by the GNARL team at Florida State University. It is --
  32 -- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
  33 -- State University (http://www.gnat.com).                                  --
  34 --                                                                          --
  35 ------------------------------------------------------------------------------
  36
  37 --  This package provides a system-independent implementation of stack
  38 --  checking using comparison with stack base and limit.
  39
  40 with System.Storage_Elements;
  41
  42 pragma Polling (Off);
  43 --  Turn off polling, we do not want polling to take place during stack
  44 --  checking operations. It causes infinite loops and other problems.
  45
  46 package System.Stack_Checking is
  47    type Stack_Info is record
  48       Limit : System.Address := System.Null_Address;
  49       Base  : System.Address := System.Null_Address;
  50       Size  : System.Storage_Elements.Storage_Offset := 0;
  51    end record;
  52    --  This record may be part of a larger data structure like the
  53    --  task control block in the tasking case.
  54    --  This specific layout has the advantage of being compatible with the
  55    --  Intel x86 BOUNDS instruction.
  56
  57    type Stack_Access is access all Stack_Info;
  58    --  Unique local storage associated with a specific task. This storage is
  59    --  used for the stack base and limit, and is returned by Checked_Self.
  60    --  Only self may write this information, it may be read by any task.
  61    --  At no time the address range Limit .. Base (or Base .. Limit for
  62    --  upgrowing stack) may contain any address that is part of another stack.
  63    --  The Stack_Access may be part of a larger data structure.
  64
  65    Multi_Processor        : constant Boolean := False; --  Not supported yet
  66
  67    ----------------------
  68    -- Client Interface --
  69    ----------------------
  70
  71    procedure Set_Stack_Size
  72      (Stack_Size : System.Storage_Elements.Storage_Offset);
  73    --  Specify the stack size for the current task.
  74
  75    procedure Update_Stack_Cache (Stack : Stack_Access);
  76    --  Set the stack cache for the current task. Note that this is only
  77    --  for optimization purposes, nothing can be assumed about the
  78    --  contents of the cache at any time, see Set_Stack_Info.
  79
  80    procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access);
  81    --  Invalidate cache entries for the task T that owns Any_Stack.
  82    --  This causes the Set_Stack_Info function to be called during
  83    --  the next stack check done by T. This can be used to interrupt
  84    --  task T asynchronously.
  85    --  Stack_Check should be called in loops for this to work reliably.
  86
  87    function Stack_Check (Stack_Address : System.Address) return Stack_Access;
  88    --  This version of Stack_Check should not be inlined.
  89
  90 private
  91
  92    Null_Stack_Info  : aliased Stack_Info :=
  93      (Limit => System.Null_Address,
  94       Base  => System.Null_Address,
  95       Size  => 0);
  96    --  Use explicit assignment to avoid elaboration code (call to _init_proc).
  97
  98    Null_Stack       : constant Stack_Access := Null_Stack_Info'Access;
  99    --  Stack_Access value that will return a Stack_Base and Stack_Limit
 100    --  that fail any stack check.
 101
 102    Cache            : aliased Stack_Access := Null_Stack;
 103
 104    pragma Export (C, Cache, "_gnat_stack_cache");
 105    pragma Export (C, Stack_Check, "_gnat_stack_check");
 106
 107 end System.Stack_Checking;