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 --           Copyright (C) 1999-2003 Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNARL was developed by the GNARL team at Florida State University.       --
  30 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides a system-independent implementation of stack
  35 --  checking using comparison with stack base and limit.
  36
  37 with System.Storage_Elements;
  38
  39 pragma Polling (Off);
  40 --  Turn off polling, we do not want polling to take place during stack
  41 --  checking operations. It causes infinite loops and other problems.
  42
  43 package System.Stack_Checking is
  44    type Stack_Info is record
  45       Limit : System.Address := System.Null_Address;
  46       Base  : System.Address := System.Null_Address;
  47       Size  : System.Storage_Elements.Storage_Offset := 0;
  48    end record;
  49    --  This record may be part of a larger data structure like the
  50    --  task control block in the tasking case.
  51    --  This specific layout has the advantage of being compatible with the
  52    --  Intel x86 BOUNDS instruction.
  53
  54    type Stack_Access is access all Stack_Info;
  55    --  Unique local storage associated with a specific task. This storage is
  56    --  used for the stack base and limit, and is returned by Checked_Self.
  57    --  Only self may write this information, it may be read by any task.
  58    --  At no time the address range Limit .. Base (or Base .. Limit for
  59    --  upgrowing stack) may contain any address that is part of another stack.
  60    --  The Stack_Access may be part of a larger data structure.
  61
  62    Multi_Processor        : constant Boolean := False; --  Not supported yet
  63
  64    ----------------------
  65    -- Client Interface --
  66    ----------------------
  67
  68    procedure Set_Stack_Size
  69      (Stack_Size : System.Storage_Elements.Storage_Offset);
  70    --  Specify the stack size for the current task.
  71
  72    procedure Update_Stack_Cache (Stack : Stack_Access);
  73    --  Set the stack cache for the current task. Note that this is only
  74    --  for optimization purposes, nothing can be assumed about the
  75    --  contents of the cache at any time, see Set_Stack_Info.
  76
  77    procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access);
  78    --  Invalidate cache entries for the task T that owns Any_Stack.
  79    --  This causes the Set_Stack_Info function to be called during
  80    --  the next stack check done by T. This can be used to interrupt
  81    --  task T asynchronously.
  82    --  Stack_Check should be called in loops for this to work reliably.
  83
  84    function Stack_Check (Stack_Address : System.Address) return Stack_Access;
  85    --  This version of Stack_Check should not be inlined.
  86
  87 private
  88
  89    Null_Stack_Info  : aliased Stack_Info :=
  90      (Limit => System.Null_Address,
  91       Base  => System.Null_Address,
  92       Size  => 0);
  93    --  Use explicit assignment to avoid elaboration code (call to init proc).
  94
  95    Null_Stack       : constant Stack_Access := Null_Stack_Info'Access;
  96    --  Stack_Access value that will return a Stack_Base and Stack_Limit
  97    --  that fail any stack check.
  98
  99    Cache            : aliased Stack_Access := Null_Stack;
 100
 101    pragma Export (C, Cache, "_gnat_stack_cache");
 102    pragma Export (C, Stack_Check, "_gnat_stack_check");
 103    pragma Export (C, Set_Stack_Size, "__gnat_set_stack_size");
 104
 105 end System.Stack_Checking;