1------------------------------------------------------------------------------
2--                                                                          --
3--                 GNAT 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 . O P E R A T I O N S      --
6--                                                                          --
7--                                  S p e c                                 --
8--                                                                          --
9--          Copyright (C) 1999-2018, 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 3,  or (at your option) any later ver- --
14-- sion.  GNAT 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.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNARL was developed by the GNARL team at Florida State University.       --
28-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package provides a implementation of stack checking operations using
33--  comparison with stack base and limit.
34
35pragma Restrictions (No_Elaboration_Code);
36--  We want to guarantee the absence of elaboration code because the binder
37--  does not handle references to this package.
38
39pragma 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
43with System.Storage_Elements;
44
45package System.Stack_Checking.Operations is
46   pragma Preelaborate;
47
48   procedure Update_Stack_Cache (Stack : Stack_Access);
49   --  Set the stack cache for the current task. Note that this is only for
50   --  optimization purposes, nothing can be assumed about the contents of the
51   --  cache at any time, see Set_Stack_Info.
52   --
53   --  The stack cache should contain the bounds of the current task.  But
54   --  because the RTS is not aware of task switches, the stack cache may be
55   --  incorrect.  So when the stack pointer is not within the bounds of the
56   --  stack cache, Stack_Check first update the cache (which is a costly
57   --  operation hence the need of a cache).
58
59   procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access);
60   --  Invalidate cache entries for the task T that owns Any_Stack. This causes
61   --  the Set_Stack_Info function to be called during the next stack check
62   --  done by T. This can be used to interrupt task T asynchronously.
63   --  Stack_Check should be called in loops for this to work reliably.
64
65   function Stack_Check (Stack_Address : System.Address) return Stack_Access;
66   --  This version of Stack_Check should not be inlined
67
68   procedure Notify_Stack_Attributes
69     (Initial_SP : System.Address;
70      Size       : System.Storage_Elements.Storage_Offset);
71   --  Register Initial_SP as the initial stack pointer value for the current
72   --  task when it starts and Size as the associated stack area size. This
73   --  should be called once, after the soft-links have been initialized and
74   --  prior to the first "Stack_Check" call.
75
76private
77   Cache : aliased Stack_Access := Null_Stack;
78
79   pragma Export (C, Cache, "_gnat_stack_cache");
80   pragma Export (C, Stack_Check, "_gnat_stack_check");
81
82end System.Stack_Checking.Operations;
83