File : s-stchop.ads
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) 1999-2009, 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 -- --
19 -- --
20 -- --
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
35 pragma 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
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 with System.Storage_Elements;
44
45 package 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
76 private
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
82 end System.Stack_Checking.Operations;