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------------------------------------------------------------------------------
-- --
-- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
-- --
-- S Y S T E M . S T A C K _ C H E C K I N G --
-- --
-- S p e c --
-- --
-- Copyright (C) 1999-2001 Free Software Foundation, Inc. --
-- --
-- GNARL is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNARL; see file COPYING. If not, write --
-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNARL was developed by the GNARL team at Florida State University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package provides a system-independent implementation of stack
-- checking using comparison with stack base and limit.
with System.Storage_Elements;
pragma Polling (Off);
-- Turn off polling, we do not want polling to take place during stack
-- checking operations. It causes infinite loops and other problems.
package System.Stack_Checking is
type Stack_Info is record
Limit : System.Address := System.Null_Address;
Base : System.Address := System.Null_Address;
Size : System.Storage_Elements.Storage_Offset := 0;
end record;
-- This record may be part of a larger data structure like the
-- task control block in the tasking case.
-- This specific layout has the advantage of being compatible with the
-- Intel x86 BOUNDS instruction.
type Stack_Access is access all Stack_Info;
-- Unique local storage associated with a specific task. This storage is
-- used for the stack base and limit, and is returned by Checked_Self.
-- Only self may write this information, it may be read by any task.
-- At no time the address range Limit .. Base (or Base .. Limit for
-- upgrowing stack) may contain any address that is part of another stack.
-- The Stack_Access may be part of a larger data structure.
Multi_Processor : constant Boolean := False; -- Not supported yet
----------------------
-- Client Interface --
----------------------
procedure Set_Stack_Size
(Stack_Size : System.Storage_Elements.Storage_Offset);
-- Specify the stack size for the current task.
procedure Update_Stack_Cache (Stack : Stack_Access);
-- Set the stack cache for the current task. Note that this is only
-- for optimization purposes, nothing can be assumed about the
-- contents of the cache at any time, see Set_Stack_Info.
procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access);
-- Invalidate cache entries for the task T that owns Any_Stack.
-- This causes the Set_Stack_Info function to be called during
-- the next stack check done by T. This can be used to interrupt
-- task T asynchronously.
-- Stack_Check should be called in loops for this to work reliably.
function Stack_Check (Stack_Address : System.Address) return Stack_Access;
-- This version of Stack_Check should not be inlined.
private
Null_Stack_Info : aliased Stack_Info :=
(Limit => System.Null_Address,
Base => System.Null_Address,
Size => 0);
-- Use explicit assignment to avoid elaboration code (call to _init_proc).
Null_Stack : constant Stack_Access := Null_Stack_Info'Access;
-- Stack_Access value that will return a Stack_Base and Stack_Limit
-- that fail any stack check.
Cache : aliased Stack_Access := Null_Stack;
pragma Export (C, Cache, "_gnat_stack_cache");
pragma Export (C, Stack_Check, "_gnat_stack_check");
end System.Stack_Checking;
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