File : s-stache.adb
------------------------------------------------------------------------------
-- --
-- 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 --
-- --
-- B o d y --
-- --
-- $Revision: 1.5 $ --
-- --
-- Copyright (C) 1999 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. It is --
-- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
-- State University (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
with System.Storage_Elements; use System.Storage_Elements;
with System.Parameters; use System.Parameters;
with System.Soft_Links;
package body System.Stack_Checking is
function Set_Stack_Info (Stack : access Stack_Access) return Stack_Access;
-- The function Set_Stack_Info is the actual function that updates
-- the cache containing a pointer to the Stack_Info. It may also
-- be used for detecting asynchronous abort in combination with
-- Invalidate_Self_Cache.
-- Set_Stack_Info should do the following things in order:
-- 1) Get the Stack_Access value for the current task
-- 2) Set Stack.all to the value obtained in 1)
-- 3) Optionally Poll to check for asynchronous abort
-- This order is important because if at any time a write to
-- the stack cache is is pending, that write should be followed
-- by a Poll to prevent loosing signals.
-- Note: This function must be compiled with Polling turned off
-- Note: on systems like VxWorks and OS/2 with real thread-local storage,
-- Set_Stack_Info should return an access value for such local
-- storage. In those cases the cache will always be up-to-date.
-- The following constants should be imported from some system-specific
-- constants package. The constants must be static for performance reasons.
-----------------
-- Stack_Check --
-----------------
function Stack_Check
(Stack_Address : System.Address)
return Stack_Access
is
type Frame_Marker is null record;
Marker : Frame_Marker;
Cached_Stack : constant Stack_Access := Cache;
Frame_Address : constant System.Address := Marker'Address;
begin
-- This function first does a "cheap" check which is correct
-- if it succeeds. In case of failure, the full check is done.
-- Ideally the cheap check should be done in an optimized manner,
-- or be inlined.
if (Stack_Grows_Down and then
(Frame_Address <= Cached_Stack.Base
and
Stack_Address > Cached_Stack.Limit))
or else
(not Stack_Grows_Down and then
(Frame_Address >= Cached_Stack.Base
and
Stack_Address < Cached_Stack.Limit))
then
-- Cached_Stack is valid as it passed the stack check
return Cached_Stack;
end if;
Full_Check :
declare
My_Stack : Stack_Access := Set_Stack_Info (Cache'Access);
-- At this point Stack.all might already be invalid, so
-- it is essential to use our local copy of Stack!
begin
if (Stack_Grows_Down and then
(not (Frame_Address <= My_Stack.Base)))
or else
(not Stack_Grows_Down and then
(not (Frame_Address >= My_Stack.Base)))
then
-- The returned Base is lower than the stored one,
-- so assume that the original one wasn't right and use the
-- current Frame_Address as new one. This allows initializing
-- Base with the Frame_Address as approximation.
-- During initialization the Frame_Address will be close to
-- the stack base anyway: the difference should be compensated
-- for in the stack reserve.
My_Stack.Base := Frame_Address;
end if;
if (Stack_Grows_Down and then
Stack_Address < My_Stack.Limit)
or else
(not Stack_Grows_Down and then
Stack_Address > My_Stack.Limit)
then
raise Storage_Error;
end if;
return My_Stack;
end Full_Check;
end Stack_Check;
----------------------------
-- Invalidate_Stack_Cache --
----------------------------
procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access) is
begin
Cache := Null_Stack;
end Invalidate_Stack_Cache;
--------------------
-- Set_Stack_Info --
--------------------
function Set_Stack_Info
(Stack : access Stack_Access)
return Stack_Access
is
type Frame_Mark is null record;
Frame_Location : Frame_Mark;
Frame_Address : Address := Frame_Location'Address;
My_Stack : Stack_Access;
Limit_Chars : System.Address;
Limit : Integer;
function getenv (S : String) return System.Address;
pragma Import (C, getenv, External_Name => "getenv");
function atoi (A : System.Address) return Integer;
pragma Import (C, atoi);
begin
-- The order of steps 1 .. 3 is important, see specification.
-- 1) Get the Stack_Access value for the current task
My_Stack := Soft_Links.Get_Stack_Info.all;
if My_Stack.Base = Null_Address then
-- First invocation, initialize based on the assumption that
-- there are Environment_Stack_Size bytes available beyond
-- the current frame address.
if My_Stack.Size = 0 then
My_Stack.Size := Storage_Offset'Last;
-- When the environment variable GNAT_STACK_LIMIT is set,
-- set Environment_Stack_Size to that number of kB.
Limit_Chars := getenv ("GNAT_STACK_LIMIT" & Ascii.Nul);
if Limit_Chars /= Null_Address then
Limit := atoi (Limit_Chars);
if Limit >= 0 then
My_Stack.Size := Storage_Offset (Limit) * 1024;
end if;
end if;
end if;
My_Stack.Base := Frame_Address;
if Stack_Grows_Down then
-- Prevent wrap-around on too big stack sizes
My_Stack.Limit := My_Stack.Base - My_Stack.Size;
if My_Stack.Limit > My_Stack.Base then
My_Stack.Limit := Address'First;
end if;
else
My_Stack.Limit := My_Stack.Base + My_Stack.Size;
-- Prevent wrap-around on too big stack sizes
if My_Stack.Limit < My_Stack.Base then
My_Stack.Limit := Address'Last;
end if;
end if;
end if;
-- 2) Set Stack.all to the value obtained in 1)
Stack.all := My_Stack;
-- 3) Optionally Poll to check for asynchronous abort
if Soft_Links.Check_Abort_Status.all /= 0 then
raise Standard'Abort_Signal;
end if;
return My_Stack; -- Never trust the cached value, but return local copy!
end Set_Stack_Info;
--------------------
-- Set_Stack_Size --
--------------------
procedure Set_Stack_Size
(Stack_Size : System.Storage_Elements.Storage_Offset)
is
My_Stack : Stack_Access;
Frame_Address : constant System.Address := My_Stack'Address;
begin
My_Stack := Stack_Check (Frame_Address);
if Stack_Grows_Down then
My_Stack.Limit := My_Stack.Base - Stack_Size;
else
My_Stack.Limit := My_Stack.Base + Stack_Size;
end if;
end Set_Stack_Size;
-- Specify the stack size for the current frame.
------------------------
-- Update_Stack_Cache --
------------------------
procedure Update_Stack_Cache (Stack : Stack_Access) is
begin
if not Multi_Processor then
Cache := Stack;
end if;
end Update_Stack_Cache;
end System.Stack_Checking;