------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- 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 -- -- -- -- B o d y -- -- -- -- Copyright (C) 1999-2006 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, 51 Franklin Street, Fifth Floor, -- -- Boston, MA 02110-1301, 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 is the general implementation of this package. There is a VxWorks -- specific version of this package (5zstchop.adb). This file should -- be kept synchronized with it. pragma Restrictions (No_Elaboration_Code); -- We want to guarantee the absence of elaboration code because the -- binder does not handle references to this package. with Ada.Exceptions; with System.Storage_Elements; use System.Storage_Elements; with System.Parameters; use System.Parameters; with System.Soft_Links; with System.CRTL; package body System.Stack_Checking.Operations is Kilobyte : constant := 1024; 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 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. ---------------------------- -- Invalidate_Stack_Cache -- ---------------------------- procedure Invalidate_Stack_Cache (Any_Stack : Stack_Access) is pragma Warnings (Off, Any_Stack); 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 : constant Address := Frame_Location'Address; My_Stack : Stack_Access; Limit_Chars : System.Address; Limit : Integer; 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 (Default_Env_Stack_Size); -- When the environment variable GNAT_STACK_LIMIT is set, -- set Environment_Stack_Size to that number of kB. Limit_Chars := System.CRTL.getenv ("GNAT_STACK_LIMIT" & ASCII.NUL); if Limit_Chars /= Null_Address then Limit := System.CRTL.atoi (Limit_Chars); if Limit >= 0 then My_Stack.Size := Storage_Offset (Limit) * Kilobyte; 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; ----------------- -- 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 -- The parameter may have wrapped around in System.Address arithmetics. -- In that case, we have no other choices than raising the exception. if (Stack_Grows_Down and then Stack_Address > Frame_Address) or else (not Stack_Grows_Down and then Stack_Address < Frame_Address) then Ada.Exceptions.Raise_Exception (E => Storage_Error'Identity, Message => "stack overflow detected"); end if; -- 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 : constant 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 Ada.Exceptions.Raise_Exception (E => Storage_Error'Identity, Message => "stack overflow detected"); end if; return My_Stack; end Full_Check; end Stack_Check; ------------------------ -- 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.Operations;