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-------------------------------------------------------------------------------
--- --
--- 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) 1999-2009, 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 3, or (at your option) any later ver- --
--- sion. GNAT 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. --
--- --
--- As a special exception under Section 7 of GPL version 3, you are granted --
--- additional permissions described in the GCC Runtime Library Exception, --
--- version 3.1, as published by the Free Software Foundation. --
--- --
--- You should have received a copy of the GNU General Public License and --
--- a copy of the GCC Runtime Library Exception along with this program; --
--- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
--- <http://www.gnu.org/licenses/>. --
--- --
--- 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 (s-stchop-vxworks.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 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 : not null 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;
-
- -----------------------------
- -- Notify_Stack_Attributes --
- -----------------------------
-
- procedure Notify_Stack_Attributes
- (Initial_SP : System.Address;
- Size : System.Storage_Elements.Storage_Offset)
- is
- My_Stack : constant Stack_Access := Soft_Links.Get_Stack_Info.all;
-
- -- We piggyback on the 'Limit' field to store what will be used as the
- -- 'Base' and leave the 'Size' alone to not interfere with the logic in
- -- Set_Stack_Info below.
-
- pragma Unreferenced (Size);
-
- begin
- My_Stack.Limit := Initial_SP;
- end Notify_Stack_Attributes;
-
- --------------------
- -- Set_Stack_Info --
- --------------------
-
- function Set_Stack_Info
- (Stack : not null 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;
-
- -- If a stack base address has been registered, honor it.
- -- Fallback to the address of a local object otherwise.
-
- if My_Stack.Limit /= System.Null_Address then
- My_Stack.Base := My_Stack.Limit;
- else
- My_Stack.Base := Frame_Address;
- end if;
-
- 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
- raise Storage_Error with "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
- raise Storage_Error with "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;