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--                                  B o d y                                 --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
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 is the verson for VxWorks 5 and VxWorks MILS
33
34--  This file should be kept synchronized with the general implementation
35--  provided by s-stchop.adb.
36
37pragma Restrictions (No_Elaboration_Code);
38--  We want to guarantee the absence of elaboration code because the
39--  binder does not handle references to this package.
40
41with System.Storage_Elements; use System.Storage_Elements;
42with System.Parameters; use System.Parameters;
43with Interfaces.C;
44
45package body System.Stack_Checking.Operations is
46
47   --  In order to have stack checking working appropriately on VxWorks we need
48   --  to extract the stack size information from the VxWorks kernel itself.
49
50   --  For VxWorks 5 the library for showing task-related information needs to
51   --  be linked into the VxWorks system, when using stack checking. The
52   --  taskShow library can be linked into the VxWorks system by either:
53
54   --    * defining INCLUDE_SHOW_ROUTINES in config.h when using
55   --      configuration header files, or
56
57   --    * selecting INCLUDE_TASK_SHOW when using the Tornado project
58   --      facility.
59
60   --  VxWorks MILS includes the necessary routine in taskLib, so nothing
61   --  special needs to be done there.
62
63   Stack_Limit : Address :=
64                   Boolean'Pos (Stack_Grows_Down) * Address'First
65                   + Boolean'Pos (not Stack_Grows_Down) * Address'Last;
66   pragma Export (C, Stack_Limit, "__gnat_stack_limit");
67   --  Stack_Limit contains the limit of the stack. This variable is later made
68   --  a task variable (by calling taskVarAdd) and then correctly set to the
69   --  stack limit of the task. Before being so initialized its value must be
70   --  valid so that any subprogram with stack checking enabled will run. We
71   --  use extreme values according to the direction of the stack.
72
73   type Set_Stack_Limit_Proc_Acc is access procedure;
74   pragma Convention (C, Set_Stack_Limit_Proc_Acc);
75
76   Set_Stack_Limit_Hook : Set_Stack_Limit_Proc_Acc;
77   pragma Import (C, Set_Stack_Limit_Hook, "__gnat_set_stack_limit_hook");
78   --  Procedure to be called when a task is created to set stack
79   --  limit.
80
81   procedure Set_Stack_Limit_For_Current_Task;
82   pragma Convention (C, Set_Stack_Limit_For_Current_Task);
83   --  Register Initial_SP as the initial stack pointer value for the current
84   --  task when it starts and Size as the associated stack area size. This
85   --  should be called once, after the soft-links have been initialized?
86
87   -----------------------------
88   --  Initialize_Stack_Limit --
89   -----------------------------
90
91   procedure Initialize_Stack_Limit is
92   begin
93      --  For the environment task
94
95      Set_Stack_Limit_For_Current_Task;
96
97      --  Will be called by every created task
98
99      Set_Stack_Limit_Hook := Set_Stack_Limit_For_Current_Task'Access;
100   end Initialize_Stack_Limit;
101
102   --------------------------------------
103   -- Set_Stack_Limit_For_Current_Task --
104   --------------------------------------
105
106   procedure Set_Stack_Limit_For_Current_Task is
107      use Interfaces.C;
108
109      function Task_Var_Add (Tid : Interfaces.C.int; Var : Address)
110                            return Interfaces.C.int;
111      pragma Import (C, Task_Var_Add, "taskVarAdd");
112      --  Import from VxWorks
113
114      type OS_Stack_Info is record
115         Size  : Interfaces.C.int;
116         Base  : System.Address;
117         Limit : System.Address;
118      end record;
119      pragma Convention (C, OS_Stack_Info);
120      --  Type representing the information that we want to extract from the
121      --  underlying kernel.
122
123      procedure Get_Stack_Info (Stack : not null access OS_Stack_Info);
124      pragma Import (C, Get_Stack_Info, "__gnat_get_stack_info");
125      --  Procedure that fills the stack information associated to the
126      --  currently executing task.
127
128      Stack_Info : aliased OS_Stack_Info;
129
130      Limit : System.Address;
131
132   begin
133      --  Get stack bounds from VxWorks
134
135      Get_Stack_Info (Stack_Info'Access);
136
137      --  In s-stchop.adb, we check for overflow in the following operations,
138      --  but we have no such check in this vxworks version. Why not ???
139
140      if Stack_Grows_Down then
141         Limit := Stack_Info.Base - Storage_Offset (Stack_Info.Size);
142      else
143         Limit := Stack_Info.Base + Storage_Offset (Stack_Info.Size);
144      end if;
145
146      --  Note: taskVarAdd implicitly calls taskVarInit if required
147
148      if Task_Var_Add (0, Stack_Limit'Address) = 0 then
149         Stack_Limit := Limit;
150      end if;
151   end Set_Stack_Limit_For_Current_Task;
152
153end System.Stack_Checking.Operations;
154