gcc/ada/libgnat/s-stache.ads

   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                --
   6 --                                                                          --
   7 --                                  S p e c                                 --
   8 --                                                                          --
   9 --           Copyright (C) 1999-2018, 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 package provides a system-independent implementation of stack
  33 --  checking using comparison with stack base and limit.
  34
  35 --  This package defines basic types and objects. Operations related to
  36 --  stack checking can be found in package System.Stack_Checking.Operations.
  37
  38 pragma Compiler_Unit_Warning;
  39
  40 with System.Storage_Elements;
  41
  42 package System.Stack_Checking is
  43    pragma Preelaborate;
  44    pragma Elaborate_Body;
  45    --  This unit has a junk null body. The reason is that historically we
  46    --  used to have a real body, and it causes bootstrapping path problems
  47    --  to eliminate it, since the old body may still be present in the
  48    --  compilation environment for a build.
  49
  50    type Stack_Info is record
  51       Limit : System.Address := System.Null_Address;
  52       Base  : System.Address := System.Null_Address;
  53       Size  : System.Storage_Elements.Storage_Offset := 0;
  54    end record;
  55    --  This record may be part of a larger data structure like the
  56    --  task control block in the tasking case.
  57    --  This specific layout has the advantage of being compatible with the
  58    --  Intel x86 BOUNDS instruction.
  59
  60    type Stack_Access is access all Stack_Info;
  61    --  Unique local storage associated with a specific task. This storage is
  62    --  used for the stack base and limit, and is returned by Checked_Self.
  63    --  Only self may write this information, it may be read by any task.
  64    --  At no time the address range Limit .. Base (or Base .. Limit for
  65    --  upgrowing stack) may contain any address that is part of another stack.
  66    --  The Stack_Access may be part of a larger data structure.
  67
  68    Multi_Processor : constant Boolean := False; --  Not supported yet
  69
  70 private
  71
  72    Null_Stack_Info  : aliased Stack_Info :=
  73      (Limit => System.Null_Address,
  74       Base  => System.Null_Address,
  75       Size  => 0);
  76    --  Use explicit assignment to avoid elaboration code (call to init proc)
  77
  78    Null_Stack : constant Stack_Access := Null_Stack_Info'Access;
  79    --  Stack_Access value that will return a Stack_Base and Stack_Limit
  80    --  that fail any stack check.
  81
  82 end System.Stack_Checking;