gcc/vtable-verify.h

   1 /* Copyright (C) 2013-2015 Free Software Foundation, Inc.
   2
   3 This file is part of GCC.
   4
   5 GCC is free software; you can redistribute it and/or modify it under
   6 the terms of the GNU General Public License as published by the Free
   7 Software Foundation; either version 3, or (at your option) any later
   8 version.
   9
  10 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  11 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13 for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with GCC; see the file COPYING3.  If not see
  17 <http://www.gnu.org/licenses/>.  */
  18
  19 /* Virtual Table Pointer Security.  */
  20
  21 #ifndef VTABLE_VERIFY_H
  22 #define VTABLE_VERIFY_H
  23
  24 #include "sbitmap.h"
  25
  26 /* The function decl used to create calls to __VLTVtableVerify.  It must
  27    be global because it needs to be initialized in the C++ front end, but
  28    used in the middle end (in the vtable verification pass).  */
  29
  30 extern tree verify_vtbl_ptr_fndecl;
  31
  32 /* Global variable keeping track of how many vtable map variables we
  33    have created. */
  34 extern unsigned num_vtable_map_nodes;
  35
  36 /* Keep track of how many virtual calls we are actually verifying.  */
  37 extern int total_num_virtual_calls;
  38 extern int total_num_verified_vcalls;
  39
  40 /* Each vtable map variable corresponds to a virtual class.  Each
  41    vtable map variable has a hash table associated with it, that keeps
  42    track of the vtable pointers for which we have generated a call to
  43    __VLTRegisterPair (with the current vtable map variable).  This is
  44    the hash table node that is used for each entry in this hash table
  45    of vtable pointers.
  46
  47    Sometimes there are multiple valid vtable pointer entries that use
  48    the same vtable pointer decl with different offsets.  Therefore,
  49    for each vtable pointer in the hash table, there is also an array
  50    of offsets used with that vtable. */
  51
  52 struct vtable_registration
  53 {
  54   tree vtable_decl;            /* The var decl of the vtable.               */
  55   vec<unsigned> offsets;       /* The offsets array.                        */
  56 };
  57
  58 struct registration_hasher : typed_noop_remove <struct vtable_registration>
  59 {
  60   typedef struct vtable_registration *value_type;
  61   typedef struct vtable_registration *compare_type;
  62   static inline hashval_t hash (const vtable_registration *);
  63   static inline bool equal (const vtable_registration *,
  64                             const vtable_registration *);
  65 };
  66
  67 typedef hash_table<registration_hasher> register_table_type;
  68 typedef register_table_type::iterator registration_iterator_type;
  69
  70 /*  This struct is used to represent the class hierarchy information
  71     that we need.  Each vtable map variable has an associated class
  72     hierarchy node (struct vtv_graph_node).  Note: In this struct,
  73     'children' means immediate descendants in the class hierarchy;
  74     'descendant' means any descendant however many levels deep. */
  75
  76 struct vtv_graph_node {
  77   tree class_type;                  /* The record_type of the class.        */
  78   unsigned class_uid;               /* A unique, monotonically
  79                                        ascending id for class node.
  80                                        Each vtable map node also has
  81                                        an id.  The class uid is the
  82                                        same as the vtable map node id
  83                                        for nodes corresponding to the
  84                                        same class.                          */
  85   unsigned num_processed_children;  /* # of children for whom we have
  86                                        computed the class hierarchy
  87                                        transitive closure.                  */
  88   vec<struct vtv_graph_node *> parents;  /* Vector of parents in the graph. */
  89   vec<struct vtv_graph_node *> children; /* Vector of children in the graph.*/
  90   sbitmap descendants;              /* Bitmap representing all this node's
  91                                        descendants in the graph.            */
  92 };
  93
  94 /* This is the node used for our hashtable of vtable map variable
  95    information.  When we create a vtable map variable (var decl) we
  96    put it into one of these nodes; create a corresponding
  97    vtv_graph_node for our class hierarchy info and store that in this
  98    node; generate a unique (monotonically ascending) id for both the
  99    vtbl_map_node and the vtv_graph_node; and insert the node into two
 100    data structures (to make it easy to find in several different
 101    ways): 1). A hash table ("vtbl_map_hash" in vtable-verify.c).
 102    This gives us an easy way to check to see if we already have a node
 103    for the vtable map variable or not; and 2). An array (vector) of
 104    vtbl_map_nodes, where the array index corresponds to the unique id
 105    of the vtbl_map_node, which gives us an easy way to use bitmaps to
 106    represent and find the vtable map nodes.  */
 107
 108 struct vtbl_map_node {
 109   tree vtbl_map_decl;                 /* The var decl for the vtable map
 110                                          variable.                          */
 111   tree class_name;                    /* The DECL_ASSEMBLER_NAME of the
 112                                          class.                             */
 113   struct vtv_graph_node *class_info;  /* Our class hierarchy info for the
 114                                          class.                             */
 115   unsigned uid;                       /* The unique id for the vtable map
 116                                          variable.                          */
 117   struct vtbl_map_node *next, *prev;  /* Pointers for the linked list
 118                                          structure.                         */
 119   register_table_type *registered;     /* Hashtable of vtable pointers for which
 120                                          we have generated a _VLTRegisterPair
 121                                          call with this vtable map variable. */
 122   bool is_used;          /* Boolean indicating if we used this vtable map
 123                             variable in a call to __VLTVerifyVtablePointer. */
 124 };
 125
 126 /* Controls debugging for vtable verification.  */
 127 extern bool vtv_debug;
 128
 129 /* The global vector of vtbl_map_nodes.  */
 130 extern vec<struct vtbl_map_node *> vtbl_map_nodes_vec;
 131
 132 extern struct vtbl_map_node *vtbl_map_get_node (tree);
 133 extern struct vtbl_map_node *find_or_create_vtbl_map_node (tree);
 134 extern void vtbl_map_node_class_insert (struct vtbl_map_node *, unsigned);
 135 extern bool vtbl_map_node_registration_find (struct vtbl_map_node *,
 136                                              tree, unsigned);
 137 extern bool vtbl_map_node_registration_insert (struct vtbl_map_node *,
 138                                                tree, unsigned);
 139
 140 #endif /* VTABLE_VERIFY_H */