gcc/vtable-verify.h

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