gcc/cp/cp-ubsan.c

   1 /* UndefinedBehaviorSanitizer, undefined behavior detector.
   2    Copyright (C) 2014 Free Software Foundation, Inc.
   3    Contributed by Jakub Jelinek <jakub@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "input.h"
  25 #include "alias.h"
  26 #include "symtab.h"
  27 #include "options.h"
  28 #include "tree.h"
  29 #include "alloc-pool.h"
  30 #include "output.h"
  31 #include "toplev.h"
  32 #include "ubsan.h"
  33 #include "cp-tree.h"
  34 #include "c-family/c-common.h"
  35 #include "c-family/c-ubsan.h"
  36 #include "asan.h"
  37 #include "internal-fn.h"
  38 #include "stor-layout.h"
  39 #include "builtins.h"
  40 #include "fold-const.h"
  41 #include "stringpool.h"
  42 #include "is-a.h"
  43 #include "predict.h"
  44 #include "tree-ssa-alias.h"
  45 #include "basic-block.h"
  46 #include "gimple-expr.h"
  47 #include "gimple.h"
  48 #include "ipa-ref.h"
  49 #include "lto-streamer.h"
  50 #include "cgraph.h"
  51
  52 /* Test if we should instrument vptr access.  */
  53
  54 static bool
  55 cp_ubsan_instrument_vptr_p (tree type)
  56 {
  57   if (!flag_rtti || flag_sanitize_undefined_trap_on_error)
  58     return false;
  59
  60   if (current_function_decl
  61       && lookup_attribute ("no_sanitize_undefined",
  62                            DECL_ATTRIBUTES (current_function_decl)))
  63     return false;
  64
  65   if (type)
  66     {
  67       type = TYPE_MAIN_VARIANT (type);
  68       if (!CLASS_TYPE_P (type) || !CLASSTYPE_VTABLES (type))
  69         return false;
  70     }
  71
  72   return true;
  73 }
  74
  75 /* Helper function for
  76    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
  77    Instrument vptr access.  */
  78
  79 static tree
  80 cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
  81                           enum ubsan_null_ckind ckind)
  82 {
  83   type = TYPE_MAIN_VARIANT (type);
  84   const char *mangled = mangle_type_string (type);
  85   hashval_t str_hash1 = htab_hash_string (mangled);
  86   hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0);
  87   tree str_hash = wide_int_to_tree (uint64_type_node,
  88                                     wi::uhwi (((uint64_t) str_hash1 << 32)
  89                                               | str_hash2, 64));
  90   if (!is_addr)
  91     op = build_fold_addr_expr_loc (loc, op);
  92   op = save_expr (op);
  93   tree vptr = fold_build3_loc (loc, COMPONENT_REF,
  94                                TREE_TYPE (TYPE_VFIELD (type)),
  95                                build_fold_indirect_ref_loc (loc, op),
  96                                TYPE_VFIELD (type), NULL_TREE);
  97   vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
  98   vptr = fold_convert_loc (loc, uint64_type_node, vptr);
  99   if (ckind == UBSAN_DOWNCAST_POINTER)
 100     vptr = fold_build3 (COND_EXPR, uint64_type_node,
 101                         fold_build2 (NE_EXPR, boolean_type_node, op,
 102                                      build_zero_cst (TREE_TYPE (op))),
 103                         vptr, build_int_cst (uint64_type_node, 0));
 104   tree ti_decl = get_tinfo_decl (type);
 105   mark_used (ti_decl);
 106   tree ptype = build_pointer_type (type);
 107   tree call
 108     = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR,
 109                                     void_type_node, 5, op, vptr, str_hash,
 110                                     build_address (ti_decl),
 111                                     build_int_cst (ptype, ckind));
 112   TREE_SIDE_EFFECTS (call) = 1;
 113   return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
 114 }
 115
 116 /* Helper function for
 117    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
 118    Instrument vptr access if it should be instrumented, otherwise return
 119    NULL_TREE.  */
 120
 121 static tree
 122 cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type,
 123                                 bool is_addr, enum ubsan_null_ckind ckind)
 124 {
 125   if (!cp_ubsan_instrument_vptr_p (type))
 126     return NULL_TREE;
 127   return cp_ubsan_instrument_vptr (loc, op, type, is_addr, ckind);
 128 }
 129
 130 /* Instrument a member call (but not constructor call) if needed.  */
 131
 132 void
 133 cp_ubsan_maybe_instrument_member_call (tree stmt)
 134 {
 135   if (call_expr_nargs (stmt) == 0)
 136     return;
 137   tree *opp = &CALL_EXPR_ARG (stmt, 0);
 138   tree op = *opp;
 139   if (op == error_mark_node
 140       || !POINTER_TYPE_P (TREE_TYPE (op)))
 141     return;
 142   while (TREE_CODE (op) == COMPOUND_EXPR)
 143     {
 144       opp = &TREE_OPERAND (op, 1);
 145       op = *opp;
 146     }
 147   op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op,
 148                                        TREE_TYPE (TREE_TYPE (op)),
 149                                        true, UBSAN_MEMBER_CALL);
 150   if (op)
 151     *opp = op;
 152 }
 153
 154 /* Data passed to cp_ubsan_check_member_access_r.  */
 155
 156 struct cp_ubsan_check_member_access_data
 157 {
 158   hash_set<tree> *pset;
 159   bool is_addr;
 160 };
 161
 162 static tree cp_ubsan_check_member_access_r (tree *, int *, void *);
 163
 164 /* Instrument a member access.  */
 165
 166 static bool
 167 cp_ubsan_maybe_instrument_member_access
 168      (tree stmt, cp_ubsan_check_member_access_data *ucmd)
 169 {
 170   if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1)))
 171     return false;
 172
 173   tree base = TREE_OPERAND (stmt, 0);
 174   if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base)))
 175     return false;
 176
 177   cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset);
 178
 179   base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base,
 180                                    TREE_TYPE (base), false,
 181                                    UBSAN_MEMBER_ACCESS);
 182   TREE_OPERAND (stmt, 0)
 183     = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base);
 184   return true;
 185 }
 186
 187 /* Attempt to instrument member accesses inside of the function.
 188    cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs
 189    in the GENERIC IL, but only when the field is actually accessed, not
 190    merely when it's address is taken.  Therefore we track in is_addr field
 191    whether in the current context we are processing address taken
 192    handled components or not.  E.g. for &x->y[w->z] we want to call
 193    cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but
 194    not on *x.y.  */
 195
 196 static tree
 197 cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data)
 198 {
 199   tree stmt = *stmt_p, t;
 200   cp_ubsan_check_member_access_data *ucmd
 201     = (cp_ubsan_check_member_access_data *) data;
 202   switch (TREE_CODE (stmt))
 203     {
 204     case ADDR_EXPR:
 205       t = TREE_OPERAND (stmt, 0);
 206       while ((TREE_CODE (t) == MEM_REF || TREE_CODE (t) == INDIRECT_REF)
 207              && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR)
 208         t = TREE_OPERAND (TREE_OPERAND (t, 0), 0);
 209       if (handled_component_p (t))
 210         {
 211           *walk_subtrees = 0;
 212           ucmd->is_addr = true;
 213           cp_walk_tree (&t, cp_ubsan_check_member_access_r,
 214                         data, ucmd->pset);
 215           ucmd->is_addr = false;
 216         }
 217       break;
 218     case MEM_REF:
 219     case INDIRECT_REF:
 220       t = TREE_OPERAND (stmt, 0);
 221       if (TREE_CODE (t) == ADDR_EXPR)
 222         {
 223           *walk_subtrees = 0;
 224           t = TREE_OPERAND (stmt, 0);
 225           cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset);
 226         }
 227       break;
 228     case COMPONENT_REF:
 229       if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd))
 230         {
 231           *walk_subtrees = 0;
 232           break;
 233         }
 234       /* FALLTHRU */
 235     default:
 236       if (ucmd->is_addr && handled_component_p (stmt))
 237         {
 238           int i, len = TREE_OPERAND_LENGTH (stmt);
 239           *walk_subtrees = 0;
 240           if (!handled_component_p (TREE_OPERAND (stmt, 0)))
 241             ucmd->is_addr = false;
 242           for (i = 0; i < len; i++)
 243             {
 244               cp_walk_tree (&TREE_OPERAND (stmt, i),
 245                             cp_ubsan_check_member_access_r, data, ucmd->pset);
 246               ucmd->is_addr = false;
 247             }
 248           ucmd->is_addr = true;
 249         }
 250       break;
 251     }
 252   return NULL_TREE;
 253 }
 254
 255 /* Instrument all member accesses inside GENERIC *T_P.  */
 256
 257 void
 258 cp_ubsan_instrument_member_accesses (tree *t_p)
 259 {
 260   if (cp_ubsan_instrument_vptr_p (NULL_TREE))
 261     {
 262       hash_set<tree> pset;
 263       cp_ubsan_check_member_access_data ucmd;
 264       ucmd.pset = &pset;
 265       ucmd.is_addr = false;
 266       cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset);
 267     }
 268 }
 269
 270 /* Instrument downcast.  */
 271
 272 tree
 273 cp_ubsan_maybe_instrument_downcast (location_t loc, tree type, tree op)
 274 {
 275   if (!POINTER_TYPE_P (type)
 276       || !POINTER_TYPE_P (TREE_TYPE (op))
 277       || !CLASS_TYPE_P (TREE_TYPE (type))
 278       || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
 279       || !DERIVED_FROM_P (TREE_TYPE (TREE_TYPE (op)), TREE_TYPE (type)))
 280     return NULL_TREE;
 281
 282   return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true,
 283                                          TREE_CODE (type) == POINTER_TYPE
 284                                          ? UBSAN_DOWNCAST_POINTER
 285                                          : UBSAN_DOWNCAST_REFERENCE);
 286 }
 287
 288 /* Instrument cast to virtual base.  */
 289
 290 tree
 291 cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op)
 292 {
 293   return cp_ubsan_maybe_instrument_vptr (loc, op, type, true,
 294                                          UBSAN_CAST_TO_VBASE);
 295 }