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 "alias.h"
  25 #include "predict.h"
  26 #include "basic-block.h"
  27 #include "tree.h"
  28 #include "cp-tree.h"
  29 #include "gimple.h"
  30 #include "options.h"
  31 #include "alloc-pool.h"
  32 #include "output.h"
  33 #include "toplev.h"
  34 #include "ubsan.h"
  35 #include "c-family/c-common.h"
  36 #include "c-family/c-ubsan.h"
  37 #include "asan.h"
  38 #include "internal-fn.h"
  39 #include "stor-layout.h"
  40 #include "builtins.h"
  41 #include "fold-const.h"
  42 #include "stringpool.h"
  43 #include "lto-streamer.h"
  44 #include "cgraph.h"
  45
  46 /* Test if we should instrument vptr access.  */
  47
  48 static bool
  49 cp_ubsan_instrument_vptr_p (tree type)
  50 {
  51   if (!flag_rtti || flag_sanitize_undefined_trap_on_error)
  52     return false;
  53
  54   if (current_function_decl
  55       && lookup_attribute ("no_sanitize_undefined",
  56                            DECL_ATTRIBUTES (current_function_decl)))
  57     return false;
  58
  59   if (type)
  60     {
  61       type = TYPE_MAIN_VARIANT (type);
  62       if (!CLASS_TYPE_P (type) || !CLASSTYPE_VTABLES (type))
  63         return false;
  64     }
  65
  66   return true;
  67 }
  68
  69 /* Helper function for
  70    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
  71    Instrument vptr access.  */
  72
  73 static tree
  74 cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
  75                           enum ubsan_null_ckind ckind)
  76 {
  77   type = TYPE_MAIN_VARIANT (type);
  78   const char *mangled = mangle_type_string (type);
  79   hashval_t str_hash1 = htab_hash_string (mangled);
  80   hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0);
  81   tree str_hash = wide_int_to_tree (uint64_type_node,
  82                                     wi::uhwi (((uint64_t) str_hash1 << 32)
  83                                               | str_hash2, 64));
  84   if (!is_addr)
  85     op = build_fold_addr_expr_loc (loc, op);
  86   op = save_expr (op);
  87   tree vptr = fold_build3_loc (loc, COMPONENT_REF,
  88                                TREE_TYPE (TYPE_VFIELD (type)),
  89                                build_fold_indirect_ref_loc (loc, op),
  90                                TYPE_VFIELD (type), NULL_TREE);
  91   vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
  92   vptr = fold_convert_loc (loc, uint64_type_node, vptr);
  93   if (ckind == UBSAN_DOWNCAST_POINTER)
  94     vptr = fold_build3 (COND_EXPR, uint64_type_node,
  95                         fold_build2 (NE_EXPR, boolean_type_node, op,
  96                                      build_zero_cst (TREE_TYPE (op))),
  97                         vptr, build_int_cst (uint64_type_node, 0));
  98   tree ti_decl = get_tinfo_decl (type);
  99   mark_used (ti_decl);
 100   tree ptype = build_pointer_type (type);
 101   tree call
 102     = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR,
 103                                     void_type_node, 5, op, vptr, str_hash,
 104                                     build_address (ti_decl),
 105                                     build_int_cst (ptype, ckind));
 106   TREE_SIDE_EFFECTS (call) = 1;
 107   return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
 108 }
 109
 110 /* Helper function for
 111    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
 112    Instrument vptr access if it should be instrumented, otherwise return
 113    NULL_TREE.  */
 114
 115 static tree
 116 cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type,
 117                                 bool is_addr, enum ubsan_null_ckind ckind)
 118 {
 119   if (!cp_ubsan_instrument_vptr_p (type))
 120     return NULL_TREE;
 121   return cp_ubsan_instrument_vptr (loc, op, type, is_addr, ckind);
 122 }
 123
 124 /* Instrument a member call (but not constructor call) if needed.  */
 125
 126 void
 127 cp_ubsan_maybe_instrument_member_call (tree stmt)
 128 {
 129   if (call_expr_nargs (stmt) == 0)
 130     return;
 131   tree *opp = &CALL_EXPR_ARG (stmt, 0);
 132   tree op = *opp;
 133   if (op == error_mark_node
 134       || !POINTER_TYPE_P (TREE_TYPE (op)))
 135     return;
 136   while (TREE_CODE (op) == COMPOUND_EXPR)
 137     {
 138       opp = &TREE_OPERAND (op, 1);
 139       op = *opp;
 140     }
 141   op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op,
 142                                        TREE_TYPE (TREE_TYPE (op)),
 143                                        true, UBSAN_MEMBER_CALL);
 144   if (op)
 145     *opp = op;
 146 }
 147
 148 /* Data passed to cp_ubsan_check_member_access_r.  */
 149
 150 struct cp_ubsan_check_member_access_data
 151 {
 152   hash_set<tree> *pset;
 153   bool is_addr;
 154 };
 155
 156 static tree cp_ubsan_check_member_access_r (tree *, int *, void *);
 157
 158 /* Instrument a member access.  */
 159
 160 static bool
 161 cp_ubsan_maybe_instrument_member_access
 162      (tree stmt, cp_ubsan_check_member_access_data *ucmd)
 163 {
 164   if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1)))
 165     return false;
 166
 167   tree base = TREE_OPERAND (stmt, 0);
 168   if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base)))
 169     return false;
 170
 171   cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset);
 172
 173   base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base,
 174                                    TREE_TYPE (base), false,
 175                                    UBSAN_MEMBER_ACCESS);
 176   TREE_OPERAND (stmt, 0)
 177     = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base);
 178   return true;
 179 }
 180
 181 /* Attempt to instrument member accesses inside of the function.
 182    cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs
 183    in the GENERIC IL, but only when the field is actually accessed, not
 184    merely when it's address is taken.  Therefore we track in is_addr field
 185    whether in the current context we are processing address taken
 186    handled components or not.  E.g. for &x->y[w->z] we want to call
 187    cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but
 188    not on *x.y.  */
 189
 190 static tree
 191 cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data)
 192 {
 193   tree stmt = *stmt_p, t;
 194   cp_ubsan_check_member_access_data *ucmd
 195     = (cp_ubsan_check_member_access_data *) data;
 196   switch (TREE_CODE (stmt))
 197     {
 198     case ADDR_EXPR:
 199       t = TREE_OPERAND (stmt, 0);
 200       while ((TREE_CODE (t) == MEM_REF || INDIRECT_REF_P (t))
 201              && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR)
 202         t = TREE_OPERAND (TREE_OPERAND (t, 0), 0);
 203       if (handled_component_p (t))
 204         {
 205           *walk_subtrees = 0;
 206           ucmd->is_addr = true;
 207           cp_walk_tree (&t, cp_ubsan_check_member_access_r,
 208                         data, ucmd->pset);
 209           ucmd->is_addr = false;
 210         }
 211       break;
 212     case MEM_REF:
 213     case INDIRECT_REF:
 214       t = TREE_OPERAND (stmt, 0);
 215       if (TREE_CODE (t) == ADDR_EXPR)
 216         {
 217           *walk_subtrees = 0;
 218           t = TREE_OPERAND (stmt, 0);
 219           cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset);
 220         }
 221       break;
 222     case COMPONENT_REF:
 223       if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd))
 224         {
 225           *walk_subtrees = 0;
 226           break;
 227         }
 228       /* FALLTHRU */
 229     default:
 230       if (ucmd->is_addr && handled_component_p (stmt))
 231         {
 232           int i, len = TREE_OPERAND_LENGTH (stmt);
 233           *walk_subtrees = 0;
 234           if (!handled_component_p (TREE_OPERAND (stmt, 0)))
 235             ucmd->is_addr = false;
 236           for (i = 0; i < len; i++)
 237             {
 238               cp_walk_tree (&TREE_OPERAND (stmt, i),
 239                             cp_ubsan_check_member_access_r, data, ucmd->pset);
 240               ucmd->is_addr = false;
 241             }
 242           ucmd->is_addr = true;
 243         }
 244       break;
 245     }
 246   return NULL_TREE;
 247 }
 248
 249 /* Instrument all member accesses inside GENERIC *T_P.  */
 250
 251 void
 252 cp_ubsan_instrument_member_accesses (tree *t_p)
 253 {
 254   if (cp_ubsan_instrument_vptr_p (NULL_TREE))
 255     {
 256       hash_set<tree> pset;
 257       cp_ubsan_check_member_access_data ucmd;
 258       ucmd.pset = &pset;
 259       ucmd.is_addr = false;
 260       cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset);
 261     }
 262 }
 263
 264 /* Instrument downcast.  */
 265
 266 tree
 267 cp_ubsan_maybe_instrument_downcast (location_t loc, tree type, tree op)
 268 {
 269   if (!POINTER_TYPE_P (type)
 270       || !POINTER_TYPE_P (TREE_TYPE (op))
 271       || !CLASS_TYPE_P (TREE_TYPE (type))
 272       || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
 273       || !DERIVED_FROM_P (TREE_TYPE (TREE_TYPE (op)), TREE_TYPE (type)))
 274     return NULL_TREE;
 275
 276   return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true,
 277                                          TREE_CODE (type) == POINTER_TYPE
 278                                          ? UBSAN_DOWNCAST_POINTER
 279                                          : UBSAN_DOWNCAST_REFERENCE);
 280 }
 281
 282 /* Instrument cast to virtual base.  */
 283
 284 tree
 285 cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op)
 286 {
 287   return cp_ubsan_maybe_instrument_vptr (loc, op, type, true,
 288                                          UBSAN_CAST_TO_VBASE);
 289 }