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