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 "symtab.h"
  26 #include "options.h"
  27 #include "tree.h"
  28 #include "alloc-pool.h"
  29 #include "output.h"
  30 #include "toplev.h"
  31 #include "ubsan.h"
  32 #include "cp-tree.h"
  33 #include "c-family/c-common.h"
  34 #include "c-family/c-ubsan.h"
  35 #include "asan.h"
  36 #include "internal-fn.h"
  37 #include "stor-layout.h"
  38 #include "builtins.h"
  39 #include "fold-const.h"
  40 #include "stringpool.h"
  41 #include "predict.h"
  42 #include "tree-ssa-alias.h"
  43 #include "basic-block.h"
  44 #include "gimple-expr.h"
  45 #include "gimple.h"
  46 #include "lto-streamer.h"
  47 #include "cgraph.h"
  48
  49 /* Test if we should instrument vptr access.  */
  50
  51 static bool
  52 cp_ubsan_instrument_vptr_p (tree type)
  53 {
  54   if (!flag_rtti || flag_sanitize_undefined_trap_on_error)
  55     return false;
  56
  57   if (current_function_decl
  58       && lookup_attribute ("no_sanitize_undefined",
  59                            DECL_ATTRIBUTES (current_function_decl)))
  60     return false;
  61
  62   if (type)
  63     {
  64       type = TYPE_MAIN_VARIANT (type);
  65       if (!CLASS_TYPE_P (type) || !CLASSTYPE_VTABLES (type))
  66         return false;
  67     }
  68
  69   return true;
  70 }
  71
  72 /* Helper function for
  73    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
  74    Instrument vptr access.  */
  75
  76 static tree
  77 cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr,
  78                           enum ubsan_null_ckind ckind)
  79 {
  80   type = TYPE_MAIN_VARIANT (type);
  81   const char *mangled = mangle_type_string (type);
  82   hashval_t str_hash1 = htab_hash_string (mangled);
  83   hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0);
  84   tree str_hash = wide_int_to_tree (uint64_type_node,
  85                                     wi::uhwi (((uint64_t) str_hash1 << 32)
  86                                               | str_hash2, 64));
  87   if (!is_addr)
  88     op = build_fold_addr_expr_loc (loc, op);
  89   op = save_expr (op);
  90   tree vptr = fold_build3_loc (loc, COMPONENT_REF,
  91                                TREE_TYPE (TYPE_VFIELD (type)),
  92                                build_fold_indirect_ref_loc (loc, op),
  93                                TYPE_VFIELD (type), NULL_TREE);
  94   vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr);
  95   vptr = fold_convert_loc (loc, uint64_type_node, vptr);
  96   if (ckind == UBSAN_DOWNCAST_POINTER)
  97     vptr = fold_build3 (COND_EXPR, uint64_type_node,
  98                         fold_build2 (NE_EXPR, boolean_type_node, op,
  99                                      build_zero_cst (TREE_TYPE (op))),
 100                         vptr, build_int_cst (uint64_type_node, 0));
 101   tree ti_decl = get_tinfo_decl (type);
 102   mark_used (ti_decl);
 103   tree ptype = build_pointer_type (type);
 104   tree call
 105     = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR,
 106                                     void_type_node, 5, op, vptr, str_hash,
 107                                     build_address (ti_decl),
 108                                     build_int_cst (ptype, ckind));
 109   TREE_SIDE_EFFECTS (call) = 1;
 110   return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op);
 111 }
 112
 113 /* Helper function for
 114    cp_ubsan_maybe_instrument_{member_{call,access},downcast}.
 115    Instrument vptr access if it should be instrumented, otherwise return
 116    NULL_TREE.  */
 117
 118 static tree
 119 cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type,
 120                                 bool is_addr, enum ubsan_null_ckind ckind)
 121 {
 122   if (!cp_ubsan_instrument_vptr_p (type))
 123     return NULL_TREE;
 124   return cp_ubsan_instrument_vptr (loc, op, type, is_addr, ckind);
 125 }
 126
 127 /* Instrument a member call (but not constructor call) if needed.  */
 128
 129 void
 130 cp_ubsan_maybe_instrument_member_call (tree stmt)
 131 {
 132   if (call_expr_nargs (stmt) == 0)
 133     return;
 134   tree *opp = &CALL_EXPR_ARG (stmt, 0);
 135   tree op = *opp;
 136   if (op == error_mark_node
 137       || !POINTER_TYPE_P (TREE_TYPE (op)))
 138     return;
 139   while (TREE_CODE (op) == COMPOUND_EXPR)
 140     {
 141       opp = &TREE_OPERAND (op, 1);
 142       op = *opp;
 143     }
 144   op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op,
 145                                        TREE_TYPE (TREE_TYPE (op)),
 146                                        true, UBSAN_MEMBER_CALL);
 147   if (op)
 148     *opp = op;
 149 }
 150
 151 /* Data passed to cp_ubsan_check_member_access_r.  */
 152
 153 struct cp_ubsan_check_member_access_data
 154 {
 155   hash_set<tree> *pset;
 156   bool is_addr;
 157 };
 158
 159 static tree cp_ubsan_check_member_access_r (tree *, int *, void *);
 160
 161 /* Instrument a member access.  */
 162
 163 static bool
 164 cp_ubsan_maybe_instrument_member_access
 165      (tree stmt, cp_ubsan_check_member_access_data *ucmd)
 166 {
 167   if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1)))
 168     return false;
 169
 170   tree base = TREE_OPERAND (stmt, 0);
 171   if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base)))
 172     return false;
 173
 174   cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset);
 175
 176   base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base,
 177                                    TREE_TYPE (base), false,
 178                                    UBSAN_MEMBER_ACCESS);
 179   TREE_OPERAND (stmt, 0)
 180     = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base);
 181   return true;
 182 }
 183
 184 /* Attempt to instrument member accesses inside of the function.
 185    cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs
 186    in the GENERIC IL, but only when the field is actually accessed, not
 187    merely when it's address is taken.  Therefore we track in is_addr field
 188    whether in the current context we are processing address taken
 189    handled components or not.  E.g. for &x->y[w->z] we want to call
 190    cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but
 191    not on *x.y.  */
 192
 193 static tree
 194 cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data)
 195 {
 196   tree stmt = *stmt_p, t;
 197   cp_ubsan_check_member_access_data *ucmd
 198     = (cp_ubsan_check_member_access_data *) data;
 199   switch (TREE_CODE (stmt))
 200     {
 201     case ADDR_EXPR:
 202       t = TREE_OPERAND (stmt, 0);
 203       while ((TREE_CODE (t) == MEM_REF || INDIRECT_REF_P (t))
 204              && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR)
 205         t = TREE_OPERAND (TREE_OPERAND (t, 0), 0);
 206       if (handled_component_p (t))
 207         {
 208           *walk_subtrees = 0;
 209           ucmd->is_addr = true;
 210           cp_walk_tree (&t, cp_ubsan_check_member_access_r,
 211                         data, ucmd->pset);
 212           ucmd->is_addr = false;
 213         }
 214       break;
 215     case MEM_REF:
 216     case INDIRECT_REF:
 217       t = TREE_OPERAND (stmt, 0);
 218       if (TREE_CODE (t) == ADDR_EXPR)
 219         {
 220           *walk_subtrees = 0;
 221           t = TREE_OPERAND (stmt, 0);
 222           cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset);
 223         }
 224       break;
 225     case COMPONENT_REF:
 226       if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd))
 227         {
 228           *walk_subtrees = 0;
 229           break;
 230         }
 231       /* FALLTHRU */
 232     default:
 233       if (ucmd->is_addr && handled_component_p (stmt))
 234         {
 235           int i, len = TREE_OPERAND_LENGTH (stmt);
 236           *walk_subtrees = 0;
 237           if (!handled_component_p (TREE_OPERAND (stmt, 0)))
 238             ucmd->is_addr = false;
 239           for (i = 0; i < len; i++)
 240             {
 241               cp_walk_tree (&TREE_OPERAND (stmt, i),
 242                             cp_ubsan_check_member_access_r, data, ucmd->pset);
 243               ucmd->is_addr = false;
 244             }
 245           ucmd->is_addr = true;
 246         }
 247       break;
 248     }
 249   return NULL_TREE;
 250 }
 251
 252 /* Instrument all member accesses inside GENERIC *T_P.  */
 253
 254 void
 255 cp_ubsan_instrument_member_accesses (tree *t_p)
 256 {
 257   if (cp_ubsan_instrument_vptr_p (NULL_TREE))
 258     {
 259       hash_set<tree> pset;
 260       cp_ubsan_check_member_access_data ucmd;
 261       ucmd.pset = &pset;
 262       ucmd.is_addr = false;
 263       cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset);
 264     }
 265 }
 266
 267 /* Instrument downcast.  */
 268
 269 tree
 270 cp_ubsan_maybe_instrument_downcast (location_t loc, tree type, tree op)
 271 {
 272   if (!POINTER_TYPE_P (type)
 273       || !POINTER_TYPE_P (TREE_TYPE (op))
 274       || !CLASS_TYPE_P (TREE_TYPE (type))
 275       || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op)))
 276       || !DERIVED_FROM_P (TREE_TYPE (TREE_TYPE (op)), TREE_TYPE (type)))
 277     return NULL_TREE;
 278
 279   return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true,
 280                                          TREE_CODE (type) == POINTER_TYPE
 281                                          ? UBSAN_DOWNCAST_POINTER
 282                                          : UBSAN_DOWNCAST_REFERENCE);
 283 }
 284
 285 /* Instrument cast to virtual base.  */
 286
 287 tree
 288 cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op)
 289 {
 290   return cp_ubsan_maybe_instrument_vptr (loc, op, type, true,
 291                                          UBSAN_CAST_TO_VBASE);
 292 }