1 /* UndefinedBehaviorSanitizer, undefined behavior detector. 2 Copyright (C) 2014-2018 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 "cp-tree.h" 25 #include "ubsan.h" 26 #include "stringpool.h" 27 #include "attribs.h" 28 #include "asan.h" 29 30 /* Test if we should instrument vptr access. */ 31 32 static bool 33 cp_ubsan_instrument_vptr_p (tree type) 34 { 35 if (!flag_rtti || flag_sanitize_undefined_trap_on_error) 36 return false; 37 38 if (!sanitize_flags_p (SANITIZE_VPTR)) 39 return false; 40 41 if (current_function_decl == NULL_TREE) 42 return false; 43 44 if (type) 45 { 46 type = TYPE_MAIN_VARIANT (type); 47 if (!CLASS_TYPE_P (type) || !CLASSTYPE_VTABLES (type)) 48 return false; 49 } 50 51 return true; 52 } 53 54 /* Helper function for 55 cp_ubsan_maybe_instrument_{member_{call,access},downcast}. 56 Instrument vptr access. */ 57 58 static tree 59 cp_ubsan_instrument_vptr (location_t loc, tree op, tree type, bool is_addr, 60 enum ubsan_null_ckind ckind) 61 { 62 type = TYPE_MAIN_VARIANT (type); 63 const char *mangled = mangle_type_string (type); 64 hashval_t str_hash1 = htab_hash_string (mangled); 65 hashval_t str_hash2 = iterative_hash (mangled, strlen (mangled), 0); 66 tree str_hash = wide_int_to_tree (uint64_type_node, 67 wi::uhwi (((uint64_t) str_hash1 << 32) 68 | str_hash2, 64)); 69 if (!is_addr) 70 op = build_fold_addr_expr_loc (loc, op); 71 op = save_expr (op); 72 tree vptr = fold_build3_loc (loc, COMPONENT_REF, 73 TREE_TYPE (TYPE_VFIELD (type)), 74 build_fold_indirect_ref_loc (loc, op), 75 TYPE_VFIELD (type), NULL_TREE); 76 vptr = fold_convert_loc (loc, pointer_sized_int_node, vptr); 77 vptr = fold_convert_loc (loc, uint64_type_node, vptr); 78 if (ckind == UBSAN_DOWNCAST_POINTER) 79 { 80 tree cond = build2_loc (loc, NE_EXPR, boolean_type_node, op, 81 build_zero_cst (TREE_TYPE (op))); 82 /* This is a compiler generated comparison, don't emit 83 e.g. -Wnonnull-compare warning for it. */ 84 TREE_NO_WARNING (cond) = 1; 85 vptr = build3_loc (loc, COND_EXPR, uint64_type_node, cond, 86 vptr, build_int_cst (uint64_type_node, 0)); 87 } 88 tree ti_decl = get_tinfo_decl (type); 89 mark_used (ti_decl); 90 tree ptype = build_pointer_type (type); 91 tree call 92 = build_call_expr_internal_loc (loc, IFN_UBSAN_VPTR, 93 void_type_node, 5, op, vptr, str_hash, 94 build_address (ti_decl), 95 build_int_cst (ptype, ckind)); 96 TREE_SIDE_EFFECTS (call) = 1; 97 return fold_build2 (COMPOUND_EXPR, TREE_TYPE (op), call, op); 98 } 99 100 /* Helper function for 101 cp_ubsan_maybe_instrument_{member_{call,access},downcast}. 102 Instrument vptr access if it should be instrumented, otherwise return 103 NULL_TREE. */ 104 105 static tree 106 cp_ubsan_maybe_instrument_vptr (location_t loc, tree op, tree type, 107 bool is_addr, enum ubsan_null_ckind ckind) 108 { 109 if (!cp_ubsan_instrument_vptr_p (type)) 110 return NULL_TREE; 111 return cp_ubsan_instrument_vptr (loc, op, type, is_addr, ckind); 112 } 113 114 /* Instrument a member call (but not constructor call) if needed. */ 115 116 void 117 cp_ubsan_maybe_instrument_member_call (tree stmt) 118 { 119 if (call_expr_nargs (stmt) == 0) 120 return; 121 tree *opp = &CALL_EXPR_ARG (stmt, 0); 122 tree op = *opp; 123 if (op == error_mark_node 124 || !POINTER_TYPE_P (TREE_TYPE (op))) 125 return; 126 while (TREE_CODE (op) == COMPOUND_EXPR) 127 { 128 opp = &TREE_OPERAND (op, 1); 129 op = *opp; 130 } 131 op = cp_ubsan_maybe_instrument_vptr (EXPR_LOCATION (stmt), op, 132 TREE_TYPE (TREE_TYPE (op)), 133 true, UBSAN_MEMBER_CALL); 134 if (op) 135 *opp = op; 136 } 137 138 /* Data passed to cp_ubsan_check_member_access_r. */ 139 140 struct cp_ubsan_check_member_access_data 141 { 142 hash_set<tree> *pset; 143 bool is_addr; 144 }; 145 146 static tree cp_ubsan_check_member_access_r (tree *, int *, void *); 147 148 /* Instrument a member access. */ 149 150 static bool 151 cp_ubsan_maybe_instrument_member_access 152 (tree stmt, cp_ubsan_check_member_access_data *ucmd) 153 { 154 if (DECL_ARTIFICIAL (TREE_OPERAND (stmt, 1))) 155 return false; 156 157 tree base = TREE_OPERAND (stmt, 0); 158 if (!cp_ubsan_instrument_vptr_p (TREE_TYPE (base))) 159 return false; 160 161 cp_walk_tree (&base, cp_ubsan_check_member_access_r, ucmd, ucmd->pset); 162 163 base = cp_ubsan_instrument_vptr (EXPR_LOCATION (stmt), base, 164 TREE_TYPE (base), false, 165 UBSAN_MEMBER_ACCESS); 166 TREE_OPERAND (stmt, 0) 167 = build_fold_indirect_ref_loc (EXPR_LOCATION (stmt), base); 168 return true; 169 } 170 171 /* Attempt to instrument member accesses inside of the function. 172 cp_ubsan_maybe_instrument_member_access should be called on COMPONENT_REFs 173 in the GENERIC IL, but only when the field is actually accessed, not 174 merely when it's address is taken. Therefore we track in is_addr field 175 whether in the current context we are processing address taken 176 handled components or not. E.g. for &x->y[w->z] we want to call 177 cp_ubsan_maybe_instrument_member_access on *w.z COMPONENT_REF, but 178 not on *x.y. */ 179 180 static tree 181 cp_ubsan_check_member_access_r (tree *stmt_p, int *walk_subtrees, void *data) 182 { 183 tree stmt = *stmt_p, t; 184 cp_ubsan_check_member_access_data *ucmd 185 = (cp_ubsan_check_member_access_data *) data; 186 switch (TREE_CODE (stmt)) 187 { 188 case ADDR_EXPR: 189 t = TREE_OPERAND (stmt, 0); 190 while ((TREE_CODE (t) == MEM_REF || INDIRECT_REF_P (t)) 191 && TREE_CODE (TREE_OPERAND (t, 0)) == ADDR_EXPR) 192 t = TREE_OPERAND (TREE_OPERAND (t, 0), 0); 193 if (handled_component_p (t)) 194 { 195 *walk_subtrees = 0; 196 ucmd->is_addr = true; 197 cp_walk_tree (&t, cp_ubsan_check_member_access_r, 198 data, ucmd->pset); 199 ucmd->is_addr = false; 200 } 201 break; 202 case MEM_REF: 203 case INDIRECT_REF: 204 t = TREE_OPERAND (stmt, 0); 205 if (TREE_CODE (t) == ADDR_EXPR) 206 { 207 *walk_subtrees = 0; 208 t = TREE_OPERAND (t, 0); 209 cp_walk_tree (&t, cp_ubsan_check_member_access_r, data, ucmd->pset); 210 } 211 break; 212 case COMPONENT_REF: 213 if (!ucmd->is_addr && cp_ubsan_maybe_instrument_member_access (stmt, ucmd)) 214 { 215 *walk_subtrees = 0; 216 break; 217 } 218 /* FALLTHRU */ 219 default: 220 if (ucmd->is_addr && handled_component_p (stmt)) 221 { 222 int i, len = TREE_OPERAND_LENGTH (stmt); 223 *walk_subtrees = 0; 224 if (!handled_component_p (TREE_OPERAND (stmt, 0))) 225 ucmd->is_addr = false; 226 for (i = 0; i < len; i++) 227 { 228 cp_walk_tree (&TREE_OPERAND (stmt, i), 229 cp_ubsan_check_member_access_r, data, ucmd->pset); 230 ucmd->is_addr = false; 231 } 232 ucmd->is_addr = true; 233 } 234 break; 235 } 236 return NULL_TREE; 237 } 238 239 /* Instrument all member accesses inside GENERIC *T_P. */ 240 241 void 242 cp_ubsan_instrument_member_accesses (tree *t_p) 243 { 244 if (cp_ubsan_instrument_vptr_p (NULL_TREE)) 245 { 246 hash_set<tree> pset; 247 cp_ubsan_check_member_access_data ucmd; 248 ucmd.pset = &pset; 249 ucmd.is_addr = false; 250 cp_walk_tree (t_p, cp_ubsan_check_member_access_r, &ucmd, &pset); 251 } 252 } 253 254 /* Instrument downcast. */ 255 256 tree 257 cp_ubsan_maybe_instrument_downcast (location_t loc, tree type, 258 tree intype, tree op) 259 { 260 if (!POINTER_TYPE_P (type) 261 || !POINTER_TYPE_P (intype) 262 || !POINTER_TYPE_P (TREE_TYPE (op)) 263 || !CLASS_TYPE_P (TREE_TYPE (TREE_TYPE (op))) 264 || !is_properly_derived_from (TREE_TYPE (type), TREE_TYPE (intype))) 265 return NULL_TREE; 266 267 return cp_ubsan_maybe_instrument_vptr (loc, op, TREE_TYPE (type), true, 268 TREE_CODE (type) == POINTER_TYPE 269 ? UBSAN_DOWNCAST_POINTER 270 : UBSAN_DOWNCAST_REFERENCE); 271 } 272 273 /* Instrument cast to virtual base. */ 274 275 tree 276 cp_ubsan_maybe_instrument_cast_to_vbase (location_t loc, tree type, tree op) 277 { 278 return cp_ubsan_maybe_instrument_vptr (loc, op, type, true, 279 UBSAN_CAST_TO_VBASE); 280 } 281 282 /* Called from initialize_vtbl_ptrs via dfs_walk. BINFO is the base 283 which we want to initialize the vtable pointer for, DATA is 284 TREE_LIST whose TREE_VALUE is the this ptr expression. */ 285 286 static tree 287 cp_ubsan_dfs_initialize_vtbl_ptrs (tree binfo, void *data) 288 { 289 if (!TYPE_CONTAINS_VPTR_P (BINFO_TYPE (binfo))) 290 return dfs_skip_bases; 291 292 if (!BINFO_PRIMARY_P (binfo)) 293 { 294 tree base_ptr = TREE_VALUE ((tree) data); 295 296 base_ptr = build_base_path (PLUS_EXPR, base_ptr, binfo, /*nonnull=*/1, 297 tf_warning_or_error); 298 299 /* Compute the location of the vtpr. */ 300 tree vtbl_ptr 301 = build_vfield_ref (cp_build_fold_indirect_ref (base_ptr), 302 TREE_TYPE (binfo)); 303 gcc_assert (vtbl_ptr != error_mark_node); 304 305 /* Assign NULL to the vptr. */ 306 tree vtbl = build_zero_cst (TREE_TYPE (vtbl_ptr)); 307 tree stmt = cp_build_modify_expr (input_location, vtbl_ptr, NOP_EXPR, 308 vtbl, tf_warning_or_error); 309 if (vptr_via_virtual_p (binfo)) 310 /* If this vptr comes from a virtual base of the complete object, only 311 clear it if we're in charge of virtual bases. */ 312 stmt = build_if_in_charge (stmt); 313 finish_expr_stmt (stmt); 314 } 315 316 return NULL_TREE; 317 } 318 319 /* Initialize all the vtable pointers in the object pointed to by 320 ADDR to NULL, so that we catch invalid calls to methods before 321 mem-initializers are completed. */ 322 323 void 324 cp_ubsan_maybe_initialize_vtbl_ptrs (tree addr) 325 { 326 if (!cp_ubsan_instrument_vptr_p (NULL_TREE)) 327 return; 328 329 tree type = TREE_TYPE (TREE_TYPE (addr)); 330 tree list = build_tree_list (type, addr); 331 /* We cannot rely on the vtable being set up. We have to indirect via the 332 vtt_parm. */ 333 int save_in_base_initializer = in_base_initializer; 334 in_base_initializer = 1; 335 336 /* Walk through the hierarchy, initializing the vptr in each base 337 class to NULL. */ 338 dfs_walk_once (TYPE_BINFO (type), cp_ubsan_dfs_initialize_vtbl_ptrs, 339 NULL, list); 340 341 in_base_initializer = save_in_base_initializer; 342 } 343