1 /* 2 * Copyright (C) 2014 Oracle. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 2 7 * of the License, or (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt 16 */ 17 18 /* 19 * This file started out by saying that if you have: 20 * 21 * struct foo one, two; 22 * ... 23 * one = two; 24 * 25 * That's equivalent to saying: 26 * 27 * one.x = two.x; 28 * one.y = two.y; 29 * 30 * Turning an assignment like that into a bunch of small fake assignments is 31 * really useful. 32 * 33 * The call to memcpy(&one, &two, sizeof(foo)); is the same as "one = two;" so 34 * we can re-use the code. And we may as well use it for memset() too. 35 * Assigning pointers is almost the same: 36 * 37 * p1 = p2; 38 * 39 * Is the same as: 40 * 41 * p1->x = p2->x; 42 * p1->y = p2->y; 43 * 44 * The problem is that you can go a bit crazy with pointers to pointers. 45 * 46 * p1->x->y->z->one->two->three = p2->x->y->z->one->two->three; 47 * 48 * I don't have a proper solution for this problem right now. I just copy one 49 * level and don't nest. It should handle limitted nesting but intelligently. 50 * 51 * The other thing is that you end up with a lot of garbage assignments where 52 * we record "x could be anything. x->y could be anything. x->y->z->a->b->c 53 * could *also* be anything!". There should be a better way to filter this 54 * useless information. 55 * 56 */ 57 58 #include "scope.h" 59 #include "smatch.h" 60 #include "smatch_slist.h" 61 #include "smatch_extra.h" 62 63 enum { 64 COPY_NORMAL, 65 COPY_MEMCPY, 66 COPY_MEMSET, 67 }; 68 69 static struct symbol *get_struct_type(struct expression *expr) 70 { 71 struct symbol *type; 72 73 type = get_type(expr); 74 if (!type) 75 return NULL; 76 if (type->type == SYM_PTR) { 77 type = get_real_base_type(type); 78 if (!type) 79 return NULL; 80 } 81 if (type->type == SYM_STRUCT) 82 return type; 83 if (type->type == SYM_UNION) 84 return type; 85 return NULL; 86 } 87 88 static struct expression *get_right_base_expr(struct symbol *left_type, struct expression *right) 89 { 90 struct symbol *struct_type; 91 92 if (!right) 93 return NULL; 94 95 struct_type = get_struct_type(right); 96 if (!struct_type) 97 return NULL; 98 if (struct_type != left_type) 99 return NULL; 100 101 if (right->type == EXPR_PREOP && right->op == '&') 102 right = strip_expr(right->unop); 103 104 if (right->type == EXPR_CALL) 105 return NULL; 106 107 if (is_pointer(right)) 108 right = deref_expression(right); 109 110 return right; 111 } 112 113 static struct expression *remove_addr(struct expression *expr) 114 { 115 struct symbol *type; 116 117 expr = strip_expr(expr); 118 if (!expr) 119 return NULL; 120 121 if (expr->type == EXPR_PREOP && expr->op == '&') 122 return strip_expr(expr->unop); 123 type = get_type(expr); 124 if (!type) 125 return expr; 126 if (type->type != SYM_PTR && type->type != SYM_ARRAY) 127 return expr; 128 129 return deref_expression(expr); 130 } 131 132 static struct expression *faked_expression; 133 struct expression *get_faked_expression(void) 134 { 135 if (!__in_fake_assign) 136 return NULL; 137 return faked_expression; 138 } 139 140 static void split_fake_expr(struct expression *expr) 141 { 142 __in_fake_assign++; 143 __in_fake_struct_assign++; 144 __split_expr(expr); 145 __in_fake_struct_assign--; 146 __in_fake_assign--; 147 } 148 149 static void handle_non_struct_assignments(struct expression *left, struct expression *right) 150 { 151 struct symbol *type; 152 struct expression *assign; 153 154 type = get_type(left); 155 if (!type) 156 return; 157 if (type->type == SYM_PTR) { 158 left = deref_expression(left); 159 if (right) 160 right = deref_expression(right); 161 else 162 right = unknown_value_expression(left); 163 assign = assign_expression(left, '=', right); 164 split_fake_expr(assign); 165 return; 166 } 167 if (type->type != SYM_BASETYPE) 168 return; 169 right = strip_expr(right); 170 type = get_type(right); 171 if (!right || !type || type->type == SYM_ARRAY) 172 right = unknown_value_expression(left); 173 assign = assign_expression(left, '=', right); 174 split_fake_expr(assign); 175 } 176 177 static void set_inner_struct_members(int mode, struct expression *faked, struct expression *left, struct expression *right, struct symbol *member) 178 { 179 struct expression *left_member; 180 struct expression *right_member = NULL; /* silence GCC */ 181 struct expression *assign; 182 struct symbol *base = get_real_base_type(member); 183 struct symbol *tmp; 184 185 if (member->ident) { 186 left = member_expression(left, '.', member->ident); 187 if (mode != COPY_MEMSET && right) 188 right = member_expression(right, '.', member->ident); 189 } 190 191 FOR_EACH_PTR(base->symbol_list, tmp) { 192 struct symbol *type; 193 194 type = get_real_base_type(tmp); 195 if (!type) 196 continue; 197 198 if (type->type == SYM_ARRAY) 199 continue; 200 if (type->type == SYM_UNION || type->type == SYM_STRUCT) { 201 set_inner_struct_members(mode, faked, left, right, tmp); 202 continue; 203 } 204 if (!tmp->ident) 205 continue; 206 207 left_member = member_expression(left, '.', tmp->ident); 208 209 switch (mode) { 210 case COPY_NORMAL: 211 case COPY_MEMCPY: 212 if (right) 213 right_member = member_expression(right, '.', tmp->ident); 214 else 215 right_member = unknown_value_expression(left_member); 216 break; 217 case COPY_MEMSET: 218 right_member = right; 219 break; 220 } 221 222 assign = assign_expression(left_member, '=', right_member); 223 split_fake_expr(assign); 224 } END_FOR_EACH_PTR(tmp); 225 } 226 227 static void __struct_members_copy(int mode, struct expression *faked, 228 struct expression *left, 229 struct expression *right) 230 { 231 struct symbol *struct_type, *tmp, *type; 232 struct expression *left_member; 233 struct expression *right_member; 234 struct expression *assign; 235 int op = '.'; 236 237 238 if (__in_fake_assign) 239 return; 240 faked_expression = faked; 241 242 left = strip_expr(left); 243 right = strip_expr(right); 244 245 struct_type = get_struct_type(left); 246 if (!struct_type) { 247 /* 248 * This is not a struct assignment obviously. But this is where 249 * memcpy() is handled so it feels like a good place to add this 250 * code. 251 */ 252 handle_non_struct_assignments(left, right); 253 goto done; 254 } 255 256 if (is_pointer(left)) { 257 left = deref_expression(left); 258 op = '*'; 259 } 260 if (mode != COPY_MEMSET) 261 right = get_right_base_expr(struct_type, right); 262 263 FOR_EACH_PTR(struct_type->symbol_list, tmp) { 264 type = get_real_base_type(tmp); 265 if (!type) 266 continue; 267 if (type->type == SYM_ARRAY) 268 continue; 269 270 if (type->type == SYM_UNION || type->type == SYM_STRUCT) { 271 set_inner_struct_members(mode, faked, left, right, tmp); 272 continue; 273 } 274 275 if (!tmp->ident) 276 continue; 277 278 left_member = member_expression(left, op, tmp->ident); 279 right_member = NULL; 280 281 switch (mode) { 282 case COPY_NORMAL: 283 case COPY_MEMCPY: 284 if (right) 285 right_member = member_expression(right, op, tmp->ident); 286 else 287 right_member = unknown_value_expression(left_member); 288 break; 289 case COPY_MEMSET: 290 right_member = right; 291 break; 292 } 293 if (!right_member) { 294 sm_perror("No right member"); 295 continue; 296 } 297 assign = assign_expression(left_member, '=', right_member); 298 split_fake_expr(assign); 299 } END_FOR_EACH_PTR(tmp); 300 301 done: 302 faked_expression = NULL; 303 } 304 305 static int returns_zeroed_mem(struct expression *expr) 306 { 307 char *fn; 308 309 if (expr->type != EXPR_CALL || expr->fn->type != EXPR_SYMBOL) 310 return 0; 311 fn = expr_to_var(expr->fn); 312 if (!fn) 313 return 0; 314 if (strcmp(fn, "kcalloc") == 0) 315 return 1; 316 if (option_project == PROJ_KERNEL && strstr(fn, "zalloc")) 317 return 1; 318 return 0; 319 } 320 321 static int copy_containter_states(struct expression *left, struct expression *right, int offset) 322 { 323 char *left_name = NULL, *right_name = NULL; 324 struct symbol *left_sym, *right_sym; 325 struct sm_state *sm, *new_sm; 326 int ret = 0; 327 int len; 328 char buf[64]; 329 char new_name[128]; 330 331 right_name = expr_to_var_sym(right, &right_sym); 332 if (!right_name || !right_sym) 333 goto free; 334 left_name = expr_to_var_sym(left, &left_sym); 335 if (!left_name || !left_sym) 336 goto free; 337 338 len = snprintf(buf, sizeof(buf), "%s(-%d)", right_name, offset); 339 if (len >= sizeof(buf)) 340 goto free; 341 342 FOR_EACH_SM(__get_cur_stree(), sm) { 343 if (sm->sym != right_sym) 344 continue; 345 if (strncmp(sm->name, buf, len) != 0) 346 continue; 347 snprintf(new_name, sizeof(new_name), "%s%s", left_name, sm->name + len); 348 new_sm = clone_sm(sm); 349 new_sm->name = alloc_sname(new_name); 350 new_sm->sym = left_sym; 351 __set_sm(new_sm); 352 ret = 1; 353 } END_FOR_EACH_SM(sm); 354 free: 355 free_string(left_name); 356 free_string(right_name); 357 return ret; 358 } 359 360 static int handle_param_offsets(struct expression *expr) 361 { 362 struct expression *right; 363 sval_t sval; 364 365 right = strip_expr(expr->right); 366 367 if (right->type != EXPR_BINOP || right->op != '-') 368 return 0; 369 370 if (!get_value(right->right, &sval)) 371 return 0; 372 373 right = get_assigned_expr(right->left); 374 if (!right) 375 return 0; 376 return copy_containter_states(expr->left, right, sval.value); 377 } 378 379 static void returns_container_of(struct expression *expr, int param, char *key, char *value) 380 { 381 struct expression *call, *arg; 382 int offset; 383 384 if (expr->type != EXPR_ASSIGNMENT || expr->op != '=') 385 return; 386 call = strip_expr(expr->right); 387 if (call->type != EXPR_CALL) 388 return; 389 if (param != -1) 390 return; 391 param = atoi(key); 392 offset = atoi(value); 393 394 arg = get_argument_from_call_expr(call->args, param); 395 if (!arg) 396 return; 397 398 copy_containter_states(expr->left, arg, -offset); 399 } 400 401 void __fake_struct_member_assignments(struct expression *expr) 402 { 403 struct symbol *left_type; 404 405 if (expr->op != '=') 406 return; 407 408 if (expr_is_zero(expr->right)) 409 return; 410 411 left_type = get_type(expr->left); 412 if (!left_type || 413 (left_type->type != SYM_PTR && 414 left_type->type != SYM_STRUCT)) 415 return; 416 417 if (handle_param_offsets(expr)) 418 return; 419 420 if (returns_zeroed_mem(expr->right)) 421 __struct_members_copy(COPY_MEMSET, expr, expr->left, zero_expr()); 422 else 423 __struct_members_copy(COPY_NORMAL, expr, expr->left, expr->right); 424 } 425 426 static void match_memset(const char *fn, struct expression *expr, void *_size_arg) 427 { 428 struct expression *buf; 429 struct expression *val; 430 431 buf = get_argument_from_call_expr(expr->args, 0); 432 val = get_argument_from_call_expr(expr->args, 1); 433 434 buf = strip_expr(buf); 435 __struct_members_copy(COPY_MEMSET, expr, remove_addr(buf), val); 436 } 437 438 static void match_memcpy(const char *fn, struct expression *expr, void *_arg) 439 { 440 struct expression *dest; 441 struct expression *src; 442 443 dest = get_argument_from_call_expr(expr->args, 0); 444 src = get_argument_from_call_expr(expr->args, 1); 445 446 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(dest), remove_addr(src)); 447 } 448 449 static void match_memdup(const char *fn, struct expression *call_expr, 450 struct expression *expr, void *_unused) 451 { 452 struct expression *left, *right, *arg; 453 454 if (!expr || expr->type != EXPR_ASSIGNMENT) 455 return; 456 457 left = strip_expr(expr->left); 458 right = strip_expr(expr->right); 459 460 if (right->type != EXPR_CALL) 461 return; 462 arg = get_argument_from_call_expr(right->args, 0); 463 __struct_members_copy(COPY_MEMCPY, expr, left, arg); 464 } 465 466 static void match_memcpy_unknown(const char *fn, struct expression *expr, void *_arg) 467 { 468 struct expression *dest; 469 470 dest = get_argument_from_call_expr(expr->args, 0); 471 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(dest), NULL); 472 } 473 474 static void match_sscanf(const char *fn, struct expression *expr, void *unused) 475 { 476 struct expression *arg; 477 int i; 478 479 i = -1; 480 FOR_EACH_PTR(expr->args, arg) { 481 if (++i < 2) 482 continue; 483 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(arg), NULL); 484 } END_FOR_EACH_PTR(arg); 485 } 486 487 static void unop_expr(struct expression *expr) 488 { 489 if (expr->op != SPECIAL_INCREMENT && 490 expr->op != SPECIAL_DECREMENT) 491 return; 492 493 if (!is_pointer(expr)) 494 return; 495 faked_expression = expr; 496 __struct_members_copy(COPY_MEMCPY, expr, expr->unop, NULL); 497 faked_expression = NULL; 498 } 499 500 static void register_clears_param(void) 501 { 502 struct token *token; 503 char name[256]; 504 const char *function; 505 int param; 506 507 if (option_project == PROJ_NONE) 508 return; 509 510 snprintf(name, 256, "%s.clears_argument", option_project_str); 511 512 token = get_tokens_file(name); 513 if (!token) 514 return; 515 if (token_type(token) != TOKEN_STREAMBEGIN) 516 return; 517 token = token->next; 518 while (token_type(token) != TOKEN_STREAMEND) { 519 if (token_type(token) != TOKEN_IDENT) 520 return; 521 function = show_ident(token->ident); 522 token = token->next; 523 if (token_type(token) != TOKEN_NUMBER) 524 return; 525 param = atoi(token->number); 526 add_function_hook(function, &match_memcpy_unknown, INT_PTR(param)); 527 token = token->next; 528 } 529 clear_token_alloc(); 530 } 531 532 static void db_param_cleared(struct expression *expr, int param, char *key, char *value) 533 { 534 struct expression *arg; 535 536 while (expr->type == EXPR_ASSIGNMENT) 537 expr = strip_expr(expr->right); 538 if (expr->type != EXPR_CALL) 539 return; 540 541 /* 542 * FIXME: __struct_members_copy() requires an expression but 543 * get_variable_from_key() returns a name/sym pair so that doesn't 544 * work here. 545 */ 546 if (strcmp(key, "$") != 0) 547 return; 548 549 arg = get_argument_from_call_expr(expr->args, param); 550 if (!arg) 551 return; 552 553 if (strcmp(value, "0") == 0) 554 __struct_members_copy(COPY_MEMSET, expr, remove_addr(arg), zero_expr()); 555 else 556 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(arg), NULL); 557 } 558 559 void register_struct_assignment(int id) 560 { 561 add_function_hook("memset", &match_memset, NULL); 562 add_function_hook("__memset", &match_memset, NULL); 563 564 add_function_hook("memcpy", &match_memcpy, INT_PTR(0)); 565 add_function_hook("memmove", &match_memcpy, INT_PTR(0)); 566 add_function_hook("__memcpy", &match_memcpy, INT_PTR(0)); 567 add_function_hook("__memmove", &match_memcpy, INT_PTR(0)); 568 569 if (option_project == PROJ_KERNEL) 570 return_implies_state_sval("kmemdup", valid_ptr_min_sval, valid_ptr_max_sval, &match_memdup, NULL); 571 572 add_function_hook("sscanf", &match_sscanf, NULL); 573 574 add_hook(&unop_expr, OP_HOOK); 575 register_clears_param(); 576 select_return_states_hook(PARAM_CLEARED, &db_param_cleared); 577 578 select_return_states_hook(CONTAINER, &returns_container_of); 579 } 580