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 if (!right) 171 right = unknown_value_expression(left); 172 assign = assign_expression(left, '=', right); 173 split_fake_expr(assign); 174 } 175 176 static void set_inner_struct_members(int mode, struct expression *faked, struct expression *left, struct expression *right, struct symbol *member) 177 { 178 struct expression *left_member; 179 struct expression *right_member = NULL; /* silence GCC */ 180 struct expression *assign; 181 struct symbol *base = get_real_base_type(member); 182 struct symbol *tmp; 183 184 if (member->ident) { 185 left = member_expression(left, '.', member->ident); 186 if (mode != COPY_MEMSET && right) 187 right = member_expression(right, '.', member->ident); 188 } 189 190 FOR_EACH_PTR(base->symbol_list, tmp) { 191 struct symbol *type; 192 193 type = get_real_base_type(tmp); 194 if (!type) 195 continue; 196 197 if (type->type == SYM_ARRAY) 198 continue; 199 if (type->type == SYM_UNION || type->type == SYM_STRUCT) { 200 set_inner_struct_members(mode, faked, left, right, tmp); 201 continue; 202 } 203 if (!tmp->ident) 204 continue; 205 206 left_member = member_expression(left, '.', tmp->ident); 207 208 switch (mode) { 209 case COPY_NORMAL: 210 case COPY_MEMCPY: 211 if (right) 212 right_member = member_expression(right, '.', tmp->ident); 213 else 214 right_member = unknown_value_expression(left_member); 215 break; 216 case COPY_MEMSET: 217 right_member = right; 218 break; 219 } 220 221 assign = assign_expression(left_member, '=', right_member); 222 split_fake_expr(assign); 223 } END_FOR_EACH_PTR(tmp); 224 } 225 226 static void __struct_members_copy(int mode, struct expression *faked, 227 struct expression *left, 228 struct expression *right) 229 { 230 struct symbol *struct_type, *tmp, *type; 231 struct expression *left_member; 232 struct expression *right_member; 233 struct expression *assign; 234 int op = '.'; 235 236 237 if (__in_fake_assign) 238 return; 239 faked_expression = faked; 240 241 left = strip_expr(left); 242 right = strip_expr(right); 243 244 struct_type = get_struct_type(left); 245 if (!struct_type) { 246 /* 247 * This is not a struct assignment obviously. But this is where 248 * memcpy() is handled so it feels like a good place to add this 249 * code. 250 */ 251 handle_non_struct_assignments(left, right); 252 goto done; 253 } 254 255 if (is_pointer(left)) { 256 left = deref_expression(left); 257 op = '*'; 258 } 259 if (mode != COPY_MEMSET) 260 right = get_right_base_expr(struct_type, right); 261 262 FOR_EACH_PTR(struct_type->symbol_list, tmp) { 263 type = get_real_base_type(tmp); 264 if (!type) 265 continue; 266 if (type->type == SYM_ARRAY) 267 continue; 268 269 if (type->type == SYM_UNION || type->type == SYM_STRUCT) { 270 set_inner_struct_members(mode, faked, left, right, tmp); 271 continue; 272 } 273 274 if (!tmp->ident) 275 continue; 276 277 left_member = member_expression(left, op, tmp->ident); 278 right_member = NULL; 279 280 switch (mode) { 281 case COPY_NORMAL: 282 case COPY_MEMCPY: 283 if (right) 284 right_member = member_expression(right, op, tmp->ident); 285 else 286 right_member = unknown_value_expression(left_member); 287 break; 288 case COPY_MEMSET: 289 right_member = right; 290 break; 291 } 292 if (!right_member) { 293 sm_perror("No right member"); 294 continue; 295 } 296 assign = assign_expression(left_member, '=', right_member); 297 split_fake_expr(assign); 298 } END_FOR_EACH_PTR(tmp); 299 300 done: 301 faked_expression = NULL; 302 } 303 304 static int returns_zeroed_mem(struct expression *expr) 305 { 306 char *fn; 307 308 if (expr->type != EXPR_CALL || expr->fn->type != EXPR_SYMBOL) 309 return 0; 310 fn = expr_to_var(expr->fn); 311 if (!fn) 312 return 0; 313 if (strcmp(fn, "kcalloc") == 0) 314 return 1; 315 if (option_project == PROJ_KERNEL && strstr(fn, "zalloc")) 316 return 1; 317 return 0; 318 } 319 320 static int copy_containter_states(struct expression *left, struct expression *right, int offset) 321 { 322 char *left_name = NULL, *right_name = NULL; 323 struct symbol *left_sym, *right_sym; 324 struct sm_state *sm, *new_sm; 325 int ret = 0; 326 int len; 327 char buf[64]; 328 char new_name[128]; 329 330 right_name = expr_to_var_sym(right, &right_sym); 331 if (!right_name || !right_sym) 332 goto free; 333 left_name = expr_to_var_sym(left, &left_sym); 334 if (!left_name || !left_sym) 335 goto free; 336 337 len = snprintf(buf, sizeof(buf), "%s(-%d)", right_name, offset); 338 if (len >= sizeof(buf)) 339 goto free; 340 341 FOR_EACH_SM(__get_cur_stree(), sm) { 342 if (sm->sym != right_sym) 343 continue; 344 if (strncmp(sm->name, buf, len) != 0) 345 continue; 346 snprintf(new_name, sizeof(new_name), "%s%s", left_name, sm->name + len); 347 new_sm = clone_sm(sm); 348 new_sm->name = alloc_sname(new_name); 349 new_sm->sym = left_sym; 350 __set_sm(new_sm); 351 ret = 1; 352 } END_FOR_EACH_SM(sm); 353 free: 354 free_string(left_name); 355 free_string(right_name); 356 return ret; 357 } 358 359 static int handle_param_offsets(struct expression *expr) 360 { 361 struct expression *right; 362 sval_t sval; 363 364 right = strip_expr(expr->right); 365 366 if (right->type != EXPR_BINOP || right->op != '-') 367 return 0; 368 369 if (!get_value(right->right, &sval)) 370 return 0; 371 372 right = get_assigned_expr(right->left); 373 if (!right) 374 return 0; 375 return copy_containter_states(expr->left, right, sval.value); 376 } 377 378 static void returns_container_of(struct expression *expr, int param, char *key, char *value) 379 { 380 struct expression *call, *arg; 381 int offset; 382 383 if (expr->type != EXPR_ASSIGNMENT || expr->op != '=') 384 return; 385 call = strip_expr(expr->right); 386 if (call->type != EXPR_CALL) 387 return; 388 if (param != -1) 389 return; 390 param = atoi(key); 391 offset = atoi(value); 392 393 arg = get_argument_from_call_expr(call->args, param); 394 if (!arg) 395 return; 396 397 copy_containter_states(expr->left, arg, -offset); 398 } 399 400 void __fake_struct_member_assignments(struct expression *expr) 401 { 402 struct symbol *left_type; 403 404 if (expr->op != '=') 405 return; 406 407 if (is_zero(expr->right)) 408 return; 409 410 left_type = get_type(expr->left); 411 if (!left_type || 412 (left_type->type != SYM_PTR && 413 left_type->type != SYM_STRUCT)) 414 return; 415 416 if (handle_param_offsets(expr)) 417 return; 418 419 if (returns_zeroed_mem(expr->right)) 420 __struct_members_copy(COPY_MEMSET, expr, expr->left, zero_expr()); 421 else 422 __struct_members_copy(COPY_NORMAL, expr, expr->left, expr->right); 423 } 424 425 static void match_memset(const char *fn, struct expression *expr, void *_size_arg) 426 { 427 struct expression *buf; 428 struct expression *val; 429 430 buf = get_argument_from_call_expr(expr->args, 0); 431 val = get_argument_from_call_expr(expr->args, 1); 432 433 buf = strip_expr(buf); 434 __struct_members_copy(COPY_MEMSET, expr, remove_addr(buf), val); 435 } 436 437 static void match_memcpy(const char *fn, struct expression *expr, void *_arg) 438 { 439 struct expression *dest; 440 struct expression *src; 441 442 dest = get_argument_from_call_expr(expr->args, 0); 443 src = get_argument_from_call_expr(expr->args, 1); 444 445 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(dest), remove_addr(src)); 446 } 447 448 static void match_memcpy_unknown(const char *fn, struct expression *expr, void *_arg) 449 { 450 struct expression *dest; 451 452 dest = get_argument_from_call_expr(expr->args, 0); 453 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(dest), NULL); 454 } 455 456 static void match_sscanf(const char *fn, struct expression *expr, void *unused) 457 { 458 struct expression *arg; 459 int i; 460 461 i = -1; 462 FOR_EACH_PTR(expr->args, arg) { 463 if (++i < 2) 464 continue; 465 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(arg), NULL); 466 } END_FOR_EACH_PTR(arg); 467 } 468 469 static void unop_expr(struct expression *expr) 470 { 471 if (expr->op != SPECIAL_INCREMENT && 472 expr->op != SPECIAL_DECREMENT) 473 return; 474 475 if (!is_pointer(expr)) 476 return; 477 faked_expression = expr; 478 __struct_members_copy(COPY_MEMCPY, expr, expr->unop, NULL); 479 faked_expression = NULL; 480 } 481 482 static void register_clears_param(void) 483 { 484 struct token *token; 485 char name[256]; 486 const char *function; 487 int param; 488 489 if (option_project == PROJ_NONE) 490 return; 491 492 snprintf(name, 256, "%s.clears_argument", option_project_str); 493 494 token = get_tokens_file(name); 495 if (!token) 496 return; 497 if (token_type(token) != TOKEN_STREAMBEGIN) 498 return; 499 token = token->next; 500 while (token_type(token) != TOKEN_STREAMEND) { 501 if (token_type(token) != TOKEN_IDENT) 502 return; 503 function = show_ident(token->ident); 504 token = token->next; 505 if (token_type(token) != TOKEN_NUMBER) 506 return; 507 param = atoi(token->number); 508 add_function_hook(function, &match_memcpy_unknown, INT_PTR(param)); 509 token = token->next; 510 } 511 clear_token_alloc(); 512 } 513 514 static void db_param_cleared(struct expression *expr, int param, char *key, char *value) 515 { 516 struct expression *arg; 517 518 while (expr->type == EXPR_ASSIGNMENT) 519 expr = strip_expr(expr->right); 520 if (expr->type != EXPR_CALL) 521 return; 522 523 /* 524 * FIXME: __struct_members_copy() requires an expression but 525 * get_variable_from_key() returns a name/sym pair so that doesn't 526 * work here. 527 */ 528 if (strcmp(key, "$") != 0) 529 return; 530 531 arg = get_argument_from_call_expr(expr->args, param); 532 if (!arg) 533 return; 534 535 if (strcmp(value, "0") == 0) 536 __struct_members_copy(COPY_MEMSET, expr, remove_addr(arg), zero_expr()); 537 else 538 __struct_members_copy(COPY_MEMCPY, expr, remove_addr(arg), NULL); 539 } 540 541 void register_struct_assignment(int id) 542 { 543 add_function_hook("memset", &match_memset, NULL); 544 add_function_hook("__memset", &match_memset, NULL); 545 546 add_function_hook("memcpy", &match_memcpy, INT_PTR(0)); 547 add_function_hook("memmove", &match_memcpy, INT_PTR(0)); 548 add_function_hook("__memcpy", &match_memcpy, INT_PTR(0)); 549 add_function_hook("__memmove", &match_memcpy, INT_PTR(0)); 550 551 add_function_hook("sscanf", &match_sscanf, NULL); 552 553 add_hook(&unop_expr, OP_HOOK); 554 register_clears_param(); 555 select_return_states_hook(PARAM_CLEARED, &db_param_cleared); 556 557 select_return_states_hook(CONTAINER, &returns_container_of); 558 } 559