smatch_math.c

   1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   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 #include "symbol.h"
  19 #include "smatch.h"
  20 #include "smatch_slist.h"
  21 #include "smatch_extra.h"
  22
  23 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt);
  24 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt);
  25 static struct range_list *(*custom_handle_variable)(struct expression *expr);
  26
  27 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  28 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  29
  30 struct range_list *rl_zero(void)
  31 {
  32         return alloc_rl(zero, zero);
  33 }
  34
  35 struct range_list *rl_one(void)
  36 {
  37         return alloc_rl(one, one);
  38 }
  39
  40 enum {
  41         RL_EXACT,
  42         RL_HARD,
  43         RL_FUZZY,
  44         RL_IMPLIED,
  45         RL_ABSOLUTE
  46 };
  47
  48 static struct range_list *last_stmt_rl(struct statement *stmt, int implied, int *recurse_cnt)
  49 {
  50         if (!stmt)
  51                 return NULL;
  52
  53         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  54         if (stmt->type != STMT_EXPRESSION)
  55                 return NULL;
  56         return _get_rl(stmt->expression, implied, recurse_cnt);
  57 }
  58
  59 static struct range_list *handle_expression_statement_rl(struct expression *expr, int implied, int *recurse_cnt)
  60 {
  61         return last_stmt_rl(get_expression_statement(expr), implied, recurse_cnt);
  62 }
  63
  64 static struct range_list *handle_ampersand_rl(struct expression *expr, int implied, int *recurse_cnt)
  65 {
  66         struct range_list *rl;
  67
  68         if (implied == RL_EXACT || implied == RL_HARD)
  69                 return NULL;
  70         if (get_address_rl(expr, &rl))
  71                 return rl;
  72         return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
  73 }
  74
  75 static struct range_list *handle_negate_rl(struct expression *expr, int implied, int *recurse_cnt)
  76 {
  77         if (known_condition_true(expr->unop))
  78                 return rl_zero();
  79         if (known_condition_false(expr->unop))
  80                 return rl_one();
  81
  82         if (implied == RL_EXACT)
  83                 return NULL;
  84
  85         if (implied_condition_true(expr->unop))
  86                 return rl_zero();
  87         if (implied_condition_false(expr->unop))
  88                 return rl_one();
  89         return alloc_rl(zero, one);
  90 }
  91
  92 static struct range_list *handle_bitwise_negate(struct expression *expr, int implied, int *recurse_cnt)
  93 {
  94         struct range_list *rl;
  95         sval_t sval;
  96
  97         rl = _get_rl(expr->unop, implied, recurse_cnt);
  98         if (!rl_to_sval(rl, &sval))
  99                 return NULL;
 100         sval = sval_preop(sval, '~');
 101         sval_cast(get_type(expr->unop), sval);
 102         return alloc_rl(sval, sval);
 103 }
 104
 105 static struct range_list *handle_minus_preop(struct expression *expr, int implied, int *recurse_cnt)
 106 {
 107         struct range_list *rl;
 108         sval_t sval;
 109
 110         rl = _get_rl(expr->unop, implied, recurse_cnt);
 111         if (!rl_to_sval(rl, &sval))
 112                 return NULL;
 113         sval = sval_preop(sval, '-');
 114         return alloc_rl(sval, sval);
 115 }
 116
 117 static struct range_list *handle_preop_rl(struct expression *expr, int implied, int *recurse_cnt)
 118 {
 119         switch (expr->op) {
 120         case '&':
 121                 return handle_ampersand_rl(expr, implied, recurse_cnt);
 122         case '!':
 123                 return handle_negate_rl(expr, implied, recurse_cnt);
 124         case '~':
 125                 return handle_bitwise_negate(expr, implied, recurse_cnt);
 126         case '-':
 127                 return handle_minus_preop(expr, implied, recurse_cnt);
 128         case '*':
 129                 return handle_variable(expr, implied, recurse_cnt);
 130         case '(':
 131                 return handle_expression_statement_rl(expr, implied, recurse_cnt);
 132         default:
 133                 return NULL;
 134         }
 135 }
 136
 137 static struct range_list *handle_divide_rl(struct expression *expr, int implied, int *recurse_cnt)
 138 {
 139         struct range_list *left_rl, *right_rl;
 140         struct symbol *type;
 141
 142         type = get_type(expr);
 143
 144         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 145         left_rl = cast_rl(type, left_rl);
 146         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 147         right_rl = cast_rl(type, right_rl);
 148
 149         if (!left_rl || !right_rl)
 150                 return NULL;
 151         if (is_whole_rl(left_rl) || is_whole_rl(right_rl))
 152                 return NULL;
 153
 154         return rl_binop(left_rl, '/', right_rl);
 155 }
 156
 157 static struct range_list *handle_subtract_rl(struct expression *expr, int implied, int *recurse_cnt)
 158 {
 159         struct symbol *type;
 160         struct range_list *left_rl, *right_rl;
 161         sval_t max, min, tmp;
 162         int comparison;
 163
 164         type = get_type(expr);
 165         comparison = get_comparison(expr->left, expr->right);
 166
 167         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 168         left_rl = cast_rl(type, left_rl);
 169         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 170         right_rl = cast_rl(type, right_rl);
 171
 172         if ((!left_rl || !right_rl) &&
 173             (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY))
 174                 return NULL;
 175
 176         if (!left_rl)
 177                 left_rl = alloc_whole_rl(type);
 178         if (!right_rl)
 179                 right_rl = alloc_whole_rl(type);
 180
 181         /* negative values complicate everything fix this later */
 182         if (sval_is_negative(rl_min(right_rl)))
 183                 return NULL;
 184         max = rl_max(left_rl);
 185
 186         switch (comparison) {
 187         case '>':
 188         case SPECIAL_UNSIGNED_GT:
 189                 min = sval_type_val(type, 1);
 190                 max = rl_max(left_rl);
 191                 break;
 192         case SPECIAL_GTE:
 193         case SPECIAL_UNSIGNED_GTE:
 194                 min = sval_type_val(type, 0);
 195                 max = rl_max(left_rl);
 196                 break;
 197         default:
 198                 if (sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl)))
 199                         return NULL;
 200                 min = sval_type_min(type);
 201         }
 202
 203         if (!sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl))) {
 204                 tmp = sval_binop(rl_min(left_rl), '-', rl_max(right_rl));
 205                 if (sval_cmp(tmp, min) > 0)
 206                         min = tmp;
 207         }
 208
 209         if (!sval_is_max(rl_max(left_rl))) {
 210                 tmp = sval_binop(rl_max(left_rl), '-', rl_min(right_rl));
 211                 if (sval_cmp(tmp, max) < 0)
 212                         max = tmp;
 213         }
 214
 215         if (sval_is_min(min) && sval_is_max(max))
 216                 return NULL;
 217
 218         return cast_rl(type, alloc_rl(min, max));
 219 }
 220
 221 static struct range_list *handle_mod_rl(struct expression *expr, int implied, int *recurse_cnt)
 222 {
 223         struct range_list *rl;
 224         sval_t left, right, sval;
 225
 226         if (implied == RL_EXACT) {
 227                 if (!get_value(expr->right, &right))
 228                         return NULL;
 229                 if (!get_value(expr->left, &left))
 230                         return NULL;
 231                 sval = sval_binop(left, '%', right);
 232                 return alloc_rl(sval, sval);
 233         }
 234         /* if we can't figure out the right side it's probably hopeless */
 235         if (!get_implied_value(expr->right, &right))
 236                 return NULL;
 237
 238         right = sval_cast(get_type(expr), right);
 239         right.value--;
 240
 241         rl = _get_rl(expr->left, implied, recurse_cnt);
 242         if (rl && rl_max(rl).uvalue < right.uvalue)
 243                 right.uvalue = rl_max(rl).uvalue;
 244
 245         return alloc_rl(zero, right);
 246 }
 247
 248 static sval_t sval_lowest_set_bit(sval_t sval)
 249 {
 250         int i;
 251         int found = 0;
 252
 253         for (i = 0; i < 64; i++) {
 254                 if (sval.uvalue & 1ULL << i) {
 255                         if (!found++)
 256                                 continue;
 257                         sval.uvalue &= ~(1ULL << i);
 258                 }
 259         }
 260         return sval;
 261 }
 262
 263 static struct range_list *handle_bitwise_AND(struct expression *expr, int implied, int *recurse_cnt)
 264 {
 265         struct symbol *type;
 266         struct range_list *left_rl, *right_rl;
 267         sval_t known;
 268
 269         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE)
 270                 return NULL;
 271
 272         type = get_type(expr);
 273
 274         if (get_implied_value(expr->left, &known)) {
 275                 sval_t min;
 276
 277                 min = sval_lowest_set_bit(known);
 278                 left_rl = alloc_rl(min, known);
 279                 left_rl = cast_rl(type, left_rl);
 280                 add_range(&left_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 281         } else {
 282                 left_rl = _get_rl(expr->left, implied, recurse_cnt);
 283                 if (left_rl) {
 284                         left_rl = cast_rl(type, left_rl);
 285                         left_rl = alloc_rl(sval_type_val(type, 0), rl_max(left_rl));
 286                 } else {
 287                         if (implied == RL_HARD)
 288                                 return NULL;
 289                         left_rl = alloc_whole_rl(type);
 290                 }
 291         }
 292
 293         if (get_implied_value(expr->right, &known)) {
 294                 sval_t min, left_max, mod;
 295
 296                 min = sval_lowest_set_bit(known);
 297                 right_rl = alloc_rl(min, known);
 298                 right_rl = cast_rl(type, right_rl);
 299                 add_range(&right_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 300
 301                 if (min.value != 0) {
 302                         left_max = rl_max(left_rl);
 303                         mod = sval_binop(left_max, '%', min);
 304                         if (mod.value) {
 305                                 left_max = sval_binop(left_max, '-', mod);
 306                                 left_max.value++;
 307                                 if (left_max.value > 0 && sval_cmp(left_max, rl_max(left_rl)) < 0)
 308                                         left_rl = remove_range(left_rl, left_max, rl_max(left_rl));
 309                         }
 310                 }
 311         } else {
 312                 right_rl = _get_rl(expr->right, implied, recurse_cnt);
 313                 if (right_rl) {
 314                         right_rl = cast_rl(type, right_rl);
 315                         right_rl = alloc_rl(sval_type_val(type, 0), rl_max(right_rl));
 316                 } else {
 317                         if (implied == RL_HARD)
 318                                 return NULL;
 319                         right_rl = alloc_whole_rl(type);
 320                 }
 321         }
 322
 323         return rl_intersection(left_rl, right_rl);
 324 }
 325
 326 static struct range_list *handle_bitwise_OR(struct expression *expr, int implied, int *recurse_cnt)
 327 {
 328         struct symbol *type;
 329         struct range_list *left_rl, *right_rl;
 330
 331         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE)
 332                 return NULL;
 333
 334         type = get_type(expr);
 335
 336         get_absolute_rl(expr->left, &left_rl);
 337         get_absolute_rl(expr->right, &right_rl);
 338         left_rl = cast_rl(type, left_rl);
 339         right_rl = cast_rl(type, right_rl);
 340         if (!left_rl || !right_rl)
 341                 return NULL;
 342
 343         return rl_binop(left_rl, '|', right_rl);
 344 }
 345
 346 static struct range_list *handle_right_shift(struct expression *expr, int implied, int *recurse_cnt)
 347 {
 348         struct range_list *left_rl;
 349         sval_t right;
 350         sval_t min, max;
 351
 352         if (implied == RL_EXACT || implied == RL_HARD)
 353                 return NULL;
 354
 355         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 356         if (left_rl) {
 357                 max = rl_max(left_rl);
 358                 min = rl_min(left_rl);
 359         } else {
 360                 if (implied == RL_FUZZY)
 361                         return NULL;
 362                 max = sval_type_max(get_type(expr->left));
 363                 min = sval_type_val(get_type(expr->left), 0);
 364         }
 365
 366         if (get_implied_value(expr->right, &right)) {
 367                 min = sval_binop(min, SPECIAL_RIGHTSHIFT, right);
 368                 max = sval_binop(max, SPECIAL_RIGHTSHIFT, right);
 369         } else if (!sval_is_negative(min)) {
 370                 min.value = 0;
 371                 max = sval_type_max(max.type);
 372         } else {
 373                 return NULL;
 374         }
 375
 376         return alloc_rl(min, max);
 377 }
 378
 379 static struct range_list *handle_left_shift(struct expression *expr, int implied, int *recurse_cnt)
 380 {
 381         struct range_list *left_rl, *res;
 382         sval_t right;
 383         sval_t min, max;
 384         int add_zero = 0;
 385
 386         if (implied == RL_EXACT || implied == RL_HARD)
 387                 return NULL;
 388         /* this is hopeless without the right side */
 389         if (!get_implied_value(expr->right, &right))
 390                 return NULL;
 391         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 392         if (left_rl) {
 393                 max = rl_max(left_rl);
 394                 min = rl_min(left_rl);
 395                 if (min.value == 0) {
 396                         min.value = 1;
 397                         add_zero = 1;
 398                 }
 399         } else {
 400                 if (implied == RL_FUZZY)
 401                         return NULL;
 402                 max = sval_type_max(get_type(expr->left));
 403                 min = sval_type_val(get_type(expr->left), 1);
 404                 add_zero = 1;
 405         }
 406
 407         max = sval_binop(max, SPECIAL_LEFTSHIFT, right);
 408         min = sval_binop(min, SPECIAL_LEFTSHIFT, right);
 409         res = alloc_rl(min, max);
 410         if (add_zero)
 411                 res = rl_union(res, rl_zero());
 412         return res;
 413 }
 414
 415 static struct range_list *handle_known_binop(struct expression *expr)
 416 {
 417         sval_t left, right;
 418
 419         if (!get_value(expr->left, &left))
 420                 return NULL;
 421         if (!get_value(expr->right, &right))
 422                 return NULL;
 423         left = sval_binop(left, expr->op, right);
 424         return alloc_rl(left, left);
 425 }
 426
 427 static int has_actual_ranges(struct range_list *rl)
 428 {
 429         struct data_range *tmp;
 430
 431         FOR_EACH_PTR(rl, tmp) {
 432                 if (sval_cmp(tmp->min, tmp->max) != 0)
 433                         return 1;
 434         } END_FOR_EACH_PTR(tmp);
 435         return 0;
 436 }
 437
 438 static struct range_list *handle_implied_binop(struct range_list *left_rl, int op, struct range_list *right_rl)
 439 {
 440         struct range_list *res_rl;
 441         struct data_range *left_drange, *right_drange;
 442         sval_t res;
 443
 444         if (!left_rl || !right_rl)
 445                 return NULL;
 446         if (has_actual_ranges(left_rl))
 447                 return NULL;
 448         if (has_actual_ranges(right_rl))
 449                 return NULL;
 450
 451         if (ptr_list_size((struct ptr_list *)left_rl) * ptr_list_size((struct ptr_list *)right_rl) > 20)
 452                 return NULL;
 453
 454         res_rl = NULL;
 455
 456         FOR_EACH_PTR(left_rl, left_drange) {
 457                 FOR_EACH_PTR(right_rl, right_drange) {
 458                         if ((op == '%' || op == '/') &&
 459                             right_drange->min.value == 0)
 460                                 return NULL;
 461                         res = sval_binop(left_drange->min, op, right_drange->min);
 462                         add_range(&res_rl, res, res);
 463                 } END_FOR_EACH_PTR(right_drange);
 464         } END_FOR_EACH_PTR(left_drange);
 465
 466         return res_rl;
 467 }
 468
 469 static struct range_list *handle_binop_rl(struct expression *expr, int implied, int *recurse_cnt)
 470 {
 471         struct smatch_state *state;
 472         struct symbol *type;
 473         struct range_list *left_rl, *right_rl, *rl;
 474         sval_t min, max;
 475
 476         rl = handle_known_binop(expr);
 477         if (rl)
 478                 return rl;
 479         if (implied == RL_EXACT)
 480                 return NULL;
 481
 482         state = get_extra_state(expr);
 483         if (state && !is_whole_rl(estate_rl(state)))
 484                 return clone_rl(estate_rl(state));
 485
 486         type = get_type(expr);
 487         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 488         left_rl = cast_rl(type, left_rl);
 489         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 490         right_rl = cast_rl(type, right_rl);
 491
 492         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 493         if (rl)
 494                 return rl;
 495
 496         switch (expr->op) {
 497         case '%':
 498                 return handle_mod_rl(expr, implied, recurse_cnt);
 499         case '&':
 500                 return handle_bitwise_AND(expr, implied, recurse_cnt);
 501         case '|':
 502                 return handle_bitwise_OR(expr, implied, recurse_cnt);
 503         case SPECIAL_RIGHTSHIFT:
 504                 return handle_right_shift(expr, implied, recurse_cnt);
 505         case SPECIAL_LEFTSHIFT:
 506                 return handle_left_shift(expr, implied, recurse_cnt);
 507         case '-':
 508                 return handle_subtract_rl(expr, implied, recurse_cnt);
 509         case '/':
 510                 return handle_divide_rl(expr, implied, recurse_cnt);
 511         }
 512
 513         if (!left_rl || !right_rl)
 514                 return NULL;
 515
 516         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 517                 return NULL;
 518         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 519
 520         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl))) {
 521                 switch (implied) {
 522                 case RL_FUZZY:
 523                 case RL_HARD:
 524                         return NULL;
 525                 default:
 526                         max = sval_type_max(get_type(expr));
 527                 }
 528         } else {
 529                 max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 530         }
 531
 532         return alloc_rl(min, max);
 533 }
 534
 535 static int do_comparison(struct expression *expr)
 536 {
 537         struct range_list *left_ranges = NULL;
 538         struct range_list *right_ranges = NULL;
 539         int poss_true, poss_false;
 540         struct symbol *type;
 541
 542         type = get_type(expr);
 543         get_absolute_rl(expr->left, &left_ranges);
 544         get_absolute_rl(expr->right, &right_ranges);
 545
 546         left_ranges = cast_rl(type, left_ranges);
 547         right_ranges = cast_rl(type, right_ranges);
 548
 549         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 550         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 551
 552         free_rl(&left_ranges);
 553         free_rl(&right_ranges);
 554
 555         if (!poss_true && !poss_false)
 556                 return 0x0;
 557         if (poss_true && !poss_false)
 558                 return 0x1;
 559         if (!poss_true && poss_false)
 560                 return 0x2;
 561         return 0x3;
 562 }
 563
 564 static struct range_list *handle_comparison_rl(struct expression *expr, int implied)
 565 {
 566         sval_t left, right;
 567         int res;
 568
 569         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 570                 struct data_range tmp_left, tmp_right;
 571
 572                 tmp_left.min = left;
 573                 tmp_left.max = left;
 574                 tmp_right.min = right;
 575                 tmp_right.max = right;
 576                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 577                         return rl_one();
 578                 return rl_zero();
 579         }
 580
 581         if (implied == RL_EXACT)
 582                 return NULL;
 583
 584         res = do_comparison(expr);
 585         if (res == 1)
 586                 return rl_one();
 587         if (res == 2)
 588                 return rl_zero();
 589
 590         return alloc_rl(zero, one);
 591 }
 592
 593 static struct range_list *handle_logical_rl(struct expression *expr, int implied)
 594 {
 595         sval_t left, right;
 596         int left_known = 0;
 597         int right_known = 0;
 598
 599         if (implied == RL_EXACT) {
 600                 if (get_value(expr->left, &left))
 601                         left_known = 1;
 602                 if (get_value(expr->right, &right))
 603                         right_known = 1;
 604         } else {
 605                 if (get_implied_value(expr->left, &left))
 606                         left_known = 1;
 607                 if (get_implied_value(expr->right, &right))
 608                         right_known = 1;
 609         }
 610
 611         switch (expr->op) {
 612         case SPECIAL_LOGICAL_OR:
 613                 if (left_known && left.value)
 614                         return rl_one();
 615                 if (right_known && right.value)
 616                         return rl_one();
 617                 if (left_known && right_known)
 618                         return rl_zero();
 619                 break;
 620         case SPECIAL_LOGICAL_AND:
 621                 if (left_known && right_known) {
 622                         if (left.value && right.value)
 623                                 return rl_one();
 624                         return rl_zero();
 625                 }
 626                 break;
 627         default:
 628                 return NULL;
 629         }
 630
 631         if (implied == RL_EXACT)
 632                 return NULL;
 633
 634         return alloc_rl(zero, one);
 635 }
 636
 637 static struct range_list *handle_conditional_rl(struct expression *expr, int implied, int *recurse_cnt)
 638 {
 639         struct range_list *true_rl, *false_rl;
 640         struct symbol *type;
 641         int final_pass_orig = final_pass;
 642
 643         if (known_condition_true(expr->conditional))
 644                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 645         if (known_condition_false(expr->conditional))
 646                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 647
 648         if (implied == RL_EXACT)
 649                 return NULL;
 650
 651         if (implied_condition_true(expr->conditional))
 652                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 653         if (implied_condition_false(expr->conditional))
 654                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 655
 656
 657         /* this becomes a problem with deeply nested conditional statements */
 658         if (low_on_memory())
 659                 return NULL;
 660
 661         type = get_type(expr);
 662
 663         __push_fake_cur_stree();
 664         final_pass = 0;
 665         __split_whole_condition(expr->conditional);
 666         true_rl = _get_rl(expr->cond_true, implied, recurse_cnt);
 667         __push_true_states();
 668         __use_false_states();
 669         false_rl = _get_rl(expr->cond_false, implied, recurse_cnt);
 670         __merge_true_states();
 671         __free_fake_cur_stree();
 672         final_pass = final_pass_orig;
 673
 674         if (!true_rl || !false_rl)
 675                 return NULL;
 676         true_rl = cast_rl(type, true_rl);
 677         false_rl = cast_rl(type, false_rl);
 678
 679         return rl_union(true_rl, false_rl);
 680 }
 681
 682 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 683 {
 684         struct smatch_state *state;
 685         sval_t sval;
 686
 687         if (get_hard_max(expr, &sval)) {
 688                 *max = sval;
 689                 return 1;
 690         }
 691
 692         state = get_extra_state(expr);
 693         if (!state || !estate_has_fuzzy_max(state))
 694                 return 0;
 695         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 696         return 1;
 697 }
 698
 699 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 700 {
 701         struct smatch_state *state;
 702         sval_t sval;
 703
 704         state = get_extra_state(expr);
 705         if (!state || !estate_rl(state))
 706                 return 0;
 707
 708         sval = estate_min(state);
 709         if (sval_is_negative(sval) && sval_is_min(sval))
 710                 return 0;
 711
 712         if (sval_is_max(sval))
 713                 return 0;
 714
 715         *min = sval_cast(get_type(expr), sval);
 716         return 1;
 717 }
 718
 719 int get_const_value(struct expression *expr, sval_t *sval)
 720 {
 721         struct symbol *sym;
 722         sval_t right;
 723
 724         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 725                 return 0;
 726         sym = expr->symbol;
 727         if (!(sym->ctype.modifiers & MOD_CONST))
 728                 return 0;
 729         if (get_value(sym->initializer, &right)) {
 730                 *sval = sval_cast(get_type(expr), right);
 731                 return 1;
 732         }
 733         return 0;
 734 }
 735
 736 struct range_list *var_to_absolute_rl(struct expression *expr)
 737 {
 738         struct smatch_state *state;
 739         struct range_list *rl;
 740
 741         state = get_extra_state(expr);
 742         if (!state) {
 743                 if (get_local_rl(expr, &rl))
 744                         return rl;
 745                 if (get_db_type_rl(expr, &rl))
 746                         return rl;
 747                 return alloc_whole_rl(get_type(expr));
 748         }
 749         /* err on the side of saying things are possible */
 750         if (!estate_rl(state))
 751                 return alloc_whole_rl(get_type(expr));
 752         return clone_rl(estate_rl(state));
 753 }
 754
 755 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt)
 756 {
 757         struct smatch_state *state;
 758         struct range_list *rl;
 759         sval_t sval, min, max;
 760
 761         if (get_const_value(expr, &sval))
 762                 return alloc_rl(sval, sval);
 763
 764         if (custom_handle_variable) {
 765                 rl = custom_handle_variable(expr);
 766                 if (!rl)
 767                         return var_to_absolute_rl(expr);
 768                 return rl;
 769         }
 770
 771         switch (implied) {
 772         case RL_EXACT:
 773                 return NULL;
 774         case RL_HARD:
 775         case RL_IMPLIED:
 776         case RL_ABSOLUTE:
 777                 state = get_extra_state(expr);
 778                 if (!state || !state->data) {
 779                         if (implied == RL_HARD)
 780                                 return NULL;
 781                         if (get_local_rl(expr, &rl))
 782                                 return rl;
 783                         if (get_db_type_rl(expr, &rl))
 784                                 return rl;
 785                         return NULL;
 786                 }
 787                 if (implied == RL_HARD && !estate_has_hard_max(state))
 788                         return NULL;
 789                 return clone_rl(estate_rl(state));
 790         case RL_FUZZY:
 791                 if (!get_fuzzy_min_helper(expr, &min))
 792                         min = sval_type_min(get_type(expr));
 793                 if (!get_fuzzy_max_helper(expr, &max))
 794                         return NULL;
 795                 /* fuzzy ranges are often inverted */
 796                 if (sval_cmp(min, max) > 0) {
 797                         sval = min;
 798                         min = max;
 799                         max = sval;
 800                 }
 801                 return alloc_rl(min, max);
 802         }
 803         return NULL;
 804 }
 805
 806 static sval_t handle_sizeof(struct expression *expr)
 807 {
 808         struct symbol *sym;
 809         sval_t ret;
 810
 811         ret = sval_blank(expr);
 812         sym = expr->cast_type;
 813         if (!sym) {
 814                 sym = evaluate_expression(expr->cast_expression);
 815                 /*
 816                  * Expressions of restricted types will possibly get
 817                  * promoted - check that here
 818                  */
 819                 if (is_restricted_type(sym)) {
 820                         if (type_bits(sym) < bits_in_int)
 821                                 sym = &int_ctype;
 822                 } else if (is_fouled_type(sym)) {
 823                         sym = &int_ctype;
 824                 }
 825         }
 826         examine_symbol_type(sym);
 827
 828         ret.type = size_t_ctype;
 829         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 830                 if (get_real_base_type(sym) == &void_ctype)
 831                         ret.value = 1;
 832                 else
 833                         ret.value = 0;
 834         } else
 835                 ret.value = type_bytes(sym);
 836
 837         return ret;
 838 }
 839
 840 static struct range_list *handle_call_rl(struct expression *expr, int implied, int *recurse_cnt)
 841 {
 842         struct range_list *rl;
 843
 844         if (sym_name_is("__builtin_expect", expr->fn)) {
 845                 struct expression *arg;
 846
 847                 arg = get_argument_from_call_expr(expr->args, 0);
 848                 return _get_rl(arg, implied, recurse_cnt);
 849         }
 850
 851         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
 852                 return NULL;
 853
 854         if (get_implied_return(expr, &rl))
 855                 return rl;
 856         return db_return_vals(expr);
 857 }
 858
 859 static struct range_list *handle_cast(struct expression *expr, int implied, int *recurse_cnt)
 860 {
 861         struct range_list *rl;
 862         struct symbol *type;
 863
 864         type = get_type(expr);
 865         rl = _get_rl(expr->cast_expression, implied, recurse_cnt);
 866         if (rl)
 867                 return cast_rl(type, rl);
 868         if (implied == RL_ABSOLUTE)
 869                 return alloc_whole_rl(type);
 870         if (implied == RL_IMPLIED && type &&
 871             type_bits(type) > 0 && type_bits(type) < 32)
 872                 return alloc_whole_rl(type);
 873         return NULL;
 874 }
 875
 876 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt)
 877 {
 878         struct range_list *rl;
 879         struct symbol *type;
 880         sval_t sval;
 881
 882         type = get_type(expr);
 883         expr = strip_parens(expr);
 884         if (!expr)
 885                 return NULL;
 886
 887         if (++(*recurse_cnt) >= 200)
 888                 return NULL;
 889
 890         switch(expr->type) {
 891         case EXPR_CAST:
 892         case EXPR_FORCE_CAST:
 893         case EXPR_IMPLIED_CAST:
 894                 rl = handle_cast(expr, implied, recurse_cnt);
 895                 goto out_cast;
 896         }
 897
 898         expr = strip_expr(expr);
 899         if (!expr)
 900                 return NULL;
 901
 902         switch (expr->type) {
 903         case EXPR_VALUE:
 904                 sval = sval_from_val(expr, expr->value);
 905                 rl = alloc_rl(sval, sval);
 906                 break;
 907         case EXPR_PREOP:
 908                 rl = handle_preop_rl(expr, implied, recurse_cnt);
 909                 break;
 910         case EXPR_POSTOP:
 911                 rl = _get_rl(expr->unop, implied, recurse_cnt);
 912                 break;
 913         case EXPR_BINOP:
 914                 rl = handle_binop_rl(expr, implied, recurse_cnt);
 915                 break;
 916         case EXPR_COMPARE:
 917                 rl = handle_comparison_rl(expr, implied);
 918                 break;
 919         case EXPR_LOGICAL:
 920                 rl = handle_logical_rl(expr, implied);
 921                 break;
 922         case EXPR_PTRSIZEOF:
 923         case EXPR_SIZEOF:
 924                 sval = handle_sizeof(expr);
 925                 rl = alloc_rl(sval, sval);
 926                 break;
 927         case EXPR_SELECT:
 928         case EXPR_CONDITIONAL:
 929                 rl = handle_conditional_rl(expr, implied, recurse_cnt);
 930                 break;
 931         case EXPR_CALL:
 932                 rl = handle_call_rl(expr, implied, recurse_cnt);
 933                 break;
 934         default:
 935                 rl = handle_variable(expr, implied, recurse_cnt);
 936         }
 937
 938 out_cast:
 939         if (rl)
 940                 return rl;
 941         if (type && implied == RL_ABSOLUTE)
 942                 return alloc_whole_rl(type);
 943         return NULL;
 944 }
 945
 946 /* returns 1 if it can get a value literal or else returns 0 */
 947 int get_value(struct expression *expr, sval_t *sval)
 948 {
 949         struct range_list *rl;
 950         int recurse_cnt = 0;
 951
 952         rl = _get_rl(expr, RL_EXACT, &recurse_cnt);
 953         if (!rl_to_sval(rl, sval))
 954                 return 0;
 955         return 1;
 956 }
 957
 958 int get_implied_value(struct expression *expr, sval_t *sval)
 959 {
 960         struct range_list *rl;
 961         int recurse_cnt = 0;
 962
 963         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 964         if (!rl_to_sval(rl, sval))
 965                 return 0;
 966         return 1;
 967 }
 968
 969 int get_implied_min(struct expression *expr, sval_t *sval)
 970 {
 971         struct range_list *rl;
 972         int recurse_cnt = 0;
 973
 974         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 975         if (!rl)
 976                 return 0;
 977         *sval = rl_min(rl);
 978         return 1;
 979 }
 980
 981 int get_implied_max(struct expression *expr, sval_t *sval)
 982 {
 983         struct range_list *rl;
 984         int recurse_cnt = 0;
 985
 986         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 987         if (!rl)
 988                 return 0;
 989         *sval = rl_max(rl);
 990         return 1;
 991 }
 992
 993 int get_implied_rl(struct expression *expr, struct range_list **rl)
 994 {
 995         int recurse_cnt = 0;
 996
 997         *rl = _get_rl(expr, RL_IMPLIED, &recurse_cnt);
 998         if (*rl)
 999                 return 1;
1000         return 0;
1001 }
1002
1003 int get_absolute_rl(struct expression *expr, struct range_list **rl)
1004 {
1005         int recurse_cnt = 0;
1006
1007         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1008         if (!*rl)
1009                 *rl = alloc_whole_rl(get_type(expr));
1010         return 1;
1011 }
1012
1013 int custom_get_absolute_rl(struct expression *expr,
1014                            struct range_list *(*fn)(struct expression *expr),
1015                            struct range_list **rl)
1016 {
1017         int recurse_cnt = 0;
1018
1019         *rl = NULL;
1020         custom_handle_variable = fn;
1021         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1022         custom_handle_variable = NULL;
1023         return 1;
1024 }
1025
1026 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1027 {
1028         struct smatch_state *state;
1029
1030         state = get_state(SMATCH_EXTRA, var, sym);
1031         *rl = estate_rl(state);
1032         if (*rl)
1033                 return 1;
1034         return 0;
1035 }
1036
1037 int get_hard_max(struct expression *expr, sval_t *sval)
1038 {
1039         struct range_list *rl;
1040         int recurse_cnt = 0;
1041
1042         rl =  _get_rl(expr, RL_HARD, &recurse_cnt);
1043         if (!rl)
1044                 return 0;
1045         *sval = rl_max(rl);
1046         return 1;
1047 }
1048
1049 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1050 {
1051         struct range_list *rl;
1052         sval_t tmp;
1053         int recurse_cnt = 0;
1054
1055         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1056         if (!rl)
1057                 return 0;
1058         tmp = rl_min(rl);
1059         if (sval_is_negative(tmp) && sval_is_min(tmp))
1060                 return 0;
1061         *sval = tmp;
1062         return 1;
1063 }
1064
1065 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1066 {
1067         struct range_list *rl;
1068         sval_t max;
1069         int recurse_cnt = 0;
1070
1071         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1072         if (!rl)
1073                 return 0;
1074         max = rl_max(rl);
1075         if (max.uvalue > INT_MAX - 10000)
1076                 return 0;
1077         *sval = max;
1078         return 1;
1079 }
1080
1081 int get_absolute_min(struct expression *expr, sval_t *sval)
1082 {
1083         struct range_list *rl;
1084         struct symbol *type;
1085         int recurse_cnt = 0;
1086
1087         type = get_type(expr);
1088         if (!type)
1089                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1090         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1091         if (rl)
1092                 *sval = rl_min(rl);
1093         else
1094                 *sval = sval_type_min(type);
1095
1096         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1097                 *sval = sval_type_min(type);
1098         return 1;
1099 }
1100
1101 int get_absolute_max(struct expression *expr, sval_t *sval)
1102 {
1103         struct range_list *rl;
1104         struct symbol *type;
1105         int recurse_cnt = 0;
1106
1107         type = get_type(expr);
1108         if (!type)
1109                 type = &llong_ctype;
1110         rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1111         if (rl)
1112                 *sval = rl_max(rl);
1113         else
1114                 *sval = sval_type_max(type);
1115
1116         if (sval_cmp(sval_type_max(type), *sval) < 0)
1117                 *sval = sval_type_max(type);
1118         return 1;
1119 }
1120
1121 int known_condition_true(struct expression *expr)
1122 {
1123         sval_t tmp;
1124
1125         if (!expr)
1126                 return 0;
1127
1128         if (get_value(expr, &tmp) && tmp.value)
1129                 return 1;
1130
1131         return 0;
1132 }
1133
1134 int known_condition_false(struct expression *expr)
1135 {
1136         if (!expr)
1137                 return 0;
1138
1139         if (is_zero(expr))
1140                 return 1;
1141
1142         if (expr->type == EXPR_CALL) {
1143                 if (sym_name_is("__builtin_constant_p", expr->fn))
1144                         return 1;
1145         }
1146         return 0;
1147 }
1148
1149 int implied_condition_true(struct expression *expr)
1150 {
1151         sval_t tmp;
1152
1153         if (!expr)
1154                 return 0;
1155
1156         if (known_condition_true(expr))
1157                 return 1;
1158         if (get_implied_value(expr, &tmp) && tmp.value)
1159                 return 1;
1160
1161         if (expr->type == EXPR_POSTOP)
1162                 return implied_condition_true(expr->unop);
1163
1164         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1165                 return implied_not_equal(expr->unop, 1);
1166         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1167                 return implied_not_equal(expr->unop, -1);
1168
1169         expr = strip_expr(expr);
1170         switch (expr->type) {
1171         case EXPR_COMPARE:
1172                 if (do_comparison(expr) == 1)
1173                         return 1;
1174                 break;
1175         case EXPR_PREOP:
1176                 if (expr->op == '!') {
1177                         if (implied_condition_false(expr->unop))
1178                                 return 1;
1179                         break;
1180                 }
1181                 break;
1182         default:
1183                 if (implied_not_equal(expr, 0) == 1)
1184                         return 1;
1185                 break;
1186         }
1187         return 0;
1188 }
1189
1190 int implied_condition_false(struct expression *expr)
1191 {
1192         struct expression *tmp;
1193         sval_t sval;
1194
1195         if (!expr)
1196                 return 0;
1197
1198         if (known_condition_false(expr))
1199                 return 1;
1200
1201         switch (expr->type) {
1202         case EXPR_COMPARE:
1203                 if (do_comparison(expr) == 2)
1204                         return 1;
1205         case EXPR_PREOP:
1206                 if (expr->op == '!') {
1207                         if (implied_condition_true(expr->unop))
1208                                 return 1;
1209                         break;
1210                 }
1211                 tmp = strip_expr(expr);
1212                 if (tmp != expr)
1213                         return implied_condition_false(tmp);
1214                 break;
1215         default:
1216                 if (get_implied_value(expr, &sval) && sval.value == 0)
1217                         return 1;
1218                 break;
1219         }
1220         return 0;
1221 }
1222
1223 int can_integer_overflow(struct symbol *type, struct expression *expr)
1224 {
1225         int op;
1226         sval_t lmax, rmax, res;
1227
1228         if (!type)
1229                 type = &int_ctype;
1230
1231         expr = strip_expr(expr);
1232
1233         if (expr->type == EXPR_ASSIGNMENT) {
1234                 switch(expr->op) {
1235                 case SPECIAL_MUL_ASSIGN:
1236                         op = '*';
1237                         break;
1238                 case SPECIAL_ADD_ASSIGN:
1239                         op = '+';
1240                         break;
1241                 case SPECIAL_SHL_ASSIGN:
1242                         op = SPECIAL_LEFTSHIFT;
1243                         break;
1244                 default:
1245                         return 0;
1246                 }
1247         } else if (expr->type == EXPR_BINOP) {
1248                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1249                         return 0;
1250                 op = expr->op;
1251         } else {
1252                 return 0;
1253         }
1254
1255         get_absolute_max(expr->left, &lmax);
1256         get_absolute_max(expr->right, &rmax);
1257
1258         if (sval_binop_overflows(lmax, op, rmax))
1259                 return 1;
1260
1261         res = sval_binop(lmax, op, rmax);
1262         if (sval_cmp(res, sval_type_max(type)) > 0)
1263                 return 1;
1264         return 0;
1265 }