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);
  24 static struct range_list *handle_variable(struct expression *expr, int implied);
  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)
  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);
  57 }
  58
  59 static struct range_list *handle_expression_statement_rl(struct expression *expr, int implied)
  60 {
  61         return last_stmt_rl(get_expression_statement(expr), implied);
  62 }
  63
  64 static struct range_list *handle_ampersand_rl(struct expression *expr, int implied)
  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)
  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)
  93 {
  94         struct range_list *rl;
  95         sval_t sval;
  96
  97         rl = _get_rl(expr->unop, implied);
  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)
 106 {
 107         struct range_list *rl;
 108         sval_t sval;
 109
 110         rl = _get_rl(expr->unop, implied);
 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)
 118 {
 119         switch (expr->op) {
 120         case '&':
 121                 return handle_ampersand_rl(expr, implied);
 122         case '!':
 123                 return handle_negate_rl(expr, implied);
 124         case '~':
 125                 return handle_bitwise_negate(expr, implied);
 126         case '-':
 127                 return handle_minus_preop(expr, implied);
 128         case '*':
 129                 return handle_variable(expr, implied);
 130         case '(':
 131                 return handle_expression_statement_rl(expr, implied);
 132         default:
 133                 return NULL;
 134         }
 135 }
 136
 137 static struct range_list *handle_divide_rl(struct expression *expr, int implied)
 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);
 145         left_rl = cast_rl(type, left_rl);
 146         right_rl = _get_rl(expr->right, implied);
 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)
 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);
 168         left_rl = cast_rl(type, left_rl);
 169         right_rl = _get_rl(expr->right, implied);
 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)
 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);
 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)
 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);
 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);
 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)
 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)
 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);
 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)
 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);
 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)
 470 {
 471         struct symbol *type;
 472         struct range_list *left_rl, *right_rl, *rl;
 473         sval_t min, max;
 474
 475         rl = handle_known_binop(expr);
 476         if (rl)
 477                 return rl;
 478         if (implied == RL_EXACT)
 479                 return NULL;
 480
 481         type = get_type(expr);
 482         left_rl = _get_rl(expr->left, implied);
 483         left_rl = cast_rl(type, left_rl);
 484         right_rl = _get_rl(expr->right, implied);
 485         right_rl = cast_rl(type, right_rl);
 486
 487         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 488         if (rl)
 489                 return rl;
 490
 491         switch (expr->op) {
 492         case '%':
 493                 return handle_mod_rl(expr, implied);
 494         case '&':
 495                 return handle_bitwise_AND(expr, implied);
 496         case '|':
 497                 return handle_bitwise_OR(expr, implied);
 498         case SPECIAL_RIGHTSHIFT:
 499                 return handle_right_shift(expr, implied);
 500         case SPECIAL_LEFTSHIFT:
 501                 return handle_left_shift(expr, implied);
 502         case '-':
 503                 return handle_subtract_rl(expr, implied);
 504         case '/':
 505                 return handle_divide_rl(expr, implied);
 506         }
 507
 508         if (!left_rl || !right_rl)
 509                 return NULL;
 510
 511         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 512                 return NULL;
 513         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 514
 515         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl))) {
 516                 switch (implied) {
 517                 case RL_FUZZY:
 518                 case RL_HARD:
 519                         return NULL;
 520                 default:
 521                         max = sval_type_max(get_type(expr));
 522                 }
 523         } else {
 524                 max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 525         }
 526
 527         return alloc_rl(min, max);
 528 }
 529
 530 static int do_comparison(struct expression *expr)
 531 {
 532         struct range_list *left_ranges = NULL;
 533         struct range_list *right_ranges = NULL;
 534         int poss_true, poss_false;
 535         struct symbol *type;
 536
 537         type = get_type(expr);
 538         get_absolute_rl(expr->left, &left_ranges);
 539         get_absolute_rl(expr->right, &right_ranges);
 540
 541         left_ranges = cast_rl(type, left_ranges);
 542         right_ranges = cast_rl(type, right_ranges);
 543
 544         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 545         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 546
 547         free_rl(&left_ranges);
 548         free_rl(&right_ranges);
 549
 550         if (!poss_true && !poss_false)
 551                 return 0x0;
 552         if (poss_true && !poss_false)
 553                 return 0x1;
 554         if (!poss_true && poss_false)
 555                 return 0x2;
 556         return 0x3;
 557 }
 558
 559 static struct range_list *handle_comparison_rl(struct expression *expr, int implied)
 560 {
 561         sval_t left, right;
 562         int res;
 563
 564         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 565                 struct data_range tmp_left, tmp_right;
 566
 567                 tmp_left.min = left;
 568                 tmp_left.max = left;
 569                 tmp_right.min = right;
 570                 tmp_right.max = right;
 571                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 572                         return rl_one();
 573                 return rl_zero();
 574         }
 575
 576         if (implied == RL_EXACT)
 577                 return NULL;
 578
 579         res = do_comparison(expr);
 580         if (res == 1)
 581                 return rl_one();
 582         if (res == 2)
 583                 return rl_zero();
 584
 585         return alloc_rl(zero, one);
 586 }
 587
 588 static struct range_list *handle_logical_rl(struct expression *expr, int implied)
 589 {
 590         sval_t left, right;
 591         int left_known = 0;
 592         int right_known = 0;
 593
 594         if (implied == RL_EXACT) {
 595                 if (get_value(expr->left, &left))
 596                         left_known = 1;
 597                 if (get_value(expr->right, &right))
 598                         right_known = 1;
 599         } else {
 600                 if (get_implied_value(expr->left, &left))
 601                         left_known = 1;
 602                 if (get_implied_value(expr->right, &right))
 603                         right_known = 1;
 604         }
 605
 606         switch (expr->op) {
 607         case SPECIAL_LOGICAL_OR:
 608                 if (left_known && left.value)
 609                         return rl_one();
 610                 if (right_known && right.value)
 611                         return rl_one();
 612                 if (left_known && right_known)
 613                         return rl_zero();
 614                 break;
 615         case SPECIAL_LOGICAL_AND:
 616                 if (left_known && right_known) {
 617                         if (left.value && right.value)
 618                                 return rl_one();
 619                         return rl_zero();
 620                 }
 621                 break;
 622         default:
 623                 return NULL;
 624         }
 625
 626         if (implied == RL_EXACT)
 627                 return NULL;
 628
 629         return alloc_rl(zero, one);
 630 }
 631
 632 static struct range_list *handle_conditional_rl(struct expression *expr, int implied)
 633 {
 634         struct range_list *true_rl, *false_rl;
 635         struct symbol *type;
 636         int final_pass_orig = final_pass;
 637
 638         if (known_condition_true(expr->conditional))
 639                 return _get_rl(expr->cond_true, implied);
 640         if (known_condition_false(expr->conditional))
 641                 return _get_rl(expr->cond_false, implied);
 642
 643         if (implied == RL_EXACT)
 644                 return NULL;
 645
 646         if (implied_condition_true(expr->conditional))
 647                 return _get_rl(expr->cond_true, implied);
 648         if (implied_condition_false(expr->conditional))
 649                 return _get_rl(expr->cond_false, implied);
 650
 651
 652         /* this becomes a problem with deeply nested conditional statements */
 653         if (low_on_memory())
 654                 return NULL;
 655
 656         type = get_type(expr);
 657
 658         __push_fake_cur_stree();
 659         final_pass = 0;
 660         __split_whole_condition(expr->conditional);
 661         true_rl = _get_rl(expr->cond_true, implied);
 662         __push_true_states();
 663         __use_false_states();
 664         false_rl = _get_rl(expr->cond_false, implied);
 665         __merge_true_states();
 666         __free_fake_cur_stree();
 667         final_pass = final_pass_orig;
 668
 669         if (!true_rl || !false_rl)
 670                 return NULL;
 671         true_rl = cast_rl(type, true_rl);
 672         false_rl = cast_rl(type, false_rl);
 673
 674         return rl_union(true_rl, false_rl);
 675 }
 676
 677 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 678 {
 679         struct smatch_state *state;
 680         sval_t sval;
 681
 682         if (get_hard_max(expr, &sval)) {
 683                 *max = sval;
 684                 return 1;
 685         }
 686
 687         state = get_extra_state(expr);
 688         if (!state || !estate_has_fuzzy_max(state))
 689                 return 0;
 690         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 691         return 1;
 692 }
 693
 694 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 695 {
 696         struct smatch_state *state;
 697         sval_t sval;
 698
 699         state = get_extra_state(expr);
 700         if (!state || !estate_rl(state))
 701                 return 0;
 702
 703         sval = estate_min(state);
 704         if (sval_is_negative(sval) && sval_is_min(sval))
 705                 return 0;
 706
 707         if (sval_is_max(sval))
 708                 return 0;
 709
 710         *min = sval_cast(get_type(expr), sval);
 711         return 1;
 712 }
 713
 714 int get_const_value(struct expression *expr, sval_t *sval)
 715 {
 716         struct symbol *sym;
 717         sval_t right;
 718
 719         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 720                 return 0;
 721         sym = expr->symbol;
 722         if (!(sym->ctype.modifiers & MOD_CONST))
 723                 return 0;
 724         if (get_value(sym->initializer, &right)) {
 725                 *sval = sval_cast(get_type(expr), right);
 726                 return 1;
 727         }
 728         return 0;
 729 }
 730
 731 struct range_list *var_to_absolute_rl(struct expression *expr)
 732 {
 733         struct smatch_state *state;
 734         struct range_list *rl;
 735
 736         state = get_extra_state(expr);
 737         if (!state) {
 738                 if (get_local_rl(expr, &rl))
 739                         return rl;
 740                 if (get_db_type_rl(expr, &rl))
 741                         return rl;
 742                 return alloc_whole_rl(get_type(expr));
 743         }
 744         /* err on the side of saying things are possible */
 745         if (!estate_rl(state))
 746                 return alloc_whole_rl(get_type(expr));
 747         return clone_rl(estate_rl(state));
 748 }
 749
 750 static struct range_list *handle_variable(struct expression *expr, int implied)
 751 {
 752         struct smatch_state *state;
 753         struct range_list *rl;
 754         sval_t sval, min, max;
 755
 756         if (get_const_value(expr, &sval))
 757                 return alloc_rl(sval, sval);
 758
 759         if (custom_handle_variable) {
 760                 rl = custom_handle_variable(expr);
 761                 if (!rl)
 762                         return var_to_absolute_rl(expr);
 763                 return rl;
 764         }
 765
 766         switch (implied) {
 767         case RL_EXACT:
 768                 return NULL;
 769         case RL_HARD:
 770         case RL_IMPLIED:
 771         case RL_ABSOLUTE:
 772                 state = get_extra_state(expr);
 773                 if (!state || !state->data) {
 774                         if (implied == RL_HARD)
 775                                 return NULL;
 776                         if (get_local_rl(expr, &rl))
 777                                 return rl;
 778                         if (get_db_type_rl(expr, &rl))
 779                                 return rl;
 780                         return NULL;
 781                 }
 782                 if (implied == RL_HARD && !estate_has_hard_max(state))
 783                         return NULL;
 784                 return clone_rl(estate_rl(state));
 785         case RL_FUZZY:
 786                 if (!get_fuzzy_min_helper(expr, &min))
 787                         min = sval_type_min(get_type(expr));
 788                 if (!get_fuzzy_max_helper(expr, &max))
 789                         return NULL;
 790                 /* fuzzy ranges are often inverted */
 791                 if (sval_cmp(min, max) > 0) {
 792                         sval = min;
 793                         min = max;
 794                         max = sval;
 795                 }
 796                 return alloc_rl(min, max);
 797         }
 798         return NULL;
 799 }
 800
 801 static sval_t handle_sizeof(struct expression *expr)
 802 {
 803         struct symbol *sym;
 804         sval_t ret;
 805
 806         ret = sval_blank(expr);
 807         sym = expr->cast_type;
 808         if (!sym) {
 809                 sym = evaluate_expression(expr->cast_expression);
 810                 /*
 811                  * Expressions of restricted types will possibly get
 812                  * promoted - check that here
 813                  */
 814                 if (is_restricted_type(sym)) {
 815                         if (type_bits(sym) < bits_in_int)
 816                                 sym = &int_ctype;
 817                 } else if (is_fouled_type(sym)) {
 818                         sym = &int_ctype;
 819                 }
 820         }
 821         examine_symbol_type(sym);
 822
 823         ret.type = size_t_ctype;
 824         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 825                 if (get_real_base_type(sym) == &void_ctype)
 826                         ret.value = 1;
 827                 else
 828                         ret.value = 0;
 829         } else
 830                 ret.value = type_bytes(sym);
 831
 832         return ret;
 833 }
 834
 835 static struct range_list *handle_call_rl(struct expression *expr, int implied)
 836 {
 837         struct range_list *rl;
 838
 839         if (sym_name_is("__builtin_expect", expr->fn)) {
 840                 struct expression *arg;
 841
 842                 arg = get_argument_from_call_expr(expr->args, 0);
 843                 return _get_rl(arg, implied);
 844         }
 845
 846         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
 847                 return NULL;
 848
 849         if (get_implied_return(expr, &rl))
 850                 return rl;
 851         return db_return_vals(expr);
 852 }
 853
 854 static struct range_list *handle_cast(struct expression *expr, int implied)
 855 {
 856         struct range_list *rl;
 857         struct symbol *type;
 858
 859         type = get_type(expr);
 860         rl = _get_rl(expr->cast_expression, implied);
 861         if (rl)
 862                 return cast_rl(type, rl);
 863         if (implied == RL_ABSOLUTE)
 864                 return alloc_whole_rl(type);
 865         if (implied == RL_IMPLIED && type &&
 866             type_bits(type) > 0 && type_bits(type) < 32)
 867                 return alloc_whole_rl(type);
 868         return NULL;
 869 }
 870
 871 static struct range_list *_get_rl(struct expression *expr, int implied)
 872 {
 873         struct range_list *rl;
 874         struct symbol *type;
 875         sval_t sval;
 876
 877         type = get_type(expr);
 878         expr = strip_parens(expr);
 879         if (!expr)
 880                 return NULL;
 881
 882         switch(expr->type) {
 883         case EXPR_CAST:
 884         case EXPR_FORCE_CAST:
 885         case EXPR_IMPLIED_CAST:
 886                 rl = handle_cast(expr, implied);
 887                 goto out_cast;
 888         }
 889
 890         expr = strip_expr(expr);
 891         if (!expr)
 892                 return NULL;
 893
 894         switch (expr->type) {
 895         case EXPR_VALUE:
 896                 sval = sval_from_val(expr, expr->value);
 897                 rl = alloc_rl(sval, sval);
 898                 break;
 899         case EXPR_PREOP:
 900                 rl = handle_preop_rl(expr, implied);
 901                 break;
 902         case EXPR_POSTOP:
 903                 rl = _get_rl(expr->unop, implied);
 904                 break;
 905         case EXPR_BINOP:
 906                 rl = handle_binop_rl(expr, implied);
 907                 break;
 908         case EXPR_COMPARE:
 909                 rl = handle_comparison_rl(expr, implied);
 910                 break;
 911         case EXPR_LOGICAL:
 912                 rl = handle_logical_rl(expr, implied);
 913                 break;
 914         case EXPR_PTRSIZEOF:
 915         case EXPR_SIZEOF:
 916                 sval = handle_sizeof(expr);
 917                 rl = alloc_rl(sval, sval);
 918                 break;
 919         case EXPR_SELECT:
 920         case EXPR_CONDITIONAL:
 921                 rl = handle_conditional_rl(expr, implied);
 922                 break;
 923         case EXPR_CALL:
 924                 rl = handle_call_rl(expr, implied);
 925                 break;
 926         default:
 927                 rl = handle_variable(expr, implied);
 928         }
 929
 930 out_cast:
 931         if (rl)
 932                 return rl;
 933         if (type && implied == RL_ABSOLUTE)
 934                 return alloc_whole_rl(type);
 935         return NULL;
 936 }
 937
 938 /* returns 1 if it can get a value literal or else returns 0 */
 939 int get_value(struct expression *expr, sval_t *sval)
 940 {
 941         struct range_list *rl;
 942
 943         rl = _get_rl(expr, RL_EXACT);
 944         if (!rl_to_sval(rl, sval))
 945                 return 0;
 946         return 1;
 947 }
 948
 949 int get_implied_value(struct expression *expr, sval_t *sval)
 950 {
 951         struct range_list *rl;
 952
 953         rl =  _get_rl(expr, RL_IMPLIED);
 954         if (!rl_to_sval(rl, sval))
 955                 return 0;
 956         return 1;
 957 }
 958
 959 int get_implied_min(struct expression *expr, sval_t *sval)
 960 {
 961         struct range_list *rl;
 962
 963         rl =  _get_rl(expr, RL_IMPLIED);
 964         if (!rl)
 965                 return 0;
 966         *sval = rl_min(rl);
 967         return 1;
 968 }
 969
 970 int get_implied_max(struct expression *expr, sval_t *sval)
 971 {
 972         struct range_list *rl;
 973
 974         rl =  _get_rl(expr, RL_IMPLIED);
 975         if (!rl)
 976                 return 0;
 977         *sval = rl_max(rl);
 978         return 1;
 979 }
 980
 981 int get_implied_rl(struct expression *expr, struct range_list **rl)
 982 {
 983         *rl = _get_rl(expr, RL_IMPLIED);
 984         if (*rl)
 985                 return 1;
 986         return 0;
 987 }
 988
 989 int get_absolute_rl(struct expression *expr, struct range_list **rl)
 990 {
 991         *rl = _get_rl(expr, RL_ABSOLUTE);
 992         if (!*rl)
 993                 *rl = alloc_whole_rl(get_type(expr));
 994         return 1;
 995 }
 996
 997 int custom_get_absolute_rl(struct expression *expr,
 998                            struct range_list *(*fn)(struct expression *expr),
 999                            struct range_list **rl)
1000 {
1001         *rl = NULL;
1002         custom_handle_variable = fn;
1003         *rl = _get_rl(expr, RL_ABSOLUTE);
1004         custom_handle_variable = NULL;
1005         return 1;
1006 }
1007
1008 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1009 {
1010         struct smatch_state *state;
1011
1012         state = get_state(SMATCH_EXTRA, var, sym);
1013         *rl = estate_rl(state);
1014         if (*rl)
1015                 return 1;
1016         return 0;
1017 }
1018
1019 int get_hard_max(struct expression *expr, sval_t *sval)
1020 {
1021         struct range_list *rl;
1022
1023         rl =  _get_rl(expr, RL_HARD);
1024         if (!rl)
1025                 return 0;
1026         *sval = rl_max(rl);
1027         return 1;
1028 }
1029
1030 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1031 {
1032         struct range_list *rl;
1033         sval_t tmp;
1034
1035         rl =  _get_rl(expr, RL_FUZZY);
1036         if (!rl)
1037                 return 0;
1038         tmp = rl_min(rl);
1039         if (sval_is_negative(tmp) && sval_is_min(tmp))
1040                 return 0;
1041         *sval = tmp;
1042         return 1;
1043 }
1044
1045 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1046 {
1047         struct range_list *rl;
1048         sval_t max;
1049
1050         rl =  _get_rl(expr, RL_FUZZY);
1051         if (!rl)
1052                 return 0;
1053         max = rl_max(rl);
1054         if (max.uvalue > INT_MAX - 10000)
1055                 return 0;
1056         *sval = max;
1057         return 1;
1058 }
1059
1060 int get_absolute_min(struct expression *expr, sval_t *sval)
1061 {
1062         struct range_list *rl;
1063         struct symbol *type;
1064
1065         type = get_type(expr);
1066         if (!type)
1067                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1068         rl = _get_rl(expr, RL_ABSOLUTE);
1069         if (rl)
1070                 *sval = rl_min(rl);
1071         else
1072                 *sval = sval_type_min(type);
1073
1074         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1075                 *sval = sval_type_min(type);
1076         return 1;
1077 }
1078
1079 int get_absolute_max(struct expression *expr, sval_t *sval)
1080 {
1081         struct range_list *rl;
1082         struct symbol *type;
1083
1084         type = get_type(expr);
1085         if (!type)
1086                 type = &llong_ctype;
1087         rl = _get_rl(expr, RL_ABSOLUTE);
1088         if (rl)
1089                 *sval = rl_max(rl);
1090         else
1091                 *sval = sval_type_max(type);
1092
1093         if (sval_cmp(sval_type_max(type), *sval) < 0)
1094                 *sval = sval_type_max(type);
1095         return 1;
1096 }
1097
1098 int known_condition_true(struct expression *expr)
1099 {
1100         sval_t tmp;
1101
1102         if (!expr)
1103                 return 0;
1104
1105         if (get_value(expr, &tmp) && tmp.value)
1106                 return 1;
1107
1108         return 0;
1109 }
1110
1111 int known_condition_false(struct expression *expr)
1112 {
1113         if (!expr)
1114                 return 0;
1115
1116         if (is_zero(expr))
1117                 return 1;
1118
1119         if (expr->type == EXPR_CALL) {
1120                 if (sym_name_is("__builtin_constant_p", expr->fn))
1121                         return 1;
1122         }
1123         return 0;
1124 }
1125
1126 int implied_condition_true(struct expression *expr)
1127 {
1128         sval_t tmp;
1129
1130         if (!expr)
1131                 return 0;
1132
1133         if (known_condition_true(expr))
1134                 return 1;
1135         if (get_implied_value(expr, &tmp) && tmp.value)
1136                 return 1;
1137
1138         if (expr->type == EXPR_POSTOP)
1139                 return implied_condition_true(expr->unop);
1140
1141         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1142                 return implied_not_equal(expr->unop, 1);
1143         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1144                 return implied_not_equal(expr->unop, -1);
1145
1146         expr = strip_expr(expr);
1147         switch (expr->type) {
1148         case EXPR_COMPARE:
1149                 if (do_comparison(expr) == 1)
1150                         return 1;
1151                 break;
1152         case EXPR_PREOP:
1153                 if (expr->op == '!') {
1154                         if (implied_condition_false(expr->unop))
1155                                 return 1;
1156                         break;
1157                 }
1158                 break;
1159         default:
1160                 if (implied_not_equal(expr, 0) == 1)
1161                         return 1;
1162                 break;
1163         }
1164         return 0;
1165 }
1166
1167 int implied_condition_false(struct expression *expr)
1168 {
1169         struct expression *tmp;
1170         sval_t sval;
1171
1172         if (!expr)
1173                 return 0;
1174
1175         if (known_condition_false(expr))
1176                 return 1;
1177
1178         switch (expr->type) {
1179         case EXPR_COMPARE:
1180                 if (do_comparison(expr) == 2)
1181                         return 1;
1182         case EXPR_PREOP:
1183                 if (expr->op == '!') {
1184                         if (implied_condition_true(expr->unop))
1185                                 return 1;
1186                         break;
1187                 }
1188                 tmp = strip_expr(expr);
1189                 if (tmp != expr)
1190                         return implied_condition_false(tmp);
1191                 break;
1192         default:
1193                 if (get_implied_value(expr, &sval) && sval.value == 0)
1194                         return 1;
1195                 break;
1196         }
1197         return 0;
1198 }
1199
1200 int can_integer_overflow(struct symbol *type, struct expression *expr)
1201 {
1202         int op;
1203         sval_t lmax, rmax, res;
1204
1205         if (!type)
1206                 type = &int_ctype;
1207
1208         expr = strip_expr(expr);
1209
1210         if (expr->type == EXPR_ASSIGNMENT) {
1211                 switch(expr->op) {
1212                 case SPECIAL_MUL_ASSIGN:
1213                         op = '*';
1214                         break;
1215                 case SPECIAL_ADD_ASSIGN:
1216                         op = '+';
1217                         break;
1218                 case SPECIAL_SHL_ASSIGN:
1219                         op = SPECIAL_LEFTSHIFT;
1220                         break;
1221                 default:
1222                         return 0;
1223                 }
1224         } else if (expr->type == EXPR_BINOP) {
1225                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1226                         return 0;
1227                 op = expr->op;
1228         } else {
1229                 return 0;
1230         }
1231
1232         get_absolute_max(expr->left, &lmax);
1233         get_absolute_max(expr->right, &rmax);
1234
1235         if (sval_binop_overflows(lmax, op, rmax))
1236                 return 1;
1237
1238         res = sval_binop(lmax, op, rmax);
1239         if (sval_cmp(res, sval_type_max(type)) > 0)
1240                 return 1;
1241         return 0;
1242 }