smatch_extra.c

   1 /*
   2  * sparse/smatch_extra.c
   3  *
   4  * Copyright (C) 2008 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * smatch_extra.c is supposed to track the value of every variable.
  12  */
  13
  14 #include <stdlib.h>
  15 #ifndef __USE_ISOC99
  16 #define __USE_ISOC99
  17 #endif
  18 #include <limits.h>
  19 #include "parse.h"
  20 #include "smatch.h"
  21 #include "smatch_slist.h"
  22 #include "smatch_extra.h"
  23
  24 static int my_id;
  25
  26 static struct symbol *cur_func;
  27
  28 struct data_range whole_range = {
  29         .min = LLONG_MIN,
  30         .max = LLONG_MAX,
  31 };
  32
  33 static struct smatch_state *alloc_extra_state_empty(void)
  34 {
  35         struct smatch_state *state;
  36         struct data_info *dinfo;
  37
  38         dinfo = __alloc_data_info(0);
  39         dinfo->type = DATA_RANGE;
  40         dinfo->value_ranges = NULL;
  41         state = __alloc_smatch_state(0);
  42         state->data = dinfo;
  43         return state;
  44 }
  45
  46 static struct smatch_state *alloc_extra_state_no_name(int val)
  47 {
  48         struct smatch_state *state;
  49
  50         state = __alloc_smatch_state(0);
  51         state->data = (void *)alloc_dinfo_range(val, val);
  52         return state;
  53 }
  54
  55 /* We do this because ->value_ranges is a list */
  56 struct smatch_state *extra_undefined(void)
  57 {
  58         struct data_info *dinfo;
  59         static struct smatch_state *ret;
  60         static struct symbol *prev_func;
  61
  62         if  (prev_func == cur_func)
  63                 return ret;
  64         prev_func = cur_func;
  65
  66         dinfo = alloc_dinfo_range(whole_range.min, whole_range.max);
  67         ret = __alloc_smatch_state(0);
  68         ret->name = "unknown";
  69         ret->data = dinfo;
  70         return ret;
  71 }
  72
  73 struct smatch_state *alloc_extra_state(int val)
  74 {
  75         struct smatch_state *state;
  76
  77         state = alloc_extra_state_no_name(val);
  78         state->name = show_ranges(get_dinfo(state)->value_ranges);
  79         return state;
  80 }
  81
  82 struct smatch_state *alloc_extra_state_range(long long min, long long max)
  83 {
  84         struct smatch_state *state;
  85
  86         if (min == whole_range.min && max == whole_range.max)
  87                 return extra_undefined();
  88         state = __alloc_smatch_state(0);
  89         state->data = (void *)alloc_dinfo_range(min, max);
  90         state->name = show_ranges(get_dinfo(state)->value_ranges);
  91         return state;
  92 }
  93
  94 struct smatch_state *alloc_extra_state_range_list(struct range_list *rl)
  95 {
  96         struct smatch_state *state;
  97
  98         state = __alloc_smatch_state(0);
  99         state->data = (void *)alloc_dinfo_range_list(rl);
 100         state->name = show_ranges(get_dinfo(state)->value_ranges);
 101         return state;
 102 }
 103
 104 struct data_info *get_dinfo(struct smatch_state *state)
 105 {
 106         if (!state)
 107                 return NULL;
 108         return (struct data_info *)state->data;
 109
 110 }
 111
 112 struct smatch_state *filter_range(struct smatch_state *orig,
 113                                  long long filter_min, long long filter_max)
 114 {
 115         struct smatch_state *ret;
 116         struct data_info *orig_info;
 117         struct data_info *ret_info;
 118
 119         if (!orig)
 120                 orig = extra_undefined();
 121         orig_info = get_dinfo(orig);
 122         ret = alloc_extra_state_empty();
 123         ret_info = get_dinfo(ret);
 124         ret_info->value_ranges = remove_range(orig_info->value_ranges, filter_min, filter_max);
 125         ret->name = show_ranges(ret_info->value_ranges);
 126         return ret;
 127 }
 128
 129 struct smatch_state *add_filter(struct smatch_state *orig, long long num)
 130 {
 131         return filter_range(orig, num, num);
 132 }
 133
 134 static struct smatch_state *merge_func(const char *name, struct symbol *sym,
 135                                        struct smatch_state *s1,
 136                                        struct smatch_state *s2)
 137 {
 138         struct data_info *info1 = get_dinfo(s1);
 139         struct data_info *info2 = get_dinfo(s2);
 140         struct data_info *ret_info;
 141         struct smatch_state *tmp;
 142         struct range_list *value_ranges;
 143
 144         value_ranges = range_list_union(info1->value_ranges, info2->value_ranges);
 145         tmp = alloc_extra_state_empty();
 146         ret_info = get_dinfo(tmp);
 147         ret_info->value_ranges = value_ranges;
 148         tmp->name = show_ranges(ret_info->value_ranges);
 149         return tmp;
 150 }
 151
 152 struct sm_state *__extra_pre_loop_hook_before(struct statement *iterator_pre_statement)
 153 {
 154         struct expression *expr;
 155         char *name;
 156         struct symbol *sym;
 157         struct sm_state *ret = NULL;
 158
 159         if (!iterator_pre_statement)
 160                 return NULL;
 161         if (iterator_pre_statement->type != STMT_EXPRESSION)
 162                 return NULL;
 163         expr = iterator_pre_statement->expression;
 164         if (expr->type != EXPR_ASSIGNMENT)
 165                 return NULL;
 166         name = get_variable_from_expr(expr->left, &sym);
 167         if (!name || !sym)
 168                 goto free;
 169         ret = get_sm_state(my_id, name, sym);
 170 free:
 171         free_string(name);
 172         return ret;
 173 }
 174
 175 int __iterator_unchanged(struct sm_state *sm, struct statement *iterator)
 176 {
 177         struct expression *iter_expr;
 178         char *name;
 179         struct symbol *sym;
 180         int ret = 0;
 181
 182         if (!iterator)
 183                 return 0;
 184         if (iterator->type != STMT_EXPRESSION)
 185                 return 0;
 186         iter_expr = iterator->expression;
 187         if (iter_expr->op != SPECIAL_INCREMENT && iter_expr->op != SPECIAL_DECREMENT)
 188                 return 0;
 189         name = get_variable_from_expr(iter_expr->unop, &sym);
 190         if (!name || !sym)
 191                 goto free;
 192         if (get_sm_state(my_id, name, sym) == sm)
 193                 ret = 1;
 194 free:
 195         free_string(name);
 196         return ret;
 197 }
 198
 199 void __extra_pre_loop_hook_after(struct sm_state *sm,
 200                                 struct statement *iterator,
 201                                 struct expression *condition)
 202 {
 203         struct expression *iter_expr;
 204         char *name;
 205         struct symbol *sym;
 206         long long value;
 207         int left = 0;
 208         struct smatch_state *state;
 209         struct data_info *dinfo;
 210         long long min, max;
 211
 212         iter_expr = iterator->expression;
 213
 214         if (condition->type != EXPR_COMPARE)
 215                 return;
 216         if (!get_value(condition->left, &value)) {
 217                 if (!get_value(condition->right, &value))
 218                         return;
 219                 left = 1;
 220         }
 221         if (left)
 222                 name = get_variable_from_expr(condition->left, &sym);
 223         else
 224                 name = get_variable_from_expr(condition->right, &sym);
 225         if (!name || !sym)
 226                 goto free;
 227         if (sym != sm->sym || strcmp(name, sm->name))
 228                 goto free;
 229         state = get_state(my_id, name, sym);
 230         dinfo = get_dinfo(state);
 231         min = get_dinfo_min(dinfo);
 232         max = get_dinfo_max(dinfo);
 233         if (iter_expr->op == SPECIAL_INCREMENT && min != whole_range.min && max == whole_range.max) {
 234                 set_state(my_id, name, sym, alloc_extra_state(min));
 235         } else if (min == whole_range.min && max != whole_range.max) {
 236                 set_state(my_id, name, sym, alloc_extra_state(max));
 237         }
 238 free:
 239         free_string(name);
 240         return;
 241 }
 242
 243 static struct smatch_state *unmatched_state(struct sm_state *sm)
 244 {
 245         return extra_undefined();
 246 }
 247
 248 static void match_function_call(struct expression *expr)
 249 {
 250         struct expression *tmp;
 251         struct symbol *sym;
 252         char *name;
 253         int i = 0;
 254
 255         FOR_EACH_PTR(expr->args, tmp) {
 256                 if (tmp->type == EXPR_PREOP && tmp->op == '&') {
 257                         name = get_variable_from_expr(tmp->unop, &sym);
 258                         if (name) {
 259                                 set_state(my_id, name, sym, extra_undefined());
 260                         }
 261                         free_string(name);
 262                 }
 263                 i++;
 264         } END_FOR_EACH_PTR(tmp);
 265 }
 266
 267 static void match_assign(struct expression *expr)
 268 {
 269         struct expression *left;
 270         struct expression *right;
 271         struct symbol *sym;
 272         char *name;
 273         long long value;
 274         int known;
 275         long long min = whole_range.min;
 276         long long max = whole_range.max;
 277         long long tmp;
 278         struct range_list *rl = NULL;
 279
 280         left = strip_expr(expr->left);
 281         name = get_variable_from_expr(left, &sym);
 282         if (!name)
 283                 return;
 284         right = strip_expr(expr->right);
 285         while (right->type == EXPR_ASSIGNMENT && right->op == '=')
 286                 right = strip_expr(right->left);
 287
 288         known = get_implied_range_list(right, &rl);
 289         if (expr->op == '=') {
 290                 if (known)
 291                         set_state(my_id, name, sym, alloc_extra_state_range_list(rl));
 292                 else
 293                         set_state(my_id, name, sym, extra_undefined());
 294                 goto free;
 295         }
 296
 297         known = get_implied_value(right, &value);
 298         if (expr->op == SPECIAL_ADD_ASSIGN) {
 299                 if (get_implied_min(left, &tmp)) {
 300                         if (known)
 301                                 min = tmp + value;
 302                         else
 303                                 min = tmp;
 304                 }
 305
 306         }
 307         if (expr->op == SPECIAL_SUB_ASSIGN) {
 308                 if (get_implied_max(left, &tmp)) {
 309                         if (known)
 310                                 max = tmp - value;
 311                         else
 312                                 max = tmp;
 313                 }
 314
 315         }
 316         set_state(my_id, name, sym, alloc_extra_state_range(min, max));
 317 free:
 318         free_string(name);
 319 }
 320
 321 static void unop_expr(struct expression *expr)
 322 {
 323         struct symbol *sym;
 324         char *name;
 325         long long min = whole_range.min;
 326         long long max = whole_range.max;
 327         long long val;
 328
 329         if (expr->op == '*')
 330                 return;
 331         if (expr->op == '(')
 332                 return;
 333
 334         name = get_variable_from_expr(expr->unop, &sym);
 335         if (!name)
 336                 goto free;
 337         if (expr->op == SPECIAL_INCREMENT) {
 338                 if (get_implied_min(expr->unop, &val))
 339                         min = val + 1;
 340         }
 341         if (expr->op == SPECIAL_DECREMENT) {
 342                 if (get_implied_max(expr->unop, &val))
 343                         max = val - 1;
 344         }
 345         set_state(my_id, name, sym, alloc_extra_state_range(min, max));
 346 free:
 347         free_string(name);
 348 }
 349
 350 static void match_declarations(struct symbol *sym)
 351 {
 352         const char *name;
 353         long long val;
 354
 355         if (sym->ident) {
 356                 name = sym->ident->name;
 357                 if (sym->initializer) {
 358                         if (get_value(sym->initializer, &val))
 359                                 set_state(my_id, name, sym, alloc_extra_state(val));
 360                         else
 361                                 set_state(my_id, name, sym, extra_undefined());
 362                         scoped_state(my_id, name, sym);
 363                 } else {
 364                         set_state(my_id, name, sym, extra_undefined());
 365                         scoped_state(my_id, name, sym);
 366                 }
 367         }
 368 }
 369
 370 static void match_function_def(struct symbol *sym)
 371 {
 372         struct symbol *arg;
 373
 374         cur_func = sym;
 375         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 376                 if (!arg->ident) {
 377                         continue;
 378                 }
 379                 set_state(my_id, arg->ident->name, arg, extra_undefined());
 380         } END_FOR_EACH_PTR(arg);
 381 }
 382
 383 #define VAL_SINGLE 0
 384 #define VAL_MAX    1
 385 #define VAL_MIN    2
 386
 387 static int get_implied_value_helper(struct expression *expr, long long *val, int what)
 388 {
 389         struct smatch_state *state;
 390         struct symbol *sym;
 391         char *name;
 392
 393         if (get_value(expr, val))
 394                 return 1;
 395
 396         name = get_variable_from_expr(expr, &sym);
 397         if (!name)
 398                 return 0;
 399         state = get_state(my_id, name, sym);
 400         free_string(name);
 401         if (!state || !state->data)
 402                 return 0;
 403         if (what == VAL_SINGLE)
 404                 return get_single_value_from_range(get_dinfo(state), val);
 405         if (what == VAL_MAX) {
 406                 *val = get_dinfo_max(get_dinfo(state));
 407                 if (*val == whole_range.max) /* this means just guessing */
 408                         return 0;
 409                 return 1;
 410         }
 411         *val = get_dinfo_min(get_dinfo(state));
 412         if (*val == whole_range.min)
 413                 return 0;
 414         return 1;
 415 }
 416
 417 int get_implied_single_val(struct expression *expr, long long *val)
 418 {
 419         return get_implied_value_helper(expr, val, VAL_SINGLE);
 420 }
 421
 422 int get_implied_max(struct expression *expr, long long *val)
 423 {
 424         return get_implied_value_helper(expr, val, VAL_MAX);
 425 }
 426
 427 int get_implied_min(struct expression *expr, long long *val)
 428 {
 429         return get_implied_value_helper(expr, val, VAL_MIN);
 430 }
 431
 432 int get_implied_single_fuzzy_max(struct expression *expr, long long *max)
 433 {
 434         struct sm_state *sm;
 435         struct sm_state *tmp;
 436
 437         if (get_implied_max(expr, max))
 438                 return 1;
 439
 440         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 441         if (!sm)
 442                 return 0;
 443
 444         *max = whole_range.min;
 445         FOR_EACH_PTR(sm->possible, tmp) {
 446                 long long new_min;
 447
 448                 new_min = get_dinfo_min(get_dinfo(tmp->state));
 449                 if (new_min > *max)
 450                         *max = new_min;
 451         } END_FOR_EACH_PTR(tmp);
 452
 453         if (*max > whole_range.min)
 454                 return 1;
 455         return 0;
 456 }
 457
 458 static int last_stmt_val(struct statement *stmt, long long *val)
 459 {
 460         struct expression *expr;
 461
 462         if (!stmt)
 463                 return 0;
 464
 465         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
 466         if (stmt->type != STMT_EXPRESSION)
 467                 return 0;
 468         expr = stmt->expression;
 469         return get_value(expr, val);
 470 }
 471
 472 static void match_comparison(struct expression *expr)
 473 {
 474         long long fixed;
 475         char *name = NULL;
 476         struct symbol *sym;
 477         struct smatch_state *one_state;
 478         struct smatch_state *two_state;
 479         struct smatch_state *orig;
 480         int left = 0;
 481         int comparison = expr->op;
 482         struct expression *varies = expr->right;
 483
 484         if (!get_value(expr->left, &fixed)) {
 485                 if (!get_value(expr->right, &fixed))
 486                         return;
 487                 varies = expr->left;
 488                 left = 1;
 489         }
 490         if (varies->op == SPECIAL_INCREMENT || varies->op == SPECIAL_DECREMENT)
 491                 varies = varies->unop;
 492         if (varies->type == EXPR_CALL) {
 493                 function_comparison(comparison, varies, fixed, left);
 494                 return;
 495         }
 496
 497         name = get_variable_from_expr(varies, &sym);
 498         if (!name || !sym)
 499                 goto free;
 500
 501         orig = get_state(my_id, name, sym);
 502         if (!orig)
 503                 orig = extra_undefined();
 504
 505         switch (comparison) {
 506         case '<':
 507         case SPECIAL_UNSIGNED_LT:
 508                 one_state = filter_range(orig, whole_range.min, fixed - 1);
 509                 two_state = filter_range(orig, fixed, whole_range.max);
 510                 if (left)
 511                         set_true_false_states(my_id, name, sym, two_state, one_state);
 512                 else
 513                         set_true_false_states(my_id, name, sym, one_state, two_state);
 514                 return;
 515         case SPECIAL_UNSIGNED_LTE:
 516         case SPECIAL_LTE:
 517                 one_state = filter_range(orig, whole_range.min, fixed);
 518                 two_state = filter_range(orig, fixed + 1, whole_range.max);
 519                 if (left)
 520                         set_true_false_states(my_id, name, sym, two_state, one_state);
 521                 else
 522                         set_true_false_states(my_id, name, sym, one_state, two_state);
 523                 return;
 524         case SPECIAL_EQUAL:
 525                 // todo.  print a warning here for impossible conditions.
 526                 one_state = alloc_extra_state(fixed);
 527                 two_state = filter_range(orig, fixed, fixed);
 528                 set_true_false_states(my_id, name, sym, one_state, two_state);
 529                 return;
 530         case SPECIAL_UNSIGNED_GTE:
 531         case SPECIAL_GTE:
 532                 one_state = filter_range(orig, whole_range.min, fixed - 1);
 533                 two_state = filter_range(orig, fixed, whole_range.max);
 534                 if (left)
 535                         set_true_false_states(my_id, name, sym, one_state, two_state);
 536                 else
 537                         set_true_false_states(my_id, name, sym, two_state, one_state);
 538                 return;
 539         case '>':
 540         case SPECIAL_UNSIGNED_GT:
 541                 one_state = filter_range(orig, whole_range.min, fixed);
 542                 two_state = filter_range(orig, fixed + 1, whole_range.max);
 543                 if (left)
 544                         set_true_false_states(my_id, name, sym, one_state, two_state);
 545                 else
 546                         set_true_false_states(my_id, name, sym, two_state, one_state);
 547                 return;
 548         case SPECIAL_NOTEQUAL:
 549                 one_state = alloc_extra_state(fixed);
 550                 two_state = filter_range(orig, fixed, fixed);
 551                 set_true_false_states(my_id, name, sym, two_state, one_state);
 552                 return;
 553         default:
 554                 sm_msg("unhandled comparison %d\n", comparison);
 555                 return;
 556         }
 557         return;
 558 free:
 559         free_string(name);
 560 }
 561
 562 /* this is actually hooked from smatch_implied.c...  it's hacky, yes */
 563 void __extra_match_condition(struct expression *expr)
 564 {
 565         struct symbol *sym;
 566         char *name;
 567         struct smatch_state *pre_state;
 568         struct smatch_state *true_state;
 569         struct smatch_state *false_state;
 570
 571         expr = strip_expr(expr);
 572         switch (expr->type) {
 573         case EXPR_CALL:
 574                 function_comparison(SPECIAL_NOTEQUAL, expr, 0, 1);
 575                 return;
 576         case EXPR_PREOP:
 577         case EXPR_SYMBOL:
 578         case EXPR_DEREF:
 579                 name = get_variable_from_expr(expr, &sym);
 580                 if (!name)
 581                         return;
 582                 pre_state = get_state(my_id, name, sym);
 583                 true_state = add_filter(pre_state, 0);
 584                 false_state = alloc_extra_state(0);
 585                 set_true_false_states(my_id, name, sym, true_state, false_state);
 586                 free_string(name);
 587                 return;
 588         case EXPR_COMPARE:
 589                 match_comparison(expr);
 590                 return;
 591         case EXPR_ASSIGNMENT:
 592                 __extra_match_condition(expr->left);
 593                 return;
 594         }
 595 }
 596
 597 /* returns 1 if it is not possible for expr to be value, otherwise returns 0 */
 598 int implied_not_equal(struct expression *expr, long long val)
 599 {
 600         char *name;
 601         struct symbol *sym;
 602         struct smatch_state *state;
 603         int ret = 0;
 604
 605         name = get_variable_from_expr(expr, &sym);
 606         if (!name || !sym)
 607                 goto exit;
 608         state = get_state(my_id, name, sym);
 609         if (!state || !state->data)
 610                 goto exit;
 611         ret = !possibly_false(SPECIAL_NOTEQUAL, get_dinfo(state), val, 1);
 612 exit:
 613         free_string(name);
 614         return ret;
 615 }
 616
 617 int known_condition_true(struct expression *expr)
 618 {
 619         long long tmp;
 620
 621         if (!expr)
 622                 return 0;
 623
 624         if (get_value(expr, &tmp) && tmp)
 625                 return 1;
 626
 627         expr = strip_expr(expr);
 628         switch (expr->type) {
 629         case EXPR_PREOP:
 630                 if (expr->op == '!') {
 631                         if (known_condition_false(expr->unop))
 632                                 return 1;
 633                         break;
 634                 }
 635                 break;
 636         default:
 637                 break;
 638         }
 639         return 0;
 640 }
 641
 642 int known_condition_false(struct expression *expr)
 643 {
 644         if (!expr)
 645                 return 0;
 646
 647         if (is_zero(expr))
 648                 return 1;
 649
 650         switch (expr->type) {
 651         case EXPR_PREOP:
 652                 if (expr->op == '!') {
 653                         if (known_condition_true(expr->unop))
 654                                 return 1;
 655                         break;
 656                 }
 657                 break;
 658         default:
 659                 break;
 660         }
 661         return 0;
 662 }
 663
 664 static int do_comparison_range(struct expression *expr)
 665 {
 666         struct symbol *sym;
 667         char *name;
 668         struct smatch_state *state;
 669         long long value;
 670         int left = 0;
 671         int poss_true, poss_false;
 672
 673         if (!get_value(expr->left, &value)) {
 674                 if (!get_value(expr->right, &value))
 675                         return 3;
 676                 left = 1;
 677         }
 678         if (left)
 679                 name = get_variable_from_expr(expr->left, &sym);
 680         else
 681                 name = get_variable_from_expr(expr->right, &sym);
 682         if (!name || !sym)
 683                 goto free;
 684         state = get_state(SMATCH_EXTRA, name, sym);
 685         if (!state)
 686                 goto free;
 687         poss_true = possibly_true(expr->op, get_dinfo(state), value, left);
 688         poss_false = possibly_false(expr->op, get_dinfo(state), value, left);
 689         if (!poss_true && !poss_false)
 690                 return 0;
 691         if (poss_true && !poss_false)
 692                 return 1;
 693         if (!poss_true && poss_false)
 694                 return 2;
 695         if (poss_true && poss_false)
 696                 return 3;
 697 free:
 698         free_string(name);
 699         return 3;
 700 }
 701
 702 int implied_condition_true(struct expression *expr)
 703 {
 704         struct statement *stmt;
 705         long long tmp;
 706         long long val;
 707
 708         if (!expr)
 709                 return 0;
 710
 711         if (get_value(expr, &tmp) && tmp)
 712                 return 1;
 713
 714         expr = strip_expr(expr);
 715         switch (expr->type) {
 716         case EXPR_COMPARE:
 717                 if (do_comparison_range(expr) == 1)
 718                         return 1;
 719                 break;
 720         case EXPR_PREOP:
 721                 if (expr->op == '!') {
 722                         if (implied_condition_false(expr->unop))
 723                                 return 1;
 724                         break;
 725                 }
 726                 stmt = get_block_thing(expr);
 727                 if (last_stmt_val(stmt, &val) && val == 1)
 728                         return 1;
 729                 break;
 730         default:
 731                 if (implied_not_equal(expr, 0) == 1)
 732                         return 1;
 733                 break;
 734         }
 735         return 0;
 736 }
 737
 738 int implied_condition_false(struct expression *expr)
 739 {
 740         struct statement *stmt;
 741         struct expression *tmp;
 742         long long val;
 743
 744         if (!expr)
 745                 return 0;
 746
 747         if (is_zero(expr))
 748                 return 1;
 749
 750         switch (expr->type) {
 751         case EXPR_COMPARE:
 752                 if (do_comparison_range(expr) == 2)
 753                         return 1;
 754         case EXPR_PREOP:
 755                 if (expr->op == '!') {
 756                         if (implied_condition_true(expr->unop))
 757                                 return 1;
 758                         break;
 759                 }
 760                 stmt = get_block_thing(expr);
 761                 if (last_stmt_val(stmt, &val) && val == 0)
 762                         return 1;
 763                 tmp = strip_expr(expr);
 764                 if (tmp != expr)
 765                         return implied_condition_false(tmp);
 766                 break;
 767         default:
 768                 if (get_implied_value(expr, &val) && val == 0)
 769                         return 1;
 770                 break;
 771         }
 772         return 0;
 773 }
 774
 775 int get_implied_range_list(struct expression *expr, struct range_list **rl)
 776 {
 777         long long val;
 778         struct smatch_state *state;
 779
 780         expr = strip_expr(expr);
 781
 782         state = get_state_expr(my_id, expr);
 783         if (state) {
 784                 *rl = clone_range_list(get_dinfo(state)->value_ranges);
 785                 return 1;
 786         }
 787
 788         if (get_implied_value(expr, &val)) {
 789                 *rl = NULL;
 790                 add_range(rl, val, val);
 791                 return 1;
 792         }
 793
 794         if (expr->type == EXPR_BINOP && expr->op == '%') {
 795                 if (!get_implied_value(expr->right, &val))
 796                         return 0;
 797                 *rl = NULL;
 798                 add_range(rl, 0, val - 1);
 799                 return 1;
 800         }
 801
 802         return 0;
 803 }
 804
 805 void register_smatch_extra(int id)
 806 {
 807         my_id = id;
 808         add_merge_hook(my_id, &merge_func);
 809         add_unmatched_state_hook(my_id, &unmatched_state);
 810         add_hook(&unop_expr, OP_HOOK);
 811         add_hook(&match_function_def, FUNC_DEF_HOOK);
 812         add_hook(&match_function_call, FUNCTION_CALL_HOOK);
 813         add_hook(&match_assign, ASSIGNMENT_HOOK);
 814         add_hook(&match_declarations, DECLARATION_HOOK);
 815
 816         if (option_project == PROJ_KERNEL) {
 817                 /* I don't know how to test for the ATTRIB_NORET attribute. :( */
 818                 add_function_hook("panic", &__match_nullify_path_hook, NULL);
 819                 add_function_hook("do_exit", &__match_nullify_path_hook, NULL);
 820                 add_function_hook("complete_and_exit", &__match_nullify_path_hook, NULL);
 821                 add_function_hook("__module_put_and_exit", &__match_nullify_path_hook, NULL);
 822                 add_function_hook("do_group_exit", &__match_nullify_path_hook, NULL);
 823         }
 824 }