1 /*
   2  * Copyright (C) 2012 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17 
  18 /*
  19  * The point here is to store the relationships between two variables.
  20  * Ie:  y > x.
  21  * To do that we create a state with the two variables in alphabetical order:
  22  * ->name = "x vs y" and the state would be "<".  On the false path the state
  23  * would be ">=".
  24  *
  25  * Part of the trick of it is that if x or y is modified then we need to reset
  26  * the state.  We need to keep a list of all the states which depend on x and
  27  * all the states which depend on y.  The link_id code handles this.
  28  *
  29  */
  30 
  31 #include "smatch.h"
  32 #include "smatch_extra.h"
  33 #include "smatch_slist.h"
  34 
  35 int comparison_id;
  36 static int link_id;
  37 static int inc_dec_id;
  38 static int inc_dec_link_id;
  39 
  40 static void add_comparison(struct expression *left, int comparison, struct expression *right);
  41 
  42 /* for handling for loops */
  43 STATE(start);
  44 STATE(incremented);
  45 
  46 ALLOCATOR(compare_data, "compare data");
  47 
  48 static struct symbol *vsl_to_sym(struct var_sym_list *vsl)
  49 {
  50         struct var_sym *vs;
  51 
  52         if (!vsl)
  53                 return NULL;
  54         if (ptr_list_size((struct ptr_list *)vsl) != 1)
  55                 return NULL;
  56         vs = first_ptr_list((struct ptr_list *)vsl);
  57         return vs->sym;
  58 }
  59 
  60 static const char *show_comparison(int comparison)
  61 {
  62         if (comparison == IMPOSSIBLE_COMPARISON)
  63                 return "impossible";
  64         if (comparison == UNKNOWN_COMPARISON)
  65                 return "unknown";
  66         return show_special(comparison);
  67 }
  68 
  69 struct smatch_state *alloc_compare_state(
  70                 struct expression *left,
  71                 const char *left_var, struct var_sym_list *left_vsl,
  72                 int comparison,
  73                 struct expression *right,
  74                 const char *right_var, struct var_sym_list *right_vsl)
  75 {
  76         struct smatch_state *state;
  77         struct compare_data *data;
  78 
  79         state = __alloc_smatch_state(0);
  80         state->name = alloc_sname(show_comparison(comparison));
  81         data = __alloc_compare_data(0);
  82         data->left = left;
  83         data->left_var = alloc_sname(left_var);
  84         data->left_vsl = clone_var_sym_list(left_vsl);
  85         data->comparison = comparison;
  86         data->right = right;
  87         data->right_var = alloc_sname(right_var);
  88         data->right_vsl = clone_var_sym_list(right_vsl);
  89         state->data = data;
  90         return state;
  91 }
  92 
  93 int state_to_comparison(struct smatch_state *state)
  94 {
  95         if (!state || !state->data)
  96                 return UNKNOWN_COMPARISON;
  97         return ((struct compare_data *)state->data)->comparison;
  98 }
  99 
 100 /*
 101  * flip_comparison() reverses the op left and right.  So "x >= y" becomes "y <= x".
 102  */
 103 int flip_comparison(int op)
 104 {
 105         switch (op) {
 106         case UNKNOWN_COMPARISON:
 107                 return UNKNOWN_COMPARISON;
 108         case '<':
 109                 return '>';
 110         case SPECIAL_UNSIGNED_LT:
 111                 return SPECIAL_UNSIGNED_GT;
 112         case SPECIAL_LTE:
 113                 return SPECIAL_GTE;
 114         case SPECIAL_UNSIGNED_LTE:
 115                 return SPECIAL_UNSIGNED_GTE;
 116         case SPECIAL_EQUAL:
 117                 return SPECIAL_EQUAL;
 118         case SPECIAL_NOTEQUAL:
 119                 return SPECIAL_NOTEQUAL;
 120         case SPECIAL_GTE:
 121                 return SPECIAL_LTE;
 122         case SPECIAL_UNSIGNED_GTE:
 123                 return SPECIAL_UNSIGNED_LTE;
 124         case '>':
 125                 return '<';
 126         case SPECIAL_UNSIGNED_GT:
 127                 return SPECIAL_UNSIGNED_LT;
 128         case IMPOSSIBLE_COMPARISON:
 129                 return UNKNOWN_COMPARISON;
 130         default:
 131                 sm_perror("unhandled comparison %d", op);
 132                 return op;
 133         }
 134 }
 135 
 136 int negate_comparison(int op)
 137 {
 138         switch (op) {
 139         case UNKNOWN_COMPARISON:
 140                 return UNKNOWN_COMPARISON;
 141         case '<':
 142                 return SPECIAL_GTE;
 143         case SPECIAL_UNSIGNED_LT:
 144                 return SPECIAL_UNSIGNED_GTE;
 145         case SPECIAL_LTE:
 146                 return '>';
 147         case SPECIAL_UNSIGNED_LTE:
 148                 return SPECIAL_UNSIGNED_GT;
 149         case SPECIAL_EQUAL:
 150                 return SPECIAL_NOTEQUAL;
 151         case SPECIAL_NOTEQUAL:
 152                 return SPECIAL_EQUAL;
 153         case SPECIAL_GTE:
 154                 return '<';
 155         case SPECIAL_UNSIGNED_GTE:
 156                 return SPECIAL_UNSIGNED_LT;
 157         case '>':
 158                 return SPECIAL_LTE;
 159         case SPECIAL_UNSIGNED_GT:
 160                 return SPECIAL_UNSIGNED_LTE;
 161         case IMPOSSIBLE_COMPARISON:
 162                 return UNKNOWN_COMPARISON;
 163         default:
 164                 sm_perror("unhandled comparison %d", op);
 165                 return op;
 166         }
 167 }
 168 
 169 static int rl_comparison(struct range_list *left_rl, struct range_list *right_rl)
 170 {
 171         sval_t left_min, left_max, right_min, right_max;
 172         struct symbol *type = &int_ctype;
 173 
 174         if (!left_rl || !right_rl)
 175                 return UNKNOWN_COMPARISON;
 176 
 177         if (type_positive_bits(rl_type(left_rl)) > type_positive_bits(type))
 178                 type = rl_type(left_rl);
 179         if (type_positive_bits(rl_type(right_rl)) > type_positive_bits(type))
 180                 type = rl_type(right_rl);
 181 
 182         left_rl = cast_rl(type, left_rl);
 183         right_rl = cast_rl(type, right_rl);
 184 
 185         left_min = rl_min(left_rl);
 186         left_max = rl_max(left_rl);
 187         right_min = rl_min(right_rl);
 188         right_max = rl_max(right_rl);
 189 
 190         if (left_min.value == left_max.value &&
 191             right_min.value == right_max.value &&
 192             left_min.value == right_min.value)
 193                 return SPECIAL_EQUAL;
 194 
 195         if (sval_cmp(left_max, right_min) < 0)
 196                 return '<';
 197         if (sval_cmp(left_max, right_min) == 0)
 198                 return SPECIAL_LTE;
 199         if (sval_cmp(left_min, right_max) > 0)
 200                 return '>';
 201         if (sval_cmp(left_min, right_max) == 0)
 202                 return SPECIAL_GTE;
 203 
 204         return UNKNOWN_COMPARISON;
 205 }
 206 
 207 static int comparison_from_extra(struct expression *a, struct expression *b)
 208 {
 209         struct range_list *left, *right;
 210 
 211         if (!get_implied_rl(a, &left))
 212                 return UNKNOWN_COMPARISON;
 213         if (!get_implied_rl(b, &right))
 214                 return UNKNOWN_COMPARISON;
 215 
 216         return rl_comparison(left, right);
 217 }
 218 
 219 static struct range_list *get_orig_rl(struct var_sym_list *vsl)
 220 {
 221         struct symbol *sym;
 222         struct smatch_state *state;
 223 
 224         if (!vsl)
 225                 return NULL;
 226         sym = vsl_to_sym(vsl);
 227         if (!sym || !sym->ident)
 228                 return NULL;
 229         state = get_orig_estate(sym->ident->name, sym);
 230         return estate_rl(state);
 231 }
 232 
 233 static struct smatch_state *unmatched_comparison(struct sm_state *sm)
 234 {
 235         struct compare_data *data = sm->state->data;
 236         struct range_list *left_rl, *right_rl;
 237         int op = UNKNOWN_COMPARISON;
 238 
 239         if (!data)
 240                 return &undefined;
 241 
 242         if (is_impossible_path()) {
 243                 op = IMPOSSIBLE_COMPARISON;
 244                 goto alloc;
 245         }
 246 
 247         if (strstr(data->left_var, " orig"))
 248                 left_rl = get_orig_rl(data->left_vsl);
 249         else if (!get_implied_rl_var_sym(data->left_var, vsl_to_sym(data->left_vsl), &left_rl))
 250                 goto alloc;
 251 
 252         if (strstr(data->right_var, " orig"))
 253                 right_rl = get_orig_rl(data->right_vsl);
 254         else if (!get_implied_rl_var_sym(data->right_var, vsl_to_sym(data->right_vsl), &right_rl))
 255                 goto alloc;
 256 
 257         op = rl_comparison(left_rl, right_rl);
 258 
 259 alloc:
 260         return alloc_compare_state(data->left, data->left_var, data->left_vsl,
 261                                    op,
 262                                    data->right, data->right_var, data->right_vsl);
 263 }
 264 
 265 /* remove_unsigned_from_comparison() is obviously a hack. */
 266 int remove_unsigned_from_comparison(int op)
 267 {
 268         switch (op) {
 269         case SPECIAL_UNSIGNED_LT:
 270                 return '<';
 271         case SPECIAL_UNSIGNED_LTE:
 272                 return SPECIAL_LTE;
 273         case SPECIAL_UNSIGNED_GTE:
 274                 return SPECIAL_GTE;
 275         case SPECIAL_UNSIGNED_GT:
 276                 return '>';
 277         default:
 278                 return op;
 279         }
 280 }
 281 
 282 /*
 283  * This is for when you merge states "a < b" and "a == b", the result is that
 284  * we can say for sure, "a <= b" after the merge.
 285  */
 286 int merge_comparisons(int one, int two)
 287 {
 288         int LT, EQ, GT;
 289 
 290         if (one == UNKNOWN_COMPARISON || two == UNKNOWN_COMPARISON)
 291                 return UNKNOWN_COMPARISON;
 292 
 293         if (one == IMPOSSIBLE_COMPARISON)
 294                 return two;
 295         if (two == IMPOSSIBLE_COMPARISON)
 296                 return one;
 297 
 298         one = remove_unsigned_from_comparison(one);
 299         two = remove_unsigned_from_comparison(two);
 300 
 301         if (one == two)
 302                 return one;
 303 
 304         LT = EQ = GT = 0;
 305 
 306         switch (one) {
 307         case '<':
 308                 LT = 1;
 309                 break;
 310         case SPECIAL_LTE:
 311                 LT = 1;
 312                 EQ = 1;
 313                 break;
 314         case SPECIAL_EQUAL:
 315                 EQ = 1;
 316                 break;
 317         case SPECIAL_GTE:
 318                 GT = 1;
 319                 EQ = 1;
 320                 break;
 321         case '>':
 322                 GT = 1;
 323         }
 324 
 325         switch (two) {
 326         case '<':
 327                 LT = 1;
 328                 break;
 329         case SPECIAL_LTE:
 330                 LT = 1;
 331                 EQ = 1;
 332                 break;
 333         case SPECIAL_EQUAL:
 334                 EQ = 1;
 335                 break;
 336         case SPECIAL_GTE:
 337                 GT = 1;
 338                 EQ = 1;
 339                 break;
 340         case '>':
 341                 GT = 1;
 342         }
 343 
 344         if (LT && EQ && GT)
 345                 return UNKNOWN_COMPARISON;
 346         if (LT && EQ)
 347                 return SPECIAL_LTE;
 348         if (LT && GT)
 349                 return SPECIAL_NOTEQUAL;
 350         if (LT)
 351                 return '<';
 352         if (EQ && GT)
 353                 return SPECIAL_GTE;
 354         if (GT)
 355                 return '>';
 356         return UNKNOWN_COMPARISON;
 357 }
 358 
 359 /*
 360  * This is for if you have "a < b" and "b <= c" and you want to see how "a
 361  * compares to c".  You would call this like get_combined_comparison('<', '<=').
 362  * The return comparison would be '<'.
 363  */
 364 int combine_comparisons(int left_compare, int right_compare)
 365 {
 366         int LT, EQ, GT;
 367 
 368         left_compare = remove_unsigned_from_comparison(left_compare);
 369         right_compare = remove_unsigned_from_comparison(right_compare);
 370 
 371         LT = EQ = GT = 0;
 372 
 373         switch (left_compare) {
 374         case '<':
 375                 LT++;
 376                 break;
 377         case SPECIAL_LTE:
 378                 LT++;
 379                 EQ++;
 380                 break;
 381         case SPECIAL_EQUAL:
 382                 return right_compare;
 383         case SPECIAL_GTE:
 384                 GT++;
 385                 EQ++;
 386                 break;
 387         case '>':
 388                 GT++;
 389         }
 390 
 391         switch (right_compare) {
 392         case '<':
 393                 LT++;
 394                 break;
 395         case SPECIAL_LTE:
 396                 LT++;
 397                 EQ++;
 398                 break;
 399         case SPECIAL_EQUAL:
 400                 return left_compare;
 401         case SPECIAL_GTE:
 402                 GT++;
 403                 EQ++;
 404                 break;
 405         case '>':
 406                 GT++;
 407         }
 408 
 409         if (LT == 2) {
 410                 if (EQ == 2)
 411                         return SPECIAL_LTE;
 412                 return '<';
 413         }
 414 
 415         if (GT == 2) {
 416                 if (EQ == 2)
 417                         return SPECIAL_GTE;
 418                 return '>';
 419         }
 420         return UNKNOWN_COMPARISON;
 421 }
 422 
 423 /*
 424  * This is mostly used when you know from extra state that a <= b but you
 425  * know from comparisons that a != b so then if take the intersection then
 426  * we know that a < b.  The name is taken from the fact that the intersection
 427  * of < and <= is <.
 428  */
 429 int comparison_intersection(int left_compare, int right_compare)
 430 {
 431         int LT, GT, EQ, NE, total;
 432 
 433         if (left_compare == IMPOSSIBLE_COMPARISON ||
 434             right_compare == IMPOSSIBLE_COMPARISON)
 435                 return IMPOSSIBLE_COMPARISON;
 436 
 437         left_compare = remove_unsigned_from_comparison(left_compare);
 438         right_compare = remove_unsigned_from_comparison(right_compare);
 439 
 440         LT = GT = EQ = NE = total = 0;
 441 
 442         /* Only one side is known. */
 443         if (!left_compare)
 444                 return right_compare;
 445         if (!right_compare)
 446                 return left_compare;
 447 
 448         switch (left_compare) {
 449         case '<':
 450                 LT++;
 451                 total += 1;
 452                 break;
 453         case SPECIAL_LTE:
 454                 LT++;
 455                 EQ++;
 456                 total += 2;
 457                 break;
 458         case SPECIAL_EQUAL:
 459                 EQ++;
 460                 total += 1;
 461                 break;
 462         case SPECIAL_NOTEQUAL:
 463                 NE++;
 464                 total += 1;
 465                 break;
 466         case SPECIAL_GTE:
 467                 GT++;
 468                 EQ++;
 469                 total += 2;
 470                 break;
 471         case '>':
 472                 GT++;
 473                 total += 1;
 474                 break;
 475         default:
 476                 return UNKNOWN_COMPARISON;
 477         }
 478 
 479         switch (right_compare) {
 480         case '<':
 481                 LT++;
 482                 total += 1;
 483                 break;
 484         case SPECIAL_LTE:
 485                 LT++;
 486                 EQ++;
 487                 total += 2;
 488                 break;
 489         case SPECIAL_EQUAL:
 490                 EQ++;
 491                 total += 1;
 492                 break;
 493         case SPECIAL_NOTEQUAL:
 494                 NE++;
 495                 total += 1;
 496                 break;
 497         case SPECIAL_GTE:
 498                 GT++;
 499                 EQ++;
 500                 total += 2;
 501                 break;
 502         case '>':
 503                 GT++;
 504                 total += 1;
 505                 break;
 506         default:
 507                 return UNKNOWN_COMPARISON;
 508         }
 509 
 510         if (LT == 2) {
 511                 if (EQ == 2)
 512                         return SPECIAL_LTE;
 513                 return '<';
 514         }
 515 
 516         if (GT == 2) {
 517                 if (EQ == 2)
 518                         return SPECIAL_GTE;
 519                 return '>';
 520         }
 521         if (EQ == 2)
 522                 return SPECIAL_EQUAL;
 523         if (total == 2 && EQ && NE)
 524                 return IMPOSSIBLE_COMPARISON;
 525         if (GT && LT)
 526                 return IMPOSSIBLE_COMPARISON;
 527         if (GT && NE)
 528                 return '>';
 529         if (LT && NE)
 530                 return '<';
 531         if (NE == 2)
 532                 return SPECIAL_NOTEQUAL;
 533         if (total == 2 && (LT || GT) && EQ)
 534                 return IMPOSSIBLE_COMPARISON;
 535 
 536         return UNKNOWN_COMPARISON;
 537 }
 538 
 539 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
 540 {
 541         struct compare_data *data = cur->state->data;
 542         int extra, new;
 543         static bool in_recurse;
 544 
 545         // FIXME.  No data is useless
 546         if (!data)
 547                 return;
 548 
 549         if (in_recurse)
 550                 return;
 551         in_recurse = true;
 552         extra = comparison_from_extra(data->left, data->right);
 553         in_recurse = false;
 554         if (!extra)
 555                 return;
 556         new = comparison_intersection(extra, data->comparison);
 557         if (new == data->comparison)
 558                 return;
 559 
 560         // FIXME: we should always preserve implications
 561         set_state(comparison_id, cur->name, NULL,
 562                   alloc_compare_state(data->left, data->left_var, data->left_vsl,
 563                                       new,
 564                                       data->right, data->right_var, data->right_vsl));
 565 }
 566 
 567 struct smatch_state *merge_compare_states(struct smatch_state *s1, struct smatch_state *s2)
 568 {
 569         struct compare_data *data = s1->data;
 570         int op;
 571 
 572         if (!data)
 573                 return &undefined;
 574 
 575         op = merge_comparisons(state_to_comparison(s1), state_to_comparison(s2));
 576         return alloc_compare_state(
 577                         data->left, data->left_var, data->left_vsl,
 578                         op,
 579                         data->right, data->right_var, data->right_vsl);
 580 }
 581 
 582 static struct smatch_state *alloc_link_state(struct string_list *links)
 583 {
 584         struct smatch_state *state;
 585         static char buf[256];
 586         char *tmp;
 587         int i;
 588 
 589         state = __alloc_smatch_state(0);
 590 
 591         i = 0;
 592         FOR_EACH_PTR(links, tmp) {
 593                 if (!i++) {
 594                         snprintf(buf, sizeof(buf), "%s", tmp);
 595                 } else {
 596                         append(buf, ", ", sizeof(buf));
 597                         append(buf, tmp, sizeof(buf));
 598                 }
 599         } END_FOR_EACH_PTR(tmp);
 600 
 601         state->name = alloc_sname(buf);
 602         state->data = links;
 603         return state;
 604 }
 605 
 606 static void save_start_states(struct statement *stmt)
 607 {
 608         struct symbol *param;
 609         char orig[64];
 610         char state_name[128];
 611         struct smatch_state *state;
 612         struct string_list *links;
 613         char *link;
 614 
 615         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
 616                 struct var_sym_list *left_vsl = NULL;
 617                 struct var_sym_list *right_vsl = NULL;
 618 
 619                 if (!param->ident)
 620                         continue;
 621                 snprintf(orig, sizeof(orig), "%s orig", param->ident->name);
 622                 snprintf(state_name, sizeof(state_name), "%s vs %s", param->ident->name, orig);
 623                 add_var_sym(&left_vsl, param->ident->name, param);
 624                 add_var_sym(&right_vsl, orig, param);
 625                 state = alloc_compare_state(
 626                                 NULL, param->ident->name, left_vsl,
 627                                 SPECIAL_EQUAL,
 628                                 NULL, alloc_sname(orig), right_vsl);
 629                 set_state(comparison_id, state_name, NULL, state);
 630 
 631                 link = alloc_sname(state_name);
 632                 links = NULL;
 633                 insert_string(&links, link);
 634                 state = alloc_link_state(links);
 635                 set_state(link_id, param->ident->name, param, state);
 636         } END_FOR_EACH_PTR(param);
 637 }
 638 
 639 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
 640 {
 641         struct smatch_state *ret;
 642         struct string_list *links;
 643 
 644         links = combine_string_lists(s1->data, s2->data);
 645         ret = alloc_link_state(links);
 646         return ret;
 647 }
 648 
 649 static void save_link_var_sym(const char *var, struct symbol *sym, const char *link)
 650 {
 651         struct smatch_state *old_state, *new_state;
 652         struct string_list *links;
 653         char *new;
 654 
 655         old_state = get_state(link_id, var, sym);
 656         if (old_state)
 657                 links = clone_str_list(old_state->data);
 658         else
 659                 links = NULL;
 660 
 661         new = alloc_sname(link);
 662         insert_string(&links, new);
 663 
 664         new_state = alloc_link_state(links);
 665         set_state(link_id, var, sym, new_state);
 666 }
 667 
 668 static void match_inc(struct sm_state *sm, bool preserve)
 669 {
 670         struct string_list *links;
 671         struct smatch_state *state, *new;
 672         struct compare_data *data;
 673         char *tmp;
 674         int flip;
 675         int op;
 676 
 677         links = sm->state->data;
 678 
 679         FOR_EACH_PTR(links, tmp) {
 680                 state = get_state(comparison_id, tmp, NULL);
 681                 if (!state)
 682                         continue;
 683                 data = state->data;
 684                 if (!data)
 685                         continue;
 686 
 687                 flip = 0;
 688                 if (strncmp(sm->name, tmp, strlen(sm->name)) != 0 ||
 689                     tmp[strlen(sm->name)] != ' ')
 690                         flip = 1;
 691 
 692                 op = state_to_comparison(state);
 693 
 694                 switch (flip ? flip_comparison(op) : op) {
 695                 case SPECIAL_EQUAL:
 696                 case SPECIAL_GTE:
 697                 case SPECIAL_UNSIGNED_GTE:
 698                 case '>':
 699                 case SPECIAL_UNSIGNED_GT:
 700                         if (preserve)
 701                                 break;
 702                         new = alloc_compare_state(
 703                                         data->left, data->left_var, data->left_vsl,
 704                                         flip ? '<' : '>',
 705                                         data->right, data->right_var, data->right_vsl);
 706                         set_state(comparison_id, tmp, NULL, new);
 707                         break;
 708                 case '<':
 709                 case SPECIAL_UNSIGNED_LT:
 710                         new = alloc_compare_state(
 711                                         data->left, data->left_var, data->left_vsl,
 712                                         flip ? SPECIAL_GTE : SPECIAL_LTE,
 713                                         data->right, data->right_var, data->right_vsl);
 714                         set_state(comparison_id, tmp, NULL, new);
 715                         break;
 716                 default:
 717                         new = alloc_compare_state(
 718                                         data->left, data->left_var, data->left_vsl,
 719                                         UNKNOWN_COMPARISON,
 720                                         data->right, data->right_var, data->right_vsl);
 721                         set_state(comparison_id, tmp, NULL, new);
 722                 }
 723         } END_FOR_EACH_PTR(tmp);
 724 }
 725 
 726 static void match_dec(struct sm_state *sm, bool preserve)
 727 {
 728         struct string_list *links;
 729         struct smatch_state *state;
 730         char *tmp;
 731 
 732         links = sm->state->data;
 733 
 734         FOR_EACH_PTR(links, tmp) {
 735                 struct compare_data *data;
 736                 struct smatch_state *new;
 737 
 738                 state = get_state(comparison_id, tmp, NULL);
 739                 if (!state || !state->data)
 740                         continue;
 741 
 742                 data = state->data;
 743 
 744                 switch (state_to_comparison(state)) {
 745                 case SPECIAL_EQUAL:
 746                 case SPECIAL_LTE:
 747                 case SPECIAL_UNSIGNED_LTE:
 748                 case '<':
 749                 case SPECIAL_UNSIGNED_LT: {
 750                         if (preserve)
 751                                 break;
 752 
 753                         new = alloc_compare_state(
 754                                         data->left, data->left_var, data->left_vsl,
 755                                         '<',
 756                                         data->right, data->right_var, data->right_vsl);
 757                         set_state(comparison_id, tmp, NULL, new);
 758                         break;
 759                         }
 760                 default:
 761                         new = alloc_compare_state(
 762                                         data->left, data->left_var, data->left_vsl,
 763                                         UNKNOWN_COMPARISON,
 764                                         data->right, data->right_var, data->right_vsl);
 765                         set_state(comparison_id, tmp, NULL, new);
 766                 }
 767         } END_FOR_EACH_PTR(tmp);
 768 }
 769 
 770 static void reset_sm(struct sm_state *sm)
 771 {
 772         struct string_list *links;
 773         char *tmp;
 774 
 775         links = sm->state->data;
 776 
 777         FOR_EACH_PTR(links, tmp) {
 778                 struct smatch_state *old, *new;
 779 
 780                 old = get_state(comparison_id, tmp, NULL);
 781                 if (!old || !old->data) {
 782                         new = &undefined;
 783                 } else {
 784                         struct compare_data *data = old->data;
 785 
 786                         new = alloc_compare_state(
 787                                         data->left, data->left_var, data->left_vsl,
 788                                         UNKNOWN_COMPARISON,
 789                                         data->right, data->right_var, data->right_vsl);
 790                 }
 791                 set_state(comparison_id, tmp, NULL, new);
 792         } END_FOR_EACH_PTR(tmp);
 793         set_state(link_id, sm->name, sm->sym, &undefined);
 794 }
 795 
 796 static bool match_add_sub_assign(struct sm_state *sm, struct expression *expr)
 797 {
 798         struct range_list *rl;
 799         sval_t zero = { .type = &int_ctype };
 800 
 801         if (!expr || expr->type != EXPR_ASSIGNMENT)
 802                 return false;
 803         if (expr->op != SPECIAL_ADD_ASSIGN && expr->op != SPECIAL_SUB_ASSIGN)
 804                 return false;
 805 
 806         get_absolute_rl(expr->right, &rl);
 807         if (sval_is_negative(rl_min(rl))) {
 808                 reset_sm(sm);
 809                 return false;
 810         }
 811 
 812         if (expr->op == SPECIAL_ADD_ASSIGN)
 813                 match_inc(sm, rl_has_sval(rl, zero));
 814         else
 815                 match_dec(sm, rl_has_sval(rl, zero));
 816         return true;
 817 }
 818 
 819 static void match_inc_dec(struct sm_state *sm, struct expression *mod_expr)
 820 {
 821         /*
 822          * if (foo > bar) then ++foo is also > bar.
 823          */
 824         if (!mod_expr)
 825                 return;
 826         if (match_add_sub_assign(sm, mod_expr))
 827                 return;
 828         if (mod_expr->type != EXPR_PREOP && mod_expr->type != EXPR_POSTOP)
 829                 return;
 830 
 831         if (mod_expr->op == SPECIAL_INCREMENT)
 832                 match_inc(sm, false);
 833         else if (mod_expr->op == SPECIAL_DECREMENT)
 834                 match_dec(sm, false);
 835 }
 836 
 837 static int is_self_assign(struct expression *expr)
 838 {
 839         if (!expr || expr->type != EXPR_ASSIGNMENT || expr->op != '=')
 840                 return 0;
 841         return expr_equiv(expr->left, expr->right);
 842 }
 843 
 844 static void match_modify(struct sm_state *sm, struct expression *mod_expr)
 845 {
 846         if (mod_expr && is_self_assign(mod_expr))
 847                 return;
 848 
 849         /* handled by match_inc_dec() */
 850         if (mod_expr &&
 851             ((mod_expr->type == EXPR_PREOP || mod_expr->type == EXPR_POSTOP) &&
 852              (mod_expr->op == SPECIAL_INCREMENT || mod_expr->op == SPECIAL_DECREMENT)))
 853                 return;
 854         if (mod_expr && mod_expr->type == EXPR_ASSIGNMENT &&
 855             (mod_expr->op == SPECIAL_ADD_ASSIGN || mod_expr->op == SPECIAL_SUB_ASSIGN))
 856                 return;
 857 
 858         reset_sm(sm);
 859 }
 860 
 861 static void match_preop(struct expression *expr)
 862 {
 863         struct expression *parent;
 864         struct range_list *left, *right;
 865         int op;
 866 
 867         /*
 868          * This is an important special case.  Say you have:
 869          *
 870          *      if (++j == limit)
 871          *
 872          * Assume that we know the range of limit is higher than the start
 873          * value for "j".  Then the first thing that we process is the ++j.  We
 874          * have not comparison states set up so it doesn't get caught by the
 875          * modification hook.  But it does get caught by smatch_extra which sets
 876          * j to unknown then we parse the "j == limit" and sets false to != but
 877          * really we want false to be <.
 878          *
 879          * So what we do is we set j < limit here, then the match_modify catches
 880          * it and we do a match_inc_dec().
 881          *
 882          */
 883 
 884         if (expr->type != EXPR_PREOP ||
 885             (expr->op != SPECIAL_INCREMENT && expr->op != SPECIAL_DECREMENT))
 886                 return;
 887 
 888         parent = expr_get_parent_expr(expr);
 889         if (!parent)
 890                 return;
 891         if (parent->type != EXPR_COMPARE || parent->op != SPECIAL_EQUAL)
 892                 return;
 893         if (parent->left != expr)
 894                 return;
 895 
 896         if (!get_implied_rl(expr->unop, &left) ||
 897            !get_implied_rl(parent->right, &right))
 898                 return;
 899 
 900         op = rl_comparison(left, right);
 901         if (op == UNKNOWN_COMPARISON)
 902                 return;
 903 
 904         add_comparison(expr->unop, op, parent->right);
 905 }
 906 
 907 static char *chunk_to_var_sym(struct expression *expr, struct symbol **sym)
 908 {
 909         expr = strip_expr(expr);
 910         if (!expr)
 911                 return NULL;
 912         if (sym)
 913                 *sym = NULL;
 914 
 915         if (expr->type == EXPR_PREOP &&
 916             (expr->op == SPECIAL_INCREMENT ||
 917              expr->op == SPECIAL_DECREMENT))
 918                 expr = strip_expr(expr->unop);
 919 
 920         if (expr->type == EXPR_CALL) {
 921                 char buf[64];
 922 
 923                 snprintf(buf, sizeof(buf), "return %p", expr);
 924                 return alloc_string(buf);
 925         }
 926 
 927         return expr_to_chunk_sym_vsl(expr, sym, NULL);
 928 }
 929 
 930 static char *chunk_to_var(struct expression *expr)
 931 {
 932         return chunk_to_var_sym(expr, NULL);
 933 }
 934 
 935 static struct smatch_state *get_state_chunk(int owner, struct expression *expr)
 936 {
 937         char *name;
 938         struct symbol *sym;
 939         struct smatch_state *ret;
 940 
 941         name = chunk_to_var_sym(expr, &sym);
 942         if (!name)
 943                 return NULL;
 944 
 945         ret = get_state(owner, name, sym);
 946         free_string(name);
 947         return ret;
 948 }
 949 
 950 static void save_link(struct expression *expr, char *link)
 951 {
 952         char *var;
 953         struct symbol *sym;
 954 
 955         expr = strip_expr(expr);
 956         if (expr->type == EXPR_BINOP) {
 957                 char *chunk;
 958 
 959                 chunk = chunk_to_var(expr);
 960                 if (!chunk)
 961                         return;
 962 
 963                 save_link(expr->left, link);
 964                 save_link(expr->right, link);
 965                 save_link_var_sym(chunk, NULL, link);
 966                 return;
 967         }
 968 
 969         var = chunk_to_var_sym(expr, &sym);
 970         if (!var)
 971                 return;
 972 
 973         save_link_var_sym(var, sym, link);
 974         free_string(var);
 975 }
 976 
 977 static int get_orig_comparison(struct stree *pre_stree, const char *left, const char *right)
 978 {
 979         struct smatch_state *state;
 980         struct compare_data *data;
 981         int flip = 0;
 982         char state_name[256];
 983 
 984         if (strcmp(left, right) > 0) {
 985                 const char *tmp = right;
 986 
 987                 flip = 1;
 988                 right = left;
 989                 left = tmp;
 990         }
 991 
 992         snprintf(state_name, sizeof(state_name), "%s vs %s", left, right);
 993         state = get_state_stree(pre_stree, comparison_id, state_name, NULL);
 994         if (!state || !state->data)
 995                 return 0;
 996         data = state->data;
 997         if (flip)
 998                 return flip_comparison(data->comparison);
 999         return data->comparison;
1000 
1001 }
1002 
1003 static int have_common_var_sym(struct var_sym_list *left_vsl, struct var_sym_list *right_vsl)
1004 {
1005         struct var_sym *tmp;
1006 
1007         FOR_EACH_PTR(left_vsl, tmp) {
1008                 if (in_var_sym_list(right_vsl, tmp->var, tmp->sym))
1009                         return 1;
1010         } END_FOR_EACH_PTR(tmp);
1011 
1012         return 0;
1013 }
1014 
1015 /*
1016  * The idea here is that we take a comparison "a < b" and then we look at all
1017  * the things which "b" is compared against "b < c" and we say that that implies
1018  * a relationship "a < c".
1019  *
1020  * The names here about because the comparisons are organized like this
1021  * "a < b < c".
1022  *
1023  */
1024 static void update_tf_links(struct stree *pre_stree,
1025                             struct expression *left_expr,
1026                             const char *left_var, struct var_sym_list *left_vsl,
1027                             int left_comparison, int left_false_comparison,
1028                             const char *mid_var, struct var_sym_list *mid_vsl,
1029                             struct string_list *links)
1030 {
1031         struct smatch_state *state;
1032         struct smatch_state *true_state, *false_state;
1033         struct compare_data *data;
1034         struct expression *right_expr;
1035         const char *right_var;
1036         struct var_sym_list *right_vsl;
1037         int orig_comparison;
1038         int right_comparison;
1039         int true_comparison;
1040         int false_comparison;
1041         char *tmp;
1042         char state_name[256];
1043         struct var_sym *vs;
1044 
1045         FOR_EACH_PTR(links, tmp) {
1046                 state = get_state_stree(pre_stree, comparison_id, tmp, NULL);
1047                 if (!state || !state->data)
1048                         continue;
1049                 data = state->data;
1050                 right_comparison = data->comparison;
1051                 right_expr = data->right;
1052                 right_var = data->right_var;
1053                 right_vsl = data->right_vsl;
1054                 if (strcmp(mid_var, right_var) == 0) {
1055                         right_expr = data->left;
1056                         right_var = data->left_var;
1057                         right_vsl = data->left_vsl;
1058                         right_comparison = flip_comparison(right_comparison);
1059                 }
1060                 if (have_common_var_sym(left_vsl, right_vsl))
1061                         continue;
1062 
1063                 orig_comparison = get_orig_comparison(pre_stree, left_var, right_var);
1064 
1065                 true_comparison = combine_comparisons(left_comparison, right_comparison);
1066                 false_comparison = combine_comparisons(left_false_comparison, right_comparison);
1067 
1068                 true_comparison = comparison_intersection(orig_comparison, true_comparison);
1069                 false_comparison = comparison_intersection(orig_comparison, false_comparison);
1070 
1071                 if (strcmp(left_var, right_var) > 0) {
1072                         struct expression *tmp_expr = left_expr;
1073                         const char *tmp_var = left_var;
1074                         struct var_sym_list *tmp_vsl = left_vsl;
1075 
1076                         left_expr = right_expr;
1077                         left_var = right_var;
1078                         left_vsl = right_vsl;
1079                         right_expr = tmp_expr;
1080                         right_var = tmp_var;
1081                         right_vsl = tmp_vsl;
1082                         true_comparison = flip_comparison(true_comparison);
1083                         false_comparison = flip_comparison(false_comparison);
1084                 }
1085 
1086                 if (!true_comparison && !false_comparison)
1087                         continue;
1088 
1089                 if (true_comparison)
1090                         true_state = alloc_compare_state(
1091                                         left_expr, left_var, left_vsl,
1092                                         true_comparison,
1093                                         right_expr, right_var, right_vsl);
1094                 else
1095                         true_state = NULL;
1096                 if (false_comparison)
1097                         false_state = alloc_compare_state(
1098                                         left_expr, left_var, left_vsl,
1099                                         false_comparison,
1100                                         right_expr, right_var, right_vsl);
1101                 else
1102                         false_state = NULL;
1103 
1104                 snprintf(state_name, sizeof(state_name), "%s vs %s", left_var, right_var);
1105                 set_true_false_states(comparison_id, state_name, NULL, true_state, false_state);
1106                 FOR_EACH_PTR(left_vsl, vs) {
1107                         save_link_var_sym(vs->var, vs->sym, state_name);
1108                 } END_FOR_EACH_PTR(vs);
1109                 FOR_EACH_PTR(right_vsl, vs) {
1110                         save_link_var_sym(vs->var, vs->sym, state_name);
1111                 } END_FOR_EACH_PTR(vs);
1112                 if (!vsl_to_sym(left_vsl))
1113                         save_link_var_sym(left_var, NULL, state_name);
1114                 if (!vsl_to_sym(right_vsl))
1115                         save_link_var_sym(right_var, NULL, state_name);
1116         } END_FOR_EACH_PTR(tmp);
1117 }
1118 
1119 static void update_tf_data(struct stree *pre_stree,
1120                 struct expression *left_expr,
1121                 const char *left_name, struct var_sym_list *left_vsl,
1122                 struct expression *right_expr,
1123                 const char *right_name, struct var_sym_list *right_vsl,
1124                 int true_comparison, int false_comparison)
1125 {
1126         struct smatch_state *state;
1127 
1128         state = get_state_stree(pre_stree, link_id, right_name, vsl_to_sym(right_vsl));
1129         if (state)
1130                 update_tf_links(pre_stree, left_expr, left_name, left_vsl, true_comparison, false_comparison, right_name, right_vsl, state->data);
1131 
1132         state = get_state_stree(pre_stree, link_id, left_name, vsl_to_sym(left_vsl));
1133         if (state)
1134                 update_tf_links(pre_stree, right_expr, right_name, right_vsl, flip_comparison(true_comparison), flip_comparison(false_comparison), left_name, left_vsl, state->data);
1135 }
1136 
1137 static void iter_modify(struct sm_state *sm, struct expression *mod_expr)
1138 {
1139         if (sm->state != &start ||
1140             !mod_expr ||
1141             (mod_expr->type != EXPR_PREOP && mod_expr->type != EXPR_POSTOP) ||
1142             mod_expr->op != SPECIAL_INCREMENT)
1143                 set_state(inc_dec_id, sm->name, sm->sym, &undefined);
1144         else
1145                 set_state(inc_dec_id, sm->name, sm->sym, &incremented);
1146 }
1147 
1148 static void handle_for_loops(struct expression *expr, char *state_name, struct smatch_state *false_state)
1149 {
1150         sval_t sval;
1151         char *iter_name, *cap_name;
1152         struct symbol *iter_sym, *cap_sym;
1153         struct compare_data *data;
1154 
1155         if (expr->op != '<' && expr->op != SPECIAL_UNSIGNED_LT)
1156                 return;
1157 
1158         if (!__cur_stmt || !__prev_stmt)
1159                 return;
1160         if (__cur_stmt->type != STMT_ITERATOR)
1161                 return;
1162         if (__cur_stmt->iterator_pre_condition != expr)
1163                 return;
1164 
1165         /* literals are handled in smatch_extra.c */
1166         if (get_value(expr->right, &sval))
1167                 return;
1168 
1169         /* First time checking the condition */
1170         if (__prev_stmt == __cur_stmt->iterator_pre_statement) {
1171                 if (!get_implied_value(expr->left, &sval) ||
1172                     sval.value != 0)
1173                         return;
1174 
1175                 iter_name = expr_to_var_sym(expr->left, &iter_sym);
1176                 cap_name = expr_to_var_sym(expr->right, &cap_sym);
1177                 if (!iter_name || !cap_name || !iter_sym || !cap_sym) {
1178                         free_string(iter_name);
1179                         free_string(cap_name);
1180                         return;
1181                 }
1182 
1183                 set_state(inc_dec_id, iter_name, iter_sym, &start);
1184                 store_link(inc_dec_link_id, cap_name, cap_sym, iter_name, iter_sym);
1185 
1186                 free_string(iter_name);
1187                 free_string(cap_name);
1188                 return;
1189         }
1190 
1191         /* Second time checking the condtion */
1192         if (__prev_stmt != __cur_stmt->iterator_post_statement)
1193                 return;
1194 
1195         if (get_state_chunk(inc_dec_id, expr->left) != &incremented)
1196                 return;
1197 
1198         data = false_state->data;
1199         false_state = alloc_compare_state(
1200                         data->left, data->left_var, data->left_vsl,
1201                         SPECIAL_EQUAL,
1202                         data->right, data->right_var, data->right_vsl);
1203 
1204         // FIXME: This doesn't handle links correct so it doesn't set "param orig"
1205         set_true_false_states(comparison_id, state_name, NULL, NULL, false_state);
1206 }
1207 
1208 static int is_plus_one(struct expression *expr)
1209 {
1210         sval_t sval;
1211 
1212         if (expr->type != EXPR_BINOP || expr->op != '+')
1213                 return 0;
1214         if (!get_implied_value(expr->right, &sval) || sval.value != 1)
1215                 return 0;
1216         return 1;
1217 }
1218 
1219 static int is_minus_one(struct expression *expr)
1220 {
1221         sval_t sval;
1222 
1223         if (expr->type != EXPR_BINOP || expr->op != '-')
1224                 return 0;
1225         if (!get_implied_value(expr->right, &sval) || sval.value != 1)
1226                 return 0;
1227         return 1;
1228 }
1229 
1230 static void move_plus_to_minus_helper(struct expression **left_p, struct expression **right_p)
1231 {
1232         struct expression *left = *left_p;
1233         struct expression *right = *right_p;
1234 
1235         /*
1236          * These two are basically equivalent: "foo + 1 != bar" and
1237          * "foo != bar - 1".  There are issues with signedness and integer
1238          * overflows.  There are also issues with type as well.  But let's
1239          * pretend we can ignore all that stuff for now.
1240          *
1241          */
1242 
1243         if (!is_plus_one(left))
1244                 return;
1245 
1246         *left_p = left->left;
1247         *right_p = binop_expression(right, '-', left->right);
1248 }
1249 
1250 static void move_plus_to_minus(struct expression **left_p, struct expression **right_p)
1251 {
1252         if (is_plus_one(*left_p) && is_plus_one(*right_p))
1253                 return;
1254 
1255         move_plus_to_minus_helper(left_p, right_p);
1256         move_plus_to_minus_helper(right_p, left_p);
1257 }
1258 
1259 static void handle_comparison(struct expression *left_expr, int op, struct expression *right_expr, char **_state_name, struct smatch_state **_false_state)
1260 {
1261         char *left = NULL;
1262         char *right = NULL;
1263         struct symbol *left_sym, *right_sym;
1264         struct var_sym_list *left_vsl = NULL;
1265         struct var_sym_list *right_vsl = NULL;
1266         int false_op;
1267         int orig_comparison;
1268         struct smatch_state *true_state, *false_state;
1269         static char state_name[256];
1270         struct stree *pre_stree;
1271         sval_t sval;
1272 
1273         if (!left_expr || !right_expr)
1274                 return;
1275 
1276         left_expr = strip_parens(left_expr);
1277         right_expr = strip_parens(right_expr);
1278 
1279         while (left_expr->type == EXPR_ASSIGNMENT)
1280                 left_expr = strip_parens(left_expr->left);
1281         while (right_expr->type == EXPR_ASSIGNMENT)
1282                 right_expr = strip_parens(right_expr->left);
1283 
1284         false_op = negate_comparison(op);
1285 
1286         move_plus_to_minus(&left_expr, &right_expr);
1287 
1288         if (op == SPECIAL_UNSIGNED_LT &&
1289             get_implied_value(left_expr, &sval) &&
1290             sval.value == 0)
1291                 false_op = SPECIAL_EQUAL;
1292 
1293         if (op == SPECIAL_UNSIGNED_GT &&
1294             get_implied_value(right_expr, &sval) &&
1295             sval.value == 0)
1296                 false_op = SPECIAL_EQUAL;
1297 
1298         left = chunk_to_var_sym(left_expr, &left_sym);
1299         if (!left)
1300                 goto free;
1301         if (left_sym)
1302                 add_var_sym(&left_vsl, left, left_sym);
1303         else
1304                 left_vsl = expr_to_vsl(left_expr);
1305         right = chunk_to_var_sym(right_expr, &right_sym);
1306         if (!right)
1307                 goto free;
1308         if (right_sym)
1309                 add_var_sym(&right_vsl, right, right_sym);
1310         else
1311                 right_vsl = expr_to_vsl(right_expr);
1312 
1313         if (strcmp(left, right) > 0) {
1314                 char *tmp_name = left;
1315                 struct var_sym_list *tmp_vsl = left_vsl;
1316                 struct expression *tmp_expr = left_expr;
1317 
1318                 left = right;
1319                 left_vsl = right_vsl;
1320                 left_expr = right_expr;
1321                 right = tmp_name;
1322                 right_vsl = tmp_vsl;
1323                 right_expr = tmp_expr;
1324                 op = flip_comparison(op);
1325                 false_op = flip_comparison(false_op);
1326         }
1327 
1328         orig_comparison = get_comparison(left_expr, right_expr);
1329         op = comparison_intersection(orig_comparison, op);
1330         false_op = comparison_intersection(orig_comparison, false_op);
1331 
1332         snprintf(state_name, sizeof(state_name), "%s vs %s", left, right);
1333         true_state = alloc_compare_state(
1334                         left_expr, left, left_vsl,
1335                         op,
1336                         right_expr, right, right_vsl);
1337         false_state = alloc_compare_state(
1338                         left_expr, left, left_vsl,
1339                         false_op,
1340                         right_expr, right, right_vsl);
1341 
1342         pre_stree = clone_stree(__get_cur_stree());
1343         update_tf_data(pre_stree, left_expr, left, left_vsl, right_expr, right, right_vsl, op, false_op);
1344         free_stree(&pre_stree);
1345 
1346         set_true_false_states(comparison_id, state_name, NULL, true_state, false_state);
1347         __compare_param_limit_hook(left_expr, right_expr, state_name, true_state, false_state);
1348         save_link(left_expr, state_name);
1349         save_link(right_expr, state_name);
1350 
1351         if (_false_state)
1352                 *_false_state = false_state;
1353         if (_state_name)
1354                 *_state_name = state_name;
1355 free:
1356         free_string(left);
1357         free_string(right);
1358 }
1359 
1360 void __comparison_match_condition(struct expression *expr)
1361 {
1362         struct expression *left, *right, *new_left, *new_right, *tmp;
1363         struct smatch_state *false_state = NULL;
1364         char *state_name = NULL;
1365         int redo, count;
1366 
1367         if (expr->type != EXPR_COMPARE)
1368                 return;
1369 
1370         handle_comparison(expr->left, expr->op, expr->right, &state_name, &false_state);
1371         if (false_state && state_name)
1372                 handle_for_loops(expr, state_name, false_state);
1373 
1374         left = strip_parens(expr->left);
1375         right = strip_parens(expr->right);
1376 
1377         if (left->type == EXPR_BINOP && left->op == '+') {
1378                 new_left = left->left;
1379                 new_right = binop_expression(right, '-', left->right);
1380                 handle_comparison(new_left, expr->op, new_right, NULL, NULL);
1381 
1382                 new_left = left->right;
1383                 new_right = binop_expression(right, '-', left->left);
1384                 handle_comparison(new_left, expr->op, new_right, NULL, NULL);
1385         }
1386 
1387         redo = 0;
1388         left = strip_parens(expr->left);
1389         right = strip_parens(expr->right);
1390         if (get_last_expr_from_expression_stmt(expr->left)) {
1391                 left = get_last_expr_from_expression_stmt(expr->left);
1392                 redo = 1;
1393         }
1394         if (get_last_expr_from_expression_stmt(expr->right)) {
1395                 right = get_last_expr_from_expression_stmt(expr->right);
1396                 redo = 1;
1397         }
1398 
1399         if (!redo)
1400                 return;
1401 
1402         count = 0;
1403         while ((tmp = get_assigned_expr(left))) {
1404                 if (count++ > 3)
1405                         break;
1406                 left = strip_expr(tmp);
1407         }
1408         count = 0;
1409         while ((tmp = get_assigned_expr(right))) {
1410                 if (count++ > 3)
1411                         break;
1412                 right = strip_expr(tmp);
1413         }
1414 
1415         handle_comparison(left, expr->op, right, NULL, NULL);
1416 }
1417 
1418 static void add_comparison_var_sym(
1419                 struct expression *left_expr,
1420                 const char *left_name, struct var_sym_list *left_vsl,
1421                 int comparison,
1422                 struct expression *right_expr,
1423                 const char *right_name, struct var_sym_list *right_vsl)
1424 {
1425         struct smatch_state *state;
1426         struct var_sym *vs;
1427         char state_name[256];
1428 
1429         if (strcmp(left_name, right_name) > 0) {
1430                 struct expression *tmp_expr = left_expr;
1431                 const char *tmp_name = left_name;
1432                 struct var_sym_list *tmp_vsl = left_vsl;
1433 
1434                 left_expr = right_expr;
1435                 left_name = right_name;
1436                 left_vsl = right_vsl;
1437                 right_expr = tmp_expr;
1438                 right_name = tmp_name;
1439                 right_vsl = tmp_vsl;
1440                 comparison = flip_comparison(comparison);
1441         }
1442         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
1443         state = alloc_compare_state(
1444                         left_expr, left_name, left_vsl,
1445                         comparison,
1446                         right_expr, right_name, right_vsl);
1447 
1448         set_state(comparison_id, state_name, NULL, state);
1449 
1450         FOR_EACH_PTR(left_vsl, vs) {
1451                 save_link_var_sym(vs->var, vs->sym, state_name);
1452         } END_FOR_EACH_PTR(vs);
1453         FOR_EACH_PTR(right_vsl, vs) {
1454                 save_link_var_sym(vs->var, vs->sym, state_name);
1455         } END_FOR_EACH_PTR(vs);
1456 }
1457 
1458 static void add_comparison(struct expression *left, int comparison, struct expression *right)
1459 {
1460         char *left_name = NULL;
1461         char *right_name = NULL;
1462         struct symbol *left_sym, *right_sym;
1463         struct var_sym_list *left_vsl, *right_vsl;
1464         struct smatch_state *state;
1465         char state_name[256];
1466 
1467         left_name = chunk_to_var_sym(left, &left_sym);
1468         if (!left_name)
1469                 goto free;
1470         left_vsl = expr_to_vsl(left);
1471         right_name = chunk_to_var_sym(right, &right_sym);
1472         if (!right_name)
1473                 goto free;
1474         right_vsl = expr_to_vsl(right);
1475 
1476         if (strcmp(left_name, right_name) > 0) {
1477                 struct expression *tmp_expr = left;
1478                 struct symbol *tmp_sym = left_sym;
1479                 char *tmp_name = left_name;
1480                 struct var_sym_list *tmp_vsl = left_vsl;
1481 
1482                 left = right;
1483                 left_name = right_name;
1484                 left_sym = right_sym;
1485                 left_vsl = right_vsl;
1486                 right = tmp_expr;
1487                 right_name = tmp_name;
1488                 right_sym = tmp_sym;
1489                 right_vsl = tmp_vsl;
1490                 comparison = flip_comparison(comparison);
1491         }
1492         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
1493         state = alloc_compare_state(
1494                         left, left_name, left_vsl,
1495                         comparison,
1496                         right, right_name, right_vsl);
1497 
1498         set_state(comparison_id, state_name, NULL, state);
1499         save_link(left, state_name);
1500         save_link(right, state_name);
1501 
1502 free:
1503         free_string(left_name);
1504         free_string(right_name);
1505 }
1506 
1507 static void match_assign_add(struct expression *expr)
1508 {
1509         struct expression *right;
1510         struct expression *r_left, *r_right;
1511         sval_t left_tmp, right_tmp;
1512 
1513         right = strip_expr(expr->right);
1514         r_left = strip_expr(right->left);
1515         r_right = strip_expr(right->right);
1516 
1517         get_absolute_min(r_left, &left_tmp);
1518         get_absolute_min(r_right, &right_tmp);
1519 
1520         if (left_tmp.value > 0)
1521                 add_comparison(expr->left, '>', r_right);
1522         else if (left_tmp.value == 0)
1523                 add_comparison(expr->left, SPECIAL_GTE, r_right);
1524 
1525         if (right_tmp.value > 0)
1526                 add_comparison(expr->left, '>', r_left);
1527         else if (right_tmp.value == 0)
1528                 add_comparison(expr->left, SPECIAL_GTE, r_left);
1529 }
1530 
1531 static void match_assign_sub(struct expression *expr)
1532 {
1533         struct expression *right;
1534         struct expression *r_left, *r_right;
1535         int comparison;
1536         sval_t min;
1537 
1538         right = strip_expr(expr->right);
1539         r_left = strip_expr(right->left);
1540         r_right = strip_expr(right->right);
1541 
1542         if (get_absolute_min(r_right, &min) && sval_is_negative(min))
1543                 return;
1544 
1545         comparison = get_comparison(r_left, r_right);
1546 
1547         switch (comparison) {
1548         case '>':
1549         case SPECIAL_GTE:
1550                 if (implied_not_equal(r_right, 0))
1551                         add_comparison(expr->left, '>', r_left);
1552                 else
1553                         add_comparison(expr->left, SPECIAL_GTE, r_left);
1554                 return;
1555         }
1556 }
1557 
1558 static void match_assign_divide(struct expression *expr)
1559 {
1560         struct expression *right;
1561         struct expression *r_left, *r_right;
1562         sval_t min;
1563 
1564         right = strip_expr(expr->right);
1565         r_left = strip_expr(right->left);
1566         r_right = strip_expr(right->right);
1567         if (!get_implied_min(r_right, &min) || min.value <= 1)
1568                 return;
1569 
1570         add_comparison(expr->left, '<', r_left);
1571 }
1572 
1573 static void match_binop_assign(struct expression *expr)
1574 {
1575         struct expression *right;
1576 
1577         right = strip_expr(expr->right);
1578         if (right->op == '+')
1579                 match_assign_add(expr);
1580         if (right->op == '-')
1581                 match_assign_sub(expr);
1582         if (right->op == '/')
1583                 match_assign_divide(expr);
1584 }
1585 
1586 static void copy_comparisons(struct expression *left, struct expression *right)
1587 {
1588         struct string_list *links;
1589         struct smatch_state *state;
1590         struct compare_data *data;
1591         struct symbol *left_sym, *right_sym;
1592         char *left_var = NULL;
1593         char *right_var = NULL;
1594         struct var_sym_list *left_vsl;
1595         struct expression *expr;
1596         const char *var;
1597         struct var_sym_list *vsl;
1598         int comparison;
1599         char *tmp;
1600 
1601         left_var = chunk_to_var_sym(left, &left_sym);
1602         if (!left_var)
1603                 goto done;
1604         left_vsl = expr_to_vsl(left);
1605         right_var = chunk_to_var_sym(right, &right_sym);
1606         if (!right_var)
1607                 goto done;
1608 
1609         state = get_state(link_id, right_var, right_sym);
1610         if (!state)
1611                 return;
1612         links = state->data;
1613 
1614         FOR_EACH_PTR(links, tmp) {
1615                 state = get_state(comparison_id, tmp, NULL);
1616                 if (!state || !state->data)
1617                         continue;
1618                 data = state->data;
1619                 comparison = data->comparison;
1620                 expr = data->right;
1621                 var = data->right_var;
1622                 vsl = data->right_vsl;
1623                 if (strcmp(var, right_var) == 0) {
1624                         expr = data->left;
1625                         var = data->left_var;
1626                         vsl = data->left_vsl;
1627                         comparison = flip_comparison(comparison);
1628                 }
1629                 /* n = copy_from_user(dest, src, n); leads to n <= n which is nonsense */
1630                 if (strcmp(left_var, var) == 0)
1631                         continue;
1632                 add_comparison_var_sym(left, left_var, left_vsl, comparison, expr, var, vsl);
1633         } END_FOR_EACH_PTR(tmp);
1634 
1635 done:
1636         free_string(right_var);
1637 }
1638 
1639 static void match_assign(struct expression *expr)
1640 {
1641         struct expression *right;
1642 
1643         if (expr->op != '=')
1644                 return;
1645         if (__in_fake_assign || outside_of_function())
1646                 return;
1647 
1648         if (is_struct(expr->left))
1649                 return;
1650 
1651         if (is_self_assign(expr))
1652                 return;
1653 
1654         copy_comparisons(expr->left, expr->right);
1655         add_comparison(expr->left, SPECIAL_EQUAL, expr->right);
1656 
1657         right = strip_expr(expr->right);
1658         if (right->type == EXPR_BINOP)
1659                 match_binop_assign(expr);
1660 }
1661 
1662 int get_comparison_strings(const char *one, const char *two)
1663 {
1664         char buf[256];
1665         struct smatch_state *state;
1666         int invert = 0;
1667         int ret = 0;
1668 
1669         if (!one || !two)
1670                 return UNKNOWN_COMPARISON;
1671 
1672         if (strcmp(one, two) == 0)
1673                 return SPECIAL_EQUAL;
1674 
1675         if (strcmp(one, two) > 0) {
1676                 const char *tmp = one;
1677 
1678                 one = two;
1679                 two = tmp;
1680                 invert = 1;
1681         }
1682 
1683         snprintf(buf, sizeof(buf), "%s vs %s", one, two);
1684         state = get_state(comparison_id, buf, NULL);
1685         if (state)
1686                 ret = state_to_comparison(state);
1687 
1688         if (invert)
1689                 ret = flip_comparison(ret);
1690 
1691         return ret;
1692 }
1693 
1694 static int get_comparison_helper(struct expression *a, struct expression *b, bool use_extra)
1695 {
1696         char *one = NULL;
1697         char *two = NULL;
1698         int ret = UNKNOWN_COMPARISON;
1699         int extra = UNKNOWN_COMPARISON;
1700 
1701         if (a == UNKNOWN_COMPARISON ||
1702             b == UNKNOWN_COMPARISON)
1703                 return UNKNOWN_COMPARISON;
1704 
1705         a = strip_parens(a);
1706         b = strip_parens(b);
1707 
1708         move_plus_to_minus(&a, &b);
1709 
1710         one = chunk_to_var(a);
1711         if (!one)
1712                 goto free;
1713         two = chunk_to_var(b);
1714         if (!two)
1715                 goto free;
1716 
1717         ret = get_comparison_strings(one, two);
1718         if (ret)
1719                 goto free;
1720 
1721         if (is_plus_one(a) || is_minus_one(a)) {
1722                 free_string(one);
1723                 one = chunk_to_var(a->left);
1724                 ret = get_comparison_strings(one, two);
1725         } else if (is_plus_one(b) || is_minus_one(b)) {
1726                 free_string(two);
1727                 two = chunk_to_var(b->left);
1728                 ret = get_comparison_strings(one, two);
1729         }
1730 
1731         if (ret == UNKNOWN_COMPARISON)
1732                 goto free;
1733 
1734         if ((is_plus_one(a) || is_minus_one(b)) && ret == '<')
1735                 ret = SPECIAL_LTE;
1736         else if ((is_minus_one(a) || is_plus_one(b)) && ret == '>')
1737                 ret = SPECIAL_GTE;
1738         else
1739                 ret = UNKNOWN_COMPARISON;
1740 
1741 free:
1742         free_string(one);
1743         free_string(two);
1744 
1745         extra = comparison_from_extra(a, b);
1746         return comparison_intersection(ret, extra);
1747 }
1748 
1749 int get_comparison(struct expression *a, struct expression *b)
1750 {
1751         return get_comparison_helper(a, b, true);
1752 }
1753 
1754 int get_comparison_no_extra(struct expression *a, struct expression *b)
1755 {
1756         return get_comparison_helper(a, b, false);
1757 }
1758 
1759 int possible_comparison(struct expression *a, int comparison, struct expression *b)
1760 {
1761         char *one = NULL;
1762         char *two = NULL;
1763         int ret = 0;
1764         char buf[256];
1765         struct sm_state *sm;
1766         int saved;
1767 
1768         one = chunk_to_var(a);
1769         if (!one)
1770                 goto free;
1771         two = chunk_to_var(b);
1772         if (!two)
1773                 goto free;
1774 
1775 
1776         if (strcmp(one, two) == 0 && comparison == SPECIAL_EQUAL) {
1777                 ret = 1;
1778                 goto free;
1779         }
1780 
1781         if (strcmp(one, two) > 0) {
1782                 char *tmp = one;
1783 
1784                 one = two;
1785                 two = tmp;
1786                 comparison = flip_comparison(comparison);
1787         }
1788 
1789         snprintf(buf, sizeof(buf), "%s vs %s", one, two);
1790         sm = get_sm_state(comparison_id, buf, NULL);
1791         if (!sm)
1792                 goto free;
1793 
1794         FOR_EACH_PTR(sm->possible, sm) {
1795                 if (!sm->state->data)
1796                         continue;
1797                 saved = ((struct compare_data *)sm->state->data)->comparison;
1798                 if (saved == comparison)
1799                         ret = 1;
1800                 if (comparison == SPECIAL_EQUAL &&
1801                     (saved == SPECIAL_LTE ||
1802                      saved == SPECIAL_GTE ||
1803                      saved == SPECIAL_UNSIGNED_LTE ||
1804                      saved == SPECIAL_UNSIGNED_GTE))
1805                         ret = 1;
1806                 if (ret == 1)
1807                         goto free;
1808         } END_FOR_EACH_PTR(sm);
1809 
1810         return ret;
1811 free:
1812         free_string(one);
1813         free_string(two);
1814         return ret;
1815 }
1816 
1817 struct state_list *get_all_comparisons(struct expression *expr)
1818 {
1819         struct smatch_state *state;
1820         struct string_list *links;
1821         struct state_list *ret = NULL;
1822         struct sm_state *sm;
1823         char *tmp;
1824 
1825         state = get_state_chunk(link_id, expr);
1826         if (!state)
1827                 return NULL;
1828         links = state->data;
1829 
1830         FOR_EACH_PTR(links, tmp) {
1831                 sm = get_sm_state(comparison_id, tmp, NULL);
1832                 if (!sm)
1833                         continue;
1834                 // FIXME have to compare name with vsl
1835                 add_ptr_list(&ret, sm);
1836         } END_FOR_EACH_PTR(tmp);
1837 
1838         return ret;
1839 }
1840 
1841 struct state_list *get_all_possible_equal_comparisons(struct expression *expr)
1842 {
1843         struct smatch_state *state;
1844         struct string_list *links;
1845         struct state_list *ret = NULL;
1846         struct sm_state *sm;
1847         char *tmp;
1848 
1849         state = get_state_chunk(link_id, expr);
1850         if (!state)
1851                 return NULL;
1852         links = state->data;
1853 
1854         FOR_EACH_PTR(links, tmp) {
1855                 sm = get_sm_state(comparison_id, tmp, NULL);
1856                 if (!sm)
1857                         continue;
1858                 if (!strchr(sm->state->name, '='))
1859                         continue;
1860                 if (strcmp(sm->state->name, "!=") == 0)
1861                         continue;
1862                 add_ptr_list(&ret, sm);
1863         } END_FOR_EACH_PTR(tmp);
1864 
1865         return ret;
1866 }
1867 
1868 struct state_list *get_all_possible_not_equal_comparisons(struct expression *expr)
1869 {
1870         struct smatch_state *state;
1871         struct string_list *links;
1872         struct state_list *ret = NULL;
1873         struct sm_state *sm;
1874         struct sm_state *possible;
1875         char *link;
1876 
1877         return NULL;
1878 
1879         state = get_state_chunk(link_id, expr);
1880         if (!state)
1881                 return NULL;
1882         links = state->data;
1883 
1884         FOR_EACH_PTR(links, link) {
1885                 sm = get_sm_state(comparison_id, link, NULL);
1886                 if (!sm)
1887                         continue;
1888                 FOR_EACH_PTR(sm->possible, possible) {
1889                         if (strcmp(possible->state->name, "!=") != 0)
1890                                 continue;
1891                         add_ptr_list(&ret, sm);
1892                         break;
1893                 } END_FOR_EACH_PTR(link);
1894         } END_FOR_EACH_PTR(link);
1895 
1896         return ret;
1897 }
1898 
1899 static void update_links_from_call(struct expression *left,
1900                                    int left_compare,
1901                                    struct expression *right)
1902 {
1903         struct string_list *links;
1904         struct smatch_state *state;
1905         struct compare_data *data;
1906         struct symbol *left_sym, *right_sym;
1907         char *left_var = NULL;
1908         char *right_var = NULL;
1909         struct var_sym_list *left_vsl;
1910         struct expression *expr;
1911         const char *var;
1912         struct var_sym_list *vsl;
1913         int comparison;
1914         char *tmp;
1915 
1916         left_var = chunk_to_var_sym(left, &left_sym);
1917         if (!left_var)
1918                 goto done;
1919         left_vsl = expr_to_vsl(left);
1920         right_var = chunk_to_var_sym(right, &right_sym);
1921         if (!right_var)
1922                 goto done;
1923 
1924         state = get_state(link_id, right_var, right_sym);
1925         if (!state)
1926                 return;
1927         links = state->data;
1928 
1929         FOR_EACH_PTR(links, tmp) {
1930                 state = get_state(comparison_id, tmp, NULL);
1931                 if (!state || !state->data)
1932                         continue;
1933                 data = state->data;
1934                 comparison = data->comparison;
1935                 expr = data->right;
1936                 var = data->right_var;
1937                 vsl = data->right_vsl;
1938                 if (strcmp(var, right_var) == 0) {
1939                         expr = data->left;
1940                         var = data->left_var;
1941                         vsl = data->left_vsl;
1942                         comparison = flip_comparison(comparison);
1943                 }
1944                 comparison = combine_comparisons(left_compare, comparison);
1945                 if (!comparison)
1946                         continue;
1947                 add_comparison_var_sym(left, left_var, left_vsl, comparison, expr, var, vsl);
1948         } END_FOR_EACH_PTR(tmp);
1949 
1950 done:
1951         free_string(right_var);
1952 }
1953 
1954 void __add_return_comparison(struct expression *call, const char *range)
1955 {
1956         struct expression *arg;
1957         int comparison;
1958         char buf[16];
1959 
1960         if (!str_to_comparison_arg(range, call, &comparison, &arg))
1961                 return;
1962         snprintf(buf, sizeof(buf), "%s", show_comparison(comparison));
1963         update_links_from_call(call, comparison, arg);
1964         add_comparison(call, comparison, arg);
1965 }
1966 
1967 void __add_comparison_info(struct expression *expr, struct expression *call, const char *range)
1968 {
1969         copy_comparisons(expr, call);
1970 }
1971 
1972 static char *get_mask_comparison(struct expression *expr, int ignore)
1973 {
1974         struct expression *tmp, *right;
1975         int count, param;
1976         char buf[256];
1977 
1978         /* The return value for "return foo & param;" is <= param */
1979 
1980         count = 0;
1981         while ((tmp = get_assigned_expr(expr))) {
1982                 expr = strip_expr(tmp);
1983                 if (count++ > 4)
1984                         break;
1985         }
1986 
1987         if (expr->type != EXPR_BINOP || expr->op != '&')
1988                 return NULL;
1989 
1990         right = strip_expr(expr->right);
1991         param = get_param_num(right);
1992         if (param < 0 || param == ignore)
1993                 return NULL;
1994 
1995         snprintf(buf, sizeof(buf), "[<=$%d]", param);
1996         return alloc_sname(buf);
1997 }
1998 
1999 static char *range_comparison_to_param_helper(struct expression *expr, char starts_with, int ignore)
2000 {
2001         struct symbol *param;
2002         char *var = NULL;
2003         char buf[256];
2004         char *ret_str = NULL;
2005         int compare;
2006         int i;
2007 
2008         if (!expr)
2009                 return NULL;
2010 
2011         var = chunk_to_var(expr);
2012         if (!var)
2013                 goto try_mask;
2014 
2015         i = -1;
2016         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
2017                 i++;
2018                 if (i == ignore)
2019                         continue;
2020                 if (!param->ident)
2021                         continue;
2022                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
2023                 compare = get_comparison_strings(var, buf);
2024                 if (compare == UNKNOWN_COMPARISON ||
2025                     compare == IMPOSSIBLE_COMPARISON)
2026                         continue;
2027                 if (show_comparison(compare)[0] != starts_with)
2028                         continue;
2029                 snprintf(buf, sizeof(buf), "[%s$%d]", show_comparison(compare), i);
2030                 ret_str = alloc_sname(buf);
2031                 break;
2032         } END_FOR_EACH_PTR(param);
2033 
2034         free_string(var);
2035         if (!ret_str)
2036                 goto try_mask;
2037 
2038         return ret_str;
2039 
2040 try_mask:
2041         if (starts_with == '<')
2042                 ret_str = get_mask_comparison(expr, ignore);
2043         return ret_str;
2044 }
2045 
2046 char *name_sym_to_param_comparison(const char *name, struct symbol *sym)
2047 {
2048         struct symbol *param;
2049         char buf[256];
2050         int compare;
2051         int i;
2052 
2053         i = -1;
2054         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
2055                 i++;
2056                 if (!param->ident)
2057                         continue;
2058                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
2059                 compare = get_comparison_strings(name, buf);
2060                 if (compare == UNKNOWN_COMPARISON ||
2061                     compare == IMPOSSIBLE_COMPARISON)
2062                         continue;
2063                 snprintf(buf, sizeof(buf), "[%s$%d]", show_comparison(compare), i);
2064                 return alloc_sname(buf);
2065         } END_FOR_EACH_PTR(param);
2066 
2067         return NULL;
2068 }
2069 
2070 char *expr_equal_to_param(struct expression *expr, int ignore)
2071 {
2072         return range_comparison_to_param_helper(expr, '=', ignore);
2073 }
2074 
2075 char *expr_lte_to_param(struct expression *expr, int ignore)
2076 {
2077         return range_comparison_to_param_helper(expr, '<', ignore);
2078 }
2079 
2080 char *expr_param_comparison(struct expression *expr, int ignore)
2081 {
2082         struct symbol *param;
2083         char *var = NULL;
2084         char buf[256];
2085         char *ret_str = NULL;
2086         int compare;
2087         int i;
2088 
2089         var = chunk_to_var(expr);
2090         if (!var)
2091                 goto free;
2092 
2093         i = -1;
2094         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
2095                 i++;
2096                 if (i == ignore)
2097                         continue;
2098                 if (!param->ident)
2099                         continue;
2100                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
2101                 compare = get_comparison_strings(var, buf);
2102                 if (!compare)
2103                         continue;
2104                 snprintf(buf, sizeof(buf), "[%s$%d]", show_comparison(compare), i);
2105                 ret_str = alloc_sname(buf);
2106                 break;
2107         } END_FOR_EACH_PTR(param);
2108 
2109 free:
2110         free_string(var);
2111         return ret_str;
2112 }
2113 
2114 char *get_printed_param_name(struct expression *call, const char *param_name, struct symbol *param_sym)
2115 {
2116         struct expression *arg;
2117         char *name;
2118         struct symbol *sym;
2119         static char buf[256];
2120         int len;
2121         int i;
2122 
2123         i = -1;
2124         FOR_EACH_PTR(call->args, arg) {
2125                 i++;
2126 
2127                 name = expr_to_var_sym(arg, &sym);
2128                 if (!name || !sym)
2129                         continue;
2130                 if (sym != param_sym)
2131                         continue;
2132 
2133                 len = strlen(name);
2134                 if (strncmp(name, param_name, len) != 0)
2135                         continue;
2136                 if (param_name[len] == '\0') {
2137                         snprintf(buf, sizeof(buf), "$%d", i);
2138                         return buf;
2139                 }
2140                 if (param_name[len] != '-')
2141                         continue;
2142                 snprintf(buf, sizeof(buf), "$%d%s", i, param_name + len);
2143                 return buf;
2144         } END_FOR_EACH_PTR(arg);
2145 
2146         return NULL;
2147 }
2148 
2149 static void match_call_info(struct expression *expr)
2150 {
2151         struct expression *arg;
2152         struct smatch_state *state;
2153         struct sm_state *sm;
2154         struct compare_data *data;
2155         int comparison;
2156         struct string_list *links;
2157         char *arg_name;
2158         const char *right_name;
2159         char *link;
2160         char info_buf[256];
2161         int i;
2162 
2163         i = -1;
2164         FOR_EACH_PTR(expr->args, arg) {
2165                 i++;
2166 
2167                 state = get_state_chunk(link_id, arg);
2168                 if (!state)
2169                         continue;
2170 
2171                 links = state->data;
2172                 FOR_EACH_PTR(links, link) {
2173                         struct var_sym_list *right_vsl;
2174                         struct var_sym *right_vs;
2175 
2176 
2177                         if (strstr(link, " orig"))
2178                                 continue;
2179                         sm = get_sm_state(comparison_id, link, NULL);
2180                         if (!sm)
2181                                 continue;
2182                         data = sm->state->data;
2183                         if (!data ||
2184                             data->comparison == UNKNOWN_COMPARISON ||
2185                             data->comparison == IMPOSSIBLE_COMPARISON)
2186                                 continue;
2187                         arg_name = expr_to_var(arg);
2188                         if (!arg_name)
2189                                 continue;
2190 
2191                         right_vsl = NULL;
2192                         if (strcmp(data->left_var, arg_name) == 0) {
2193                                 comparison = data->comparison;
2194                                 right_name = data->right_var;
2195                                 right_vsl = data->right_vsl;
2196                         } else if (strcmp(data->right_var, arg_name) == 0) {
2197                                 comparison = flip_comparison(data->comparison);
2198                                 right_name = data->left_var;
2199                                 right_vsl = data->left_vsl;
2200                         }
2201                         if (!right_vsl || ptr_list_size((struct ptr_list *)right_vsl) != 1)
2202                                 goto free;
2203 
2204                         right_vs = first_ptr_list((struct ptr_list *)right_vsl);
2205                         if (strcmp(right_vs->var, right_name) != 0)
2206                                 goto free;
2207                         right_name = get_printed_param_name(expr, right_vs->var, right_vs->sym);
2208                         if (!right_name)
2209                                 goto free;
2210                         snprintf(info_buf, sizeof(info_buf), "%s %s", show_comparison(comparison), right_name);
2211                         sql_insert_caller_info(expr, PARAM_COMPARE, i, "$", info_buf);
2212 
2213 free:
2214                         free_string(arg_name);
2215                 } END_FOR_EACH_PTR(link);
2216         } END_FOR_EACH_PTR(arg);
2217 }
2218 
2219 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct sm_state *link_sm)
2220 {
2221         struct sm_state *compare_sm;
2222         struct string_list *links;
2223         char *link;
2224         struct compare_data *data;
2225         struct var_sym *left, *right;
2226         static char info_buf[256];
2227         const char *right_name;
2228 
2229         if (strstr(printed_name, " orig"))
2230                 return;
2231 
2232         links = link_sm->state->data;
2233         FOR_EACH_PTR(links, link) {
2234                 compare_sm = get_sm_state(comparison_id, link, NULL);
2235                 if (!compare_sm)
2236                         continue;
2237                 data = compare_sm->state->data;
2238                 if (!data || !data->comparison)
2239                         continue;
2240 
2241                 if (ptr_list_size((struct ptr_list *)data->left_vsl) != 1 ||
2242                     ptr_list_size((struct ptr_list *)data->right_vsl) != 1)
2243                         continue;
2244                 left = first_ptr_list((struct ptr_list *)data->left_vsl);
2245                 right = first_ptr_list((struct ptr_list *)data->right_vsl);
2246                 if (left->sym == right->sym &&
2247                     strcmp(left->var, right->var) == 0)
2248                         continue;
2249                 /*
2250                  * Both parameters link to this comparison so only
2251                  * record the first one.
2252                  */
2253                 if (left->sym != link_sm->sym ||
2254                     strcmp(left->var, link_sm->name) != 0)
2255                         continue;
2256 
2257                 right_name = get_printed_param_name(call, right->var, right->sym);
2258                 if (!right_name)
2259                         continue;
2260                 snprintf(info_buf, sizeof(info_buf), "%s %s", show_comparison(data->comparison), right_name);
2261                 sql_insert_caller_info(call, PARAM_COMPARE, param, printed_name, info_buf);
2262         } END_FOR_EACH_PTR(link);
2263 }
2264 
2265 static void print_return_value_comparison(int return_id, char *return_ranges, struct expression *expr)
2266 {
2267         char *name;
2268         const char *tmp_name;
2269         struct symbol *sym;
2270         int param;
2271         char info_buf[256];
2272 
2273         /*
2274          * TODO: This only prints == comparisons. That's probably the most
2275          * useful comparison because == max has lots of implications.  But it
2276          * would be good to capture the rest as well.
2277          *
2278          * This information is already in the DB but it's in the parameter math
2279          * bits and it's awkward to use it.  This is is the simpler, possibly
2280          * cleaner way, but not necessarily the best, I don't know.
2281          */
2282 
2283         if (!expr)
2284                 return;
2285         name = expr_to_var_sym(expr, &sym);
2286         if (!name || !sym)
2287                 goto free;
2288 
2289         param = get_param_num_from_sym(sym);
2290         if (param < 0)
2291                 goto free;
2292         if (param_was_set_var_sym(name, sym))
2293                 goto free;
2294 
2295         tmp_name = get_param_name_var_sym(name, sym);
2296         if (!tmp_name)
2297                 goto free;
2298 
2299         snprintf(info_buf, sizeof(info_buf), "== $%d%s", param, tmp_name + 1);
2300         sql_insert_return_states(return_id, return_ranges,
2301                                 PARAM_COMPARE, -1, "$", info_buf);
2302 free:
2303         free_string(name);
2304 }
2305 
2306 static void print_return_comparison(int return_id, char *return_ranges, struct expression *expr)
2307 {
2308         struct sm_state *tmp;
2309         struct string_list *links;
2310         char *link;
2311         struct sm_state *sm;
2312         struct compare_data *data;
2313         struct var_sym *left, *right;
2314         int left_param, right_param;
2315         char left_buf[256];
2316         char right_buf[256];
2317         char info_buf[258];
2318         const char *tmp_name;
2319 
2320         print_return_value_comparison(return_id, return_ranges, expr);
2321 
2322         FOR_EACH_MY_SM(link_id, __get_cur_stree(), tmp) {
2323                 if (get_param_num_from_sym(tmp->sym) < 0)
2324                         continue;
2325                 links = tmp->state->data;
2326                 FOR_EACH_PTR(links, link) {
2327                         sm = get_sm_state(comparison_id, link, NULL);
2328                         if (!sm)
2329                                 continue;
2330                         data = sm->state->data;
2331                         if (!data ||
2332                             data->comparison == UNKNOWN_COMPARISON ||
2333                             data->comparison == IMPOSSIBLE_COMPARISON)
2334                                 continue;
2335                         if (ptr_list_size((struct ptr_list *)data->left_vsl) != 1 ||
2336                             ptr_list_size((struct ptr_list *)data->right_vsl) != 1)
2337                                 continue;
2338                         left = first_ptr_list((struct ptr_list *)data->left_vsl);
2339                         right = first_ptr_list((struct ptr_list *)data->right_vsl);
2340                         if (left->sym == right->sym &&
2341                             strcmp(left->var, right->var) == 0)
2342                                 continue;
2343                         /*
2344                          * Both parameters link to this comparison so only
2345                          * record the first one.
2346                          */
2347                         if (left->sym != tmp->sym ||
2348                             strcmp(left->var, tmp->name) != 0)
2349                                 continue;
2350 
2351                         if (strstr(right->var, " orig"))
2352                                 continue;
2353 
2354                         left_param = get_param_num_from_sym(left->sym);
2355                         right_param = get_param_num_from_sym(right->sym);
2356                         if (left_param < 0 || right_param < 0)
2357                                 continue;
2358 
2359                         tmp_name = get_param_name_var_sym(left->var, left->sym);
2360                         if (!tmp_name)
2361                                 continue;
2362                         snprintf(left_buf, sizeof(left_buf), "%s", tmp_name);
2363 
2364                         tmp_name = get_param_name_var_sym(right->var, right->sym);
2365                         if (!tmp_name || tmp_name[0] != '$')
2366                                 continue;
2367                         snprintf(right_buf, sizeof(right_buf), "$%d%s", right_param, tmp_name + 1);
2368 
2369                         /*
2370                          * FIXME: this should reject $ type variables (as
2371                          * opposed to $->foo type).  Those should come from
2372                          * smatch_param_compare_limit.c.
2373                          */
2374 
2375                         snprintf(info_buf, sizeof(info_buf), "%s %s", show_comparison(data->comparison), right_buf);
2376                         sql_insert_return_states(return_id, return_ranges,
2377                                         PARAM_COMPARE, left_param, left_buf, info_buf);
2378                 } END_FOR_EACH_PTR(link);
2379 
2380         } END_FOR_EACH_SM(tmp);
2381 }
2382 
2383 static int parse_comparison(char **value, int *op)
2384 {
2385 
2386         *op = **value;
2387 
2388         switch (*op) {
2389         case '<':
2390                 (*value)++;
2391                 if (**value == '=') {
2392                         (*value)++;
2393                         *op = SPECIAL_LTE;
2394                 }
2395                 break;
2396         case '=':
2397                 (*value)++;
2398                 (*value)++;
2399                 *op = SPECIAL_EQUAL;
2400                 break;
2401         case '!':
2402                 (*value)++;
2403                 (*value)++;
2404                 *op = SPECIAL_NOTEQUAL;
2405                 break;
2406         case '>':
2407                 (*value)++;
2408                 if (**value == '=') {
2409                         (*value)++;
2410                         *op = SPECIAL_GTE;
2411                 }
2412                 break;
2413         default:
2414                 return 0;
2415         }
2416 
2417         if (**value != ' ') {
2418                 sm_perror("parsing comparison.  %s", *value);
2419                 return 0;
2420         }
2421 
2422         (*value)++;
2423         return 1;
2424 }
2425 
2426 static int split_op_param_key(char *value, int *op, int *param, char **key)
2427 {
2428         static char buf[256];
2429         char *p;
2430 
2431         if (!parse_comparison(&value, op))
2432                 return 0;
2433 
2434         snprintf(buf, sizeof(buf), "%s", value);
2435 
2436         p = buf;
2437         if (*p++ != '$')
2438                 return 0;
2439 
2440         *param = atoi(p);
2441         if (*param < 0 || *param > 99)
2442                 return 0;
2443         p++;
2444         if (*param > 9)
2445                 p++;
2446         p--;
2447         *p = '$';
2448         *key = p;
2449 
2450         return 1;
2451 }
2452 
2453 static void db_return_comparison(struct expression *expr, int left_param, char *key, char *value)
2454 {
2455         struct expression *left_arg, *right_arg;
2456         char *left_name = NULL;
2457         struct symbol *left_sym;
2458         char *right_name = NULL;
2459         struct symbol *right_sym;
2460         int op;
2461         int right_param;
2462         char *right_key;
2463         struct var_sym_list *left_vsl = NULL, *right_vsl = NULL;
2464 
2465         if (left_param == -1) {
2466                 if (expr->type != EXPR_ASSIGNMENT)
2467                         return;
2468                 left_arg = strip_expr(expr->left);
2469 
2470                 while (expr->type == EXPR_ASSIGNMENT)
2471                         expr = strip_expr(expr->right);
2472                 if (expr->type != EXPR_CALL)
2473                         return;
2474         } else {
2475                 while (expr->type == EXPR_ASSIGNMENT)
2476                         expr = strip_expr(expr->right);
2477                 if (expr->type != EXPR_CALL)
2478                         return;
2479 
2480                 left_arg = get_argument_from_call_expr(expr->args, left_param);
2481                 if (!left_arg)
2482                         return;
2483         }
2484 
2485         if (!split_op_param_key(value, &op, &right_param, &right_key))
2486                 return;
2487 
2488         right_arg = get_argument_from_call_expr(expr->args, right_param);
2489         if (!right_arg)
2490                 return;
2491 
2492         left_name = get_variable_from_key(left_arg, key, &left_sym);
2493         if (!left_name || !left_sym)
2494                 goto free;
2495 
2496         right_name = get_variable_from_key(right_arg, right_key, &right_sym);
2497         if (!right_name || !right_sym)
2498                 goto free;
2499 
2500         add_var_sym(&left_vsl, left_name, left_sym);
2501         add_var_sym(&right_vsl, right_name, right_sym);
2502 
2503         add_comparison_var_sym(NULL, left_name, left_vsl, op, NULL, right_name, right_vsl);
2504 
2505 free:
2506         free_string(left_name);
2507         free_string(right_name);
2508 }
2509 
2510 int param_compare_limit_is_impossible(struct expression *expr, int left_param, char *left_key, char *value)
2511 {
2512         struct smatch_state *state;
2513         char *left_name = NULL;
2514         char *right_name = NULL;
2515         struct symbol *left_sym, *right_sym;
2516         struct expression *left_arg, *right_arg;
2517         int op, state_op;
2518         int right_param;
2519         char *right_key;
2520         int ret = 0;
2521         char buf[256];
2522 
2523         while (expr->type == EXPR_ASSIGNMENT)
2524                 expr = strip_expr(expr->right);
2525         if (expr->type != EXPR_CALL)
2526                 return 0;
2527 
2528         if (!split_op_param_key(value, &op, &right_param, &right_key))
2529                 return 0;
2530 
2531         left_arg = get_argument_from_call_expr(expr->args, left_param);
2532         if (!left_arg)
2533                 return 0;
2534 
2535         right_arg = get_argument_from_call_expr(expr->args, right_param);
2536         if (!right_arg)
2537                 return 0;
2538 
2539         left_name = get_variable_from_key(left_arg, left_key, &left_sym);
2540         right_name = get_variable_from_key(right_arg, right_key, &right_sym);
2541         if (!left_name || !right_name)
2542                 goto free;
2543 
2544         snprintf(buf, sizeof(buf), "%s vs %s", left_name, right_name);
2545         state = get_state(comparison_id, buf, NULL);
2546         if (!state)
2547                 goto free;
2548         state_op = state_to_comparison(state);
2549         if (!state_op)
2550                 goto free;
2551 
2552         if (!comparison_intersection(remove_unsigned_from_comparison(state_op), op))
2553                 ret = 1;
2554 free:
2555         free_string(left_name);
2556         free_string(right_name);
2557         return ret;
2558 }
2559 
2560 int impossibly_high_comparison(struct expression *expr)
2561 {
2562         struct smatch_state *link_state;
2563         struct sm_state *sm;
2564         struct string_list *links;
2565         char *link;
2566         struct compare_data *data;
2567 
2568         link_state = get_state_expr(link_id, expr);
2569         if (!link_state) {
2570                 if (expr->type == EXPR_BINOP &&
2571                     (impossibly_high_comparison(expr->left) ||
2572                      impossibly_high_comparison(expr->right)))
2573                         return 1;
2574                 return 0;
2575         }
2576 
2577         links = link_state->data;
2578         FOR_EACH_PTR(links, link) {
2579                 sm = get_sm_state(comparison_id, link, NULL);
2580                 if (!sm)
2581                         continue;
2582                 data = sm->state->data;
2583                 if (!data)
2584                         continue;
2585                 if (!possibly_true(data->left, data->comparison, data->right))
2586                         return 1;
2587         } END_FOR_EACH_PTR(link);
2588 
2589         return 0;
2590 }
2591 
2592 static void free_data(struct symbol *sym)
2593 {
2594         if (__inline_fn)
2595                 return;
2596         clear_compare_data_alloc();
2597 }
2598 
2599 void register_comparison(int id)
2600 {
2601         comparison_id = id;
2602         set_dynamic_states(comparison_id);
2603         add_hook(&save_start_states, AFTER_DEF_HOOK);
2604         add_unmatched_state_hook(comparison_id, unmatched_comparison);
2605         add_pre_merge_hook(comparison_id, &pre_merge_hook);
2606         add_merge_hook(comparison_id, &merge_compare_states);
2607         add_hook(&free_data, AFTER_FUNC_HOOK);
2608         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
2609         add_split_return_callback(&print_return_comparison);
2610 
2611         select_return_states_hook(PARAM_COMPARE, &db_return_comparison);
2612         add_hook(&match_preop, OP_HOOK);
2613 }
2614 
2615 void register_comparison_late(int id)
2616 {
2617         add_hook(&match_assign, ASSIGNMENT_HOOK);
2618 }
2619 
2620 void register_comparison_links(int id)
2621 {
2622         link_id = id;
2623         db_ignore_states(link_id);
2624         set_dynamic_states(link_id);
2625         add_merge_hook(link_id, &merge_links);
2626         add_modification_hook(link_id, &match_modify);
2627         add_modification_hook_late(link_id, match_inc_dec);
2628 
2629         add_member_info_callback(link_id, struct_member_callback);
2630 }
2631 
2632 void register_comparison_inc_dec(int id)
2633 {
2634         inc_dec_id = id;
2635         add_modification_hook_late(inc_dec_id, &iter_modify);
2636 }
2637 
2638 void register_comparison_inc_dec_links(int id)
2639 {
2640         inc_dec_link_id = id;
2641         set_dynamic_states(inc_dec_link_id);
2642         set_up_link_functions(inc_dec_id, inc_dec_link_id);
2643 }
2644 
2645 static struct sm_state *clone_partial_sm(struct sm_state *sm, int comparison)
2646 {
2647         struct compare_data *data;
2648         struct sm_state *clone;
2649         struct stree *stree;
2650 
2651         data = sm->state->data;
2652 
2653         clone = clone_sm(sm);
2654         clone->state = alloc_compare_state(data->left, data->left_var, data->left_vsl,
2655                                            comparison,
2656                                            data->right, data->right_var, data->right_vsl);
2657         free_slist(&clone->possible);
2658         add_possible_sm(clone, clone);
2659 
2660         stree = clone_stree(sm->pool);
2661         overwrite_sm_state_stree(&stree, clone);
2662         clone->pool = stree;
2663 
2664         return clone;
2665 }
2666 
2667 static void create_fake_history(struct sm_state *sm, int op,
2668                                struct state_list **true_stack,
2669                                struct state_list **false_stack)
2670 {
2671         struct sm_state *true_sm, *false_sm;
2672         struct compare_data *data;
2673         int true_comparison;
2674         int false_comparison;
2675 
2676         data = sm->state->data;
2677 
2678         if (is_merged(sm) || sm->left || sm->right)
2679                 return;
2680 
2681         true_comparison = comparison_intersection(data->comparison, op);
2682         false_comparison = comparison_intersection(data->comparison, negate_comparison(op));
2683 
2684         true_sm = clone_partial_sm(sm, true_comparison);
2685         false_sm = clone_partial_sm(sm, false_comparison);
2686 
2687         sm->merged = 1;
2688         sm->left = true_sm;
2689         sm->right = false_sm;
2690 
2691         add_ptr_list(true_stack, true_sm);
2692         add_ptr_list(false_stack, false_sm);
2693 }
2694 
2695 static void filter_by_sm(struct sm_state *sm, int op,
2696                        struct state_list **true_stack,
2697                        struct state_list **false_stack,
2698                        bool *useful)
2699 {
2700         struct compare_data *data;
2701         int is_true = 0;
2702         int is_false = 0;
2703 
2704         if (!sm)
2705                 return;
2706         data = sm->state->data;
2707         if (!data)
2708                 goto split;
2709         if (data->comparison == IMPOSSIBLE_COMPARISON)
2710                 return;
2711 
2712         /*
2713          * We want to check that "data->comparison" is totally inside "op".  So
2714          * if data->comparison is < and op is <= then that's true.  Or if
2715          * data->comparison is == and op is <= then that's true.  But if
2716          * data->comparison is <= and op is < than that's neither true nor
2717          * false.
2718          */
2719         if (data->comparison == comparison_intersection(data->comparison, op))
2720                 is_true = 1;
2721         if (data->comparison == comparison_intersection(data->comparison, negate_comparison(op)))
2722                 is_false = 1;
2723 
2724         if (!is_true && !is_false && !is_merged(sm)) {
2725                 create_fake_history(sm, op, true_stack, false_stack);
2726                 return;
2727         }
2728 
2729         if (debug_implied()) {
2730                 sm_msg("%s: %s: op = '%s' negated '%s'. true_intersect = '%s' false_insersect = '%s' sm = '%s'",
2731                        __func__,
2732                        sm->state->name,
2733                        alloc_sname(show_comparison(op)),
2734                        alloc_sname(show_comparison(negate_comparison(op))),
2735                        alloc_sname(show_comparison(comparison_intersection(data->comparison, op))),
2736                        alloc_sname(show_comparison(comparison_intersection(data->comparison, negate_comparison(op)))),
2737                        show_sm(sm));
2738         }
2739 
2740         *useful = true;
2741         if (is_true)
2742                 add_ptr_list(true_stack, sm);
2743         if (is_false)
2744                 add_ptr_list(false_stack, sm);
2745 split:
2746         filter_by_sm(sm->left, op, true_stack, false_stack, useful);
2747         filter_by_sm(sm->right, op, true_stack, false_stack, useful);
2748 }
2749 
2750 struct sm_state *comparison_implication_hook(struct expression *expr,
2751                                              struct state_list **true_stack,
2752                                              struct state_list **false_stack)
2753 {
2754         struct sm_state *sm;
2755         char *left, *right;
2756         int op;
2757         static char buf[256];
2758         bool useful = false;
2759 
2760         if (expr->type != EXPR_COMPARE)
2761                 return NULL;
2762 
2763         op = expr->op;
2764 
2765         left = expr_to_var(expr->left);
2766         right = expr_to_var(expr->right);
2767         if (!left || !right) {
2768                 free_string(left);
2769                 free_string(right);
2770                 return NULL;
2771         }
2772 
2773         if (strcmp(left, right) > 0) {
2774                 char *tmp = left;
2775 
2776                 left = right;
2777                 right = tmp;
2778                 op = flip_comparison(op);
2779         }
2780 
2781         snprintf(buf, sizeof(buf), "%s vs %s", left, right);
2782         sm = get_sm_state(comparison_id, buf, NULL);
2783         if (!sm)
2784                 return NULL;
2785         if (!sm->merged)
2786                 return NULL;
2787 
2788         filter_by_sm(sm, op, true_stack, false_stack, &useful);
2789         if (!useful)
2790                 return NULL;
2791 
2792         if (debug_implied())
2793                 sm_msg("implications from comparison: (%s)", show_sm(sm));
2794 
2795         return sm;
2796 }