smatch_buf_comparison.c

   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 that a buffer has x bytes even if we don't know
  20  * the value of x.
  21  *
  22  */
  23
  24 #include "smatch.h"
  25 #include "smatch_extra.h"
  26 #include "smatch_slist.h"
  27
  28 static int size_id;
  29 static int link_id;
  30
  31 /*
  32  * There is a bunch of code which does this:
  33  *
  34  *     if (size)
  35  *         foo = malloc(size);
  36  *
  37  * So if "size" is non-zero then the size of "foo" is size.  But really it's
  38  * also true if size is zero.  It's just better to assume to not trample over
  39  * the data that we have by merging &undefined states.
  40  *
  41  */
  42 static struct smatch_state *unmatched_state(struct sm_state *sm)
  43 {
  44         return sm->state;
  45 }
  46
  47 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
  48 {
  49         struct expression *expr1, *expr2;
  50
  51         expr1 = s1->data;
  52         expr2 = s2->data;
  53
  54         if (expr1 && expr2 && expr_equiv(expr1, expr2))
  55                 return s1;
  56         return &merged;
  57 }
  58
  59 static void match_link_modify(struct sm_state *sm, struct expression *mod_expr)
  60 {
  61         struct expression *expr;
  62         struct sm_state *tmp;
  63
  64         expr = sm->state->data;
  65         if (expr) {
  66                 set_state_expr(size_id, expr, &undefined);
  67                 set_state(link_id, sm->name, sm->sym, &undefined);
  68                 return;
  69         }
  70
  71         FOR_EACH_PTR(sm->possible, tmp) {
  72                 expr = tmp->state->data;
  73                 if (expr)
  74                         set_state_expr(size_id, expr, &undefined);
  75         } END_FOR_EACH_PTR(tmp);
  76         set_state(link_id, sm->name, sm->sym, &undefined);
  77 }
  78
  79 static const char *limit_map[] = {
  80         "byte_count",
  81         "elem_count",
  82         "elem_last",
  83         "used_count",
  84         "used_last",
  85 };
  86
  87 int state_to_limit(struct smatch_state *state)
  88 {
  89         int i;
  90
  91         if (!state || !state->data)
  92                 return -1;
  93
  94         for (i = 0; i < ARRAY_SIZE(limit_map); i++) {
  95                 if (strncmp(state->name, limit_map[i], strlen(limit_map[i])) == 0)
  96                         return i + BYTE_COUNT;
  97         }
  98
  99         return -1;
 100 }
 101
 102 const char *limit_type_str(unsigned int limit_type)
 103 {
 104         if (limit_type - BYTE_COUNT >= ARRAY_SIZE(limit_map)) {
 105                 sm_msg("internal: wrong size type %u", limit_type);
 106                 return "unknown";
 107         }
 108
 109         return limit_map[limit_type - BYTE_COUNT];
 110 }
 111
 112 static struct smatch_state *alloc_compare_size(int limit_type, struct expression *expr)
 113 {
 114         struct smatch_state *state;
 115         char *name;
 116         char buf[256];
 117
 118         state = __alloc_smatch_state(0);
 119         expr = strip_expr(expr);
 120         name = expr_to_str(expr);
 121         snprintf(buf, sizeof(buf), "%s %s", limit_type_str(limit_type), name);
 122         state->name = alloc_sname(buf);
 123         free_string(name);
 124         state->data = expr;
 125         return state;
 126 }
 127
 128 static int bytes_per_element(struct expression *expr)
 129 {
 130         struct symbol *type;
 131
 132         type = get_type(expr);
 133         if (!type)
 134                 return 0;
 135
 136         if (type->type != SYM_PTR && type->type != SYM_ARRAY)
 137                 return 0;
 138
 139         type = get_base_type(type);
 140         return type_bytes(type);
 141 }
 142
 143 static void db_save_type_links(struct expression *array, int type_limit, struct expression *size)
 144 {
 145         const char *array_name;
 146
 147         array_name = get_data_info_name(array);
 148         if (!array_name)
 149                 array_name = "";
 150         sql_insert_data_info(size, type_limit, array_name);
 151 }
 152
 153 static void match_alloc_helper(struct expression *pointer, struct expression *size)
 154 {
 155         struct expression *tmp;
 156         struct sm_state *sm;
 157         int limit_type = ELEM_COUNT;
 158         sval_t sval;
 159         int cnt = 0;
 160
 161         pointer = strip_expr(pointer);
 162         size = strip_expr(size);
 163         if (!size || !pointer)
 164                 return;
 165
 166         while ((tmp = get_assigned_expr(size))) {
 167                 size = strip_expr(tmp);
 168                 if (cnt++ > 5)
 169                         break;
 170         }
 171
 172         if (size->type == EXPR_BINOP && size->op == '*') {
 173                 struct expression *mult_left, *mult_right;
 174
 175                 mult_left = strip_expr(size->left);
 176                 mult_right = strip_expr(size->right);
 177
 178                 if (get_implied_value(mult_left, &sval) &&
 179                     sval.value == bytes_per_element(pointer))
 180                         size = mult_right;
 181                 else if (get_implied_value(mult_right, &sval) &&
 182                     sval.value == bytes_per_element(pointer))
 183                         size = mult_left;
 184                 else
 185                         return;
 186         }
 187
 188         /* Only save links to variables, not fixed sizes */
 189         if (get_value(size, &sval))
 190                 return;
 191
 192         if (size->type == EXPR_BINOP && size->op == '+' &&
 193             get_value(size->right, &sval) && sval.value == 1) {
 194                 size = size->left;
 195                 limit_type = ELEM_LAST;
 196         }
 197
 198         db_save_type_links(pointer, limit_type, size);
 199         sm = set_state_expr(size_id, pointer, alloc_compare_size(limit_type, size));
 200         if (!sm)
 201                 return;
 202         set_state_expr(link_id, size, alloc_state_expr(pointer));
 203 }
 204
 205 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 206 {
 207         int size_arg = PTR_INT(_size_arg);
 208         struct expression *pointer, *call, *arg;
 209
 210         pointer = strip_expr(expr->left);
 211         call = strip_expr(expr->right);
 212         arg = get_argument_from_call_expr(call->args, size_arg);
 213         match_alloc_helper(pointer, arg);
 214 }
 215
 216 static void match_calloc(const char *fn, struct expression *expr, void *_start_arg)
 217 {
 218         int start_arg = PTR_INT(_start_arg);
 219         struct expression *pointer, *call, *arg;
 220         struct sm_state *tmp;
 221         int limit_type = ELEM_COUNT;
 222         sval_t sval;
 223
 224         pointer = strip_expr(expr->left);
 225         call = strip_expr(expr->right);
 226         arg = get_argument_from_call_expr(call->args, start_arg);
 227         if (get_implied_value(arg, &sval) &&
 228             sval.value == bytes_per_element(pointer))
 229                 arg = get_argument_from_call_expr(call->args, start_arg + 1);
 230
 231         if (arg->type == EXPR_BINOP && arg->op == '+' &&
 232             get_value(arg->right, &sval) && sval.value == 1) {
 233                 arg = arg->left;
 234                 limit_type = ELEM_LAST;
 235         }
 236
 237         db_save_type_links(pointer, limit_type, arg);
 238         tmp = set_state_expr(size_id, pointer, alloc_compare_size(limit_type, arg));
 239         if (!tmp)
 240                 return;
 241         set_state_expr(link_id, arg, alloc_state_expr(pointer));
 242 }
 243
 244 static struct expression *get_size_variable_from_binop(struct expression *expr, int *limit_type)
 245 {
 246         struct smatch_state *state;
 247         struct expression *ret;
 248         struct symbol *type;
 249         sval_t orig_fixed;
 250         int offset_bytes;
 251         sval_t offset;
 252
 253         if (!get_value(expr->right, &offset))
 254                 return NULL;
 255         state = get_state_expr(size_id, expr->left);
 256         if (!state || !state->data)
 257                 return NULL;
 258
 259         type = get_type(expr->left);
 260         if (!type_is_ptr(type))
 261                 return NULL;
 262         type = get_real_base_type(type);
 263         if (!type_bytes(type))
 264                 return NULL;
 265         offset_bytes = offset.value * type_bytes(type);
 266
 267         ret = state->data;
 268         if (ret->type != EXPR_BINOP || ret->op != '+')
 269                 return NULL;
 270
 271         *limit_type = state_to_limit(state);
 272
 273         if (get_value(ret->left, &orig_fixed) && orig_fixed.value == offset_bytes)
 274                 return ret->right;
 275         if (get_value(ret->right, &orig_fixed) && orig_fixed.value == offset_bytes)
 276                 return ret->left;
 277
 278         return NULL;
 279 }
 280
 281 struct expression *get_size_variable(struct expression *buf, int *limit_type)
 282 {
 283         struct smatch_state *state;
 284         struct expression *ret;
 285
 286         buf = strip_expr(buf);
 287         if (!buf)
 288                 return NULL;
 289         if (buf->type == EXPR_BINOP && buf->op == '+') {
 290                 ret = get_size_variable_from_binop(buf, limit_type);
 291                 if (ret)
 292                         return ret;
 293         }
 294
 295         state = get_state_expr(size_id, buf);
 296         if (!state)
 297                 return NULL;
 298         *limit_type = state_to_limit(state);
 299         return state->data;
 300 }
 301
 302 struct expression *get_array_variable(struct expression *size)
 303 {
 304         struct smatch_state *state;
 305
 306         state = get_state_expr(link_id, size);
 307         if (state)
 308                 return state->data;
 309         return NULL;
 310 }
 311
 312 static void array_check(struct expression *expr)
 313 {
 314         struct expression *array;
 315         struct expression *size;
 316         struct expression *offset;
 317         char *array_str, *offset_str;
 318         int limit_type;
 319
 320         expr = strip_expr(expr);
 321         if (!is_array(expr))
 322                 return;
 323
 324         array = get_array_base(expr);
 325         size = get_size_variable(array, &limit_type);
 326         if (!size)
 327                 return;
 328         if (limit_type != ELEM_COUNT)
 329                 return;
 330         offset = get_array_offset(expr);
 331         if (!possible_comparison(size, SPECIAL_EQUAL, offset))
 332                 return;
 333
 334         array_str = expr_to_str(array);
 335         offset_str = expr_to_str(offset);
 336         sm_warning("potentially one past the end of array '%s[%s]'", array_str, offset_str);
 337         free_string(array_str);
 338         free_string(offset_str);
 339 }
 340
 341 struct db_info {
 342         char *name;
 343         int ret;
 344 };
 345
 346 static int db_limitter_callback(void *_info, int argc, char **argv, char **azColName)
 347 {
 348         struct db_info *info = _info;
 349
 350         /*
 351          * If possible the limitters are tied to the struct they limit.  If we
 352          * aren't sure which struct they limit then we use them as limitters for
 353          * everything.
 354          */
 355         if (!info->name || argv[0][0] == '\0' || strcmp(info->name, argv[0]) == 0)
 356                 info->ret = 1;
 357         return 0;
 358 }
 359
 360 static char *vsl_to_data_info_name(const char *name, struct var_sym_list *vsl)
 361 {
 362         struct var_sym *vs;
 363         struct symbol *type;
 364         static char buf[80];
 365         const char *p;
 366
 367         if (ptr_list_size((struct ptr_list *)vsl) != 1)
 368                 return NULL;
 369         vs = first_ptr_list((struct ptr_list *)vsl);
 370
 371         type = get_real_base_type(vs->sym);
 372         if (!type || type->type != SYM_PTR)
 373                 goto top_level_name;
 374         type = get_real_base_type(type);
 375         if (!type || type->type != SYM_STRUCT)
 376                 goto top_level_name;
 377         if (!type->ident)
 378                 goto top_level_name;
 379
 380         p = name;
 381         while ((name = strstr(p, "->")))
 382                 p = name + 2;
 383
 384         snprintf(buf, sizeof(buf),"(struct %s)->%s", type->ident->name, p);
 385         return alloc_sname(buf);
 386
 387 top_level_name:
 388         if (!(vs->sym->ctype.modifiers & MOD_TOPLEVEL))
 389                 return NULL;
 390         if (vs->sym->ctype.modifiers & MOD_STATIC)
 391                 snprintf(buf, sizeof(buf),"static %s", name);
 392         else
 393                 snprintf(buf, sizeof(buf),"global %s", name);
 394         return alloc_sname(buf);
 395 }
 396
 397 int db_var_is_array_limit(struct expression *array, const char *name, struct var_sym_list *vsl)
 398 {
 399         char *size_name;
 400         char *array_name = get_data_info_name(array);
 401         struct db_info db_info = {.name = array_name,};
 402
 403         size_name = vsl_to_data_info_name(name, vsl);
 404         if (!size_name)
 405                 return 0;
 406
 407         run_sql(db_limitter_callback, &db_info,
 408                 "select value from data_info where type = %d and data = '%s';",
 409                 ARRAY_LEN, size_name);
 410
 411         return db_info.ret;
 412 }
 413
 414 int buf_comparison_index_ok(struct expression *expr)
 415 {
 416         struct expression *array;
 417         struct expression *size;
 418         struct expression *offset;
 419         int limit_type;
 420         int comparison;
 421
 422         array = get_array_base(expr);
 423         size = get_size_variable(array, &limit_type);
 424         if (!size)
 425                 return 0;
 426         offset = get_array_offset(expr);
 427         comparison = get_comparison(offset, size);
 428         if (!comparison)
 429                 return 0;
 430
 431         if ((limit_type == ELEM_COUNT || limit_type == ELEM_LAST) &&
 432             (comparison == '<' || comparison == SPECIAL_UNSIGNED_LT))
 433                 return 1;
 434         if (limit_type == ELEM_LAST &&
 435             (comparison == SPECIAL_LTE ||
 436              comparison == SPECIAL_UNSIGNED_LTE ||
 437              comparison == SPECIAL_EQUAL))
 438                 return 1;
 439
 440         return 0;
 441 }
 442
 443 static int known_access_ok_numbers(struct expression *expr)
 444 {
 445         struct expression *array;
 446         struct expression *offset;
 447         sval_t max;
 448         int size;
 449
 450         array = get_array_base(expr);
 451         offset = get_array_offset(expr);
 452
 453         size = get_array_size(array);
 454         if (size <= 0)
 455                 return 0;
 456
 457         get_absolute_max(offset, &max);
 458         if (max.uvalue < size)
 459                 return 1;
 460         return 0;
 461 }
 462
 463 static void array_check_data_info(struct expression *expr)
 464 {
 465         struct expression *array;
 466         struct expression *offset;
 467         struct state_list *slist;
 468         struct sm_state *sm;
 469         struct compare_data *comp;
 470         char *offset_name;
 471         const char *equal_name = NULL;
 472
 473         expr = strip_expr(expr);
 474         if (!is_array(expr))
 475                 return;
 476
 477         if (known_access_ok_numbers(expr))
 478                 return;
 479         if (buf_comparison_index_ok(expr))
 480                 return;
 481
 482         array = get_array_base(expr);
 483         offset = get_array_offset(expr);
 484         offset_name = expr_to_var(offset);
 485         if (!offset_name)
 486                 return;
 487         slist = get_all_possible_equal_comparisons(offset);
 488         if (!slist)
 489                 goto free;
 490
 491         FOR_EACH_PTR(slist, sm) {
 492                 comp = sm->state->data;
 493                 if (strcmp(comp->left_var, offset_name) == 0) {
 494                         if (db_var_is_array_limit(array, comp->right_var, comp->right_vsl)) {
 495                                 equal_name = comp->right_var;
 496                                 break;
 497                         }
 498                 } else if (strcmp(comp->right_var, offset_name) == 0) {
 499                         if (db_var_is_array_limit(array, comp->left_var, comp->left_vsl)) {
 500                                 equal_name = comp->left_var;
 501                                 break;
 502                         }
 503                 }
 504         } END_FOR_EACH_PTR(sm);
 505
 506         if (equal_name) {
 507                 char *array_name = expr_to_str(array);
 508
 509                 sm_warning("potential off by one '%s[]' limit '%s'", array_name, equal_name);
 510                 free_string(array_name);
 511         }
 512
 513 free:
 514         free_slist(&slist);
 515         free_string(offset_name);
 516 }
 517
 518 static void add_allocation_function(const char *func, void *call_back, int param)
 519 {
 520         add_function_assign_hook(func, call_back, INT_PTR(param));
 521 }
 522
 523 static int is_sizeof(struct expression *expr)
 524 {
 525         const char *name;
 526
 527         if (expr->type == EXPR_SIZEOF)
 528                 return 1;
 529         name = pos_ident(expr->pos);
 530         if (name && strcmp(name, "sizeof") == 0)
 531                 return 1;
 532         return 0;
 533 }
 534
 535 static int match_size_binop(struct expression *size, struct expression *expr, int *limit_type)
 536 {
 537         int orig_type = *limit_type;
 538         struct expression *left;
 539         sval_t sval;
 540
 541         left = expr->left;
 542         if (!expr_equiv(size, left))
 543                 return 0;
 544
 545         if (expr->op == '-' &&
 546             get_value(expr->right, &sval) &&
 547             sval.value == 1 &&
 548             orig_type == ELEM_COUNT) {
 549                 *limit_type = ELEM_LAST;
 550                 return 1;
 551         }
 552
 553         if (expr->op == '+' &&
 554             get_value(expr->right, &sval) &&
 555             sval.value == 1 &&
 556             orig_type == ELEM_LAST) {
 557                 *limit_type = ELEM_COUNT;
 558                 return 1;
 559         }
 560
 561         if (expr->op == '*' &&
 562             is_sizeof(expr->right) &&
 563             orig_type == ELEM_COUNT) {
 564                 *limit_type = BYTE_COUNT;
 565                 return 1;
 566         }
 567
 568         if (expr->op == '/' &&
 569             is_sizeof(expr->right) &&
 570             orig_type == BYTE_COUNT) {
 571                 *limit_type = ELEM_COUNT;
 572                 return 1;
 573         }
 574
 575         return 0;
 576 }
 577
 578 static char *buf_size_param_comparison(struct expression *array, struct expression_list *args, int *limit_type)
 579 {
 580         struct expression *tmp, *arg;
 581         struct expression *size;
 582         static char buf[32];
 583         int i;
 584
 585         size = get_size_variable(array, limit_type);
 586         if (!size)
 587                 return NULL;
 588
 589         if (*limit_type == USED_LAST)
 590                 *limit_type = ELEM_LAST;
 591         if (*limit_type == USED_COUNT)
 592                 *limit_type = ELEM_COUNT;
 593
 594         i = -1;
 595         FOR_EACH_PTR(args, tmp) {
 596                 i++;
 597                 arg = tmp;
 598                 if (arg == array)
 599                         continue;
 600                 if (expr_equiv(arg, size) ||
 601                     (arg->type == EXPR_BINOP &&
 602                      match_size_binop(size, arg, limit_type))) {
 603                         snprintf(buf, sizeof(buf), "==$%d", i);
 604                         return buf;
 605                 }
 606         } END_FOR_EACH_PTR(tmp);
 607
 608         return NULL;
 609 }
 610
 611 static void match_call(struct expression *call)
 612 {
 613         struct expression *arg;
 614         char *compare;
 615         int param;
 616         char buf[5];
 617         int limit_type;
 618
 619         param = -1;
 620         FOR_EACH_PTR(call->args, arg) {
 621                 param++;
 622                 if (!is_pointer(arg))
 623                         continue;
 624                 compare = buf_size_param_comparison(arg, call->args, &limit_type);
 625                 if (!compare)
 626                         continue;
 627                 snprintf(buf, sizeof(buf), "%d", limit_type);
 628                 sql_insert_caller_info(call, limit_type, param, compare, buf);
 629         } END_FOR_EACH_PTR(arg);
 630 }
 631
 632 static int get_param(int param, char **name, struct symbol **sym)
 633 {
 634         struct symbol *arg;
 635         int i;
 636
 637         i = 0;
 638         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
 639                 /*
 640                  * this is a temporary hack to work around a bug (I think in sparse?)
 641                  * 2.6.37-rc1:fs/reiserfs/journal.o
 642                  * If there is a function definition without parameter name found
 643                  * after a function implementation then it causes a crash.
 644                  * int foo() {}
 645                  * int bar(char *);
 646                  */
 647                 if (arg->ident->name < (char *)100)
 648                         continue;
 649                 if (i == param) {
 650                         *name = arg->ident->name;
 651                         *sym = arg;
 652                         return TRUE;
 653                 }
 654                 i++;
 655         } END_FOR_EACH_PTR(arg);
 656
 657         return FALSE;
 658 }
 659
 660 static void set_param_compare(const char *array_name, struct symbol *array_sym, char *key, char *value)
 661 {
 662         struct expression *array_expr;
 663         struct expression *size_expr;
 664         struct symbol *size_sym;
 665         char *size_name;
 666         long param;
 667         struct sm_state *tmp;
 668         int limit_type;
 669
 670         if (strncmp(key, "==$", 3) != 0)
 671                 return;
 672         param = strtol(key + 3, NULL, 10);
 673         if (!get_param(param, &size_name, &size_sym))
 674                 return;
 675         array_expr = symbol_expression(array_sym);
 676         size_expr = symbol_expression(size_sym);
 677         limit_type = strtol(value, NULL, 10);
 678
 679         tmp = set_state_expr(size_id, array_expr, alloc_compare_size(limit_type, size_expr));
 680         if (!tmp)
 681                 return;
 682         set_state_expr(link_id, size_expr, alloc_state_expr(array_expr));
 683 }
 684
 685 static void set_implied(struct expression *call, struct expression *array_expr, char *key, char *value)
 686 {
 687         struct expression *size_expr;
 688         struct symbol *size_sym;
 689         char *size_name;
 690         long param;
 691         struct sm_state *tmp;
 692         int limit_type;
 693
 694         if (strncmp(key, "==$", 3) != 0)
 695                 return;
 696         param = strtol(key + 3, NULL, 10);
 697         if (!get_param(param, &size_name, &size_sym))
 698                 return;
 699         size_expr = symbol_expression(size_sym);
 700
 701         limit_type = strtol(value, NULL, 10);
 702         tmp = set_state_expr(size_id, array_expr, alloc_compare_size(limit_type, size_expr));
 703         if (!tmp)
 704                 return;
 705         set_state_expr(link_id, size_expr, alloc_state_expr(array_expr));
 706 }
 707
 708 static void munge_start_states(struct statement *stmt)
 709 {
 710         struct state_list *slist = NULL;
 711         struct sm_state *sm;
 712         struct sm_state *poss;
 713
 714         FOR_EACH_MY_SM(size_id, __get_cur_stree(), sm) {
 715                 if (sm->state != &merged)
 716                         continue;
 717                 /*
 718                  * screw it.  let's just assume that if one caller passes the
 719                  * size then they all do.
 720                  */
 721                 FOR_EACH_PTR(sm->possible, poss) {
 722                         if (poss->state != &merged &&
 723                             poss->state != &undefined) {
 724                                 add_ptr_list(&slist, poss);
 725                                 break;
 726                         }
 727                 } END_FOR_EACH_PTR(poss);
 728         } END_FOR_EACH_SM(sm);
 729
 730         FOR_EACH_PTR(slist, sm) {
 731                 set_state(size_id, sm->name, sm->sym, sm->state);
 732         } END_FOR_EACH_PTR(sm);
 733
 734         free_slist(&slist);
 735 }
 736
 737 static void set_used(struct expression *expr)
 738 {
 739         struct expression *parent;
 740         struct expression *array;
 741         struct expression *offset;
 742         struct sm_state *tmp;
 743         int limit_type;
 744
 745         if (expr->op != SPECIAL_INCREMENT)
 746                 return;
 747
 748         limit_type = USED_LAST;
 749         if (expr->type == EXPR_POSTOP)
 750                 limit_type = USED_COUNT;
 751
 752         parent = expr_get_parent_expr(expr);
 753         if (!parent || parent->type != EXPR_BINOP)
 754                 return;
 755         parent = expr_get_parent_expr(parent);
 756         if (!parent || !is_array(parent))
 757                 return;
 758
 759         array = get_array_base(parent);
 760         offset = get_array_offset(parent);
 761         if (offset != expr)
 762                 return;
 763
 764         tmp = set_state_expr(size_id, array, alloc_compare_size(limit_type, offset->unop));
 765         if (!tmp)
 766                 return;
 767         set_state_expr(link_id, offset->unop, alloc_state_expr(array));
 768 }
 769
 770 static int match_assign_array(struct expression *expr)
 771 {
 772         // FIXME: implement
 773         return 0;
 774 }
 775
 776 static int match_assign_size(struct expression *expr)
 777 {
 778         struct expression *right, *size, *array;
 779         struct smatch_state *state;
 780         struct sm_state *tmp;
 781         int limit_type;
 782
 783         right = expr->right;
 784         size = right;
 785         if (size->type == EXPR_BINOP)
 786                 size = size->left;
 787
 788         array = get_array_variable(size);
 789         if (!array)
 790                 return 0;
 791         state = get_state_expr(size_id, array);
 792         if (!state || !state->data)
 793                 return 0;
 794
 795         limit_type = state_to_limit(state);
 796         if (limit_type < 0)
 797                 return 0;
 798
 799         if (right->type == EXPR_BINOP && !match_size_binop(size, right, &limit_type))
 800                 return 0;
 801
 802         tmp = set_state_expr(size_id, array, alloc_compare_size(limit_type, expr->left));
 803         if (!tmp)
 804                 return 0;
 805         set_state_expr(link_id, expr->left, alloc_state_expr(array));
 806         return 1;
 807 }
 808
 809 static void match_assign(struct expression *expr)
 810 {
 811         if (expr->op != '=')
 812                 return;
 813
 814         if (match_assign_array(expr))
 815                 return;
 816         match_assign_size(expr);
 817 }
 818
 819 static void match_copy(const char *fn, struct expression *expr, void *unused)
 820 {
 821         struct expression *src, *size;
 822         int src_param, size_param;
 823
 824         src = get_argument_from_call_expr(expr->args, 1);
 825         size = get_argument_from_call_expr(expr->args, 2);
 826         src = strip_expr(src);
 827         size = strip_expr(size);
 828         if (!src || !size)
 829                 return;
 830         if (src->type != EXPR_SYMBOL || size->type != EXPR_SYMBOL)
 831                 return;
 832
 833         src_param = get_param_num_from_sym(src->symbol);
 834         size_param = get_param_num_from_sym(size->symbol);
 835         if (src_param < 0 || size_param < 0)
 836                 return;
 837
 838         sql_insert_cache(call_implies, "'%s', '%s', 0, %d, %d, %d, '==$%d', '%d'",
 839                          get_base_file(), get_function(), fn_static(),
 840                          BYTE_COUNT, src_param, size_param, BYTE_COUNT);
 841 }
 842
 843 void register_buf_comparison(int id)
 844 {
 845         int i;
 846
 847         size_id = id;
 848
 849         set_dynamic_states(size_id);
 850
 851         add_unmatched_state_hook(size_id, &unmatched_state);
 852
 853         add_allocation_function("malloc", &match_alloc, 0);
 854         add_allocation_function("memdup", &match_alloc, 1);
 855         add_allocation_function("realloc", &match_alloc, 1);
 856         if (option_project == PROJ_KERNEL) {
 857                 add_allocation_function("kmalloc", &match_alloc, 0);
 858                 add_allocation_function("kzalloc", &match_alloc, 0);
 859                 add_allocation_function("vmalloc", &match_alloc, 0);
 860                 add_allocation_function("__vmalloc", &match_alloc, 0);
 861                 add_allocation_function("sock_kmalloc", &match_alloc, 1);
 862                 add_allocation_function("kmemdup", &match_alloc, 1);
 863                 add_allocation_function("memdup_user", &match_alloc, 1);
 864                 add_allocation_function("dma_alloc_attrs", &match_alloc, 1);
 865                 add_allocation_function("pci_alloc_consistent", &match_alloc, 1);
 866                 add_allocation_function("pci_alloc_coherent", &match_alloc, 1);
 867                 add_allocation_function("devm_kmalloc", &match_alloc, 1);
 868                 add_allocation_function("devm_kzalloc", &match_alloc, 1);
 869                 add_allocation_function("kcalloc", &match_calloc, 0);
 870                 add_allocation_function("devm_kcalloc", &match_calloc, 1);
 871                 add_allocation_function("kmalloc_array", &match_calloc, 0);
 872                 add_allocation_function("krealloc", &match_alloc, 1);
 873
 874                 add_function_hook("copy_from_user", &match_copy, NULL);
 875                 add_function_hook("__copy_from_user", &match_copy, NULL);
 876         }
 877
 878         add_hook(&array_check, OP_HOOK);
 879         add_hook(&array_check_data_info, OP_HOOK);
 880         add_hook(&set_used, OP_HOOK);
 881
 882         add_hook(&match_call, FUNCTION_CALL_HOOK);
 883         add_hook(&munge_start_states, AFTER_DEF_HOOK);
 884
 885         add_hook(&match_assign, ASSIGNMENT_HOOK);
 886
 887         for (i = BYTE_COUNT; i <= USED_COUNT; i++) {
 888                 select_call_implies_hook(i, &set_implied);
 889                 select_caller_info_hook(set_param_compare, i);
 890                 select_return_implies_hook(i, &set_implied);
 891         }
 892 }
 893
 894 void register_buf_comparison_links(int id)
 895 {
 896         link_id = id;
 897         set_dynamic_states(link_id);
 898         add_merge_hook(link_id, &merge_links);
 899         add_modification_hook(link_id, &match_link_modify);
 900 }