1 /*
   2  * Copyright (C) 2009 Dan Carpenter.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17 
  18 /*
  19  * There are several types of function hooks:
  20  * add_function_hook()        - For any time a function is called.
  21  * add_function_assign_hook() - foo = the_function().
  22  * add_implied_return_hook()  - Calculates the implied return value.
  23  * add_macro_assign_hook()    - foo = the_macro().
  24  * return_implies_state()     - For when a return value of 1 implies locked
  25  *                              and 0 implies unlocked. etc. etc.
  26  *
  27  */
  28 
  29 #include <stdlib.h>
  30 #include <stdio.h>
  31 #include "smatch.h"
  32 #include "smatch_slist.h"
  33 #include "smatch_extra.h"
  34 #include "smatch_function_hashtable.h"
  35 
  36 struct fcall_back {
  37         int type;
  38         struct data_range *range;
  39         union {
  40                 func_hook *call_back;
  41                 implication_hook *ranged;
  42                 implied_return_hook *implied_return;
  43         } u;
  44         void *info;
  45 };
  46 
  47 ALLOCATOR(fcall_back, "call backs");
  48 DECLARE_PTR_LIST(call_back_list, struct fcall_back);
  49 
  50 DEFINE_FUNCTION_HASHTABLE_STATIC(callback, struct fcall_back, struct call_back_list);
  51 static struct hashtable *func_hash;
  52 
  53 int __in_fake_parameter_assign;
  54 
  55 #define REGULAR_CALL       0
  56 #define RANGED_CALL        1
  57 #define ASSIGN_CALL        2
  58 #define IMPLIED_RETURN     3
  59 #define MACRO_ASSIGN       4
  60 #define MACRO_ASSIGN_EXTRA 5
  61 
  62 struct return_implies_callback {
  63         int type;
  64         return_implies_hook *callback;
  65 };
  66 ALLOCATOR(return_implies_callback, "return_implies callbacks");
  67 DECLARE_PTR_LIST(db_implies_list, struct return_implies_callback);
  68 static struct db_implies_list *db_return_states_list;
  69 
  70 typedef void (void_fn)(void);
  71 DECLARE_PTR_LIST(void_fn_list, void_fn *);
  72 static struct void_fn_list *return_states_before;
  73 static struct void_fn_list *return_states_after;
  74 
  75 static struct fcall_back *alloc_fcall_back(int type, void *call_back,
  76                                            void *info)
  77 {
  78         struct fcall_back *cb;
  79 
  80         cb = __alloc_fcall_back(0);
  81         cb->type = type;
  82         cb->u.call_back = call_back;
  83         cb->info = info;
  84         return cb;
  85 }
  86 
  87 void add_function_hook(const char *look_for, func_hook *call_back, void *info)
  88 {
  89         struct fcall_back *cb;
  90 
  91         cb = alloc_fcall_back(REGULAR_CALL, call_back, info);
  92         add_callback(func_hash, look_for, cb);
  93 }
  94 
  95 void add_function_assign_hook(const char *look_for, func_hook *call_back,
  96                               void *info)
  97 {
  98         struct fcall_back *cb;
  99 
 100         cb = alloc_fcall_back(ASSIGN_CALL, call_back, info);
 101         add_callback(func_hash, look_for, cb);
 102 }
 103 
 104 void add_implied_return_hook(const char *look_for,
 105                              implied_return_hook *call_back,
 106                              void *info)
 107 {
 108         struct fcall_back *cb;
 109 
 110         cb = alloc_fcall_back(IMPLIED_RETURN, call_back, info);
 111         add_callback(func_hash, look_for, cb);
 112 }
 113 
 114 void add_macro_assign_hook(const char *look_for, func_hook *call_back,
 115                         void *info)
 116 {
 117         struct fcall_back *cb;
 118 
 119         cb = alloc_fcall_back(MACRO_ASSIGN, call_back, info);
 120         add_callback(func_hash, look_for, cb);
 121 }
 122 
 123 void add_macro_assign_hook_extra(const char *look_for, func_hook *call_back,
 124                         void *info)
 125 {
 126         struct fcall_back *cb;
 127 
 128         cb = alloc_fcall_back(MACRO_ASSIGN_EXTRA, call_back, info);
 129         add_callback(func_hash, look_for, cb);
 130 }
 131 
 132 void return_implies_state(const char *look_for, long long start, long long end,
 133                          implication_hook *call_back, void *info)
 134 {
 135         struct fcall_back *cb;
 136 
 137         cb = alloc_fcall_back(RANGED_CALL, call_back, info);
 138         cb->range = alloc_range_perm(ll_to_sval(start), ll_to_sval(end));
 139         add_callback(func_hash, look_for, cb);
 140 }
 141 
 142 void return_implies_state_sval(const char *look_for, sval_t start, sval_t end,
 143                          implication_hook *call_back, void *info)
 144 {
 145         struct fcall_back *cb;
 146 
 147         cb = alloc_fcall_back(RANGED_CALL, call_back, info);
 148         cb->range = alloc_range_perm(start, end);
 149         add_callback(func_hash, look_for, cb);
 150 }
 151 
 152 void select_return_states_hook(int type, return_implies_hook *callback)
 153 {
 154         struct return_implies_callback *cb = __alloc_return_implies_callback(0);
 155 
 156         cb->type = type;
 157         cb->callback = callback;
 158         add_ptr_list(&db_return_states_list, cb);
 159 }
 160 
 161 void select_return_states_before(void_fn *fn)
 162 {
 163         void_fn **p = malloc(sizeof(void_fn *));
 164         *p = fn;
 165         add_ptr_list(&return_states_before, p);
 166 }
 167 
 168 void select_return_states_after(void_fn *fn)
 169 {
 170         void_fn **p = malloc(sizeof(void_fn *));
 171         *p = fn;
 172         add_ptr_list(&return_states_after, p);
 173 }
 174 
 175 static void call_return_states_before_hooks(void)
 176 {
 177         void_fn **fn;
 178 
 179         FOR_EACH_PTR(return_states_before, fn) {
 180                 (*fn)();
 181         } END_FOR_EACH_PTR(fn);
 182 }
 183 
 184 static void call_return_states_after_hooks(struct expression *expr)
 185 {
 186         void_fn **fn;
 187 
 188         FOR_EACH_PTR(return_states_after, fn) {
 189                 (*fn)();
 190         } END_FOR_EACH_PTR(fn);
 191         __pass_to_client(expr, FUNCTION_CALL_HOOK_AFTER_DB);
 192 }
 193 
 194 static int call_call_backs(struct call_back_list *list, int type,
 195                             const char *fn, struct expression *expr)
 196 {
 197         struct fcall_back *tmp;
 198         int handled = 0;
 199 
 200         FOR_EACH_PTR(list, tmp) {
 201                 if (tmp->type == type) {
 202                         (tmp->u.call_back)(fn, expr, tmp->info);
 203                         handled = 1;
 204                 }
 205         } END_FOR_EACH_PTR(tmp);
 206 
 207         return handled;
 208 }
 209 
 210 static void call_ranged_call_backs(struct call_back_list *list,
 211                                 const char *fn, struct expression *call_expr,
 212                                 struct expression *assign_expr)
 213 {
 214         struct fcall_back *tmp;
 215 
 216         FOR_EACH_PTR(list, tmp) {
 217                 (tmp->u.ranged)(fn, call_expr, assign_expr, tmp->info);
 218         } END_FOR_EACH_PTR(tmp);
 219 }
 220 
 221 static struct call_back_list *get_same_ranged_call_backs(struct call_back_list *list,
 222                                                 struct data_range *drange)
 223 {
 224         struct call_back_list *ret = NULL;
 225         struct fcall_back *tmp;
 226 
 227         FOR_EACH_PTR(list, tmp) {
 228                 if (tmp->type != RANGED_CALL)
 229                         continue;
 230                 if (ranges_equiv(tmp->range, drange))
 231                         add_ptr_list(&ret, tmp);
 232         } END_FOR_EACH_PTR(tmp);
 233         return ret;
 234 }
 235 
 236 static int in_list_exact_sval(struct range_list *list, struct data_range *drange)
 237 {
 238         struct data_range *tmp;
 239 
 240         FOR_EACH_PTR(list, tmp) {
 241                 if (ranges_equiv(tmp, drange))
 242                         return 1;
 243         } END_FOR_EACH_PTR(tmp);
 244         return 0;
 245 }
 246 
 247 static int assign_ranged_funcs(const char *fn, struct expression *expr,
 248                                  struct call_back_list *call_backs)
 249 {
 250         struct fcall_back *tmp;
 251         struct sm_state *sm;
 252         char *var_name;
 253         struct symbol *sym;
 254         struct smatch_state *estate;
 255         struct stree *tmp_stree;
 256         struct stree *final_states = NULL;
 257         struct range_list *handled_ranges = NULL;
 258         struct call_back_list *same_range_call_backs = NULL;
 259         struct range_list *rl;
 260         int handled = 0;
 261 
 262         if (!call_backs)
 263                 return 0;
 264 
 265         var_name = expr_to_var_sym(expr->left, &sym);
 266         if (!var_name || !sym)
 267                 goto free;
 268 
 269         FOR_EACH_PTR(call_backs, tmp) {
 270                 if (tmp->type != RANGED_CALL)
 271                         continue;
 272 
 273                 if (in_list_exact_sval(handled_ranges, tmp->range))
 274                         continue;
 275                 __push_fake_cur_stree();
 276                 tack_on(&handled_ranges, tmp->range);
 277 
 278                 same_range_call_backs = get_same_ranged_call_backs(call_backs, tmp->range);
 279                 call_ranged_call_backs(same_range_call_backs, fn, expr->right, expr);
 280                 __free_ptr_list((struct ptr_list **)&same_range_call_backs);
 281 
 282                 rl = alloc_rl(tmp->range->min, tmp->range->max);
 283                 rl = cast_rl(get_type(expr->left), rl);
 284                 estate = alloc_estate_rl(rl);
 285                 set_extra_mod(var_name, sym, expr->left, estate);
 286 
 287                 tmp_stree = __pop_fake_cur_stree();
 288                 merge_fake_stree(&final_states, tmp_stree);
 289                 free_stree(&tmp_stree);
 290                 handled = 1;
 291         } END_FOR_EACH_PTR(tmp);
 292 
 293         FOR_EACH_SM(final_states, sm) {
 294                 __set_sm(sm);
 295         } END_FOR_EACH_SM(sm);
 296 
 297         free_stree(&final_states);
 298 free:
 299         free_string(var_name);
 300         return handled;
 301 }
 302 
 303 static void call_implies_callbacks(int comparison, struct expression *expr, sval_t sval, int left, struct stree **implied_true, struct stree **implied_false)
 304 {
 305         struct call_back_list *call_backs;
 306         struct fcall_back *tmp;
 307         const char *fn;
 308         struct data_range *value_range;
 309         struct stree *true_states = NULL;
 310         struct stree *false_states = NULL;
 311         struct stree *tmp_stree;
 312 
 313         *implied_true = NULL;
 314         *implied_false = NULL;
 315         if (expr->fn->type != EXPR_SYMBOL || !expr->fn->symbol)
 316                 return;
 317         fn = expr->fn->symbol->ident->name;
 318         call_backs = search_callback(func_hash, (char *)expr->fn->symbol->ident->name);
 319         if (!call_backs)
 320                 return;
 321         value_range = alloc_range(sval, sval);
 322 
 323         /* set true states */
 324         __push_fake_cur_stree();
 325         FOR_EACH_PTR(call_backs, tmp) {
 326                 if (tmp->type != RANGED_CALL)
 327                         continue;
 328                 if (!true_comparison_range_LR(comparison, tmp->range, value_range, left))
 329                         continue;
 330                 (tmp->u.ranged)(fn, expr, NULL, tmp->info);
 331         } END_FOR_EACH_PTR(tmp);
 332         tmp_stree = __pop_fake_cur_stree();
 333         merge_fake_stree(&true_states, tmp_stree);
 334         free_stree(&tmp_stree);
 335 
 336         /* set false states */
 337         __push_fake_cur_stree();
 338         FOR_EACH_PTR(call_backs, tmp) {
 339                 if (tmp->type != RANGED_CALL)
 340                         continue;
 341                 if (!false_comparison_range_LR(comparison, tmp->range, value_range, left))
 342                         continue;
 343                 (tmp->u.ranged)(fn, expr, NULL, tmp->info);
 344         } END_FOR_EACH_PTR(tmp);
 345         tmp_stree = __pop_fake_cur_stree();
 346         merge_fake_stree(&false_states, tmp_stree);
 347         free_stree(&tmp_stree);
 348 
 349         *implied_true = true_states;
 350         *implied_false = false_states;
 351 }
 352 
 353 struct db_callback_info {
 354         int true_side;
 355         int comparison;
 356         struct expression *expr;
 357         struct range_list *rl;
 358         int left;
 359         struct stree *stree;
 360         struct db_implies_list *callbacks;
 361         int prev_return_id;
 362         int cull;
 363         int has_states;
 364         char *ret_str;
 365         struct smatch_state *ret_state;
 366         struct expression *var_expr;
 367         int handled;
 368 };
 369 
 370 static void store_return_state(struct db_callback_info *db_info, const char *ret_str, struct smatch_state *state)
 371 {
 372         db_info->ret_str = alloc_sname(ret_str),
 373         db_info->ret_state = state;
 374 }
 375 
 376 static bool fake_a_param_assignment(struct expression *expr, const char *return_str, struct smatch_state *orig)
 377 {
 378         struct expression *arg, *left, *right, *tmp, *fake_assign;
 379         char *p;
 380         int param;
 381         char buf[256];
 382         char *str;
 383 
 384         if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
 385                 return false;
 386         left = expr->left;
 387         right = expr->right;
 388 
 389         while (right->type == EXPR_ASSIGNMENT)
 390                 right = strip_expr(right->right);
 391         if (!right || right->type != EXPR_CALL)
 392                 return false;
 393 
 394         p = strchr(return_str, '[');
 395         if (!p)
 396                 return false;
 397 
 398         p++;
 399         if (p[0] == '=' && p[1] == '=')
 400                 p += 2;
 401         if (p[0] != '$')
 402                 return false;
 403 
 404         snprintf(buf, sizeof(buf), "%s", p);
 405 
 406         p = buf;
 407         p += 1;
 408         param = strtol(p, &p, 10);
 409 
 410         p = strchr(p, ']');
 411         if (!p || *p != ']')
 412                 return false;
 413         *p = '\0';
 414 
 415         arg = get_argument_from_call_expr(right->args, param);
 416         if (!arg)
 417                 return false;
 418 
 419         /* There should be a get_other_name() function which returns an expr */
 420         tmp = get_assigned_expr(arg);
 421         if (tmp)
 422                 arg = tmp;
 423 
 424         /*
 425          * This is a sanity check to prevent side effects from evaluating stuff
 426          * twice.
 427          */
 428         str = expr_to_chunk_sym_vsl(arg, NULL, NULL);
 429         if (!str)
 430                 return false;
 431         free_string(str);
 432 
 433         right = gen_expression_from_key(arg, buf);
 434         if (!right)  /* Mostly fails for binops like [$0 + 4032] */
 435                 return false;
 436         fake_assign = assign_expression(left, '=', right);
 437         __in_fake_parameter_assign++;
 438         __split_expr(fake_assign);
 439         __in_fake_parameter_assign--;
 440 
 441         /*
 442          * If the return is "0-65531[$0->nla_len - 4]" the faked expression
 443          * is maybe (-4)-65531 but we know it is in the 0-65531 range so both
 444          * parts have to be considered.  We use _nomod() because it's not really
 445          * another modification, it's just a clarification.
 446          *
 447          */
 448         if (estate_rl(orig)) {
 449                 struct smatch_state *faked;
 450                 struct range_list *rl;
 451 
 452                 faked = get_extra_state(left);
 453                 if (estate_rl(faked)) {
 454                         rl = rl_intersection(estate_rl(faked), estate_rl(orig));
 455                         if (rl)
 456                                 set_extra_expr_nomod(expr, alloc_estate_rl(rl));
 457                 }
 458         }
 459 
 460         return true;
 461 }
 462 
 463 static void set_return_assign_state(struct db_callback_info *db_info)
 464 {
 465         struct expression *expr = db_info->expr->left;
 466         struct smatch_state *state;
 467 
 468         if (!db_info->ret_state)
 469                 return;
 470 
 471         state = alloc_estate_rl(cast_rl(get_type(expr), clone_rl(estate_rl(db_info->ret_state))));
 472         if (!fake_a_param_assignment(db_info->expr, db_info->ret_str, state))
 473                 set_extra_expr_mod(expr, state);
 474 
 475         db_info->ret_state = NULL;
 476         db_info->ret_str = NULL;
 477 }
 478 
 479 static void set_other_side_state(struct db_callback_info *db_info)
 480 {
 481         struct expression *expr = db_info->var_expr;
 482         struct smatch_state *state;
 483 
 484         if (!db_info->ret_state)
 485                 return;
 486 
 487         state = alloc_estate_rl(cast_rl(get_type(expr), clone_rl(estate_rl(db_info->ret_state))));
 488         set_extra_expr_nomod(expr, state);
 489         db_info->ret_state = NULL;
 490         db_info->ret_str = NULL;
 491 }
 492 
 493 static void handle_ret_equals_param(char *ret_string, struct range_list *rl, struct expression *call)
 494 {
 495         char *str;
 496         long long param;
 497         struct expression *arg;
 498         struct range_list *orig;
 499 
 500         str = strstr(ret_string, "==$");
 501         if (!str)
 502                 return;
 503         str += 3;
 504         param = strtoll(str, NULL, 10);
 505         arg = get_argument_from_call_expr(call->args, param);
 506         if (!arg)
 507                 return;
 508         get_absolute_rl(arg, &orig);
 509         rl = rl_intersection(orig, rl);
 510         if (!rl)
 511                 return;
 512         set_extra_expr_nomod(arg, alloc_estate_rl(rl));
 513 }
 514 
 515 static int impossible_limit(struct expression *expr, int param, char *key, char *value)
 516 {
 517         struct expression *arg;
 518         struct smatch_state *state;
 519         struct range_list *passed;
 520         struct range_list *limit;
 521         struct symbol *compare_type;
 522 
 523         while (expr->type == EXPR_ASSIGNMENT)
 524                 expr = strip_expr(expr->right);
 525         if (expr->type != EXPR_CALL)
 526                 return 0;
 527 
 528         arg = get_argument_from_call_expr(expr->args, param);
 529         if (!arg)
 530                 return 0;
 531 
 532         if (strcmp(key, "$") == 0) {
 533                 if (!get_implied_rl(arg, &passed))
 534                         return 0;
 535 
 536                 compare_type = get_arg_type(expr->fn, param);
 537         } else {
 538                 char *name;
 539                 struct symbol *sym;
 540 
 541                 name = get_variable_from_key(arg, key, &sym);
 542                 if (!name || !sym)
 543                         return 0;
 544 
 545                 state = get_state(SMATCH_EXTRA, name, sym);
 546                 if (!state) {
 547                         free_string(name);
 548                         return 0;
 549                 }
 550                 passed = estate_rl(state);
 551                 if (!passed || is_whole_rl(passed)) {
 552                         free_string(name);
 553                         return 0;
 554                 }
 555 
 556                 compare_type = get_member_type_from_key(arg, key);
 557         }
 558 
 559         passed = cast_rl(compare_type, passed);
 560         call_results_to_rl(expr, compare_type, value, &limit);
 561         if (!limit || is_whole_rl(limit))
 562                 return 0;
 563         if (possibly_true_rl(passed, SPECIAL_EQUAL, limit))
 564                 return 0;
 565         if (option_debug || local_debug)
 566                 sm_msg("impossible: %d '%s' limit '%s' == '%s'", param, key, show_rl(passed), value);
 567         return 1;
 568 }
 569 
 570 static int is_impossible_data(int type, struct expression *expr, int param, char *key, char *value)
 571 {
 572         if (type == PARAM_LIMIT && impossible_limit(expr, param, key, value))
 573                 return 1;
 574         if (type == COMPARE_LIMIT && param_compare_limit_is_impossible(expr, param, key, value)) {
 575                 if (local_debug)
 576                         sm_msg("param_compare_limit_is_impossible: %d %s %s", param, key, value);
 577                 return 1;
 578         }
 579         return 0;
 580 }
 581 
 582 static int func_type_mismatch(struct expression *expr, const char *value)
 583 {
 584         struct symbol *type;
 585 
 586         /* This makes faking returns easier */
 587         if (!value || value[0] == '\0')
 588                 return 0;
 589 
 590         while (expr->type == EXPR_ASSIGNMENT)
 591                 expr = strip_expr(expr->right);
 592 
 593         /*
 594          * Short cut:  We only care about function pointers that are struct
 595          * members.
 596          *
 597          */
 598         if (expr->fn->type == EXPR_SYMBOL)
 599                 return 0;
 600 
 601         type = get_type(expr->fn);
 602         if (!type)
 603                 return 0;
 604         if (type->type == SYM_PTR)
 605                 type = get_real_base_type(type);
 606 
 607         if (strcmp(type_to_str(type), value) == 0)
 608                 return 0;
 609 
 610         return 1;
 611 }
 612 
 613 static int db_compare_callback(void *_info, int argc, char **argv, char **azColName)
 614 {
 615         struct db_callback_info *db_info = _info;
 616         struct range_list *var_rl = db_info->rl;
 617         struct range_list *ret_range;
 618         int type, param;
 619         char *ret_str, *key, *value;
 620         struct return_implies_callback *tmp;
 621         struct stree *stree;
 622         int return_id;
 623         int comparison;
 624 
 625         if (argc != 6)
 626                 return 0;
 627 
 628         return_id = atoi(argv[0]);
 629         ret_str = argv[1];
 630         type = atoi(argv[2]);
 631         param = atoi(argv[3]);
 632         key = argv[4];
 633         value = argv[5];
 634 
 635         db_info->has_states = 1;
 636         if (db_info->prev_return_id != -1 && type == INTERNAL) {
 637                 set_other_side_state(db_info);
 638                 stree = __pop_fake_cur_stree();
 639 
 640                 if (!db_info->cull)
 641                         merge_fake_stree(&db_info->stree, stree);
 642                 free_stree(&stree);
 643                 __push_fake_cur_stree();
 644                 db_info->cull = 0;
 645         }
 646         db_info->prev_return_id = return_id;
 647 
 648         if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
 649                 db_info->cull = 1;
 650         if (db_info->cull)
 651                 return 0;
 652         if (type == CULL_PATH) {
 653                 db_info->cull = 1;
 654                 return 0;
 655         }
 656 
 657         if (is_impossible_data(type, db_info->expr, param, key, value)) {
 658                 db_info->cull = 1;
 659                 return 0;
 660         }
 661 
 662         call_results_to_rl(db_info->expr, get_type(strip_expr(db_info->expr)), ret_str, &ret_range);
 663         ret_range = cast_rl(get_type(db_info->expr), ret_range);
 664         if (!ret_range)
 665                 ret_range = alloc_whole_rl(get_type(db_info->expr));
 666 
 667         comparison = db_info->comparison;
 668         if (db_info->left)
 669                 comparison = flip_comparison(comparison);
 670 
 671         if (db_info->true_side) {
 672                 if (!possibly_true_rl(var_rl, comparison, ret_range))
 673                         return 0;
 674                 if (type == PARAM_LIMIT)
 675                         param_limit_implications(db_info->expr, param, key, value);
 676                 filter_by_comparison(&var_rl, comparison, ret_range);
 677                 filter_by_comparison(&ret_range, flip_comparison(comparison), var_rl);
 678         } else {
 679                 if (!possibly_false_rl(var_rl, comparison, ret_range))
 680                         return 0;
 681                 if (type == PARAM_LIMIT)
 682                         param_limit_implications(db_info->expr, param, key, value);
 683                 filter_by_comparison(&var_rl, negate_comparison(comparison), ret_range);
 684                 filter_by_comparison(&ret_range, flip_comparison(negate_comparison(comparison)), var_rl);
 685         }
 686 
 687         handle_ret_equals_param(ret_str, ret_range, db_info->expr);
 688 
 689         if (type == INTERNAL) {
 690                 set_state(-1, "unnull_path", NULL, &true_state);
 691                 __add_return_comparison(strip_expr(db_info->expr), ret_str);
 692                 __add_return_to_param_mapping(db_info->expr, ret_str);
 693                 store_return_state(db_info, ret_str, alloc_estate_rl(clone_rl(var_rl)));
 694         }
 695 
 696         FOR_EACH_PTR(db_info->callbacks, tmp) {
 697                 if (tmp->type == type)
 698                         tmp->callback(db_info->expr, param, key, value);
 699         } END_FOR_EACH_PTR(tmp);
 700 
 701         return 0;
 702 }
 703 
 704 static void compare_db_return_states_callbacks(struct expression *left, int comparison, struct expression *right, struct stree *implied_true, struct stree *implied_false)
 705 {
 706         struct stree *orig_states;
 707         struct stree *stree;
 708         struct stree *true_states;
 709         struct stree *false_states;
 710         struct sm_state *sm;
 711         struct db_callback_info db_info = {};
 712         struct expression *var_expr;
 713         struct expression *call_expr;
 714         struct range_list *rl;
 715         int call_on_left;
 716 
 717         orig_states = clone_stree(__get_cur_stree());
 718 
 719         /* legacy cruft.  need to fix call_implies_callbacks(). */
 720         call_on_left = 1;
 721         call_expr = left;
 722         var_expr = right;
 723         if (left->type != EXPR_CALL) {
 724                 call_on_left = 0;
 725                 call_expr = right;
 726                 var_expr = left;
 727         }
 728 
 729         get_absolute_rl(var_expr, &rl);
 730 
 731         db_info.comparison = comparison;
 732         db_info.expr = call_expr;
 733         db_info.rl = rl;
 734         db_info.left = call_on_left;
 735         db_info.callbacks = db_return_states_list;
 736         db_info.var_expr = var_expr;
 737 
 738         call_return_states_before_hooks();
 739 
 740         db_info.true_side = 1;
 741         db_info.stree = NULL;
 742         db_info.prev_return_id = -1;
 743         __push_fake_cur_stree();
 744         sql_select_return_states("return_id, return, type, parameter, key, value",
 745                                  call_expr, db_compare_callback, &db_info);
 746         set_other_side_state(&db_info);
 747         stree = __pop_fake_cur_stree();
 748         if (!db_info.cull)
 749                 merge_fake_stree(&db_info.stree, stree);
 750         free_stree(&stree);
 751         true_states = db_info.stree;
 752         if (!true_states && db_info.has_states) {
 753                 __push_fake_cur_stree();
 754                 set_path_impossible();
 755                 true_states = __pop_fake_cur_stree();
 756         }
 757 
 758         nullify_path();
 759         __unnullify_path();
 760         FOR_EACH_SM(orig_states, sm) {
 761                 __set_sm_cur_stree(sm);
 762         } END_FOR_EACH_SM(sm);
 763 
 764         db_info.true_side = 0;
 765         db_info.stree = NULL;
 766         db_info.prev_return_id = -1;
 767         db_info.cull = 0;
 768         __push_fake_cur_stree();
 769         sql_select_return_states("return_id, return, type, parameter, key, value", call_expr,
 770                         db_compare_callback, &db_info);
 771         set_other_side_state(&db_info);
 772         stree = __pop_fake_cur_stree();
 773         if (!db_info.cull)
 774                 merge_fake_stree(&db_info.stree, stree);
 775         free_stree(&stree);
 776         false_states = db_info.stree;
 777         if (!false_states && db_info.has_states) {
 778                 __push_fake_cur_stree();
 779                 set_path_impossible();
 780                 false_states = __pop_fake_cur_stree();
 781         }
 782 
 783         nullify_path();
 784         __unnullify_path();
 785         FOR_EACH_SM(orig_states, sm) {
 786                 __set_sm_cur_stree(sm);
 787         } END_FOR_EACH_SM(sm);
 788 
 789         free_stree(&orig_states);
 790 
 791         FOR_EACH_SM(true_states, sm) {
 792                 __set_true_false_sm(sm, NULL);
 793         } END_FOR_EACH_SM(sm);
 794         FOR_EACH_SM(false_states, sm) {
 795                 __set_true_false_sm(NULL, sm);
 796         } END_FOR_EACH_SM(sm);
 797 
 798         free_stree(&true_states);
 799         free_stree(&false_states);
 800 
 801         call_return_states_after_hooks(call_expr);
 802 
 803         FOR_EACH_SM(implied_true, sm) {
 804                 __set_true_false_sm(sm, NULL);
 805         } END_FOR_EACH_SM(sm);
 806         FOR_EACH_SM(implied_false, sm) {
 807                 __set_true_false_sm(NULL, sm);
 808         } END_FOR_EACH_SM(sm);
 809 }
 810 
 811 void function_comparison(struct expression *left, int comparison, struct expression *right)
 812 {
 813         struct expression *var_expr;
 814         struct expression *call_expr;
 815         struct stree *implied_true = NULL;
 816         struct stree *implied_false = NULL;
 817         struct range_list *rl;
 818         sval_t sval;
 819         int call_on_left;
 820 
 821         if (unreachable())
 822                 return;
 823 
 824         /* legacy cruft.  need to fix call_implies_callbacks(). */
 825         call_on_left = 1;
 826         call_expr = left;
 827         var_expr = right;
 828         if (left->type != EXPR_CALL) {
 829                 call_on_left = 0;
 830                 call_expr = right;
 831                 var_expr = left;
 832         }
 833 
 834         get_absolute_rl(var_expr, &rl);
 835 
 836         if (rl_to_sval(rl, &sval))
 837                 call_implies_callbacks(comparison, call_expr, sval, call_on_left, &implied_true, &implied_false);
 838 
 839         compare_db_return_states_callbacks(left, comparison, right, implied_true, implied_false);
 840         free_stree(&implied_true);
 841         free_stree(&implied_false);
 842 }
 843 
 844 static void call_ranged_return_hooks(struct db_callback_info *db_info)
 845 {
 846         struct call_back_list *call_backs;
 847         struct expression *expr;
 848         struct fcall_back *tmp;
 849         char *fn;
 850 
 851         expr = strip_expr(db_info->expr);
 852         while (expr->type == EXPR_ASSIGNMENT)
 853                 expr = strip_expr(expr->right);
 854         if (expr->type != EXPR_CALL ||
 855             expr->fn->type != EXPR_SYMBOL)
 856                 return;
 857 
 858         fn = expr->fn->symbol_name->name;
 859 
 860         call_backs = search_callback(func_hash, fn);
 861         FOR_EACH_PTR(call_backs, tmp) {
 862                 struct range_list *range_rl;
 863 
 864                 if (tmp->type != RANGED_CALL)
 865                         continue;
 866                 range_rl = alloc_rl(tmp->range->min, tmp->range->max);
 867                 range_rl = cast_rl(estate_type(db_info->ret_state), range_rl);
 868                 if (possibly_true_rl(range_rl, SPECIAL_EQUAL, estate_rl(db_info->ret_state)))
 869                         (tmp->u.ranged)(fn, expr, db_info->expr, tmp->info);
 870         } END_FOR_EACH_PTR(tmp);
 871 }
 872 
 873 static int db_assign_return_states_callback(void *_info, int argc, char **argv, char **azColName)
 874 {
 875         struct db_callback_info *db_info = _info;
 876         struct range_list *ret_range;
 877         int type, param;
 878         char *ret_str, *key, *value;
 879         struct return_implies_callback *tmp;
 880         struct stree *stree;
 881         int return_id;
 882 
 883         if (argc != 6)
 884                 return 0;
 885 
 886         return_id = atoi(argv[0]);
 887         ret_str = argv[1];
 888         type = atoi(argv[2]);
 889         param = atoi(argv[3]);
 890         key = argv[4];
 891         value = argv[5];
 892 
 893         if (db_info->prev_return_id != -1 && type == INTERNAL) {
 894                 call_ranged_return_hooks(db_info);
 895                 set_return_assign_state(db_info);
 896                 stree = __pop_fake_cur_stree();
 897                 if (!db_info->cull)
 898                         merge_fake_stree(&db_info->stree, stree);
 899                 free_stree(&stree);
 900                 __push_fake_cur_stree();
 901                 db_info->cull = 0;
 902         }
 903         db_info->prev_return_id = return_id;
 904 
 905         if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
 906                 db_info->cull = 1;
 907         if (db_info->cull)
 908                 return 0;
 909         if (type == CULL_PATH) {
 910                 db_info->cull = 1;
 911                 return 0;
 912         }
 913         if (is_impossible_data(type, db_info->expr, param, key, value)) {
 914                 db_info->cull = 1;
 915                 return 0;
 916         }
 917 
 918         if (type == PARAM_LIMIT)
 919                 param_limit_implications(db_info->expr, param, key, value);
 920 
 921         db_info->handled = 1;
 922         call_results_to_rl(db_info->expr->right, get_type(strip_expr(db_info->expr->right)), ret_str, &ret_range);
 923         if (!ret_range)
 924                 ret_range = alloc_whole_rl(get_type(strip_expr(db_info->expr->right)));
 925         ret_range = cast_rl(get_type(db_info->expr->right), ret_range);
 926 
 927         if (type == INTERNAL) {
 928                 set_state(-1, "unnull_path", NULL, &true_state);
 929                 __add_return_comparison(strip_expr(db_info->expr->right), ret_str);
 930                 __add_comparison_info(db_info->expr->left, strip_expr(db_info->expr->right), ret_str);
 931                 __add_return_to_param_mapping(db_info->expr, ret_str);
 932                 store_return_state(db_info, ret_str, alloc_estate_rl(ret_range));
 933         }
 934 
 935         FOR_EACH_PTR(db_return_states_list, tmp) {
 936                 if (tmp->type == type)
 937                         tmp->callback(db_info->expr, param, key, value);
 938         } END_FOR_EACH_PTR(tmp);
 939 
 940         return 0;
 941 }
 942 
 943 static int db_return_states_assign(struct expression *expr)
 944 {
 945         struct expression *right;
 946         struct sm_state *sm;
 947         struct stree *stree;
 948         struct db_callback_info db_info = {};
 949 
 950         right = strip_expr(expr->right);
 951 
 952         db_info.prev_return_id = -1;
 953         db_info.expr = expr;
 954         db_info.stree = NULL;
 955         db_info.handled = 0;
 956 
 957         call_return_states_before_hooks();
 958 
 959         __push_fake_cur_stree();
 960         sql_select_return_states("return_id, return, type, parameter, key, value",
 961                         right, db_assign_return_states_callback, &db_info);
 962         if (option_debug) {
 963                 sm_msg("%s return_id %d return_ranges %s",
 964                         db_info.cull ? "culled" : "merging",
 965                         db_info.prev_return_id,
 966                         db_info.ret_state ? db_info.ret_state->name : "'<empty>'");
 967         }
 968         if (db_info.handled)
 969                 call_ranged_return_hooks(&db_info);
 970         set_return_assign_state(&db_info);
 971         stree = __pop_fake_cur_stree();
 972         if (!db_info.cull)
 973                 merge_fake_stree(&db_info.stree, stree);
 974         free_stree(&stree);
 975 
 976         if (!db_info.stree && db_info.cull) { /* this means we culled everything */
 977                 set_extra_expr_mod(expr->left, alloc_estate_whole(get_type(expr->left)));
 978                 set_path_impossible();
 979         }
 980         FOR_EACH_SM(db_info.stree, sm) {
 981                 __set_sm(sm);
 982         } END_FOR_EACH_SM(sm);
 983 
 984         free_stree(&db_info.stree);
 985         call_return_states_after_hooks(right);
 986 
 987         return db_info.handled;
 988 }
 989 
 990 static int handle_implied_return(struct expression *expr)
 991 {
 992         struct range_list *rl;
 993 
 994         if (!get_implied_return(expr->right, &rl))
 995                 return 0;
 996         rl = cast_rl(get_type(expr->left), rl);
 997         set_extra_expr_mod(expr->left, alloc_estate_rl(rl));
 998         return 1;
 999 }
1000 
1001 static void match_assign_call(struct expression *expr)
1002 {
1003         struct call_back_list *call_backs;
1004         const char *fn;
1005         struct expression *right;
1006         int handled = 0;
1007         struct range_list *rl;
1008 
1009         if (expr->op != '=')
1010                 return;
1011 
1012         right = strip_expr(expr->right);
1013         if (right->fn->type != EXPR_SYMBOL || !right->fn->symbol) {
1014                 handled |= db_return_states_assign(expr);
1015                 if (!handled)
1016                         goto assigned_unknown;
1017                 return;
1018         }
1019         if (is_fake_call(right)) {
1020                 set_extra_expr_mod(expr->left, alloc_estate_whole(get_type(expr->left)));
1021                 return;
1022         }
1023 
1024         fn = right->fn->symbol->ident->name;
1025         call_backs = search_callback(func_hash, (char *)fn);
1026 
1027         /*
1028          * The ordering here is sort of important.
1029          * One example, of how this matters is that when we do:
1030          *
1031          *      len = strlen(str);
1032          *
1033          * That is handled by smatch_common_functions.c and smatch_strlen.c.
1034          * They use implied_return and function_assign_hook respectively.
1035          * We want to get the implied return first before we do the function
1036          * assignment hook otherwise we end up writing the wrong thing for len
1037          * in smatch_extra.c because we assume that it already holds the
1038          * strlen() when we haven't set it yet.
1039          */
1040 
1041         if (db_return_states_assign(expr) == 1)
1042                 handled = 1;
1043         else
1044                 handled = assign_ranged_funcs(fn, expr, call_backs);
1045         handled |= handle_implied_return(expr);
1046 
1047 
1048         call_call_backs(call_backs, ASSIGN_CALL, fn, expr);
1049 
1050         if (handled)
1051                 return;
1052 
1053 assigned_unknown:
1054         get_absolute_rl(expr->right, &rl);
1055         rl = cast_rl(get_type(expr->left), rl);
1056         set_extra_expr_mod(expr->left, alloc_estate_rl(rl));
1057 }
1058 
1059 static int db_return_states_callback(void *_info, int argc, char **argv, char **azColName)
1060 {
1061         struct db_callback_info *db_info = _info;
1062         struct range_list *ret_range;
1063         int type, param;
1064         char *ret_str, *key, *value;
1065         struct return_implies_callback *tmp;
1066         struct stree *stree;
1067         int return_id;
1068         char buf[64];
1069 
1070         if (argc != 6)
1071                 return 0;
1072 
1073         return_id = atoi(argv[0]);
1074         ret_str = argv[1];
1075         type = atoi(argv[2]);
1076         param = atoi(argv[3]);
1077         key = argv[4];
1078         value = argv[5];
1079 
1080         if (db_info->prev_return_id != -1 && type == INTERNAL) {
1081                 stree = __pop_fake_cur_stree();
1082                 if (!db_info->cull)
1083                         merge_fake_stree(&db_info->stree, stree);
1084                 free_stree(&stree);
1085                 __push_fake_cur_stree();
1086                 __unnullify_path();
1087                 db_info->cull = 0;
1088         }
1089         db_info->prev_return_id = return_id;
1090 
1091         if (type == INTERNAL && func_type_mismatch(db_info->expr, value))
1092                 db_info->cull = 1;
1093         if (db_info->cull)
1094                 return 0;
1095         if (type == CULL_PATH) {
1096                 db_info->cull = 1;
1097                 return 0;
1098         }
1099         if (is_impossible_data(type, db_info->expr, param, key, value)) {
1100                 db_info->cull = 1;
1101                 return 0;
1102         }
1103 
1104         if (type == PARAM_LIMIT)
1105                 param_limit_implications(db_info->expr, param, key, value);
1106 
1107         call_results_to_rl(db_info->expr, get_type(strip_expr(db_info->expr)), ret_str, &ret_range);
1108         ret_range = cast_rl(get_type(db_info->expr), ret_range);
1109 
1110         if (type == INTERNAL) {
1111                 set_state(-1, "unnull_path", NULL, &true_state);
1112                 __add_return_comparison(strip_expr(db_info->expr), ret_str);
1113                 __add_return_to_param_mapping(db_info->expr, ret_str);
1114         }
1115 
1116         FOR_EACH_PTR(db_return_states_list, tmp) {
1117                 if (tmp->type == type)
1118                         tmp->callback(db_info->expr, param, key, value);
1119         } END_FOR_EACH_PTR(tmp);
1120 
1121         /*
1122          * We want to store the return values so that we can split the strees
1123          * in smatch_db.c.  This uses set_state() directly because it's not a
1124          * real smatch_extra state.
1125          */
1126         snprintf(buf, sizeof(buf), "return %p", db_info->expr);
1127         set_state(SMATCH_EXTRA, buf, NULL, alloc_estate_rl(ret_range));
1128 
1129         return 0;
1130 }
1131 
1132 static void db_return_states(struct expression *expr)
1133 {
1134         struct sm_state *sm;
1135         struct stree *stree;
1136         struct db_callback_info db_info = {};
1137 
1138         if (!__get_cur_stree())  /* no return functions */
1139                 return;
1140 
1141         db_info.prev_return_id = -1;
1142         db_info.expr = expr;
1143         db_info.stree = NULL;
1144 
1145         call_return_states_before_hooks();
1146 
1147         __push_fake_cur_stree();
1148         __unnullify_path();
1149         sql_select_return_states("return_id, return, type, parameter, key, value",
1150                         expr, db_return_states_callback, &db_info);
1151         stree = __pop_fake_cur_stree();
1152         if (!db_info.cull)
1153                 merge_fake_stree(&db_info.stree, stree);
1154         free_stree(&stree);
1155 
1156         FOR_EACH_SM(db_info.stree, sm) {
1157                 __set_sm(sm);
1158         } END_FOR_EACH_SM(sm);
1159 
1160         free_stree(&db_info.stree);
1161         call_return_states_after_hooks(expr);
1162 }
1163 
1164 static int is_condition_call(struct expression *expr)
1165 {
1166         struct expression *tmp;
1167 
1168         FOR_EACH_PTR_REVERSE(big_condition_stack, tmp) {
1169                 if (expr == tmp || expr_get_parent_expr(expr) == tmp)
1170                         return 1;
1171                 if (tmp->pos.line < expr->pos.line)
1172                         return 0;
1173         } END_FOR_EACH_PTR_REVERSE(tmp);
1174 
1175         return 0;
1176 }
1177 
1178 static void db_return_states_call(struct expression *expr)
1179 {
1180         if (unreachable())
1181                 return;
1182 
1183         if (is_assigned_call(expr))
1184                 return;
1185         if (is_condition_call(expr))
1186                 return;
1187         db_return_states(expr);
1188 }
1189 
1190 static void match_function_call(struct expression *expr)
1191 {
1192         struct call_back_list *call_backs;
1193         struct expression *fn;
1194 
1195         fn = strip_expr(expr->fn);
1196         if (fn->type == EXPR_SYMBOL && fn->symbol) {
1197                 call_backs = search_callback(func_hash, (char *)fn->symbol->ident->name);
1198                 if (call_backs)
1199                         call_call_backs(call_backs, REGULAR_CALL,
1200                                         fn->symbol->ident->name, expr);
1201         }
1202         db_return_states_call(expr);
1203 }
1204 
1205 static void match_macro_assign(struct expression *expr)
1206 {
1207         struct call_back_list *call_backs;
1208         const char *macro;
1209         struct expression *right;
1210 
1211         right = strip_expr(expr->right);
1212         macro = get_macro_name(right->pos);
1213         call_backs = search_callback(func_hash, (char *)macro);
1214         if (!call_backs)
1215                 return;
1216         call_call_backs(call_backs, MACRO_ASSIGN, macro, expr);
1217         call_call_backs(call_backs, MACRO_ASSIGN_EXTRA, macro, expr);
1218 }
1219 
1220 int get_implied_return(struct expression *expr, struct range_list **rl)
1221 {
1222         struct call_back_list *call_backs;
1223         struct fcall_back *tmp;
1224         int handled = 0;
1225         char *fn;
1226 
1227         *rl = NULL;
1228 
1229         expr = strip_expr(expr);
1230         fn = expr_to_var(expr->fn);
1231         if (!fn)
1232                 goto out;
1233 
1234         call_backs = search_callback(func_hash, fn);
1235 
1236         FOR_EACH_PTR(call_backs, tmp) {
1237                 if (tmp->type == IMPLIED_RETURN) {
1238                         (tmp->u.implied_return)(expr, tmp->info, rl);
1239                         handled = 1;
1240                 }
1241         } END_FOR_EACH_PTR(tmp);
1242 
1243 out:
1244         free_string(fn);
1245         return handled;
1246 }
1247 
1248 void create_function_hook_hash(void)
1249 {
1250         func_hash = create_function_hashtable(5000);
1251 }
1252 
1253 void register_function_hooks(int id)
1254 {
1255         add_hook(&match_function_call, CALL_HOOK_AFTER_INLINE);
1256         add_hook(&match_assign_call, CALL_ASSIGNMENT_HOOK);
1257         add_hook(&match_macro_assign, MACRO_ASSIGNMENT_HOOK);
1258 }