smatch_container_of.c

   1 /*
   2  * Copyright (C) 2017 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 #include "smatch.h"
  19 #include "smatch_slist.h"
  20 #include "smatch_extra.h"
  21
  22 static int my_id;
  23 static int param_id;
  24
  25 static struct stree *used_stree;
  26 static struct stree_stack *saved_stack;
  27
  28 STATE(used);
  29
  30 int get_param_from_container_of(struct expression *expr)
  31 {
  32         struct expression *param_expr;
  33         struct symbol *type;
  34         sval_t sval;
  35         int param;
  36
  37
  38         type = get_type(expr);
  39         if (!type || type->type != SYM_PTR)
  40                 return -1;
  41
  42         expr = strip_expr(expr);
  43         if (expr->type != EXPR_BINOP || expr->op != '-')
  44                 return -1;
  45
  46         if (!get_value(expr->right, &sval))
  47                 return -1;
  48         if (sval.value < 0 || sval.value > 4096)
  49                 return -1;
  50
  51         param_expr = get_assigned_expr(expr->left);
  52         if (!param_expr)
  53                 return -1;
  54         param = get_param_num(param_expr);
  55         if (param < 0)
  56                 return -1;
  57
  58         return param;
  59 }
  60
  61 int get_offset_from_container_of(struct expression *expr)
  62 {
  63         struct expression *param_expr;
  64         struct symbol *type;
  65         sval_t sval;
  66
  67         type = get_type(expr);
  68         if (!type || type->type != SYM_PTR)
  69                 return -1;
  70
  71         expr = strip_expr(expr);
  72         if (expr->type != EXPR_BINOP || expr->op != '-')
  73                 return -1;
  74
  75         if (!get_value(expr->right, &sval))
  76                 return -1;
  77         if (sval.value < 0 || sval.value > 4096)
  78                 return -1;
  79
  80         param_expr = get_assigned_expr(expr->left);
  81         if (!param_expr)
  82                 return -1;
  83
  84         return sval.value;
  85 }
  86
  87 static int get_container_arg(struct symbol *sym)
  88 {
  89         struct expression *__mptr;
  90         int param;
  91
  92         if (!sym || !sym->ident)
  93                 return -1;
  94
  95         __mptr = get_assigned_expr_name_sym(sym->ident->name, sym);
  96         param = get_param_from_container_of(__mptr);
  97
  98         return param;
  99 }
 100
 101 static int get_container_offset(struct symbol *sym)
 102 {
 103         struct expression *__mptr;
 104         int offset;
 105
 106         if (!sym || !sym->ident)
 107                 return -1;
 108
 109         __mptr = get_assigned_expr_name_sym(sym->ident->name, sym);
 110         offset = get_offset_from_container_of(__mptr);
 111
 112         return offset;
 113 }
 114
 115 static char *get_container_name(struct sm_state *sm, int offset)
 116 {
 117         static char buf[256];
 118         const char *name;
 119
 120         name = get_param_name(sm);
 121         if (!name)
 122                 return NULL;
 123
 124         if (name[0] == '$')
 125                 snprintf(buf, sizeof(buf), "$(-%d)%s", offset, name + 1);
 126         else if (name[0] == '*' || name[1] == '$')
 127                 snprintf(buf, sizeof(buf), "*$(-%d)%s", offset, name + 2);
 128         else
 129                 return NULL;
 130
 131         return buf;
 132 }
 133
 134 static void get_state_hook(int owner, const char *name, struct symbol *sym)
 135 {
 136         int arg;
 137
 138         if (!option_info)
 139                 return;
 140         if (__in_fake_assign)
 141                 return;
 142
 143         arg = get_container_arg(sym);
 144         if (arg >= 0)
 145                 set_state_stree(&used_stree, my_id, name, sym, &used);
 146 }
 147
 148 static void set_param_used(struct expression *call, struct expression *arg, char *key, char *unused)
 149 {
 150         struct symbol *sym;
 151         char *name;
 152         int arg_nr;
 153
 154         name = get_variable_from_key(arg, key, &sym);
 155         if (!name || !sym)
 156                 goto free;
 157
 158         arg_nr = get_container_arg(sym);
 159         if (arg_nr >= 0)
 160                 set_state(my_id, name, sym, &used);
 161 free:
 162         free_string(name);
 163 }
 164
 165 static void process_states(void)
 166 {
 167         struct sm_state *tmp;
 168         int arg, offset;
 169         const char *name;
 170
 171         FOR_EACH_SM(used_stree, tmp) {
 172                 arg = get_container_arg(tmp->sym);
 173                 offset = get_container_offset(tmp->sym);
 174                 if (arg < 0 || offset < 0)
 175                         continue;
 176                 name = get_container_name(tmp, offset);
 177                 if (!name)
 178                         continue;
 179                 sql_insert_return_implies(CONTAINER, arg, name, "");
 180         } END_FOR_EACH_SM(tmp);
 181
 182         free_stree(&used_stree);
 183 }
 184
 185 static void match_function_def(struct symbol *sym)
 186 {
 187         free_stree(&used_stree);
 188 }
 189
 190 static void match_save_states(struct expression *expr)
 191 {
 192         push_stree(&saved_stack, used_stree);
 193         used_stree = NULL;
 194 }
 195
 196 static void match_restore_states(struct expression *expr)
 197 {
 198         free_stree(&used_stree);
 199         used_stree = pop_stree(&saved_stack);
 200 }
 201
 202 static void print_returns_container_of(int return_id, char *return_ranges, struct expression *expr)
 203 {
 204         int offset;
 205         int param;
 206         char key[64];
 207         char value[64];
 208
 209         param = get_param_from_container_of(expr);
 210         if (param < 0)
 211                 return;
 212         offset = get_offset_from_container_of(expr);
 213         if (offset < 0)
 214                 return;
 215
 216         snprintf(key, sizeof(key), "%d", param);
 217         snprintf(value, sizeof(value), "-%d", offset);
 218
 219         /* no need to add it to return_implies because it's not really param_used */
 220         sql_insert_return_states(return_id, return_ranges, CONTAINER, -1,
 221                         key, value);
 222 }
 223
 224 static void returns_container_of(struct expression *expr, int param, char *key, char *value)
 225 {
 226         struct expression *call, *arg;
 227         int offset;
 228         char buf[64];
 229
 230         if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
 231                 return;
 232         call = strip_expr(expr->right);
 233         if (call->type != EXPR_CALL)
 234                 return;
 235         if (param != -1)
 236                 return;
 237         param = atoi(key);
 238         offset = atoi(value);
 239
 240         arg = get_argument_from_call_expr(call->args, param);
 241         if (!arg)
 242                 return;
 243         if (arg->type != EXPR_SYMBOL)
 244                 return;
 245         param = get_param_num(arg);
 246         if (param < 0)
 247                 return;
 248         snprintf(buf, sizeof(buf), "$(%d)", offset);
 249         sql_insert_return_implies(CONTAINER, param, buf, "");
 250 }
 251
 252 static int get_shared_cnt(const char *one, const char *two)
 253 {
 254         int i;
 255         int on_end = false;
 256
 257         i = 0;
 258         while (true) {
 259                 if (!one[i] || !two[i]) {
 260                         on_end = true;
 261                         break;
 262                 }
 263                 if (one[i] != two[i])
 264                         break;
 265                 i++;
 266         }
 267         if (i == 0)
 268                 return 0;
 269         i--;
 270         while (i > 0 && (one[i] == '>' || one[i] == '-' || one[i] == '.')) {
 271                 on_end = true;
 272                 i--;
 273         }
 274         if (!on_end)
 275                 return 0;
 276
 277         return i + 1;
 278 }
 279
 280 static int build_offset_str(struct expression *expr, const char *name,
 281                             int shared, char *buf, int size, int op)
 282 {
 283         int chop = 0;
 284         int offset;
 285         int i;
 286
 287         i = shared;
 288         while (name[i]) {
 289                 if (name[i] == '.' || name[i] == '-')
 290                         chop++;
 291                 i++;
 292         }
 293
 294         // FIXME:  Handle more chops
 295         if (chop > 1)
 296                 return 0;
 297
 298         if (chop == 0) {
 299                 offset = 0;
 300         } else {
 301                 offset = get_member_offset_from_deref(expr);
 302                 if (offset < 0)
 303                         return 0;
 304         }
 305
 306         snprintf(buf, size, "%c%d", (op == '+') ? '+' : '-', offset);
 307         return 1;
 308 }
 309
 310 static void match_call(struct expression *call)
 311 {
 312         struct expression *fn, *arg;
 313         char *fn_name, *arg_name;
 314         int param, shared;
 315         char minus_str[64];
 316         char plus_str[64];
 317         char offset_str[64];
 318         bool star;
 319
 320         /*
 321          * We're trying to link the function with the parameter.  There are a
 322          * couple ways this can be passed:
 323          * foo->func(foo, ...);
 324          * foo->func(foo->x, ...);
 325          * foo->bar.func(&foo->bar, ...);
 326          * foo->bar->baz->func(foo, ...);
 327          *
 328          * So the method is basically to subtract the offsets until we get to
 329          * the common bit, then add the member offsets to get the parameter.
 330          *
 331          * If we're taking an address then the offset math is not stared,
 332          * otherwise it is.  Starred means dereferenced.
 333          */
 334         fn = strip_expr(call->fn);
 335         fn_name = expr_to_var(fn);
 336         if (!fn_name)
 337                 return;
 338
 339         param = -1;
 340         FOR_EACH_PTR(call->args, arg) {
 341                 param++;
 342
 343                 arg = strip_expr(arg);
 344                 star = true;
 345                 if (arg->type == EXPR_PREOP && arg->op == '&') {
 346                         arg = strip_expr(arg->unop);
 347                         star = false;
 348                 }
 349
 350                 arg_name = expr_to_var(arg);
 351                 if (!arg_name)
 352                         continue;
 353                 shared = get_shared_cnt(fn_name, arg_name);
 354                 if (!shared)
 355                         goto free_arg_name;
 356                 if (!build_offset_str(fn, fn_name, shared, minus_str, sizeof(minus_str), '-'))
 357                         goto free_arg_name;
 358                 if (!build_offset_str(arg, arg_name, shared, plus_str, sizeof(plus_str), '+'))
 359                         goto free_arg_name;
 360                 if (star)
 361                         snprintf(offset_str, sizeof(offset_str), "*(%s%s)", minus_str, plus_str);
 362                 else
 363                         snprintf(offset_str, sizeof(offset_str), "%s%s", minus_str, plus_str);
 364                 sql_insert_caller_info(call, CONTAINER, param, offset_str, "$(-1)");
 365 free_arg_name:
 366                 free_string(arg_name);
 367         } END_FOR_EACH_PTR(arg);
 368
 369         free_string(fn_name);
 370 }
 371
 372 static void db_passed_container(const char *name, struct symbol *sym, char *key, char *value)
 373 {
 374         sval_t offset = {
 375                 .type = &int_ctype,
 376         };
 377         const char *arg_offset;
 378         int star = 0;
 379         int val;
 380
 381         if (key[0] == '*') {
 382                 star = 1;
 383                 key += 2;
 384         }
 385
 386         val = atoi(key);
 387         if (val < -4095 || val > 0)
 388                 return;
 389         offset.value = -val;
 390         arg_offset = strchr(key, '+');
 391         if (!arg_offset)
 392                 return;
 393         val = atoi(arg_offset + 1);
 394         if (val > 4095 || val < 0)
 395                 return;
 396         offset.value |= val << 16;
 397         if (star)
 398                 offset.value |= 1ULL << 31;
 399
 400         set_state(param_id, name, sym, alloc_estate_sval(offset));
 401 }
 402
 403 struct db_info {
 404         struct symbol *arg;
 405         int prev_offset;
 406         struct range_list *rl;
 407         int star;
 408         struct stree *stree;
 409 };
 410
 411 static struct symbol *get_member_from_offset(struct symbol *sym, int offset)
 412 {
 413         struct symbol *type, *tmp;
 414         int cur;
 415
 416         type = get_real_base_type(sym);
 417         if (!type || type->type != SYM_PTR)
 418                 return NULL;
 419         type = get_real_base_type(type);
 420         if (!type || type->type != SYM_STRUCT)
 421                 return NULL;
 422
 423         cur = 0;
 424         FOR_EACH_PTR(type->symbol_list, tmp) {
 425                 cur = ALIGN(cur, tmp->ctype.alignment);
 426                 if (offset == cur)
 427                         return tmp;
 428                 cur += type_bytes(tmp);
 429         } END_FOR_EACH_PTR(tmp);
 430         return NULL;
 431 }
 432
 433 static struct symbol *get_member_type_from_offset(struct symbol *sym, int offset)
 434 {
 435         struct symbol *base_type;
 436         struct symbol *member;
 437
 438         base_type = get_real_base_type(sym);
 439         if (base_type && base_type->type == SYM_PTR)
 440                 base_type = get_real_base_type(base_type);
 441         if (offset == 0 && base_type && base_type->type == SYM_BASETYPE)
 442                 return base_type;
 443
 444         member = get_member_from_offset(sym, offset);
 445         if (!member)
 446                 return NULL;
 447         return get_real_base_type(member);
 448 }
 449
 450 static const char *get_name_from_offset(struct symbol *arg, int offset)
 451 {
 452         struct symbol *member, *type;
 453         const char *name;
 454         static char fullname[256];
 455
 456         name = arg->ident->name;
 457
 458         type = get_real_base_type(arg);
 459         if (!type || type->type != SYM_PTR)
 460                 return name;
 461
 462         type = get_real_base_type(type);
 463         if (!type)
 464                 return NULL;
 465         if (type->type != SYM_STRUCT) {
 466                 snprintf(fullname, sizeof(fullname), "*%s", name);
 467                 return fullname;
 468         }
 469
 470         member = get_member_from_offset(arg, offset);
 471         if (!member)
 472                 return NULL;
 473
 474         snprintf(fullname, sizeof(fullname), "%s->%s", name, member->ident->name);
 475         return fullname;
 476 }
 477
 478 static void set_param_value(struct stree **stree, struct symbol *arg, int offset, struct range_list *rl)
 479 {
 480         const char *name;
 481
 482         name = get_name_from_offset(arg, offset);
 483         if (!name)
 484                 return;
 485         set_state_stree(stree, SMATCH_EXTRA, name, arg, alloc_estate_rl(rl));
 486 }
 487
 488 static int save_vals(void *_db_info, int argc, char **argv, char **azColName)
 489 {
 490         struct db_info *db_info = _db_info;
 491         struct symbol *type;
 492         struct range_list *rl;
 493         int offset = 0;
 494         const char *value;
 495
 496         if (argc == 2) {
 497                 offset = atoi(argv[0]);
 498                 value = argv[1];
 499         } else {
 500                 value = argv[0];
 501         }
 502
 503         if (db_info->prev_offset != -1 &&
 504             db_info->prev_offset != offset) {
 505                 set_param_value(&db_info->stree, db_info->arg, db_info->prev_offset, db_info->rl);
 506                 db_info->rl = NULL;
 507         }
 508
 509         db_info->prev_offset = offset;
 510
 511         type = get_real_base_type(db_info->arg);
 512         if (db_info->star)
 513                 goto found_type;
 514         if (type->type != SYM_PTR)
 515                 return 0;
 516         type = get_real_base_type(type);
 517         if (type->type == SYM_BASETYPE)
 518                 goto found_type;
 519         type = get_member_type_from_offset(db_info->arg, offset);
 520 found_type:
 521         str_to_rl(type, (char *)value, &rl);
 522         if (db_info->rl)
 523                 db_info->rl = rl_union(db_info->rl, rl);
 524         else
 525                 db_info->rl = rl;
 526
 527         return 0;
 528 }
 529
 530 static struct stree *load_tag_info_sym(mtag_t tag, struct symbol *arg, int arg_offset, int star)
 531 {
 532         struct db_info db_info = {
 533                 .arg = arg,
 534                 .prev_offset = -1,
 535                 .star = star,
 536         };
 537         struct symbol *type;
 538
 539         if (!tag || !arg->ident)
 540                 return NULL;
 541
 542         type = get_real_base_type(arg);
 543         if (!type)
 544                 return NULL;
 545         if (!star) {
 546                 if (type->type != SYM_PTR)
 547                         return NULL;
 548                 type = get_real_base_type(type);
 549                 if (!type)
 550                         return NULL;
 551         }
 552
 553         if (star || type->type == SYM_BASETYPE) {
 554                 run_sql(save_vals, &db_info,
 555                         "select value from mtag_data where tag = %lld and offset = %d and type = %d;",
 556                         tag, arg_offset, DATA_VALUE);
 557         } else {  /* presumably the parameter is a struct pointer */
 558                 run_sql(save_vals, &db_info,
 559                         "select offset, value from mtag_data where tag = %lld and type = %d;",
 560                         tag, DATA_VALUE);
 561         }
 562
 563         if (db_info.prev_offset != -1)
 564                 set_param_value(&db_info.stree, arg, db_info.prev_offset, db_info.rl);
 565
 566         // FIXME: handle an offset correctly
 567         if (!star && !arg_offset) {
 568                 sval_t sval;
 569
 570                 sval.type = get_real_base_type(arg);
 571                 sval.uvalue = tag;
 572                 set_state_stree(&db_info.stree, SMATCH_EXTRA, arg->ident->name, arg, alloc_estate_sval(sval));
 573         }
 574         return db_info.stree;
 575 }
 576
 577 static void handle_passed_container(struct symbol *sym)
 578 {
 579         struct symbol *arg;
 580         struct smatch_state *state;
 581         struct sm_state *sm;
 582         struct stree *stree;
 583         mtag_t fn_tag, container_tag, arg_tag;
 584         sval_t offset;
 585         int container_offset, arg_offset;
 586         int star;
 587
 588         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
 589                 state = get_state(param_id, arg->ident->name, arg);
 590                 if (state)
 591                         goto found;
 592         } END_FOR_EACH_PTR(arg);
 593
 594         return;
 595 found:
 596         if (!estate_get_single_value(state, &offset))
 597                 return;
 598         container_offset = -(offset.value & 0xffff);
 599         arg_offset = (offset.value & 0xfff0000) >> 16;
 600         star = !!(offset.value & (1ULL << 31));
 601
 602         if (!get_toplevel_mtag(cur_func_sym, &fn_tag))
 603                 return;
 604         if (!mtag_map_select_container(fn_tag, container_offset, &container_tag))
 605                 return;
 606         if (!arg_offset || star) {
 607                 arg_tag = container_tag;
 608         } else {
 609                 if (!mtag_map_select_tag(container_tag, -arg_offset, &arg_tag))
 610                         return;
 611         }
 612
 613         stree = load_tag_info_sym(arg_tag, arg, arg_offset, star);
 614         FOR_EACH_SM(stree, sm) {
 615                 set_state(sm->owner, sm->name, sm->sym, sm->state);
 616         } END_FOR_EACH_SM(sm);
 617         free_stree(&stree);
 618 }
 619
 620 void register_container_of(int id)
 621 {
 622         my_id = id;
 623
 624         add_hook(&match_function_def, FUNC_DEF_HOOK);
 625
 626         add_get_state_hook(&get_state_hook);
 627
 628         add_hook(&match_save_states, INLINE_FN_START);
 629         add_hook(&match_restore_states, INLINE_FN_END);
 630
 631         select_return_implies_hook(CONTAINER, &set_param_used);
 632         all_return_states_hook(&process_states);
 633
 634         add_split_return_callback(&print_returns_container_of);
 635         select_return_states_hook(CONTAINER, &returns_container_of);
 636
 637         add_hook(&match_call, FUNCTION_CALL_HOOK);
 638 }
 639
 640 static struct smatch_state *unmatched_state(struct sm_state *sm)
 641 {
 642         return alloc_estate_whole(estate_type(sm->state));
 643 }
 644
 645 void register_container_of2(int id)
 646 {
 647         param_id = id;
 648
 649         select_caller_info_hook(db_passed_container, CONTAINER);
 650         add_hook(&handle_passed_container, AFTER_DEF_HOOK);
 651         add_unmatched_state_hook(param_id, &unmatched_state);
 652         add_merge_hook(param_id, &merge_estates);
 653 }
 654