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
 256         i = 0;
 257         while (true) {
 258                 if (!one[i] || !two[i])
 259                         break;
 260                 if (one[i] != two[i])
 261                         break;
 262                 i++;
 263         }
 264         if (i == 0)
 265                 return 0;
 266         i--;
 267         while (i > 0 && (one[i] == '>' || one[i] == '-' || one[i] == '.'))
 268                 i--;
 269
 270         return i + 1;
 271 }
 272
 273 static int build_offset_str(struct expression *expr, const char *name,
 274                             int shared, char *buf, int size, int op)
 275 {
 276         int chop = 0;
 277         int offset;
 278         int i;
 279
 280         i = shared;
 281         while (name[i]) {
 282                 if (name[i] == '.' || name[i] == '-')
 283                         chop++;
 284                 i++;
 285         }
 286
 287         // FIXME:  Handle more chops
 288         if (chop > 1)
 289                 return 0;
 290
 291         if (chop == 0) {
 292                 offset = 0;
 293         } else {
 294                 offset = get_member_offset_from_deref(expr);
 295                 if (offset < 0)
 296                         return 0;
 297         }
 298
 299         snprintf(buf, size, "%c%d", (op == '+') ? '+' : '-', offset);
 300         return 1;
 301 }
 302
 303 static void match_call(struct expression *call)
 304 {
 305         struct expression *fn, *arg;
 306         char *fn_name, *arg_name;
 307         int param, shared;
 308         char minus_str[64];
 309         char plus_str[64];
 310         char offset_str[64];
 311         bool star;
 312
 313         /*
 314          * We're trying to link the function with the parameter.  There are a
 315          * couple ways this can be passed:
 316          * foo->func(foo, ...);
 317          * foo->func(foo->x, ...);
 318          * foo->bar.func(&foo->bar, ...);
 319          * foo->bar->baz->func(foo, ...);
 320          *
 321          * So the method is basically to subtract the offsets until we get to
 322          * the common bit, then add the member offsets to get the parameter.
 323          *
 324          * If we're taking an address then the offset math is not stared,
 325          * otherwise it is.  Starred means dereferenced.
 326          */
 327         fn = strip_expr(call->fn);
 328         fn_name = expr_to_var(fn);
 329         if (!fn_name)
 330                 return;
 331
 332         param = -1;
 333         FOR_EACH_PTR(call->args, arg) {
 334                 param++;
 335
 336                 arg = strip_expr(arg);
 337                 star = true;
 338                 if (arg->type == EXPR_PREOP && arg->op == '&') {
 339                         arg = strip_expr(arg->unop);
 340                         star = false;
 341                 }
 342
 343                 arg_name = expr_to_var(arg);
 344                 if (!arg_name)
 345                         continue;
 346                 shared = get_shared_cnt(fn_name, arg_name);
 347                 if (!shared)
 348                         goto free_arg_name;
 349                 if (!build_offset_str(fn, fn_name, shared, minus_str, sizeof(minus_str), '-'))
 350                         goto free_arg_name;
 351                 if (!build_offset_str(arg, arg_name, shared, plus_str, sizeof(plus_str), '+'))
 352                         goto free_arg_name;
 353                 if (star)
 354                         snprintf(offset_str, sizeof(offset_str), "*(%s%s)", minus_str, plus_str);
 355                 else
 356                         snprintf(offset_str, sizeof(offset_str), "%s%s", minus_str, plus_str);
 357                 sql_insert_caller_info(call, CONTAINER, param, offset_str, "$(-1)");
 358 free_arg_name:
 359                 free_string(arg_name);
 360         } END_FOR_EACH_PTR(arg);
 361
 362         free_string(fn_name);
 363 }
 364
 365 static void db_passed_container(const char *name, struct symbol *sym, char *key, char *value)
 366 {
 367         sval_t offset = {
 368                 .type = &int_ctype,
 369         };
 370         const char *arg_offset;
 371         int star = 0;
 372         int val;
 373
 374         if (key[0] == '*') {
 375                 star = 1;
 376                 key += 2;
 377         }
 378
 379         val = atoi(key);
 380         if (val < -4095 || val > 0)
 381                 return;
 382         offset.value = -val;
 383         arg_offset = strchr(key, '+');
 384         if (!arg_offset)
 385                 return;
 386         val = atoi(arg_offset + 1);
 387         if (val > 4095 || val < 0)
 388                 return;
 389         offset.value |= val << 16;
 390         if (star)
 391                 offset.value |= 1ULL << 31;
 392
 393         set_state(param_id, name, sym, alloc_estate_sval(offset));
 394 }
 395
 396 struct db_info {
 397         struct symbol *arg;
 398         int prev_offset;
 399         struct range_list *rl;
 400         int star;
 401         struct stree *stree;
 402 };
 403
 404 static struct symbol *get_member_from_offset(struct symbol *sym, int offset)
 405 {
 406         struct symbol *type, *tmp;
 407         int cur;
 408
 409         type = get_real_base_type(sym);
 410         if (!type || type->type != SYM_PTR)
 411                 return NULL;
 412         type = get_real_base_type(type);
 413         if (!type || type->type != SYM_STRUCT)
 414                 return NULL;
 415
 416         cur = 0;
 417         FOR_EACH_PTR(type->symbol_list, tmp) {
 418                 cur = ALIGN(cur, tmp->ctype.alignment);
 419                 if (offset == cur)
 420                         return tmp;
 421                 cur += type_bytes(tmp);
 422         } END_FOR_EACH_PTR(tmp);
 423         return NULL;
 424 }
 425
 426 static struct symbol *get_member_type_from_offset(struct symbol *sym, int offset)
 427 {
 428         struct symbol *base_type;
 429         struct symbol *member;
 430
 431         base_type = get_real_base_type(sym);
 432         if (base_type && base_type->type == SYM_PTR)
 433                 base_type = get_real_base_type(base_type);
 434         if (offset == 0 && base_type && base_type->type == SYM_BASETYPE)
 435                 return base_type;
 436
 437         member = get_member_from_offset(sym, offset);
 438         if (!member)
 439                 return NULL;
 440         return get_real_base_type(member);
 441 }
 442
 443 static const char *get_name_from_offset(struct symbol *arg, int offset)
 444 {
 445         struct symbol *member, *type;
 446         const char *name;
 447         static char fullname[256];
 448
 449         name = arg->ident->name;
 450
 451         type = get_real_base_type(arg);
 452         if (!type || type->type != SYM_PTR)
 453                 return name;
 454
 455         type = get_real_base_type(type);
 456         if (!type)
 457                 return NULL;
 458         if (type->type != SYM_STRUCT) {
 459                 snprintf(fullname, sizeof(fullname), "*%s", name);
 460                 return fullname;
 461         }
 462
 463         member = get_member_from_offset(arg, offset);
 464         if (!member)
 465                 return NULL;
 466
 467         snprintf(fullname, sizeof(fullname), "%s->%s", name, member->ident->name);
 468         return fullname;
 469 }
 470
 471 static void set_param_value(struct stree **stree, struct symbol *arg, int offset, struct range_list *rl)
 472 {
 473         const char *name;
 474
 475         name = get_name_from_offset(arg, offset);
 476         if (!name)
 477                 return;
 478         set_state_stree(stree, SMATCH_EXTRA, name, arg, alloc_estate_rl(rl));
 479 }
 480
 481 static int save_vals(void *_db_info, int argc, char **argv, char **azColName)
 482 {
 483         struct db_info *db_info = _db_info;
 484         struct symbol *type;
 485         struct range_list *rl;
 486         int offset = 0;
 487         const char *value;
 488
 489         if (argc == 2) {
 490                 offset = atoi(argv[0]);
 491                 value = argv[1];
 492         } else {
 493                 value = argv[0];
 494         }
 495
 496         if (db_info->prev_offset != -1 &&
 497             db_info->prev_offset != offset) {
 498                 set_param_value(&db_info->stree, db_info->arg, db_info->prev_offset, db_info->rl);
 499                 db_info->rl = NULL;
 500         }
 501
 502         db_info->prev_offset = offset;
 503
 504         type = get_real_base_type(db_info->arg);
 505         if (db_info->star)
 506                 goto found_type;
 507         if (type->type != SYM_PTR)
 508                 return 0;
 509         type = get_real_base_type(type);
 510         if (type->type == SYM_BASETYPE)
 511                 goto found_type;
 512         type = get_member_type_from_offset(db_info->arg, offset);
 513 found_type:
 514         str_to_rl(type, (char *)value, &rl);
 515         if (db_info->rl)
 516                 db_info->rl = rl_union(db_info->rl, rl);
 517         else
 518                 db_info->rl = rl;
 519
 520         return 0;
 521 }
 522
 523 static struct stree *load_tag_info_sym(mtag_t tag, struct symbol *arg, int arg_offset, int star)
 524 {
 525         struct db_info db_info = {
 526                 .arg = arg,
 527                 .prev_offset = -1,
 528                 .star = star,
 529         };
 530         struct symbol *type;
 531
 532         if (!tag || !arg->ident)
 533                 return NULL;
 534
 535         type = get_real_base_type(arg);
 536         if (!type)
 537                 return NULL;
 538         if (!star) {
 539                 if (type->type != SYM_PTR)
 540                         return NULL;
 541                 type = get_real_base_type(type);
 542                 if (!type)
 543                         return NULL;
 544         }
 545
 546         if (star || type->type == SYM_BASETYPE) {
 547                 run_sql(save_vals, &db_info,
 548                         "select value from mtag_data where tag = %lld and offset = %d and type = %d;",
 549                         tag, arg_offset, DATA_VALUE);
 550         } else {  /* presumably the parameter is a struct pointer */
 551                 run_sql(save_vals, &db_info,
 552                         "select offset, value from mtag_data where tag = %lld and type = %d;",
 553                         tag, DATA_VALUE);
 554         }
 555
 556         if (db_info.prev_offset != -1)
 557                 set_param_value(&db_info.stree, arg, db_info.prev_offset, db_info.rl);
 558
 559         // FIXME: handle an offset correctly
 560         if (!star && !arg_offset) {
 561                 sval_t sval;
 562
 563                 sval.type = get_real_base_type(arg);
 564                 sval.uvalue = tag;
 565                 set_state_stree(&db_info.stree, SMATCH_EXTRA, arg->ident->name, arg, alloc_estate_sval(sval));
 566         }
 567         return db_info.stree;
 568 }
 569
 570 static void handle_passed_container(struct symbol *sym)
 571 {
 572         struct symbol *arg;
 573         struct smatch_state *state;
 574         struct sm_state *sm;
 575         struct stree *stree;
 576         mtag_t fn_tag, container_tag, arg_tag;
 577         sval_t offset;
 578         int container_offset, arg_offset;
 579         int star;
 580
 581         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
 582                 state = get_state(param_id, arg->ident->name, arg);
 583                 if (state)
 584                         goto found;
 585         } END_FOR_EACH_PTR(arg);
 586
 587         return;
 588 found:
 589         if (!estate_get_single_value(state, &offset))
 590                 return;
 591         container_offset = -(offset.value & 0xffff);
 592         arg_offset = (offset.value & 0xfff0000) >> 16;
 593         star = !!(offset.value & (1ULL << 31));
 594
 595         if (!get_toplevel_mtag(cur_func_sym, &fn_tag))
 596                 return;
 597         if (!mtag_map_select_container(fn_tag, container_offset, &container_tag))
 598                 return;
 599         if (!arg_offset || star) {
 600                 arg_tag = container_tag;
 601         } else {
 602                 if (!mtag_map_select_tag(container_tag, -arg_offset, &arg_tag))
 603                         return;
 604         }
 605
 606         stree = load_tag_info_sym(arg_tag, arg, arg_offset, star);
 607         FOR_EACH_SM(stree, sm) {
 608                 set_state(sm->owner, sm->name, sm->sym, sm->state);
 609         } END_FOR_EACH_SM(sm);
 610         free_stree(&stree);
 611 }
 612
 613 void register_container_of(int id)
 614 {
 615         my_id = id;
 616
 617         add_hook(&match_function_def, FUNC_DEF_HOOK);
 618
 619         add_get_state_hook(&get_state_hook);
 620
 621         add_hook(&match_save_states, INLINE_FN_START);
 622         add_hook(&match_restore_states, INLINE_FN_END);
 623
 624         select_return_implies_hook(CONTAINER, &set_param_used);
 625         all_return_states_hook(&process_states);
 626
 627         add_split_return_callback(&print_returns_container_of);
 628         select_return_states_hook(CONTAINER, &returns_container_of);
 629
 630         add_hook(&match_call, FUNCTION_CALL_HOOK);
 631 }
 632
 633 static struct smatch_state *unmatched_state(struct sm_state *sm)
 634 {
 635         return alloc_estate_whole(estate_type(sm->state));
 636 }
 637
 638 void register_container_of2(int id)
 639 {
 640         param_id = id;
 641
 642         select_caller_info_hook(db_passed_container, CONTAINER);
 643         add_hook(&handle_passed_container, AFTER_DEF_HOOK);
 644         add_unmatched_state_hook(param_id, &unmatched_state);
 645         add_merge_hook(param_id, &merge_estates);
 646 }
 647