smatch_param_set.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  * This is for functions like:
  20  *
  21  * int foo(int *x)
  22  * {
  23  *      if (*x == 42) {
  24  *              *x = 0;
  25  *              return 1;
  26  *      }
  27  *      return 0;
  28  * }
  29  *
  30  * If we return 1 that means the value of *x has been set to 0.  If we return
  31  * 0 then we have left *x alone.
  32  *
  33  */
  34
  35 #include "smatch.h"
  36 #include "smatch_slist.h"
  37 #include "smatch_extra.h"
  38
  39 static int my_id;
  40
  41 static struct smatch_state *unmatched_state(struct sm_state *sm)
  42 {
  43         return alloc_estate_empty();
  44 }
  45
  46 static int parent_is_set(const char *name, struct symbol *sym, struct smatch_state *state)
  47 {
  48         struct expression *faked;
  49         char *left_name;
  50         int ret = 0;
  51         int len;
  52
  53         if (!__in_fake_assign)
  54                 return 0;
  55         if (!is_whole_rl(estate_rl(state)))
  56                 return 0;
  57         if (get_state(my_id, name, sym))
  58                 return 0;
  59
  60         faked = get_faked_expression();
  61         if (!faked)
  62                 return 0;
  63         if ((faked->type == EXPR_PREOP || faked->type == EXPR_POSTOP) &&
  64             (faked->op == SPECIAL_INCREMENT || faked->op == SPECIAL_DECREMENT)) {
  65                 faked = strip_expr(faked->unop);
  66                 if (faked->type == EXPR_SYMBOL)
  67                         return 1;
  68                 return 0;
  69         }
  70         if (faked->type != EXPR_ASSIGNMENT)
  71                 return 0;
  72
  73         left_name = expr_to_var(faked->left);
  74         if (!left_name)
  75                 return 0;
  76
  77         len = strlen(left_name);
  78         if (strncmp(name, left_name, len) == 0 && name[len] == '-')
  79                 ret = 1;
  80         free_string(left_name);
  81
  82         return ret;
  83 }
  84
  85 static bool is_probably_worthless(struct expression *expr)
  86 {
  87         struct expression *faked;
  88
  89         if (!__in_fake_struct_assign)
  90                 return false;
  91
  92         faked = get_faked_expression();
  93         if (!faked || faked->type != EXPR_ASSIGNMENT)
  94                 return false;
  95
  96         if (faked->left->type == EXPR_PREOP &&
  97             faked->left->op == '*')
  98                 return false;
  99
 100         return true;
 101 }
 102
 103 static bool name_is_sym_name(const char *name, struct symbol *sym)
 104 {
 105         if (!name || !sym || !sym->ident)
 106                 return false;
 107
 108         return strcmp(name, sym->ident->name) == 0;
 109 }
 110
 111 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 112 {
 113         struct symbol *param_sym;
 114         struct symbol *type;
 115         char *param_name;
 116
 117         if (expr && expr->smatch_flags & Fake)
 118                 return;
 119
 120         if (is_probably_worthless(expr))
 121                 return;
 122
 123         type = get_type(expr);
 124         if (type && (type->type == SYM_STRUCT || type->type == SYM_UNION))
 125                 return;
 126
 127         if (name_is_sym_name(name, sym))
 128                 return;
 129
 130         param_name = get_param_var_sym_var_sym(name, sym, NULL, &param_sym);
 131         if (!param_name || !param_sym)
 132                 goto free;
 133         if (get_param_num_from_sym(param_sym) < 0)
 134                 goto free;
 135         if (parent_is_set(param_name, param_sym, state))
 136                 return;
 137
 138         set_state(my_id, param_name, param_sym, state);
 139 free:
 140         free_string(param_name);
 141 }
 142
 143 /*
 144  * This function is is a dirty hack because extra_mod_hook is giving us a NULL
 145  *  sym instead of a vsl.
 146  */
 147 static void match_array_assignment(struct expression *expr)
 148 {
 149         struct expression *array, *offset;
 150         char *name;
 151         struct symbol *sym;
 152         struct range_list *rl;
 153         sval_t sval;
 154         char buf[256];
 155
 156         if (__in_fake_assign)
 157                 return;
 158
 159         if (!is_array(expr->left))
 160                 return;
 161         array = get_array_base(expr->left);
 162         offset = get_array_offset(expr->left);
 163
 164         /* These are handled by extra_mod_hook() */
 165         if (get_value(offset, &sval))
 166                 return;
 167         name = expr_to_var_sym(array, &sym);
 168         if (!name || !sym)
 169                 goto free;
 170         if (map_to_param(name, sym) < 0)
 171                 goto free;
 172         get_absolute_rl(expr->right, &rl);
 173         rl = cast_rl(get_type(expr->left), rl);
 174
 175         snprintf(buf, sizeof(buf), "*%s", name);
 176         set_state(my_id, buf, sym, alloc_estate_rl(rl));
 177 free:
 178         free_string(name);
 179 }
 180
 181 static char *get_two_dots(const char *name)
 182 {
 183         static char buf[80];
 184         int i, cnt = 0;
 185
 186         for (i = 0; i < sizeof(buf); i++) {
 187                 if (name[i] == '.') {
 188                         cnt++;
 189                         if (cnt >= 2) {
 190                                 buf[i] = '\0';
 191                                 return buf;
 192                         }
 193                 }
 194                 buf[i] = name[i];
 195         }
 196         return NULL;
 197 }
 198
 199 /*
 200  * This relies on the fact that these states are stored so that
 201  * foo->bar is before foo->bar->baz.
 202  */
 203 static int parent_set(struct string_list *list, const char *param_name, struct sm_state *sm)
 204 {
 205         char *tmp;
 206         int len;
 207         int ret;
 208
 209         if (strncmp(param_name, "(*$)->", 6) == 0 && sm->sym && sm->sym->ident) {
 210                 char buf[64];
 211
 212                 snprintf(buf, sizeof(buf), "*%s", sm->sym->ident->name);
 213                 if (get_state(my_id, buf, sm->sym))
 214                         return true;
 215         }
 216
 217         FOR_EACH_PTR(list, tmp) {
 218                 len = strlen(tmp);
 219                 ret = strncmp(tmp, sm->name, len);
 220                 if (ret < 0)
 221                         continue;
 222                 if (ret > 0)
 223                         return 0;
 224                 if (sm->name[len] == '-')
 225                         return 1;
 226         } END_FOR_EACH_PTR(tmp);
 227
 228         return 0;
 229 }
 230
 231 static void print_return_value_param_helper(int return_id, char *return_ranges, struct expression *expr, int limit)
 232 {
 233         struct sm_state *sm;
 234         struct smatch_state *extra;
 235         int param;
 236         struct range_list *rl;
 237         const char *param_name;
 238         struct string_list *set_list = NULL;
 239         char *math_str;
 240         char buf[256];
 241         char two_dot[80] = "";
 242         int count = 0;
 243
 244         __promote_sets_to_clears(return_id, return_ranges, expr);
 245
 246         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 247                 bool untracked = false;
 248
 249                 if (!estate_rl(sm->state))
 250                         continue;
 251                 extra = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
 252                 if (extra) {
 253                         rl = rl_intersection(estate_rl(sm->state), estate_rl(extra));
 254                         if (!rl)
 255                                 untracked = true;
 256                 } else {
 257                         rl = estate_rl(sm->state);
 258                 }
 259
 260                 param = get_param_key_from_sm(sm, NULL, &param_name);
 261                 if (param < 0 || !param_name)
 262                         continue;
 263                 if (param_name[0] == '&')
 264                         continue;
 265                 if (strcmp(param_name, "$") == 0 ||
 266                     is_recursive_member(param_name) ||
 267                     is_ignored_kernel_data(param_name)) {
 268                         insert_string(&set_list, (char *)sm->name);
 269                         continue;
 270                 }
 271                 if (untracked) {
 272                         if (parent_was_PARAM_CLEAR(sm->name, sm->sym))
 273                                 continue;
 274
 275                         sql_insert_return_states(return_id, return_ranges,
 276                                                  UNTRACKED_PARAM, param, param_name, "");
 277                         continue;
 278                 }
 279
 280                 if (limit) {
 281                         char *new = get_two_dots(param_name);
 282
 283                         /* no useful information here. */
 284                         if (is_whole_rl(rl) && parent_set(set_list, param_name, sm))
 285                                 continue;
 286
 287                         if (new) {
 288                                 if (strcmp(new, two_dot) == 0)
 289                                         continue;
 290
 291                                 strncpy(two_dot, new, sizeof(two_dot));
 292                                 insert_string(&set_list, (char *)sm->name);
 293                                 sql_insert_return_states(return_id, return_ranges,
 294                                          PARAM_SET, param, new, "s64min-s64max");
 295                                 continue;
 296                         }
 297                 }
 298
 299                 math_str = get_value_in_terms_of_parameter_math_var_sym(sm->name, sm->sym);
 300                 if (math_str) {
 301                         snprintf(buf, sizeof(buf), "%s[%s]", show_rl(rl), math_str);
 302                         insert_string(&set_list, (char *)sm->name);
 303                         sql_insert_return_states(return_id, return_ranges,
 304                                         param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 305                                         param, param_name, buf);
 306                         continue;
 307                 }
 308
 309                 /* no useful information here. */
 310                 if (is_whole_rl(rl) && parent_set(set_list, param_name, sm))
 311                         continue;
 312                 if (is_whole_rl(rl) && parent_was_PARAM_CLEAR(sm->name, sm->sym))
 313                         continue;
 314                 if (rl_is_zero(rl) && parent_was_PARAM_CLEAR_ZERO(sm->name, sm->sym))
 315                         continue;
 316
 317                 insert_string(&set_list, (char *)sm->name);
 318
 319                 sql_insert_return_states(return_id, return_ranges,
 320                                          param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 321                                          param, param_name, show_rl(rl));
 322                 if (limit && ++count > limit)
 323                         break;
 324
 325         } END_FOR_EACH_SM(sm);
 326
 327         free_ptr_list((struct ptr_list **)&set_list);
 328 }
 329
 330 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 331 {
 332         print_return_value_param_helper(return_id, return_ranges, expr, 0);
 333 }
 334
 335 void print_limited_param_set(int return_id, char *return_ranges, struct expression *expr)
 336 {
 337         print_return_value_param_helper(return_id, return_ranges, expr, 1000);
 338 }
 339
 340 static int possibly_empty(struct sm_state *sm)
 341 {
 342         struct sm_state *tmp;
 343
 344         FOR_EACH_PTR(sm->possible, tmp) {
 345                 if (strcmp(tmp->name, "") == 0)
 346                         return 1;
 347         } END_FOR_EACH_PTR(tmp);
 348         return 0;
 349 }
 350
 351 static bool sym_was_set(struct symbol *sym)
 352 {
 353         char buf[80];
 354
 355         if (!sym || !sym->ident)
 356                 return false;
 357
 358         snprintf(buf, sizeof(buf), "%s orig", sym->ident->name);
 359         if (get_comparison_strings(sym->ident->name, buf) == SPECIAL_EQUAL)
 360                 return false;
 361
 362         return true;
 363 }
 364
 365 int param_was_set_var_sym(const char *name, struct symbol *sym)
 366 {
 367         struct symbol *param_sym;
 368         const char *param_name;
 369         struct sm_state *sm;
 370         char buf[80];
 371         int len, i;
 372
 373         param_name = get_param_var_sym_var_sym(name, sym, NULL, &param_sym);
 374         if (param_name && param_sym) {
 375                 name = param_name;
 376                 sym = param_sym;
 377         }
 378
 379         if (!name)
 380                 return 0;
 381
 382         if (name[0] == '&')
 383                 name++;
 384
 385         if (sym_was_set(sym))
 386                 return true;
 387
 388         len = strlen(name);
 389         if (len >= sizeof(buf))
 390                 len = sizeof(buf) - 1;
 391
 392         for (i = 0; i <= len; i++) {
 393                 if (name[i] != '-' && name[i] != '\0')
 394                         continue;
 395
 396                 memcpy(buf, name, i);
 397                 buf[i] = '\0';
 398
 399                 sm = get_sm_state(my_id, buf, sym);
 400                 if (!sm)
 401                         continue;
 402                 if (possibly_empty(sm))
 403                         continue;
 404                 return 1;
 405         }
 406
 407         if (name[0] == '*')
 408                 return param_was_set_var_sym(name + 1, sym);
 409
 410         return 0;
 411 }
 412
 413 static struct expression *get_unfaked_expr(struct expression *expr)
 414 {
 415         struct expression *tmp;
 416
 417         if (!is_fake_var(expr))
 418                 return expr;
 419         tmp = expr_get_fake_parent_expr(expr);
 420         if (!tmp || tmp->type != EXPR_ASSIGNMENT)
 421                 return expr;
 422         return tmp->right;
 423 }
 424
 425 int param_was_set(struct expression *expr)
 426 {
 427         char *name;
 428         struct symbol *sym;
 429         int ret = 0;
 430
 431         expr = get_unfaked_expr(expr);
 432
 433         name = expr_to_var_sym(expr, &sym);
 434         if (!name || !sym)
 435                 goto free;
 436
 437         ret = param_was_set_var_sym(name, sym);
 438 free:
 439         free_string(name);
 440         return ret;
 441 }
 442
 443 void register_param_set(int id)
 444 {
 445         my_id = id;
 446
 447         set_dynamic_states(my_id);
 448         add_extra_mod_hook(&extra_mod_hook);
 449         add_hook(match_array_assignment, ASSIGNMENT_HOOK);
 450         add_unmatched_state_hook(my_id, &unmatched_state);
 451         add_merge_hook(my_id, &merge_estates);
 452         add_split_return_callback(&print_return_value_param);
 453 }
 454