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