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 *name)
 205 {
 206         char *tmp;
 207         int len;
 208         int ret;
 209
 210         FOR_EACH_PTR(list, tmp) {
 211                 len = strlen(tmp);
 212                 ret = strncmp(tmp, name, len);
 213                 if (ret < 0)
 214                         continue;
 215                 if (ret > 0)
 216                         return 0;
 217                 if (name[len] == '-')
 218                         return 1;
 219         } END_FOR_EACH_PTR(tmp);
 220
 221         return 0;
 222 }
 223
 224 static void print_return_value_param_helper(int return_id, char *return_ranges, struct expression *expr, int limit)
 225 {
 226         struct sm_state *sm;
 227         struct smatch_state *extra;
 228         int param;
 229         struct range_list *rl;
 230         const char *param_name;
 231         struct string_list *set_list = NULL;
 232         char *math_str;
 233         char buf[256];
 234         char two_dot[80] = "";
 235         int count = 0;
 236
 237         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 238                 if (!estate_rl(sm->state))
 239                         continue;
 240                 extra = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
 241                 if (extra) {
 242                         rl = rl_intersection(estate_rl(sm->state), estate_rl(extra));
 243                         if (!rl)
 244                                 continue;
 245                 } else {
 246                         rl = estate_rl(sm->state);
 247                 }
 248
 249                 param = get_param_key_from_sm(sm, NULL, &param_name);
 250                 if (param < 0 || !param_name)
 251                         continue;
 252                 if (param_name[0] == '&')
 253                         continue;
 254                 if (strcmp(param_name, "$") == 0 ||
 255                     is_recursive_member(param_name) ||
 256                     is_ignored_kernel_data(param_name)) {
 257                         insert_string(&set_list, (char *)sm->name);
 258                         continue;
 259                 }
 260                 if (limit) {
 261                         char *new = get_two_dots(param_name);
 262
 263                         /* no useful information here. */
 264                         if (is_whole_rl(rl) && parent_set(set_list, sm->name))
 265                                 continue;
 266
 267                         if (new) {
 268                                 if (strcmp(new, two_dot) == 0)
 269                                         continue;
 270
 271                                 strncpy(two_dot, new, sizeof(two_dot));
 272                                 insert_string(&set_list, (char *)sm->name);
 273                                 sql_insert_return_states(return_id, return_ranges,
 274                                          PARAM_SET, param, new, "s64min-s64max");
 275                                 continue;
 276                         }
 277                 }
 278
 279                 math_str = get_value_in_terms_of_parameter_math_var_sym(sm->name, sm->sym);
 280                 if (math_str) {
 281                         snprintf(buf, sizeof(buf), "%s[%s]", show_rl(rl), math_str);
 282                         insert_string(&set_list, (char *)sm->name);
 283                         sql_insert_return_states(return_id, return_ranges,
 284                                         param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 285                                         param, param_name, buf);
 286                         continue;
 287                 }
 288
 289                 /* no useful information here. */
 290                 if (is_whole_rl(rl) && parent_set(set_list, sm->name))
 291                         continue;
 292                 if (is_whole_rl(rl) && parent_was_PARAM_CLEAR(sm->name, sm->sym))
 293                         continue;
 294                 if (rl_is_zero(rl) && parent_was_PARAM_CLEAR_ZERO(sm->name, sm->sym))
 295                         continue;
 296
 297                 insert_string(&set_list, (char *)sm->name);
 298
 299                 sql_insert_return_states(return_id, return_ranges,
 300                                          param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 301                                          param, param_name, show_rl(rl));
 302                 if (limit && ++count > limit)
 303                         break;
 304
 305         } END_FOR_EACH_SM(sm);
 306
 307         free_ptr_list((struct ptr_list **)&set_list);
 308 }
 309
 310 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 311 {
 312         print_return_value_param_helper(return_id, return_ranges, expr, 0);
 313 }
 314
 315 void print_limited_param_set(int return_id, char *return_ranges, struct expression *expr)
 316 {
 317         print_return_value_param_helper(return_id, return_ranges, expr, 1000);
 318 }
 319
 320 static int possibly_empty(struct sm_state *sm)
 321 {
 322         struct sm_state *tmp;
 323
 324         FOR_EACH_PTR(sm->possible, tmp) {
 325                 if (strcmp(tmp->name, "") == 0)
 326                         return 1;
 327         } END_FOR_EACH_PTR(tmp);
 328         return 0;
 329 }
 330
 331 static bool sym_was_set(struct symbol *sym)
 332 {
 333         char buf[80];
 334
 335         if (!sym || !sym->ident)
 336                 return false;
 337
 338         snprintf(buf, sizeof(buf), "%s orig", sym->ident->name);
 339         if (get_comparison_strings(sym->ident->name, buf) == SPECIAL_EQUAL)
 340                 return false;
 341
 342         return true;
 343 }
 344
 345 int param_was_set_var_sym(const char *name, struct symbol *sym)
 346 {
 347         struct sm_state *sm;
 348         char buf[80];
 349         int len, i;
 350
 351         if (!name)
 352                 return 0;
 353
 354         if (name[0] == '&')
 355                 name++;
 356
 357         if (sym_was_set(sym))
 358                 return true;
 359
 360         len = strlen(name);
 361         if (len >= sizeof(buf))
 362                 len = sizeof(buf) - 1;
 363
 364         for (i = 0; i <= len; i++) {
 365                 if (name[i] != '-' && name[i] != '\0')
 366                         continue;
 367
 368                 memcpy(buf, name, i);
 369                 buf[i] = '\0';
 370
 371                 sm = get_sm_state(my_id, buf, sym);
 372                 if (!sm)
 373                         continue;
 374                 if (possibly_empty(sm))
 375                         continue;
 376                 return 1;
 377         }
 378
 379         if (name[0] == '*')
 380                 return param_was_set_var_sym(name + 1, sym);
 381
 382         return 0;
 383 }
 384
 385 int param_was_set(struct expression *expr)
 386 {
 387         char *name;
 388         struct symbol *sym;
 389         int ret = 0;
 390
 391         name = expr_to_var_sym(expr, &sym);
 392         if (!name || !sym)
 393                 goto free;
 394
 395         ret = param_was_set_var_sym(name, sym);
 396 free:
 397         free_string(name);
 398         return ret;
 399 }
 400
 401 void register_param_set(int id)
 402 {
 403         my_id = id;
 404
 405         set_dynamic_states(my_id);
 406         add_extra_mod_hook(&extra_mod_hook);
 407         add_hook(match_array_assignment, ASSIGNMENT_HOOK);
 408         add_unmatched_state_hook(my_id, &unmatched_state);
 409         add_merge_hook(my_id, &merge_estates);
 410         add_split_return_callback(&print_return_value_param);
 411 }
 412