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 void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
 105 {
 106         struct symbol *param_sym;
 107         struct symbol *type;
 108         char *param_name;
 109
 110         if (expr && expr->smatch_flags & Fake)
 111                 return;
 112
 113         if (is_probably_worthless(expr))
 114                 return;
 115
 116         type = get_type(expr);
 117         if (type && (type->type == SYM_STRUCT || type->type == SYM_UNION))
 118                 return;
 119
 120         param_name = get_param_var_sym_var_sym(name, sym, NULL, &param_sym);
 121         if (!param_name || !param_sym)
 122                 goto free;
 123         if (get_param_num_from_sym(param_sym) < 0)
 124                 goto free;
 125         if (parent_is_set(param_name, param_sym, state))
 126                 return;
 127
 128         set_state(my_id, param_name, param_sym, state);
 129 free:
 130         free_string(param_name);
 131 }
 132
 133 /*
 134  * This function is is a dirty hack because extra_mod_hook is giving us a NULL
 135  *  sym instead of a vsl.
 136  */
 137 static void match_array_assignment(struct expression *expr)
 138 {
 139         struct expression *array, *offset;
 140         char *name;
 141         struct symbol *sym;
 142         struct range_list *rl;
 143         sval_t sval;
 144         char buf[256];
 145
 146         if (__in_fake_assign)
 147                 return;
 148
 149         if (!is_array(expr->left))
 150                 return;
 151         array = get_array_base(expr->left);
 152         offset = get_array_offset(expr->left);
 153
 154         /* These are handled by extra_mod_hook() */
 155         if (get_value(offset, &sval))
 156                 return;
 157         name = expr_to_var_sym(array, &sym);
 158         if (!name || !sym)
 159                 goto free;
 160         if (map_to_param(name, sym) < 0)
 161                 goto free;
 162         get_absolute_rl(expr->right, &rl);
 163         rl = cast_rl(get_type(expr->left), rl);
 164
 165         snprintf(buf, sizeof(buf), "*%s", name);
 166         set_state(my_id, buf, sym, alloc_estate_rl(rl));
 167 free:
 168         free_string(name);
 169 }
 170
 171 static char *get_two_dots(const char *name)
 172 {
 173         static char buf[80];
 174         int i, cnt = 0;
 175
 176         for (i = 0; i < sizeof(buf); i++) {
 177                 if (name[i] == '.') {
 178                         cnt++;
 179                         if (cnt >= 2) {
 180                                 buf[i] = '\0';
 181                                 return buf;
 182                         }
 183                 }
 184                 buf[i] = name[i];
 185         }
 186         return NULL;
 187 }
 188
 189 /*
 190  * This relies on the fact that these states are stored so that
 191  * foo->bar is before foo->bar->baz.
 192  */
 193 static int parent_set(struct string_list *list, const char *name)
 194 {
 195         char *tmp;
 196         int len;
 197         int ret;
 198
 199         FOR_EACH_PTR(list, tmp) {
 200                 len = strlen(tmp);
 201                 ret = strncmp(tmp, name, len);
 202                 if (ret < 0)
 203                         continue;
 204                 if (ret > 0)
 205                         return 0;
 206                 if (name[len] == '-')
 207                         return 1;
 208         } END_FOR_EACH_PTR(tmp);
 209
 210         return 0;
 211 }
 212
 213 static void print_return_value_param_helper(int return_id, char *return_ranges, struct expression *expr, int limit)
 214 {
 215         struct sm_state *sm;
 216         struct smatch_state *extra;
 217         int param;
 218         struct range_list *rl;
 219         const char *param_name;
 220         struct string_list *set_list = NULL;
 221         char *math_str;
 222         char buf[256];
 223         char two_dot[80] = "";
 224         int count = 0;
 225
 226         FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
 227                 if (!estate_rl(sm->state))
 228                         continue;
 229                 extra = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
 230                 if (extra) {
 231                         rl = rl_intersection(estate_rl(sm->state), estate_rl(extra));
 232                         if (!rl)
 233                                 continue;
 234                 } else {
 235                         rl = estate_rl(sm->state);
 236                 }
 237
 238                 param = get_param_key_from_sm(sm, NULL, &param_name);
 239                 if (param < 0 || !param_name)
 240                         continue;
 241                 if (param_name[0] == '&')
 242                         continue;
 243                 if (strcmp(param_name, "$") == 0 ||
 244                     is_recursive_member(param_name) ||
 245                     is_ignored_kernel_data(param_name)) {
 246                         insert_string(&set_list, (char *)sm->name);
 247                         continue;
 248                 }
 249                 if (limit) {
 250                         char *new = get_two_dots(param_name);
 251
 252                         /* no useful information here. */
 253                         if (is_whole_rl(rl) && parent_set(set_list, sm->name))
 254                                 continue;
 255
 256                         if (new) {
 257                                 if (strcmp(new, two_dot) == 0)
 258                                         continue;
 259
 260                                 strncpy(two_dot, new, sizeof(two_dot));
 261                                 insert_string(&set_list, (char *)sm->name);
 262                                 sql_insert_return_states(return_id, return_ranges,
 263                                          PARAM_SET, param, new, "s64min-s64max");
 264                                 continue;
 265                         }
 266                 }
 267
 268                 math_str = get_value_in_terms_of_parameter_math_var_sym(sm->name, sm->sym);
 269                 if (math_str) {
 270                         snprintf(buf, sizeof(buf), "%s[%s]", show_rl(rl), math_str);
 271                         insert_string(&set_list, (char *)sm->name);
 272                         sql_insert_return_states(return_id, return_ranges,
 273                                         param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 274                                         param, param_name, buf);
 275                         continue;
 276                 }
 277
 278                 /* no useful information here. */
 279                 if (is_whole_rl(rl) && parent_set(set_list, sm->name))
 280                         continue;
 281                 if (is_whole_rl(rl) && parent_was_PARAM_CLEAR(sm->name, sm->sym))
 282                         continue;
 283                 if (rl_is_zero(rl) && parent_was_PARAM_CLEAR_ZERO(sm->name, sm->sym))
 284                         continue;
 285
 286                 insert_string(&set_list, (char *)sm->name);
 287
 288                 sql_insert_return_states(return_id, return_ranges,
 289                                          param_has_filter_data(sm) ? PARAM_ADD : PARAM_SET,
 290                                          param, param_name, show_rl(rl));
 291                 if (limit && ++count > limit)
 292                         break;
 293
 294         } END_FOR_EACH_SM(sm);
 295
 296         free_ptr_list((struct ptr_list **)&set_list);
 297 }
 298
 299 static void print_return_value_param(int return_id, char *return_ranges, struct expression *expr)
 300 {
 301         print_return_value_param_helper(return_id, return_ranges, expr, 0);
 302 }
 303
 304 void print_limited_param_set(int return_id, char *return_ranges, struct expression *expr)
 305 {
 306         print_return_value_param_helper(return_id, return_ranges, expr, 1000);
 307 }
 308
 309 static int possibly_empty(struct sm_state *sm)
 310 {
 311         struct sm_state *tmp;
 312
 313         FOR_EACH_PTR(sm->possible, tmp) {
 314                 if (strcmp(tmp->name, "") == 0)
 315                         return 1;
 316         } END_FOR_EACH_PTR(tmp);
 317         return 0;
 318 }
 319
 320 int param_was_set_var_sym(const char *name, struct symbol *sym)
 321 {
 322         struct sm_state *sm;
 323         char buf[80];
 324         int len, i;
 325
 326         if (!name)
 327                 return 0;
 328
 329         if (name[0] == '&')
 330                 name++;
 331
 332         len = strlen(name);
 333         if (len >= sizeof(buf))
 334                 len = sizeof(buf) - 1;
 335
 336         for (i = 0; i <= len; i++) {
 337                 if (name[i] != '-' && name[i] != '\0')
 338                         continue;
 339
 340                 memcpy(buf, name, i);
 341                 buf[i] = '\0';
 342
 343                 sm = get_sm_state(my_id, buf, sym);
 344                 if (!sm)
 345                         continue;
 346                 if (possibly_empty(sm))
 347                         continue;
 348                 return 1;
 349         }
 350
 351         if (name[0] == '*')
 352                 return param_was_set_var_sym(name + 1, sym);
 353
 354         return 0;
 355 }
 356
 357 int param_was_set(struct expression *expr)
 358 {
 359         char *name;
 360         struct symbol *sym;
 361         int ret = 0;
 362
 363         name = expr_to_var_sym(expr, &sym);
 364         if (!name || !sym)
 365                 goto free;
 366
 367         ret = param_was_set_var_sym(name, sym);
 368 free:
 369         free_string(name);
 370         return ret;
 371 }
 372
 373 void register_param_set(int id)
 374 {
 375         my_id = id;
 376
 377         set_dynamic_states(my_id);
 378         add_extra_mod_hook(&extra_mod_hook);
 379         add_hook(match_array_assignment, ASSIGNMENT_HOOK);
 380         add_unmatched_state_hook(my_id, &unmatched_state);
 381         add_merge_hook(my_id, &merge_estates);
 382         add_split_return_callback(&print_return_value_param);
 383 }
 384