smatch_stored_conditions.c

   1 /*
   2  * Copyright (C) 2014 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  * Keep a record of all the things we have tested for so that we know when we
  20  * test for it again.  For example, if we have code like this:
  21  *
  22  *      if (foo & FLAG)
  23  *              lock();
  24  *
  25  *      ...
  26  *
  27  *      if (foo & FLAG)
  28  *              unlock();
  29  *
  30  * That's the end goal at least.  But actually implementing the flow of that
  31  * requires quite a bit of work because if "foo" changes the condition needs to
  32  * be retested and smatch_implications.c needs to be updated.
  33  *
  34  * For now, I just record the conditions and use it to see if we test for NULL
  35  * twice.
  36  *
  37  */
  38
  39 #include "smatch.h"
  40 #include "smatch_extra.h"
  41 #include "smatch_slist.h"
  42
  43 static int my_id;
  44 static int link_id;
  45
  46 static struct smatch_state *alloc_link_state(struct expression_list *expr_list)
  47 {
  48         struct expression *tmp;
  49         struct smatch_state *state;
  50         static char buf[256] = "";
  51         char *name;
  52         int cnt = 0;
  53
  54         state = __alloc_smatch_state(0);
  55
  56         FOR_EACH_PTR(expr_list, tmp) {
  57                 name = expr_to_str(tmp);
  58                 cnt += snprintf(buf + cnt, sizeof(buf) - cnt, "%s%s",
  59                                 cnt ? ", " : "", name);
  60                 free_string(name);
  61                 if (cnt >= sizeof(buf))
  62                         goto done;
  63         } END_FOR_EACH_PTR(tmp);
  64
  65 done:
  66         state->name = alloc_sname(buf);
  67         state->data = expr_list;
  68         return state;
  69 }
  70
  71 static struct expression_list *clone_expression_list(struct expression_list *list)
  72 {
  73         struct expression_list *ret = NULL;
  74         struct expression *expr;
  75
  76         FOR_EACH_PTR(list, expr) {
  77                 add_ptr_list(&ret, expr);
  78         } END_FOR_EACH_PTR(expr);
  79
  80         return ret;
  81 }
  82
  83 static void insert_expression(struct expression_list **list, struct expression *expr)
  84 {
  85         struct expression *tmp;
  86
  87         FOR_EACH_PTR(*list, tmp) {
  88                 if (tmp == expr)
  89                         return;
  90         } END_FOR_EACH_PTR(tmp);
  91
  92         add_ptr_list(list, expr);
  93 }
  94
  95 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
  96 {
  97         struct expression_list *list, *expr_list;
  98         struct expression *expr;
  99
 100         expr_list = clone_expression_list(s1->data);
 101
 102         list = s2->data;
 103         FOR_EACH_PTR(list, expr) {
 104                 insert_expression(&expr_list, expr);
 105         } END_FOR_EACH_PTR(expr);
 106
 107         return alloc_link_state(expr_list);
 108 }
 109
 110 static void save_link_var_sym(const char *var, struct symbol *sym, struct expression *condition)
 111 {
 112         struct smatch_state *old_state, *new_state;
 113         struct expression_list *expr_list;
 114
 115         old_state = get_state(link_id, var, sym);
 116         expr_list = clone_expression_list(old_state ? old_state->data : NULL);
 117
 118         insert_expression(&expr_list, condition);
 119
 120         new_state = alloc_link_state(expr_list);
 121         set_state(link_id, var, sym, new_state);
 122 }
 123
 124 static void match_link_modify(struct sm_state *sm, struct expression *mod_expr)
 125 {
 126         struct expression_list *expr_list;
 127         struct expression *tmp;
 128         char *name;
 129
 130         expr_list = sm->state->data;
 131
 132         FOR_EACH_PTR(expr_list, tmp) {
 133                 name = expr_to_str(tmp);
 134                 set_state(my_id, name, NULL, &undefined);
 135                 free_string(name);
 136         } END_FOR_EACH_PTR(tmp);
 137         set_state(link_id, sm->name, sm->sym, &undefined);
 138 }
 139
 140 static struct smatch_state *alloc_state(struct expression *expr, int is_true)
 141 {
 142         struct smatch_state *state;
 143
 144         state = __alloc_smatch_state(0);
 145         if (is_true)
 146                 state->name = alloc_sname("true");
 147         else
 148                 state->name = alloc_sname("false");
 149         state->data = expr;
 150         return state;
 151 }
 152
 153 static void store_all_links(struct expression *expr, struct expression *condition)
 154 {
 155         struct var_sym_list *vsl;
 156         struct var_sym *vs;
 157         char *var;
 158         struct symbol *sym;
 159
 160         expr = strip_expr(expr);
 161         if (!expr)
 162                 return;
 163
 164         vsl = expr_to_vsl(expr);
 165         FOR_EACH_PTR(vsl, vs) {
 166                 save_link_var_sym(vs->var, vs->sym, condition);
 167         } END_FOR_EACH_PTR(vs);
 168
 169         /* This is used to store "array[0]" from "if (array[0] == 1) " */
 170         var = expr_to_known_chunk_sym(expr, &sym);
 171         if (!var && !sym)
 172                 goto free;
 173         save_link_var_sym(var, sym, condition);
 174 free:
 175         free_string(var);
 176 }
 177
 178 static int is_untracked_var_helper(struct expression *expr, void *unused)
 179 {
 180         if (expr->type == EXPR_SYMBOL)
 181                 return is_untracked(expr);
 182         return 0;
 183 }
 184
 185 static int condition_too_complicated(struct expression *expr)
 186 {
 187         if (get_complication_score(expr) > 2)
 188                 return 1;
 189         if (recurse(expr, is_untracked_var_helper, NULL, 0) == 1)
 190                 return 1;
 191         return 0;
 192 }
 193
 194 void __stored_condition(struct expression *expr)
 195 {
 196         struct smatch_state *true_state, *false_state;
 197         char *name;
 198
 199         if (implied_condition_true(expr) ||
 200             implied_condition_false(expr))
 201                 return;
 202
 203         if (condition_too_complicated(expr))
 204                 return;
 205
 206         name = expr_to_str(expr);
 207         if (!name)
 208                 return;
 209         true_state = alloc_state(expr, TRUE);
 210         false_state = alloc_state(expr, FALSE);
 211
 212         set_true_false_states(my_id, name, NULL, true_state, false_state);
 213         store_all_links(expr, expr);
 214         free_string(name);
 215 }
 216
 217 struct smatch_state *get_stored_condition(struct expression *expr)
 218 {
 219         struct smatch_state *state;
 220         char *name;
 221
 222         name = expr_to_str(expr);
 223         if (!name)
 224                 return NULL;
 225
 226         state = get_state(my_id, name, NULL);
 227         free_string(name);
 228         return state;
 229 }
 230
 231 struct expression_list *get_conditions(struct expression *expr)
 232 {
 233         struct smatch_state *state;
 234
 235         state = get_state_expr(link_id, expr);
 236         if (!state)
 237                 return NULL;
 238         return state->data;
 239 }
 240
 241 void register_stored_conditions(int id)
 242 {
 243         my_id = id;
 244         set_dynamic_states(my_id);
 245 }
 246
 247 void register_stored_conditions_links(int id)
 248 {
 249         link_id = id;
 250         db_ignore_states(link_id);
 251         set_dynamic_states(link_id);
 252         add_merge_hook(link_id, &merge_links);
 253         add_modification_hook(link_id, &match_link_modify);
 254 }
 255
 256 #define RECURSE_LIMIT 50
 257
 258 static void filter_by_sm(struct sm_state *sm,
 259                        struct state_list **true_stack,
 260                        struct state_list **false_stack,
 261                        int *recurse_cnt)
 262 {
 263         if (!sm)
 264                 return;
 265
 266         if ((*recurse_cnt)++ > RECURSE_LIMIT)
 267                 return;
 268
 269         if (strcmp(sm->state->name, "true") == 0) {
 270                 add_ptr_list(true_stack, sm);
 271         } else if (strcmp(sm->state->name, "false") == 0) {
 272                 add_ptr_list(false_stack, sm);
 273         }
 274
 275         if (sm->merged) {
 276                 filter_by_sm(sm->left, true_stack, false_stack, recurse_cnt);
 277                 filter_by_sm(sm->right, true_stack, false_stack, recurse_cnt);
 278         }
 279 }
 280
 281 struct sm_state *stored_condition_implication_hook(struct expression *expr,
 282                                 struct state_list **true_stack,
 283                                 struct state_list **false_stack)
 284 {
 285         struct sm_state *sm;
 286         char *name;
 287         int recurse_cnt = 0;
 288         struct state_list *tmp_true = NULL;
 289         struct state_list *tmp_false = NULL;
 290         struct sm_state *tmp;
 291
 292         expr = strip_expr(expr);
 293
 294         name = expr_to_str(expr);
 295         if (!name)
 296                 return NULL;
 297
 298         sm = get_sm_state(my_id, name, NULL);
 299         free_string(name);
 300         if (!sm)
 301                 return NULL;
 302         if (!sm->merged)
 303                 return NULL;
 304
 305         filter_by_sm(sm, &tmp_true, &tmp_false, &recurse_cnt);
 306         if (!tmp_true && !tmp_false)
 307                 return NULL;
 308         if (recurse_cnt > RECURSE_LIMIT) {
 309                 sm = NULL;
 310                 goto free;
 311         }
 312
 313         FOR_EACH_PTR(tmp_true, tmp) {
 314                 add_ptr_list(true_stack, tmp);
 315         } END_FOR_EACH_PTR(tmp);
 316
 317         FOR_EACH_PTR(tmp_false, tmp) {
 318                 add_ptr_list(false_stack, tmp);
 319         } END_FOR_EACH_PTR(tmp);
 320
 321 free:
 322         free_slist(&tmp_true);
 323         free_slist(&tmp_false);
 324         return sm;
 325 }
 326