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_slist.h"
  41
  42 static int my_id;
  43 static int link_id;
  44
  45 static struct smatch_state *alloc_link_state(struct string_list *links)
  46 {
  47         struct smatch_state *state;
  48         static char buf[256];
  49         char *tmp;
  50         int i;
  51
  52         state = __alloc_smatch_state(0);
  53
  54         i = 0;
  55         FOR_EACH_PTR(links, tmp) {
  56                 if (!i++) {
  57                         snprintf(buf, sizeof(buf), "%s", tmp);
  58                 } else {
  59                         append(buf, ", ", sizeof(buf));
  60                         append(buf, tmp, sizeof(buf));
  61                 }
  62         } END_FOR_EACH_PTR(tmp);
  63
  64         state->name = alloc_sname(buf);
  65         state->data = links;
  66         return state;
  67 }
  68
  69 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
  70 {
  71         struct smatch_state *ret;
  72         struct string_list *links;
  73
  74         links = combine_string_lists(s1->data, s2->data);
  75         ret = alloc_link_state(links);
  76         return ret;
  77 }
  78
  79 static void save_link_var_sym(const char *var, struct symbol *sym, const char *link)
  80 {
  81         struct smatch_state *old_state, *new_state;
  82         struct string_list *links;
  83         char *new;
  84
  85         old_state = get_state(link_id, var, sym);
  86         if (old_state)
  87                 links = clone_str_list(old_state->data);
  88         else
  89                 links = NULL;
  90
  91         new = alloc_sname(link);
  92         insert_string(&links, new);
  93
  94         new_state = alloc_link_state(links);
  95         set_state(link_id, var, sym, new_state);
  96 }
  97
  98 static void match_modify(struct sm_state *sm, struct expression *mod_expr)
  99 {
 100         struct string_list *links;
 101         char *tmp;
 102
 103         links = sm->state->data;
 104
 105         FOR_EACH_PTR(links, tmp) {
 106                 set_state(my_id, tmp, NULL, &undefined);
 107         } END_FOR_EACH_PTR(tmp);
 108         set_state(link_id, sm->name, sm->sym, &undefined);
 109 }
 110
 111 static struct smatch_state *alloc_state(struct expression *expr, int is_true)
 112 {
 113         struct smatch_state *state;
 114
 115         state = __alloc_smatch_state(0);
 116         if (is_true)
 117                 state->name = alloc_sname("true");
 118         else
 119                 state->name = alloc_sname("false");
 120         state->data = expr;
 121         return state;
 122 }
 123
 124 static int is_local_variable(struct expression *expr)
 125 {
 126         struct symbol *sym;
 127         char *name;
 128
 129         name = expr_to_var_sym(expr, &sym);
 130         free_string(name);
 131         if (!sym || !sym->scope || !sym->scope->token)
 132                 return 0;
 133         if (cmp_pos(sym->scope->token->pos, cur_func_sym->pos) < 0)
 134                 return 0;
 135         if (is_static(expr))
 136                 return 0;
 137         return 1;
 138 }
 139
 140 static void store_all_links(struct expression *expr, const char *condition)
 141 {
 142         char *var;
 143         struct symbol *sym;
 144
 145         expr = strip_expr(expr);
 146
 147         switch (expr->type) {
 148         case EXPR_COMPARE:
 149         case EXPR_BINOP:
 150                 store_all_links(expr->left, condition);
 151                 store_all_links(expr->right, condition);
 152                 return;
 153         case EXPR_VALUE:
 154                 return;
 155         }
 156
 157         var = expr_to_var_sym(expr, &sym);
 158         if (!var || !sym)
 159                 goto free;
 160         save_link_var_sym(var, sym, condition);
 161 free:
 162         free_string(var);
 163 }
 164
 165 static int get_complication_score(struct expression *expr)
 166 {
 167         int score = 0;
 168
 169         expr = strip_expr(expr);
 170
 171         /*
 172          * Don't forget to keep get_complication_score() and store_all_links()
 173          * in sync.
 174          *
 175          */
 176
 177         switch (expr->type) {
 178         case EXPR_CALL:
 179                 return 999;
 180         case EXPR_COMPARE:
 181         case EXPR_BINOP:
 182                 score += get_complication_score(expr->left);
 183                 score += get_complication_score(expr->right);
 184                 return score;
 185         case EXPR_SYMBOL:
 186                 if (is_local_variable(expr))
 187                         return 1;
 188                 return 999;
 189         case EXPR_VALUE:
 190                 return 0;
 191 #if 0
 192         case EXPR_PREOP:
 193                 if (expr->op == SPECIAL_INCREMENT ||
 194                     expr->op == SPECIAL_DECREMENT)
 195                         return 999;
 196                 return get_complication_score(expr->unop);
 197 #endif
 198         default:
 199                 return 999;
 200         }
 201 }
 202
 203 static int condition_too_complicated(struct expression *expr)
 204 {
 205         if (get_complication_score(expr) > 2)
 206                 return 1;
 207         return 0;
 208
 209 }
 210
 211 static void match_condition(struct expression *expr)
 212 {
 213         struct smatch_state *true_state, *false_state;
 214         char *name;
 215         sval_t val;
 216
 217         if (get_value(expr, &val))
 218                 return;
 219
 220         if (condition_too_complicated(expr))
 221                 return;
 222
 223         name = expr_to_str(expr);
 224         if (!name)
 225                 return;
 226         true_state = alloc_state(expr, TRUE);
 227         false_state = alloc_state(expr, FALSE);
 228         set_true_false_states(my_id, name, NULL, true_state, false_state);
 229         store_all_links(expr, alloc_sname(name));
 230         free_string(name);
 231 }
 232
 233 struct smatch_state *get_stored_condition(struct expression *expr)
 234 {
 235         struct smatch_state *state;
 236         char *name;
 237
 238         name = expr_to_str(expr);
 239         if (!name)
 240                 return NULL;
 241
 242         state = get_state(my_id, name, NULL);
 243         free_string(name);
 244         return state;
 245 }
 246
 247 void register_stored_conditions(int id)
 248 {
 249         my_id = id;
 250
 251         add_hook(&match_condition, CONDITION_HOOK);
 252 }
 253
 254 void register_stored_conditions_links(int id)
 255 {
 256         link_id = id;
 257         add_merge_hook(link_id, &merge_links);
 258         add_modification_hook(link_id, &match_modify);
 259 }
 260