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 int get_complication_score(struct expression *expr)
 141 {
 142         int score = 0;
 143
 144         expr = strip_expr(expr);
 145
 146         switch (expr->type) {
 147         case EXPR_CALL:
 148                 return 999;
 149         case EXPR_LOGICAL:
 150         case EXPR_BINOP:
 151                 score += get_complication_score(expr->left);
 152                 score += get_complication_score(expr->right);
 153                 return score;
 154         case EXPR_SYMBOL:
 155                 if (is_local_variable(expr))
 156                         return 1;
 157                 return 999;
 158         case EXPR_VALUE:
 159                 return 0;
 160 #if 0
 161         case EXPR_PREOP:
 162                 if (expr->op == SPECIAL_INCREMENT ||
 163                     expr->op == SPECIAL_DECREMENT)
 164                         return 999;
 165                 return get_complication_score(expr->unop);
 166 #endif
 167         default:
 168                 return 999;
 169         }
 170 }
 171
 172 static int condition_too_complicated(struct expression *expr)
 173 {
 174         if (get_complication_score(expr) > 2)
 175                 return 1;
 176         return 0;
 177
 178 }
 179
 180 static void store_all_links(struct expression *expr, const char *condition)
 181 {
 182         char *var;
 183         struct symbol *sym;
 184
 185         expr = strip_expr(expr);
 186
 187         switch (expr->type) {
 188         case EXPR_BINOP:
 189                 store_all_links(expr->left, condition);
 190                 store_all_links(expr->right, condition);
 191                 return;
 192         case EXPR_VALUE:
 193                 return;
 194         }
 195
 196         var = expr_to_var_sym(expr, &sym);
 197         if (!var || !sym)
 198                 goto free;
 199         save_link_var_sym(var, sym, condition);
 200 free:
 201         free_string(var);
 202 }
 203
 204 static void match_condition(struct expression *expr)
 205 {
 206         struct smatch_state *true_state, *false_state;
 207         char *name;
 208
 209         if (condition_too_complicated(expr))
 210                 return;
 211
 212         name = expr_to_str(expr);
 213         if (!name)
 214                 return;
 215         true_state = alloc_state(expr, TRUE);
 216         false_state = alloc_state(expr, FALSE);
 217         set_true_false_states(my_id, name, NULL, true_state, false_state);
 218         store_all_links(expr, alloc_sname(name));
 219         free_string(name);
 220 }
 221
 222 struct smatch_state *get_stored_condition(struct expression *expr)
 223 {
 224         struct smatch_state *state;
 225         char *name;
 226
 227         name = expr_to_str(expr);
 228         if (!name)
 229                 return NULL;
 230
 231         state = get_state(my_id, name, NULL);
 232         free_string(name);
 233         return state;
 234 }
 235
 236 void register_stored_conditions(int id)
 237 {
 238         my_id = id;
 239
 240         add_hook(&match_condition, CONDITION_HOOK);
 241 }
 242
 243 void register_stored_conditions_links(int id)
 244 {
 245         link_id = id;
 246         add_merge_hook(link_id, &merge_links);
 247         add_modification_hook(link_id, &match_modify);
 248 }
 249