1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   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 #include <stdlib.h>
  19 #include "parse.h"
  20 #include "smatch.h"
  21 #include "smatch_slist.h"
  22 #include "smatch_extra.h"
  23 
  24 /*
  25  * This check has two smatch IDs.
  26  * my_used_id - keeps a record of array offsets that have been used.
  27  *              If the code checks that they are within bounds later on,
  28  *              we complain about using an array offset before checking
  29  *              that it is within bounds.
  30  */
  31 static int my_used_id;
  32 
  33 static void delete(struct sm_state *sm, struct expression *mod_expr)
  34 {
  35         set_state(my_used_id, sm->name, sm->sym, &undefined);
  36 }
  37 
  38 static int get_the_max(struct expression *expr, sval_t *sval)
  39 {
  40         struct range_list *rl;
  41 
  42         if (get_hard_max(expr, sval))
  43                 return 1;
  44         if (!option_spammy)
  45                 return 0;
  46         if (get_fuzzy_max(expr, sval))
  47                 return 1;
  48         if (get_user_rl(expr, &rl)) {
  49                 *sval = rl_max(rl);
  50                 return 1;
  51         }
  52         return 0;
  53 }
  54 
  55 static void array_check(struct expression *expr)
  56 {
  57         struct expression *array_expr;
  58         int array_size;
  59         struct expression *offset;
  60         sval_t max;
  61 
  62         expr = strip_expr(expr);
  63         if (!is_array(expr))
  64                 return;
  65 
  66         array_expr = get_array_base(expr);
  67         array_size = get_array_size(array_expr);
  68         if (!array_size || array_size == 1)
  69                 return;
  70 
  71         offset = get_array_offset(expr);
  72         if (!get_the_max(offset, &max)) {
  73                 if (getting_address())
  74                         return;
  75                 if (is_capped(offset))
  76                         return;
  77                 set_state_expr(my_used_id, offset, alloc_state_num(array_size));
  78         }
  79 }
  80 
  81 static void match_condition(struct expression *expr)
  82 {
  83         int left;
  84         sval_t sval;
  85         struct state_list *slist;
  86         struct sm_state *tmp;
  87         int boundary;
  88 
  89         if (!expr || expr->type != EXPR_COMPARE)
  90                 return;
  91         if (get_macro_name(expr->pos))
  92                 return;
  93         if (get_implied_value(expr->left, &sval))
  94                 left = 1;
  95         else if (get_implied_value(expr->right, &sval))
  96                 left = 0;
  97         else
  98                 return;
  99 
 100         if (left)
 101                 slist = get_possible_states_expr(my_used_id, expr->right);
 102         else
 103                 slist = get_possible_states_expr(my_used_id, expr->left);
 104         if (!slist)
 105                 return;
 106         FOR_EACH_PTR(slist, tmp) {
 107                 if (tmp->state == &merged || tmp->state == &undefined)
 108                         continue;
 109                 boundary = PTR_INT(tmp->state->data);
 110                 boundary -= sval.value;
 111                 if (boundary < 1 && boundary > -1) {
 112                         char *name;
 113 
 114                         name = expr_to_var(left ? expr->right : expr->left);
 115                         sm_error("testing array offset '%s' after use.", name);
 116                         return;
 117                 }
 118         } END_FOR_EACH_PTR(tmp);
 119 }
 120 
 121 void check_testing_index_after_use(int id)
 122 {
 123         my_used_id = id;
 124         add_hook(&array_check, OP_HOOK);
 125         add_hook(&match_condition, CONDITION_HOOK);
 126         add_modification_hook(my_used_id, &delete);
 127 }