smatch_real_absolute.c

   1 /*
   2  * Copyright (C) 2015 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  * Say we have a line like:
  20  * foo = bar / 8;
  21  * Assume we don't know anything about bar.  Well, now we know that foo is less
  22  * than UINT_MAX / 8.  Which might be useful, but it probably is misleading
  23  * useless knowledge.  Up to now we have ignored those but now we have said to
  24  * store them.
  25  *
  26  * It also works if you have something like "foo = (int)(char)unknown_var;".
  27  *
  28  * I feel like this data doesn't have to be perfect, it just has to be better
  29  * than nothing and that will help eliminate some false positives.
  30  *
  31  */
  32
  33 #include "smatch.h"
  34 #include "smatch_slist.h"
  35 #include "smatch_extra.h"
  36
  37 static int my_id;
  38
  39 static void pre_merge_hook(struct sm_state *sm)
  40 {
  41         struct smatch_state *abs;
  42         struct smatch_state *extra;
  43         struct range_list *rl;
  44
  45         extra = get_state(SMATCH_EXTRA, sm->name, sm->sym);
  46         if (!extra || !estate_rl(extra))
  47                 return;
  48         abs = get_state(my_id, sm->name, sm->sym);
  49         if (!abs || !estate_rl(abs)) {
  50                 set_state(my_id, sm->name, sm->sym, clone_estate(extra));
  51                 return;
  52         }
  53         rl = rl_intersection(estate_rl(abs), estate_rl(extra));
  54         set_state(my_id, sm->name, sm->sym, alloc_estate_rl(clone_rl(rl)));
  55 }
  56
  57 static struct smatch_state *empty_state(struct sm_state *sm)
  58 {
  59         return alloc_estate_empty();
  60 }
  61
  62 static void reset(struct sm_state *sm, struct expression *mod_expr)
  63 {
  64         set_state(my_id, sm->name, sm->sym, alloc_estate_whole(estate_type(sm->state)));
  65 }
  66
  67 static void match_assign(struct expression *expr)
  68 {
  69         struct range_list *rl;
  70         struct symbol *type;
  71
  72         if (expr->op != '=')
  73                 return;
  74         if (is_fake_call(expr->right))
  75                 return;
  76
  77         get_real_absolute_rl(expr->right, &rl);
  78
  79         type = get_type(expr->left);
  80         if (!type)
  81                 return;
  82
  83         rl = cast_rl(type, rl);
  84         if (sval_cmp(rl_max(rl), sval_type_max(type)) == 0 &&
  85             sval_cmp(rl_min(rl), sval_type_min(type)))
  86                 return;
  87
  88         set_state_expr(my_id, expr->left, alloc_estate_rl(clone_rl(rl)));
  89 }
  90
  91 struct smatch_state *get_real_absolute_state(struct expression *expr)
  92 {
  93         return get_state_expr(my_id, expr);
  94 }
  95
  96 void register_real_absolute(int id)
  97 {
  98         my_id = id;
  99
 100         add_pre_merge_hook(my_id, &pre_merge_hook);
 101         add_unmatched_state_hook(my_id, &empty_state);
 102         add_merge_hook(my_id, &merge_estates);
 103         add_modification_hook(my_id, &reset);
 104
 105         add_hook(&match_assign, ASSIGNMENT_HOOK);
 106 }
 107