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 int in_iterator_pre_statement(void)
  68 {
  69         struct statement *stmt;
  70
  71         /*
  72          * we can't use __cur_stmt because that isn't set for
  73          * iterator_pre_statement.  Kind of a mess.
  74          *
  75          */
  76
  77         stmt = last_ptr_list((struct ptr_list *)big_statement_stack);
  78
  79         if (!stmt || !stmt->parent)
  80                 return 0;
  81         if (stmt->parent->type != STMT_ITERATOR)
  82                 return 0;
  83         if (stmt->parent->iterator_pre_statement != stmt)
  84                 return 0;
  85         return 1;
  86 }
  87
  88 static void match_assign(struct expression *expr)
  89 {
  90         struct range_list *rl;
  91         struct symbol *type;
  92
  93         if (expr->op != '=')
  94                 return;
  95         if (is_fake_call(expr->right))
  96                 return;
  97         if (in_iterator_pre_statement())
  98                 return;
  99
 100         get_real_absolute_rl(expr->right, &rl);
 101
 102         type = get_type(expr->left);
 103         if (!type)
 104                 return;
 105
 106         rl = cast_rl(type, rl);
 107         if (is_whole_rl(rl) && !get_state_expr(my_id, expr->left))
 108                 return;
 109
 110         set_state_expr(my_id, expr->left, alloc_estate_rl(clone_rl(rl)));
 111 }
 112
 113 struct smatch_state *get_real_absolute_state(struct expression *expr)
 114 {
 115         return get_state_expr(my_id, expr);
 116 }
 117
 118 struct smatch_state *get_real_absolute_state_var_sym(const char *name, struct symbol *sym)
 119 {
 120         return get_state(my_id, name, sym);
 121 }
 122
 123 void register_real_absolute(int id)
 124 {
 125         my_id = id;
 126
 127         add_pre_merge_hook(my_id, &pre_merge_hook);
 128         add_unmatched_state_hook(my_id, &empty_state);
 129         add_merge_hook(my_id, &merge_estates);
 130         add_modification_hook(my_id, &reset);
 131
 132         add_hook(&match_assign, ASSIGNMENT_HOOK);
 133 }
 134