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 extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
  40 {
  41         struct smatch_state *abs;
  42         struct range_list *rl;
  43 
  44         abs = get_state(my_id, name, sym);
  45         if (!abs || !estate_rl(abs))
  46                 return;
  47         rl = rl_intersection(estate_rl(abs), estate_rl(state));
  48         set_state(my_id, name, sym, alloc_estate_rl(clone_rl(rl)));
  49 }
  50 
  51 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  52 {
  53         struct smatch_state *extra;
  54         struct range_list *rl;
  55 
  56         extra = get_state(SMATCH_EXTRA, cur->name, cur->sym);
  57         if (!extra || !estate_rl(extra))
  58                 return;
  59         if (!estate_rl(cur->state)) {
  60                 set_state(my_id, cur->name, cur->sym, clone_estate(extra));
  61                 return;
  62         }
  63         rl = rl_intersection(estate_rl(cur->state), estate_rl(extra));
  64         set_state(my_id, cur->name, cur->sym, alloc_estate_rl(clone_rl(rl)));
  65 }
  66 
  67 static struct smatch_state *empty_state(struct sm_state *sm)
  68 {
  69         return alloc_estate_empty();
  70 }
  71 
  72 static int in_iterator_pre_statement(void)
  73 {
  74         struct statement *stmt;
  75 
  76         /*
  77          * we can't use __cur_stmt because that isn't set for
  78          * iterator_pre_statement.  Kind of a mess.
  79          *
  80          */
  81 
  82         stmt = last_ptr_list((struct ptr_list *)big_statement_stack);
  83 
  84         if (!stmt || !stmt->parent)
  85                 return 0;
  86         if (stmt->parent->type != STMT_ITERATOR)
  87                 return 0;
  88         if (stmt->parent->iterator_pre_statement != stmt)
  89                 return 0;
  90         return 1;
  91 }
  92 
  93 static void match_assign(struct expression *expr)
  94 {
  95         struct range_list *rl;
  96         struct symbol *type;
  97         sval_t sval;
  98 
  99         if (expr->op != '=')
 100                 return;
 101         if (is_fake_call(expr->right))
 102                 return;
 103         if (in_iterator_pre_statement())
 104                 return;
 105 
 106         get_real_absolute_rl(expr->right, &rl);
 107 
 108         type = get_type(expr->left);
 109         if (!type)
 110                 return;
 111         if (type->type != SYM_PTR && type->type != SYM_BASETYPE &&
 112             type->type != SYM_ENUM)
 113                 return;
 114 
 115         rl = cast_rl(type, rl);
 116         if (is_whole_rl(rl) && !get_state_expr(my_id, expr->left))
 117                 return;
 118         /* These are handled by smatch_extra.c */
 119         if (rl_to_sval(rl, &sval) && !get_state_expr(my_id, expr->left))
 120                 return;
 121 
 122         set_state_expr(my_id, expr->left, alloc_estate_rl(clone_rl(rl)));
 123 }
 124 
 125 struct smatch_state *get_real_absolute_state(struct expression *expr)
 126 {
 127         return get_state_expr(my_id, expr);
 128 }
 129 
 130 struct smatch_state *get_real_absolute_state_var_sym(const char *name, struct symbol *sym)
 131 {
 132         return __get_state(my_id, name, sym);
 133 }
 134 
 135 void register_real_absolute(int id)
 136 {
 137         my_id = id;
 138 
 139         set_dynamic_states(my_id);
 140         add_pre_merge_hook(my_id, &pre_merge_hook);
 141         add_unmatched_state_hook(my_id, &empty_state);
 142         add_merge_hook(my_id, &merge_estates);
 143         add_extra_mod_hook(&extra_mod_hook);
 144 
 145         add_hook(&match_assign, ASSIGNMENT_HOOK);
 146 }
 147