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 void set_real_absolute(struct expression *expr, struct smatch_state *state)
  40 {
  41         set_state_expr(my_id, expr, clone_estate(state));
  42 }
  43
  44 static void extra_mod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
  45 {
  46         struct smatch_state *abs;
  47         struct range_list *rl;
  48
  49         abs = get_state(my_id, name, sym);
  50         if (!abs || !estate_rl(abs))
  51                 return;
  52         rl = rl_intersection(estate_rl(abs), estate_rl(state));
  53         set_state(my_id, name, sym, alloc_estate_rl(clone_rl(rl)));
  54 }
  55
  56 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  57 {
  58         struct smatch_state *extra;
  59         struct range_list *rl;
  60
  61         extra = get_state(SMATCH_EXTRA, cur->name, cur->sym);
  62         if (!extra || !estate_rl(extra))
  63                 return;
  64         if (!estate_rl(cur->state)) {
  65                 set_state(my_id, cur->name, cur->sym, clone_estate(extra));
  66                 return;
  67         }
  68         rl = rl_intersection(estate_rl(cur->state), estate_rl(extra));
  69         set_state(my_id, cur->name, cur->sym, alloc_estate_rl(clone_rl(rl)));
  70 }
  71
  72 static struct smatch_state *empty_state(struct sm_state *sm)
  73 {
  74         return alloc_estate_empty();
  75 }
  76
  77 static int in_iterator_pre_statement(void)
  78 {
  79         struct statement *stmt;
  80
  81         /*
  82          * we can't use __cur_stmt because that isn't set for
  83          * iterator_pre_statement.  Kind of a mess.
  84          *
  85          */
  86
  87         stmt = last_ptr_list((struct ptr_list *)big_statement_stack);
  88
  89         if (!stmt || !stmt->parent)
  90                 return 0;
  91         if (stmt->parent->type != STMT_ITERATOR)
  92                 return 0;
  93         if (stmt->parent->iterator_pre_statement != stmt)
  94                 return 0;
  95         return 1;
  96 }
  97
  98 static bool get_absolute(struct expression *expr, struct range_list **rl)
  99 {
 100         struct smatch_state *state;
 101
 102         if (__in_fake_struct_assign) {
 103                 state = get_state_expr(my_id, expr);
 104                 if (!state)
 105                         return false;
 106                 *rl = estate_rl(state);
 107                 return true;
 108         }
 109         get_real_absolute_rl(expr, rl);
 110         return true;
 111 }
 112
 113 static void match_assign(struct expression *expr)
 114 {
 115         struct expression *right;
 116         struct range_list *rl;
 117         struct symbol *type;
 118         sval_t sval;
 119
 120         if (expr->op != '=')
 121                 goto clear;
 122         right = strip_expr(expr->right);
 123         if (right->type == EXPR_CALL)
 124                 goto clear;
 125         if (in_iterator_pre_statement())
 126                 goto clear;
 127
 128         if (!get_absolute(expr->right, &rl))
 129                 goto clear;
 130
 131         type = get_type(expr->left);
 132         if (!type)
 133                 goto clear;
 134         if (type->type != SYM_BASETYPE && type->type != SYM_ENUM)
 135                 goto clear;
 136
 137         rl = cast_rl(type, rl);
 138         if (is_whole_rl(rl) && !get_state_expr(my_id, expr->left))
 139                 goto clear;
 140         /* These are handled by smatch_extra.c */
 141         if (rl_to_sval(rl, &sval) && !get_state_expr(my_id, expr->left))
 142                 goto clear;
 143
 144         set_state_expr(my_id, expr->left, alloc_estate_rl(clone_rl(rl)));
 145         return;
 146
 147 clear:
 148         if (get_state_expr(my_id, expr->left))
 149                 set_state_expr(my_id, expr->left, alloc_estate_whole(get_type(expr->left)));
 150 }
 151
 152 struct smatch_state *get_real_absolute_state(struct expression *expr)
 153 {
 154         return get_state_expr(my_id, expr);
 155 }
 156
 157 struct smatch_state *get_real_absolute_state_var_sym(const char *name, struct symbol *sym)
 158 {
 159         return __get_state(my_id, name, sym);
 160 }
 161
 162 void register_real_absolute(int id)
 163 {
 164         my_id = id;
 165
 166         set_dynamic_states(my_id);
 167         add_pre_merge_hook(my_id, &pre_merge_hook);
 168         add_unmatched_state_hook(my_id, &empty_state);
 169         add_merge_hook(my_id, &merge_estates);
 170         add_extra_mod_hook(&extra_mod_hook);
 171
 172         add_hook(&match_assign, ASSIGNMENT_HOOK);
 173 }
 174