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 	sval_t sval;
93 
94 	if (expr->op != '=')
95 		return;
96 	if (is_fake_call(expr->right))
97 		return;
98 	if (in_iterator_pre_statement())
99 		return;
100 
101 	get_real_absolute_rl(expr->right, &rl);
102 
103 	type = get_type(expr->left);
104 	if (!type)
105 		return;
106 
107 	rl = cast_rl(type, rl);
108 	if (is_whole_rl(rl) && !get_state_expr(my_id, expr->left))
109 		return;
110 	/* These are handled by smatch_extra.c */
111 	if (rl_to_sval(rl, &sval) && !get_state_expr(my_id, expr->left))
112 		return;
113 
114 	set_state_expr(my_id, expr->left, alloc_estate_rl(clone_rl(rl)));
115 }
116 
117 struct smatch_state *get_real_absolute_state(struct expression *expr)
118 {
119 	return get_state_expr(my_id, expr);
120 }
121 
122 struct smatch_state *get_real_absolute_state_var_sym(const char *name, struct symbol *sym)
123 {
124 	return get_state(my_id, name, sym);
125 }
126 
127 void register_real_absolute(int id)
128 {
129 	my_id = id;
130 
131 	add_pre_merge_hook(my_id, &pre_merge_hook);
132 	add_unmatched_state_hook(my_id, &empty_state);
133 	add_merge_hook(my_id, &merge_estates);
134 	add_modification_hook(my_id, &reset);
135 
136 	add_hook(&match_assign, ASSIGNMENT_HOOK);
137 }
138 
139