1 /*
2  * Copyright (C) 2010 Dan Carpenter.
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 #include <stdlib.h>
19 #include "parse.h"
20 #include "smatch.h"
21 #include "smatch_slist.h"
22 #include "smatch_extra.h"
23 
24 /*
25  * This check has two smatch IDs.
26  * my_used_id - keeps a record of array offsets that have been used.
27  *              If the code checks that they are within bounds later on,
28  *              we complain about using an array offset before checking
29  *              that it is within bounds.
30  */
31 static int my_used_id;
32 
33 static void delete(struct sm_state *sm, struct expression *mod_expr)
34 {
35 	set_state(my_used_id, sm->name, sm->sym, &undefined);
36 }
37 
38 static int get_the_max(struct expression *expr, sval_t *sval)
39 {
40 	struct range_list *rl;
41 
42 	if (get_hard_max(expr, sval))
43 		return 1;
44 	if (!option_spammy)
45 		return 0;
46 	if (get_fuzzy_max(expr, sval))
47 		return 1;
48 	if (get_user_rl(expr, &rl)) {
49 		*sval = rl_max(rl);
50 		return 1;
51 	}
52 	return 0;
53 }
54 
55 static void array_check(struct expression *expr)
56 {
57 	struct expression *array_expr;
58 	int array_size;
59 	struct expression *offset;
60 	sval_t max;
61 
62 	expr = strip_expr(expr);
63 	if (!is_array(expr))
64 		return;
65 
66 	array_expr = get_array_base(expr);
67 	array_size = get_array_size(array_expr);
68 	if (!array_size || array_size == 1)
69 		return;
70 
71 	offset = get_array_offset(expr);
72 	if (!get_the_max(offset, &max)) {
73 		if (getting_address())
74 			return;
75 		if (is_capped(offset))
76 			return;
77 		set_state_expr(my_used_id, offset, alloc_state_num(array_size));
78 	}
79 }
80 
81 static void match_condition(struct expression *expr)
82 {
83 	int left;
84 	sval_t sval;
85 	struct state_list *slist;
86 	struct sm_state *tmp;
87 	int boundary;
88 
89 	if (!expr || expr->type != EXPR_COMPARE)
90 		return;
91 	if (get_macro_name(expr->pos))
92 		return;
93 	if (get_implied_value(expr->left, &sval))
94 		left = 1;
95 	else if (get_implied_value(expr->right, &sval))
96 		left = 0;
97 	else
98 		return;
99 
100 	if (left)
101 		slist = get_possible_states_expr(my_used_id, expr->right);
102 	else
103 		slist = get_possible_states_expr(my_used_id, expr->left);
104 	if (!slist)
105 		return;
106 	FOR_EACH_PTR(slist, tmp) {
107 		if (tmp->state == &merged || tmp->state == &undefined)
108 			continue;
109 		boundary = PTR_INT(tmp->state->data);
110 		boundary -= sval.value;
111 		if (boundary < 1 && boundary > -1) {
112 			char *name;
113 
114 			name = expr_to_var(left ? expr->right : expr->left);
115 			sm_error("testing array offset '%s' after use.", name);
116 			return;
117 		}
118 	} END_FOR_EACH_PTR(tmp);
119 }
120 
121 void check_testing_index_after_use(int id)
122 {
123 	my_used_id = id;
124 	add_hook(&array_check, OP_HOOK);
125 	add_hook(&match_condition, CONDITION_HOOK);
126 	add_modification_hook(my_used_id, &delete);
127 }
128