1/*
2 * Copyright (C) 2014 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#include "smatch.h"
19
20static int my_id;
21
22static void match_binop(struct expression *expr)
23{
24	struct symbol *type;
25	sval_t bits;
26
27	if (expr->op != SPECIAL_RIGHTSHIFT)
28		return;
29
30	if (!get_implied_value(expr->right, &bits))
31		return;
32
33	type = get_type(expr->left);
34	if (!type)
35		return;
36	if (type_bits(type) == -1 || type_bits(type) > bits.value)
37		return;
38	if (is_ignored_expr(my_id, expr))
39		return;
40	sm_warning("right shifting more than type allows %d vs %lld", type_bits(type), bits.value);
41}
42
43static void match_binop2(struct expression *expr)
44{
45	struct expression *left;
46	struct expression *tmp;
47	sval_t mask, shift;
48
49	if (expr->op != SPECIAL_RIGHTSHIFT)
50		return;
51
52	left = strip_expr(expr->left);
53	tmp = get_assigned_expr(left);
54	if (tmp)
55		left = tmp;
56	if (left->type != EXPR_BINOP || left->op != '&')
57		return;
58
59	if (!get_implied_value(expr->right, &shift))
60		return;
61	if (!get_implied_value(left->right, &mask))
62		return;
63
64	if (mask.uvalue >> shift.uvalue)
65		return;
66
67	sm_warning("mask and shift to zero");
68}
69
70static void match_assign(struct expression *expr)
71{
72	struct symbol *type;
73	sval_t bits;
74
75	if (expr->op != SPECIAL_SHR_ASSIGN)
76		return;
77
78	if (!get_implied_value(expr->right, &bits))
79		return;
80	type = get_type(expr->left);
81	if (!type)
82		return;
83	if (type_bits(type) > bits.value)
84		return;
85	sm_warning("right shift assign to zero");
86}
87
88void check_shift_to_zero(int id)
89{
90	my_id = id;
91
92	add_hook(&match_binop, BINOP_HOOK);
93	add_hook(&match_binop2, BINOP_HOOK);
94
95	add_hook(&match_assign, ASSIGNMENT_HOOK);
96
97}
98