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
20 static int my_id;
21
match_binop(struct expression * expr)22 static 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
match_binop2(struct expression * expr)43 static 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_value(expr->right, &shift))
60 return;
61 if (!get_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
match_assign(struct expression * expr)70 static 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
check_shift_to_zero(int id)88 void 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