1 /*
2 * Copyright (C) 2018 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 #include "smatch_extra.h"
20
21 static int my_id;
22 extern int second_half_id;
23 extern void set_spectre_first_half(struct expression *expr);
24
25 static int suppress_multiple = 1;
26
27 static int is_write(struct expression *expr)
28 {
29 return 0;
30 }
31
32 static int is_read(struct expression *expr)
33 {
34 struct expression *parent, *last_parent;
35 struct statement *stmt;
36
37 if (is_write(expr))
38 return 0;
39
40 last_parent = expr;
41 while ((parent = expr_get_parent_expr(expr))){
42
43 last_parent = parent;
44
45 /* If we pass a value as a parameter that's a read, probably? */
46 // if (parent->type == EXPR_CALL)
47 // return 1;
48
49 if (parent->type == EXPR_ASSIGNMENT) {
50 if (parent->right == expr)
51 return 1;
52 if (parent->left == expr)
53 return 0;
54 }
55 expr = parent;
56 }
57
58 stmt = expr_get_parent_stmt(last_parent);
59 if (stmt && stmt->type == STMT_RETURN)
60 return 1;
61
62 return 0;
63 }
64
65 static int is_harmless(struct expression *expr)
66 {
67 struct expression *tmp, *parent;
68 struct statement *stmt;
69 int count = 0;
70
71 parent = expr;
72 while ((tmp = expr_get_parent_expr(parent))) {
73 if (tmp->type == EXPR_ASSIGNMENT || tmp->type == EXPR_CALL)
74 return 0;
75 parent = tmp;
76 if (count++ > 4)
77 break;
78 }
79
80 stmt = expr_get_parent_stmt(parent);
81 if (!stmt)
82 return 0;
83 if (stmt->type == STMT_IF && stmt->if_conditional == parent)
84 return 1;
85 if (stmt->type == STMT_ITERATOR &&
86 (stmt->iterator_pre_condition == parent ||
87 stmt->iterator_post_condition == parent))
88 return 1;
89
90 return 0;
91 }
92
93 static unsigned long long get_max_by_type(struct expression *expr)
94 {
95 struct symbol *type;
96 int cnt = 0;
97 sval_t max;
98
99 max.type = &ullong_ctype;
100 max.uvalue = -1ULL;
101
102 while (true) {
103 expr = strip_parens(expr);
104 type = get_type(expr);
105 if (type && sval_type_max(type).uvalue < max.uvalue)
106 max = sval_type_max(type);
107 if (expr->type == EXPR_PREOP) {
108 expr = expr->unop;
109 } else if (expr->type == EXPR_BINOP) {
110 if (expr->op == '%' || expr->op == '&')
111 expr = expr->right;
112 else
113 return max.uvalue;
114 } else {
115 expr = get_assigned_expr(expr);
116 if (!expr)
117 return max.uvalue;
118 }
119 if (cnt++ > 5)
120 return max.uvalue;
121 }
122
123 return max.uvalue;
124 }
125
126 static unsigned long long get_mask(struct expression *expr)
127 {
128 struct expression *tmp;
129 sval_t mask;
130 int cnt = 0;
131
132 expr = strip_expr(expr);
133
134 tmp = get_assigned_expr(expr);
135 while (tmp) {
136 expr = tmp;
137 if (++cnt > 3)
138 break;
139 tmp = get_assigned_expr(expr);
140 }
141
142 if (expr->type == EXPR_BINOP && expr->op == '&') {
143 if (get_value(expr->right, &mask)) /* right is the common case */
144 return mask.uvalue;
145 if (get_value(expr->left, &mask))
146 return mask.uvalue;
147 }
148
149 return ULLONG_MAX;
150 }
151
152 static void array_check(struct expression *expr)
153 {
154 struct expression_list *conditions;
155 struct expression *array_expr, *offset;
156 unsigned long long mask;
157 int array_size;
158 char *name;
159
160 expr = strip_expr(expr);
161 if (!is_array(expr))
162 return;
163
164 if (is_impossible_path())
165 return;
166 if (is_harmless(expr))
167 return;
168
169 array_expr = get_array_base(expr);
170 if (suppress_multiple && is_ignored_expr(my_id, array_expr)) {
171 set_spectre_first_half(expr);
172 return;
173 }
174
175 offset = get_array_offset(expr);
176 if (!is_user_rl(offset))
177 return;
178 if (is_nospec(offset))
179 return;
180
181 array_size = get_array_size(array_expr);
182 if (array_size > 0 && get_max_by_type(offset) < array_size)
183 return;
184 // binfo = get_bit_info(offset);
185 // if (array_size > 0 && binfo && binfo->possible < array_size)
186 // return;
187
188 mask = get_mask(offset);
189 if (mask <= array_size)
190 return;
191
192 conditions = get_conditions(offset);
193
194 name = expr_to_str(array_expr);
195 sm_warning("potential spectre issue '%s' [%s]%s",
196 name,
197 is_read(expr) ? "r" : "w",
198 conditions ? " (local cap)" : "");
199
200 set_spectre_first_half(expr);
201 if (suppress_multiple)
202 add_ignore_expr(my_id, array_expr);
203 free_string(name);
204 }
205
206 void check_spectre(int id)
207 {
208 my_id = id;
209
210 suppress_multiple = getenv("FULL_SPECTRE") == NULL;
211
212 if (option_project != PROJ_KERNEL)
213 return;
214
215 add_hook(&array_check, OP_HOOK);
216 }