1 /* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
2 /*
3 * Test interface for Jitter RNG.
4 *
5 * Copyright (C) 2023, Stephan Mueller <smueller@chronox.de>
6 */
7
8 #include <linux/debugfs.h>
9 #include <linux/module.h>
10 #include <linux/uaccess.h>
11
12 #include "jitterentropy.h"
13
14 #define JENT_TEST_RINGBUFFER_SIZE (1<<10)
15 #define JENT_TEST_RINGBUFFER_MASK (JENT_TEST_RINGBUFFER_SIZE - 1)
16
17 struct jent_testing {
18 u32 jent_testing_rb[JENT_TEST_RINGBUFFER_SIZE];
19 u32 rb_reader;
20 atomic_t rb_writer;
21 atomic_t jent_testing_enabled;
22 spinlock_t lock;
23 wait_queue_head_t read_wait;
24 };
25
26 static struct dentry *jent_raw_debugfs_root = NULL;
27
28 /*************************** Generic Data Handling ****************************/
29
30 /*
31 * boot variable:
32 * 0 ==> No boot test, gathering of runtime data allowed
33 * 1 ==> Boot test enabled and ready for collecting data, gathering runtime
34 * data is disabled
35 * 2 ==> Boot test completed and disabled, gathering of runtime data is
36 * disabled
37 */
38
39 static void jent_testing_reset(struct jent_testing *data)
40 {
41 unsigned long flags;
42
43 spin_lock_irqsave(&data->lock, flags);
44 data->rb_reader = 0;
45 atomic_set(&data->rb_writer, 0);
46 spin_unlock_irqrestore(&data->lock, flags);
47 }
48
49 static void jent_testing_data_init(struct jent_testing *data, u32 boot)
50 {
51 /*
52 * The boot time testing implies we have a running test. If the
53 * caller wants to clear it, he has to unset the boot_test flag
54 * at runtime via sysfs to enable regular runtime testing
55 */
56 if (boot)
57 return;
58
59 jent_testing_reset(data);
60 atomic_set(&data->jent_testing_enabled, 1);
61 pr_warn("Enabling data collection\n");
62 }
63
64 static void jent_testing_fini(struct jent_testing *data, u32 boot)
65 {
66 /* If we have boot data, we do not reset yet to allow data to be read */
67 if (boot)
68 return;
69
70 atomic_set(&data->jent_testing_enabled, 0);
71 jent_testing_reset(data);
72 pr_warn("Disabling data collection\n");
73 }
74
75 static bool jent_testing_store(struct jent_testing *data, u32 value,
76 u32 *boot)
77 {
78 unsigned long flags;
79
80 if (!atomic_read(&data->jent_testing_enabled) && (*boot != 1))
81 return false;
82
83 spin_lock_irqsave(&data->lock, flags);
84
85 /*
86 * Disable entropy testing for boot time testing after ring buffer
87 * is filled.
88 */
89 if (*boot) {
90 if (((u32)atomic_read(&data->rb_writer)) >
91 JENT_TEST_RINGBUFFER_SIZE) {
92 *boot = 2;
93 pr_warn_once("One time data collection test disabled\n");
94 spin_unlock_irqrestore(&data->lock, flags);
95 return false;
96 }
97
98 if (atomic_read(&data->rb_writer) == 1)
99 pr_warn("One time data collection test enabled\n");
100 }
101
102 data->jent_testing_rb[((u32)atomic_read(&data->rb_writer)) &
103 JENT_TEST_RINGBUFFER_MASK] = value;
104 atomic_inc(&data->rb_writer);
105
106 spin_unlock_irqrestore(&data->lock, flags);
107
108 if (wq_has_sleeper(&data->read_wait))
109 wake_up_interruptible(&data->read_wait);
110
111 return true;
112 }
113
114 static bool jent_testing_have_data(struct jent_testing *data)
115 {
116 return ((((u32)atomic_read(&data->rb_writer)) &
117 JENT_TEST_RINGBUFFER_MASK) !=
118 (data->rb_reader & JENT_TEST_RINGBUFFER_MASK));
119 }
120
121 static int jent_testing_reader(struct jent_testing *data, u32 *boot,
122 u8 *outbuf, u32 outbuflen)
123 {
124 unsigned long flags;
125 int collected_data = 0;
126
127 jent_testing_data_init(data, *boot);
128
129 while (outbuflen) {
130 u32 writer = (u32)atomic_read(&data->rb_writer);
131
132 spin_lock_irqsave(&data->lock, flags);
133
134 /* We have no data or reached the writer. */
135 if (!writer || (writer == data->rb_reader)) {
136
137 spin_unlock_irqrestore(&data->lock, flags);
138
139 /*
140 * Now we gathered all boot data, enable regular data
141 * collection.
142 */
143 if (*boot) {
144 *boot = 0;
145 goto out;
146 }
147
148 wait_event_interruptible(data->read_wait,
149 jent_testing_have_data(data));
150 if (signal_pending(current)) {
151 collected_data = -ERESTARTSYS;
152 goto out;
153 }
154
155 continue;
156 }
157
158 /* We copy out word-wise */
159 if (outbuflen < sizeof(u32)) {
160 spin_unlock_irqrestore(&data->lock, flags);
161 goto out;
162 }
163
164 memcpy(outbuf, &data->jent_testing_rb[data->rb_reader],
165 sizeof(u32));
166 data->rb_reader++;
167
168 spin_unlock_irqrestore(&data->lock, flags);
169
170 outbuf += sizeof(u32);
171 outbuflen -= sizeof(u32);
172 collected_data += sizeof(u32);
173 }
174
175 out:
176 jent_testing_fini(data, *boot);
177 return collected_data;
178 }
179
180 static int jent_testing_extract_user(struct file *file, char __user *buf,
181 size_t nbytes, loff_t *ppos,
182 int (*reader)(u8 *outbuf, u32 outbuflen))
183 {
184 u8 *tmp, *tmp_aligned;
185 int ret = 0, large_request = (nbytes > 256);
186
187 if (!nbytes)
188 return 0;
189
190 /*
191 * The intention of this interface is for collecting at least
192 * 1000 samples due to the SP800-90B requirements. So, we make no
193 * effort in avoiding allocating more memory that actually needed
194 * by the user. Hence, we allocate sufficient memory to always hold
195 * that amount of data.
196 */
197 tmp = kmalloc(JENT_TEST_RINGBUFFER_SIZE + sizeof(u32), GFP_KERNEL);
198 if (!tmp)
199 return -ENOMEM;
200
201 tmp_aligned = PTR_ALIGN(tmp, sizeof(u32));
202
203 while (nbytes) {
204 int i;
205
206 if (large_request && need_resched()) {
207 if (signal_pending(current)) {
208 if (ret == 0)
209 ret = -ERESTARTSYS;
210 break;
211 }
212 schedule();
213 }
214
215 i = min_t(int, nbytes, JENT_TEST_RINGBUFFER_SIZE);
216 i = reader(tmp_aligned, i);
217 if (i <= 0) {
218 if (i < 0)
219 ret = i;
220 break;
221 }
222 if (copy_to_user(buf, tmp_aligned, i)) {
223 ret = -EFAULT;
224 break;
225 }
226
227 nbytes -= i;
228 buf += i;
229 ret += i;
230 }
231
232 kfree_sensitive(tmp);
233
234 if (ret > 0)
235 *ppos += ret;
236
237 return ret;
238 }
239
240 /************** Raw High-Resolution Timer Entropy Data Handling **************/
241
242 static u32 boot_raw_hires_test = 0;
243 module_param(boot_raw_hires_test, uint, 0644);
244 MODULE_PARM_DESC(boot_raw_hires_test,
245 "Enable gathering boot time high resolution timer entropy of the first Jitter RNG entropy events");
246
247 static struct jent_testing jent_raw_hires = {
248 .rb_reader = 0,
249 .rb_writer = ATOMIC_INIT(0),
250 .lock = __SPIN_LOCK_UNLOCKED(jent_raw_hires.lock),
251 .read_wait = __WAIT_QUEUE_HEAD_INITIALIZER(jent_raw_hires.read_wait)
252 };
253
254 int jent_raw_hires_entropy_store(__u32 value)
255 {
256 return jent_testing_store(&jent_raw_hires, value, &boot_raw_hires_test);
257 }
258 EXPORT_SYMBOL(jent_raw_hires_entropy_store);
259
260 static int jent_raw_hires_entropy_reader(u8 *outbuf, u32 outbuflen)
261 {
262 return jent_testing_reader(&jent_raw_hires, &boot_raw_hires_test,
263 outbuf, outbuflen);
264 }
265
266 static ssize_t jent_raw_hires_read(struct file *file, char __user *to,
267 size_t count, loff_t *ppos)
268 {
269 return jent_testing_extract_user(file, to, count, ppos,
270 jent_raw_hires_entropy_reader);
271 }
272
273 static const struct file_operations jent_raw_hires_fops = {
274 .owner = THIS_MODULE,
275 .read = jent_raw_hires_read,
276 };
277
278 /******************************* Initialization *******************************/
279
280 void jent_testing_init(void)
281 {
282 jent_raw_debugfs_root = debugfs_create_dir(KBUILD_MODNAME, NULL);
283
284 debugfs_create_file_unsafe("jent_raw_hires", 0400,
285 jent_raw_debugfs_root, NULL,
286 &jent_raw_hires_fops);
287 }
288 EXPORT_SYMBOL(jent_testing_init);
289
290 void jent_testing_exit(void)
291 {
292 debugfs_remove_recursive(jent_raw_debugfs_root);
293 }
294 EXPORT_SYMBOL(jent_testing_exit);
295
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