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
17struct 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
26static 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
39static 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
49static 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
64static 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
75static 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
114static 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
121static 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
175out:
176	jent_testing_fini(data, *boot);
177	return collected_data;
178}
179
180static 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
242static u32 boot_raw_hires_test = 0;
243module_param(boot_raw_hires_test, uint, 0644);
244MODULE_PARM_DESC(boot_raw_hires_test,
245		 "Enable gathering boot time high resolution timer entropy of the first Jitter RNG entropy events");
246
247static 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
254int jent_raw_hires_entropy_store(__u32 value)
255{
256	return jent_testing_store(&jent_raw_hires, value, &boot_raw_hires_test);
257}
258EXPORT_SYMBOL(jent_raw_hires_entropy_store);
259
260static 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
266static 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
273static const struct file_operations jent_raw_hires_fops = {
274	.owner = THIS_MODULE,
275	.read = jent_raw_hires_read,
276};
277
278/******************************* Initialization *******************************/
279
280void 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}
288EXPORT_SYMBOL(jent_testing_init);
289
290void jent_testing_exit(void)
291{
292	debugfs_remove_recursive(jent_raw_debugfs_root);
293}
294EXPORT_SYMBOL(jent_testing_exit);
295