1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Turris Mox rWTM firmware driver
4  *
5  * Copyright (C) 2019 Marek Behun <marek.behun@nic.cz>
6  */
7 
8 #include <linux/armada-37xx-rwtm-mailbox.h>
9 #include <linux/completion.h>
10 #include <linux/debugfs.h>
11 #include <linux/dma-mapping.h>
12 #include <linux/hw_random.h>
13 #include <linux/mailbox_client.h>
14 #include <linux/module.h>
15 #include <linux/mutex.h>
16 #include <linux/of.h>
17 #include <linux/platform_device.h>
18 #include <linux/slab.h>
19 
20 #define DRIVER_NAME		"turris-mox-rwtm"
21 
22 /*
23  * The macros and constants below come from Turris Mox's rWTM firmware code.
24  * This firmware is open source and it's sources can be found at
25  * https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi.
26  */
27 
28 #define MBOX_STS_SUCCESS	(0 << 30)
29 #define MBOX_STS_FAIL		(1 << 30)
30 #define MBOX_STS_BADCMD		(2 << 30)
31 #define MBOX_STS_ERROR(s)	((s) & (3 << 30))
32 #define MBOX_STS_VALUE(s)	(((s) >> 10) & 0xfffff)
33 #define MBOX_STS_CMD(s)		((s) & 0x3ff)
34 
35 enum mbox_cmd {
36 	MBOX_CMD_GET_RANDOM	= 1,
37 	MBOX_CMD_BOARD_INFO	= 2,
38 	MBOX_CMD_ECDSA_PUB_KEY	= 3,
39 	MBOX_CMD_HASH		= 4,
40 	MBOX_CMD_SIGN		= 5,
41 	MBOX_CMD_VERIFY		= 6,
42 
43 	MBOX_CMD_OTP_READ	= 7,
44 	MBOX_CMD_OTP_WRITE	= 8,
45 };
46 
47 struct mox_kobject;
48 
49 struct mox_rwtm {
50 	struct device *dev;
51 	struct mbox_client mbox_client;
52 	struct mbox_chan *mbox;
53 	struct mox_kobject *kobj;
54 	struct hwrng hwrng;
55 
56 	struct armada_37xx_rwtm_rx_msg reply;
57 
58 	void *buf;
59 	dma_addr_t buf_phys;
60 
61 	struct mutex busy;
62 	struct completion cmd_done;
63 
64 	/* board information */
65 	int has_board_info;
66 	u64 serial_number;
67 	int board_version, ram_size;
68 	u8 mac_address1[6], mac_address2[6];
69 
70 	/* public key burned in eFuse */
71 	int has_pubkey;
72 	u8 pubkey[135];
73 
74 #ifdef CONFIG_DEBUG_FS
75 	/*
76 	 * Signature process. This is currently done via debugfs, because it
77 	 * does not conform to the sysfs standard "one file per attribute".
78 	 * It should be rewritten via crypto API once akcipher API is available
79 	 * from userspace.
80 	 */
81 	struct dentry *debugfs_root;
82 	u32 last_sig[34];
83 	int last_sig_done;
84 #endif
85 };
86 
87 struct mox_kobject {
88 	struct kobject kobj;
89 	struct mox_rwtm *rwtm;
90 };
91 
92 static inline struct kobject *rwtm_to_kobj(struct mox_rwtm *rwtm)
93 {
94 	return &rwtm->kobj->kobj;
95 }
96 
97 static inline struct mox_rwtm *to_rwtm(struct kobject *kobj)
98 {
99 	return container_of(kobj, struct mox_kobject, kobj)->rwtm;
100 }
101 
102 static void mox_kobj_release(struct kobject *kobj)
103 {
104 	kfree(to_rwtm(kobj)->kobj);
105 }
106 
107 static struct kobj_type mox_kobj_ktype = {
108 	.release	= mox_kobj_release,
109 	.sysfs_ops	= &kobj_sysfs_ops,
110 };
111 
112 static int mox_kobj_create(struct mox_rwtm *rwtm)
113 {
114 	rwtm->kobj = kzalloc(sizeof(*rwtm->kobj), GFP_KERNEL);
115 	if (!rwtm->kobj)
116 		return -ENOMEM;
117 
118 	kobject_init(rwtm_to_kobj(rwtm), &mox_kobj_ktype);
119 	if (kobject_add(rwtm_to_kobj(rwtm), firmware_kobj, "turris-mox-rwtm")) {
120 		kobject_put(rwtm_to_kobj(rwtm));
121 		return -ENXIO;
122 	}
123 
124 	rwtm->kobj->rwtm = rwtm;
125 
126 	return 0;
127 }
128 
129 #define MOX_ATTR_RO(name, format, cat)				\
130 static ssize_t							\
131 name##_show(struct kobject *kobj, struct kobj_attribute *a,	\
132 	    char *buf)						\
133 {								\
134 	struct mox_rwtm *rwtm = to_rwtm(kobj);	\
135 	if (!rwtm->has_##cat)					\
136 		return -ENODATA;				\
137 	return sprintf(buf, format, rwtm->name);		\
138 }								\
139 static struct kobj_attribute mox_attr_##name = __ATTR_RO(name)
140 
141 MOX_ATTR_RO(serial_number, "%016llX\n", board_info);
142 MOX_ATTR_RO(board_version, "%i\n", board_info);
143 MOX_ATTR_RO(ram_size, "%i\n", board_info);
144 MOX_ATTR_RO(mac_address1, "%pM\n", board_info);
145 MOX_ATTR_RO(mac_address2, "%pM\n", board_info);
146 MOX_ATTR_RO(pubkey, "%s\n", pubkey);
147 
148 static int mox_get_status(enum mbox_cmd cmd, u32 retval)
149 {
150 	if (MBOX_STS_CMD(retval) != cmd ||
151 	    MBOX_STS_ERROR(retval) != MBOX_STS_SUCCESS)
152 		return -EIO;
153 	else if (MBOX_STS_ERROR(retval) == MBOX_STS_FAIL)
154 		return -(int)MBOX_STS_VALUE(retval);
155 	else
156 		return MBOX_STS_VALUE(retval);
157 }
158 
159 static const struct attribute *mox_rwtm_attrs[] = {
160 	&mox_attr_serial_number.attr,
161 	&mox_attr_board_version.attr,
162 	&mox_attr_ram_size.attr,
163 	&mox_attr_mac_address1.attr,
164 	&mox_attr_mac_address2.attr,
165 	&mox_attr_pubkey.attr,
166 	NULL
167 };
168 
169 static void mox_rwtm_rx_callback(struct mbox_client *cl, void *data)
170 {
171 	struct mox_rwtm *rwtm = dev_get_drvdata(cl->dev);
172 	struct armada_37xx_rwtm_rx_msg *msg = data;
173 
174 	rwtm->reply = *msg;
175 	complete(&rwtm->cmd_done);
176 }
177 
178 static void reply_to_mac_addr(u8 *mac, u32 t1, u32 t2)
179 {
180 	mac[0] = t1 >> 8;
181 	mac[1] = t1;
182 	mac[2] = t2 >> 24;
183 	mac[3] = t2 >> 16;
184 	mac[4] = t2 >> 8;
185 	mac[5] = t2;
186 }
187 
188 static int mox_get_board_info(struct mox_rwtm *rwtm)
189 {
190 	struct armada_37xx_rwtm_tx_msg msg;
191 	struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
192 	int ret;
193 
194 	msg.command = MBOX_CMD_BOARD_INFO;
195 	ret = mbox_send_message(rwtm->mbox, &msg);
196 	if (ret < 0)
197 		return ret;
198 
199 	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
200 	if (ret < 0)
201 		return ret;
202 
203 	ret = mox_get_status(MBOX_CMD_BOARD_INFO, reply->retval);
204 	if (ret < 0 && ret != -ENODATA) {
205 		return ret;
206 	} else if (ret == -ENODATA) {
207 		dev_warn(rwtm->dev,
208 			 "Board does not have manufacturing information burned!\n");
209 	} else {
210 		rwtm->serial_number = reply->status[1];
211 		rwtm->serial_number <<= 32;
212 		rwtm->serial_number |= reply->status[0];
213 		rwtm->board_version = reply->status[2];
214 		rwtm->ram_size = reply->status[3];
215 		reply_to_mac_addr(rwtm->mac_address1, reply->status[4],
216 				  reply->status[5]);
217 		reply_to_mac_addr(rwtm->mac_address2, reply->status[6],
218 				  reply->status[7]);
219 		rwtm->has_board_info = 1;
220 
221 		pr_info("Turris Mox serial number %016llX\n",
222 			rwtm->serial_number);
223 		pr_info("           board version %i\n", rwtm->board_version);
224 		pr_info("           burned RAM size %i MiB\n", rwtm->ram_size);
225 	}
226 
227 	msg.command = MBOX_CMD_ECDSA_PUB_KEY;
228 	ret = mbox_send_message(rwtm->mbox, &msg);
229 	if (ret < 0)
230 		return ret;
231 
232 	ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
233 	if (ret < 0)
234 		return ret;
235 
236 	ret = mox_get_status(MBOX_CMD_ECDSA_PUB_KEY, reply->retval);
237 	if (ret < 0 && ret != -ENODATA) {
238 		return ret;
239 	} else if (ret == -ENODATA) {
240 		dev_warn(rwtm->dev, "Board has no public key burned!\n");
241 	} else {
242 		u32 *s = reply->status;
243 
244 		rwtm->has_pubkey = 1;
245 		sprintf(rwtm->pubkey,
246 			"%06x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x",
247 			ret, s[0], s[1], s[2], s[3], s[4], s[5], s[6], s[7],
248 			s[8], s[9], s[10], s[11], s[12], s[13], s[14], s[15]);
249 	}
250 
251 	return 0;
252 }
253 
254 static int mox_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
255 {
256 	struct mox_rwtm *rwtm = (struct mox_rwtm *) rng->priv;
257 	struct armada_37xx_rwtm_tx_msg msg;
258 	int ret;
259 
260 	if (max > 4096)
261 		max = 4096;
262 
263 	msg.command = MBOX_CMD_GET_RANDOM;
264 	msg.args[0] = 1;
265 	msg.args[1] = rwtm->buf_phys;
266 	msg.args[2] = (max + 3) & ~3;
267 
268 	if (!wait) {
269 		if (!mutex_trylock(&rwtm->busy))
270 			return -EBUSY;
271 	} else {
272 		mutex_lock(&rwtm->busy);
273 	}
274 
275 	ret = mbox_send_message(rwtm->mbox, &msg);
276 	if (ret < 0)
277 		goto unlock_mutex;
278 
279 	ret = wait_for_completion_interruptible(&rwtm->cmd_done);
280 	if (ret < 0)
281 		goto unlock_mutex;
282 
283 	ret = mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
284 	if (ret < 0)
285 		goto unlock_mutex;
286 
287 	memcpy(data, rwtm->buf, max);
288 	ret = max;
289 
290 unlock_mutex:
291 	mutex_unlock(&rwtm->busy);
292 	return ret;
293 }
294 
295 #ifdef CONFIG_DEBUG_FS
296 static int rwtm_debug_open(struct inode *inode, struct file *file)
297 {
298 	file->private_data = inode->i_private;
299 
300 	return nonseekable_open(inode, file);
301 }
302 
303 static ssize_t do_sign_read(struct file *file, char __user *buf, size_t len,
304 			    loff_t *ppos)
305 {
306 	struct mox_rwtm *rwtm = file->private_data;
307 	ssize_t ret;
308 
309 	/* only allow one read, of 136 bytes, from position 0 */
310 	if (*ppos != 0)
311 		return 0;
312 
313 	if (len < 136)
314 		return -EINVAL;
315 
316 	if (!rwtm->last_sig_done)
317 		return -ENODATA;
318 
319 	/* 2 arrays of 17 32-bit words are 136 bytes */
320 	ret = simple_read_from_buffer(buf, len, ppos, rwtm->last_sig, 136);
321 	rwtm->last_sig_done = 0;
322 
323 	return ret;
324 }
325 
326 static ssize_t do_sign_write(struct file *file, const char __user *buf,
327 			     size_t len, loff_t *ppos)
328 {
329 	struct mox_rwtm *rwtm = file->private_data;
330 	struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
331 	struct armada_37xx_rwtm_tx_msg msg;
332 	loff_t dummy = 0;
333 	ssize_t ret;
334 
335 	/* the input is a SHA-512 hash, so exactly 64 bytes have to be read */
336 	if (len != 64)
337 		return -EINVAL;
338 
339 	/* if last result is not zero user has not read that information yet */
340 	if (rwtm->last_sig_done)
341 		return -EBUSY;
342 
343 	if (!mutex_trylock(&rwtm->busy))
344 		return -EBUSY;
345 
346 	/*
347 	 * Here we have to send:
348 	 *   1. Address of the input to sign.
349 	 *      The input is an array of 17 32-bit words, the first (most
350 	 *      significat) is 0, the rest 16 words are copied from the SHA-512
351 	 *      hash given by the user and converted from BE to LE.
352 	 *   2. Address of the buffer where ECDSA signature value R shall be
353 	 *      stored by the rWTM firmware.
354 	 *   3. Address of the buffer where ECDSA signature value S shall be
355 	 *      stored by the rWTM firmware.
356 	 */
357 	memset(rwtm->buf, 0, 4);
358 	ret = simple_write_to_buffer(rwtm->buf + 4, 64, &dummy, buf, len);
359 	if (ret < 0)
360 		goto unlock_mutex;
361 	be32_to_cpu_array(rwtm->buf, rwtm->buf, 17);
362 
363 	msg.command = MBOX_CMD_SIGN;
364 	msg.args[0] = 1;
365 	msg.args[1] = rwtm->buf_phys;
366 	msg.args[2] = rwtm->buf_phys + 68;
367 	msg.args[3] = rwtm->buf_phys + 2 * 68;
368 	ret = mbox_send_message(rwtm->mbox, &msg);
369 	if (ret < 0)
370 		goto unlock_mutex;
371 
372 	ret = wait_for_completion_interruptible(&rwtm->cmd_done);
373 	if (ret < 0)
374 		goto unlock_mutex;
375 
376 	ret = MBOX_STS_VALUE(reply->retval);
377 	if (MBOX_STS_ERROR(reply->retval) != MBOX_STS_SUCCESS)
378 		goto unlock_mutex;
379 
380 	/*
381 	 * Here we read the R and S values of the ECDSA signature
382 	 * computed by the rWTM firmware and convert their words from
383 	 * LE to BE.
384 	 */
385 	memcpy(rwtm->last_sig, rwtm->buf + 68, 136);
386 	cpu_to_be32_array(rwtm->last_sig, rwtm->last_sig, 34);
387 	rwtm->last_sig_done = 1;
388 
389 	mutex_unlock(&rwtm->busy);
390 	return len;
391 unlock_mutex:
392 	mutex_unlock(&rwtm->busy);
393 	return ret;
394 }
395 
396 static const struct file_operations do_sign_fops = {
397 	.owner	= THIS_MODULE,
398 	.open	= rwtm_debug_open,
399 	.read	= do_sign_read,
400 	.write	= do_sign_write,
401 	.llseek	= no_llseek,
402 };
403 
404 static int rwtm_register_debugfs(struct mox_rwtm *rwtm)
405 {
406 	struct dentry *root, *entry;
407 
408 	root = debugfs_create_dir("turris-mox-rwtm", NULL);
409 
410 	if (IS_ERR(root))
411 		return PTR_ERR(root);
412 
413 	entry = debugfs_create_file_unsafe("do_sign", 0600, root, rwtm,
414 					   &do_sign_fops);
415 	if (IS_ERR(entry))
416 		goto err_remove;
417 
418 	rwtm->debugfs_root = root;
419 
420 	return 0;
421 err_remove:
422 	debugfs_remove_recursive(root);
423 	return PTR_ERR(entry);
424 }
425 
426 static void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
427 {
428 	debugfs_remove_recursive(rwtm->debugfs_root);
429 }
430 #else
431 static inline int rwtm_register_debugfs(struct mox_rwtm *rwtm)
432 {
433 	return 0;
434 }
435 
436 static inline void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
437 {
438 }
439 #endif
440 
441 static int turris_mox_rwtm_probe(struct platform_device *pdev)
442 {
443 	struct mox_rwtm *rwtm;
444 	struct device *dev = &pdev->dev;
445 	int ret;
446 
447 	rwtm = devm_kzalloc(dev, sizeof(*rwtm), GFP_KERNEL);
448 	if (!rwtm)
449 		return -ENOMEM;
450 
451 	rwtm->dev = dev;
452 	rwtm->buf = dmam_alloc_coherent(dev, PAGE_SIZE, &rwtm->buf_phys,
453 					GFP_KERNEL);
454 	if (!rwtm->buf)
455 		return -ENOMEM;
456 
457 	ret = mox_kobj_create(rwtm);
458 	if (ret < 0) {
459 		dev_err(dev, "Cannot create turris-mox-rwtm kobject!\n");
460 		return ret;
461 	}
462 
463 	ret = sysfs_create_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
464 	if (ret < 0) {
465 		dev_err(dev, "Cannot create sysfs files!\n");
466 		goto put_kobj;
467 	}
468 
469 	platform_set_drvdata(pdev, rwtm);
470 
471 	mutex_init(&rwtm->busy);
472 
473 	rwtm->mbox_client.dev = dev;
474 	rwtm->mbox_client.rx_callback = mox_rwtm_rx_callback;
475 
476 	rwtm->mbox = mbox_request_channel(&rwtm->mbox_client, 0);
477 	if (IS_ERR(rwtm->mbox)) {
478 		ret = PTR_ERR(rwtm->mbox);
479 		if (ret != -EPROBE_DEFER)
480 			dev_err(dev, "Cannot request mailbox channel: %i\n",
481 				ret);
482 		goto remove_files;
483 	}
484 
485 	init_completion(&rwtm->cmd_done);
486 
487 	ret = mox_get_board_info(rwtm);
488 	if (ret < 0)
489 		dev_warn(dev, "Cannot read board information: %i\n", ret);
490 
491 	rwtm->hwrng.name = DRIVER_NAME "_hwrng";
492 	rwtm->hwrng.read = mox_hwrng_read;
493 	rwtm->hwrng.priv = (unsigned long) rwtm;
494 	rwtm->hwrng.quality = 1024;
495 
496 	ret = devm_hwrng_register(dev, &rwtm->hwrng);
497 	if (ret < 0) {
498 		dev_err(dev, "Cannot register HWRNG: %i\n", ret);
499 		goto free_channel;
500 	}
501 
502 	ret = rwtm_register_debugfs(rwtm);
503 	if (ret < 0) {
504 		dev_err(dev, "Failed creating debugfs entries: %i\n", ret);
505 		goto free_channel;
506 	}
507 
508 	return 0;
509 
510 free_channel:
511 	mbox_free_channel(rwtm->mbox);
512 remove_files:
513 	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
514 put_kobj:
515 	kobject_put(rwtm_to_kobj(rwtm));
516 	return ret;
517 }
518 
519 static int turris_mox_rwtm_remove(struct platform_device *pdev)
520 {
521 	struct mox_rwtm *rwtm = platform_get_drvdata(pdev);
522 
523 	rwtm_unregister_debugfs(rwtm);
524 	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
525 	kobject_put(rwtm_to_kobj(rwtm));
526 	mbox_free_channel(rwtm->mbox);
527 
528 	return 0;
529 }
530 
531 static const struct of_device_id turris_mox_rwtm_match[] = {
532 	{ .compatible = "cznic,turris-mox-rwtm", },
533 	{ },
534 };
535 
536 MODULE_DEVICE_TABLE(of, turris_mox_rwtm_match);
537 
538 static struct platform_driver turris_mox_rwtm_driver = {
539 	.probe	= turris_mox_rwtm_probe,
540 	.remove	= turris_mox_rwtm_remove,
541 	.driver	= {
542 		.name		= DRIVER_NAME,
543 		.of_match_table	= turris_mox_rwtm_match,
544 	},
545 };
546 module_platform_driver(turris_mox_rwtm_driver);
547 
548 MODULE_LICENSE("GPL v2");
549 MODULE_DESCRIPTION("Turris Mox rWTM firmware driver");
550 MODULE_AUTHOR("Marek Behun <marek.behun@nic.cz>");
551