xref: /openbmc/linux/drivers/char/tpm/xen-tpmfront.c (revision 7cffcade)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Implementation of the Xen vTPM device frontend
4  *
5  * Author:  Daniel De Graaf <dgdegra@tycho.nsa.gov>
6  */
7 #include <linux/errno.h>
8 #include <linux/err.h>
9 #include <linux/interrupt.h>
10 #include <linux/freezer.h>
11 #include <xen/xen.h>
12 #include <xen/events.h>
13 #include <xen/interface/io/tpmif.h>
14 #include <xen/grant_table.h>
15 #include <xen/xenbus.h>
16 #include <xen/page.h>
17 #include "tpm.h"
18 #include <xen/platform_pci.h>
19 
20 struct tpm_private {
21 	struct tpm_chip *chip;
22 	struct xenbus_device *dev;
23 
24 	struct vtpm_shared_page *shr;
25 
26 	unsigned int evtchn;
27 	int ring_ref;
28 	domid_t backend_id;
29 	int irq;
30 	wait_queue_head_t read_queue;
31 };
32 
33 enum status_bits {
34 	VTPM_STATUS_RUNNING  = 0x1,
35 	VTPM_STATUS_IDLE     = 0x2,
36 	VTPM_STATUS_RESULT   = 0x4,
37 	VTPM_STATUS_CANCELED = 0x8,
38 };
39 
wait_for_tpm_stat_cond(struct tpm_chip * chip,u8 mask,bool check_cancel,bool * canceled)40 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
41 					bool check_cancel, bool *canceled)
42 {
43 	u8 status = chip->ops->status(chip);
44 
45 	*canceled = false;
46 	if ((status & mask) == mask)
47 		return true;
48 	if (check_cancel && chip->ops->req_canceled(chip, status)) {
49 		*canceled = true;
50 		return true;
51 	}
52 	return false;
53 }
54 
wait_for_tpm_stat(struct tpm_chip * chip,u8 mask,unsigned long timeout,wait_queue_head_t * queue,bool check_cancel)55 static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
56 		unsigned long timeout, wait_queue_head_t *queue,
57 		bool check_cancel)
58 {
59 	unsigned long stop;
60 	long rc;
61 	u8 status;
62 	bool canceled = false;
63 
64 	/* check current status */
65 	status = chip->ops->status(chip);
66 	if ((status & mask) == mask)
67 		return 0;
68 
69 	stop = jiffies + timeout;
70 
71 	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
72 again:
73 		timeout = stop - jiffies;
74 		if ((long)timeout <= 0)
75 			return -ETIME;
76 		rc = wait_event_interruptible_timeout(*queue,
77 			wait_for_tpm_stat_cond(chip, mask, check_cancel,
78 					       &canceled),
79 			timeout);
80 		if (rc > 0) {
81 			if (canceled)
82 				return -ECANCELED;
83 			return 0;
84 		}
85 		if (rc == -ERESTARTSYS && freezing(current)) {
86 			clear_thread_flag(TIF_SIGPENDING);
87 			goto again;
88 		}
89 	} else {
90 		do {
91 			tpm_msleep(TPM_TIMEOUT);
92 			status = chip->ops->status(chip);
93 			if ((status & mask) == mask)
94 				return 0;
95 		} while (time_before(jiffies, stop));
96 	}
97 	return -ETIME;
98 }
99 
vtpm_status(struct tpm_chip * chip)100 static u8 vtpm_status(struct tpm_chip *chip)
101 {
102 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
103 	switch (priv->shr->state) {
104 	case VTPM_STATE_IDLE:
105 		return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED;
106 	case VTPM_STATE_FINISH:
107 		return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT;
108 	case VTPM_STATE_SUBMIT:
109 	case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */
110 		return VTPM_STATUS_RUNNING;
111 	default:
112 		return 0;
113 	}
114 }
115 
vtpm_req_canceled(struct tpm_chip * chip,u8 status)116 static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
117 {
118 	return status & VTPM_STATUS_CANCELED;
119 }
120 
vtpm_cancel(struct tpm_chip * chip)121 static void vtpm_cancel(struct tpm_chip *chip)
122 {
123 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
124 	priv->shr->state = VTPM_STATE_CANCEL;
125 	wmb();
126 	notify_remote_via_evtchn(priv->evtchn);
127 }
128 
shr_data_offset(struct vtpm_shared_page * shr)129 static size_t shr_data_offset(struct vtpm_shared_page *shr)
130 {
131 	return struct_size(shr, extra_pages, shr->nr_extra_pages);
132 }
133 
vtpm_send(struct tpm_chip * chip,u8 * buf,size_t count)134 static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
135 {
136 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
137 	struct vtpm_shared_page *shr = priv->shr;
138 	size_t offset = shr_data_offset(shr);
139 
140 	u32 ordinal;
141 	unsigned long duration;
142 
143 	if (offset > PAGE_SIZE)
144 		return -EINVAL;
145 
146 	if (offset + count > PAGE_SIZE)
147 		return -EINVAL;
148 
149 	/* Wait for completion of any existing command or cancellation */
150 	if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->timeout_c,
151 			&priv->read_queue, true) < 0) {
152 		vtpm_cancel(chip);
153 		return -ETIME;
154 	}
155 
156 	memcpy(offset + (u8 *)shr, buf, count);
157 	shr->length = count;
158 	barrier();
159 	shr->state = VTPM_STATE_SUBMIT;
160 	wmb();
161 	notify_remote_via_evtchn(priv->evtchn);
162 
163 	ordinal = be32_to_cpu(((struct tpm_header *)buf)->ordinal);
164 	duration = tpm_calc_ordinal_duration(chip, ordinal);
165 
166 	if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
167 			&priv->read_queue, true) < 0) {
168 		/* got a signal or timeout, try to cancel */
169 		vtpm_cancel(chip);
170 		return -ETIME;
171 	}
172 
173 	return 0;
174 }
175 
vtpm_recv(struct tpm_chip * chip,u8 * buf,size_t count)176 static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
177 {
178 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
179 	struct vtpm_shared_page *shr = priv->shr;
180 	size_t offset = shr_data_offset(shr);
181 	size_t length = shr->length;
182 
183 	if (shr->state == VTPM_STATE_IDLE)
184 		return -ECANCELED;
185 
186 	/* In theory the wait at the end of _send makes this one unnecessary */
187 	if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->timeout_c,
188 			&priv->read_queue, true) < 0) {
189 		vtpm_cancel(chip);
190 		return -ETIME;
191 	}
192 
193 	if (offset > PAGE_SIZE)
194 		return -EIO;
195 
196 	if (offset + length > PAGE_SIZE)
197 		length = PAGE_SIZE - offset;
198 
199 	if (length > count)
200 		length = count;
201 
202 	memcpy(buf, offset + (u8 *)shr, length);
203 
204 	return length;
205 }
206 
207 static const struct tpm_class_ops tpm_vtpm = {
208 	.status = vtpm_status,
209 	.recv = vtpm_recv,
210 	.send = vtpm_send,
211 	.cancel = vtpm_cancel,
212 	.req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
213 	.req_complete_val  = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
214 	.req_canceled      = vtpm_req_canceled,
215 };
216 
tpmif_interrupt(int dummy,void * dev_id)217 static irqreturn_t tpmif_interrupt(int dummy, void *dev_id)
218 {
219 	struct tpm_private *priv = dev_id;
220 
221 	switch (priv->shr->state) {
222 	case VTPM_STATE_IDLE:
223 	case VTPM_STATE_FINISH:
224 		wake_up_interruptible(&priv->read_queue);
225 		break;
226 	case VTPM_STATE_SUBMIT:
227 	case VTPM_STATE_CANCEL:
228 	default:
229 		break;
230 	}
231 	return IRQ_HANDLED;
232 }
233 
setup_chip(struct device * dev,struct tpm_private * priv)234 static int setup_chip(struct device *dev, struct tpm_private *priv)
235 {
236 	struct tpm_chip *chip;
237 
238 	chip = tpmm_chip_alloc(dev, &tpm_vtpm);
239 	if (IS_ERR(chip))
240 		return PTR_ERR(chip);
241 
242 	init_waitqueue_head(&priv->read_queue);
243 
244 	priv->chip = chip;
245 	dev_set_drvdata(&chip->dev, priv);
246 
247 	return 0;
248 }
249 
250 /* caller must clean up in case of errors */
setup_ring(struct xenbus_device * dev,struct tpm_private * priv)251 static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
252 {
253 	struct xenbus_transaction xbt;
254 	const char *message = NULL;
255 	int rv;
256 
257 	rv = xenbus_setup_ring(dev, GFP_KERNEL, (void **)&priv->shr, 1,
258 			       &priv->ring_ref);
259 	if (rv < 0)
260 		return rv;
261 
262 	rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
263 	if (rv)
264 		return rv;
265 
266 	rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
267 				       "tpmif", priv);
268 	if (rv <= 0) {
269 		xenbus_dev_fatal(dev, rv, "allocating TPM irq");
270 		return rv;
271 	}
272 	priv->irq = rv;
273 
274  again:
275 	rv = xenbus_transaction_start(&xbt);
276 	if (rv) {
277 		xenbus_dev_fatal(dev, rv, "starting transaction");
278 		return rv;
279 	}
280 
281 	rv = xenbus_printf(xbt, dev->nodename,
282 			"ring-ref", "%u", priv->ring_ref);
283 	if (rv) {
284 		message = "writing ring-ref";
285 		goto abort_transaction;
286 	}
287 
288 	rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
289 			priv->evtchn);
290 	if (rv) {
291 		message = "writing event-channel";
292 		goto abort_transaction;
293 	}
294 
295 	rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
296 	if (rv) {
297 		message = "writing feature-protocol-v2";
298 		goto abort_transaction;
299 	}
300 
301 	rv = xenbus_transaction_end(xbt, 0);
302 	if (rv == -EAGAIN)
303 		goto again;
304 	if (rv) {
305 		xenbus_dev_fatal(dev, rv, "completing transaction");
306 		return rv;
307 	}
308 
309 	xenbus_switch_state(dev, XenbusStateInitialised);
310 
311 	return 0;
312 
313  abort_transaction:
314 	xenbus_transaction_end(xbt, 1);
315 	if (message)
316 		xenbus_dev_error(dev, rv, "%s", message);
317 
318 	return rv;
319 }
320 
ring_free(struct tpm_private * priv)321 static void ring_free(struct tpm_private *priv)
322 {
323 	if (!priv)
324 		return;
325 
326 	xenbus_teardown_ring((void **)&priv->shr, 1, &priv->ring_ref);
327 
328 	if (priv->irq)
329 		unbind_from_irqhandler(priv->irq, priv);
330 
331 	kfree(priv);
332 }
333 
tpmfront_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)334 static int tpmfront_probe(struct xenbus_device *dev,
335 		const struct xenbus_device_id *id)
336 {
337 	struct tpm_private *priv;
338 	int rv;
339 
340 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
341 	if (!priv) {
342 		xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
343 		return -ENOMEM;
344 	}
345 
346 	rv = setup_chip(&dev->dev, priv);
347 	if (rv) {
348 		kfree(priv);
349 		return rv;
350 	}
351 
352 	rv = setup_ring(dev, priv);
353 	if (rv) {
354 		ring_free(priv);
355 		return rv;
356 	}
357 
358 	tpm_get_timeouts(priv->chip);
359 
360 	return tpm_chip_register(priv->chip);
361 }
362 
tpmfront_remove(struct xenbus_device * dev)363 static void tpmfront_remove(struct xenbus_device *dev)
364 {
365 	struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
366 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
367 	tpm_chip_unregister(chip);
368 	ring_free(priv);
369 	dev_set_drvdata(&chip->dev, NULL);
370 }
371 
tpmfront_resume(struct xenbus_device * dev)372 static int tpmfront_resume(struct xenbus_device *dev)
373 {
374 	/* A suspend/resume/migrate will interrupt a vTPM anyway */
375 	tpmfront_remove(dev);
376 	return tpmfront_probe(dev, NULL);
377 }
378 
backend_changed(struct xenbus_device * dev,enum xenbus_state backend_state)379 static void backend_changed(struct xenbus_device *dev,
380 		enum xenbus_state backend_state)
381 {
382 	switch (backend_state) {
383 	case XenbusStateInitialised:
384 	case XenbusStateConnected:
385 		if (dev->state == XenbusStateConnected)
386 			break;
387 
388 		if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
389 					  0)) {
390 			xenbus_dev_fatal(dev, -EINVAL,
391 					"vTPM protocol 2 required");
392 			return;
393 		}
394 		xenbus_switch_state(dev, XenbusStateConnected);
395 		break;
396 
397 	case XenbusStateClosing:
398 	case XenbusStateClosed:
399 		device_unregister(&dev->dev);
400 		xenbus_frontend_closed(dev);
401 		break;
402 	default:
403 		break;
404 	}
405 }
406 
407 static const struct xenbus_device_id tpmfront_ids[] = {
408 	{ "vtpm" },
409 	{ "" }
410 };
411 MODULE_ALIAS("xen:vtpm");
412 
413 static struct xenbus_driver tpmfront_driver = {
414 	.ids = tpmfront_ids,
415 	.probe = tpmfront_probe,
416 	.remove = tpmfront_remove,
417 	.resume = tpmfront_resume,
418 	.otherend_changed = backend_changed,
419 };
420 
xen_tpmfront_init(void)421 static int __init xen_tpmfront_init(void)
422 {
423 	if (!xen_domain())
424 		return -ENODEV;
425 
426 	if (!xen_has_pv_devices())
427 		return -ENODEV;
428 
429 	return xenbus_register_frontend(&tpmfront_driver);
430 }
431 module_init(xen_tpmfront_init);
432 
xen_tpmfront_exit(void)433 static void __exit xen_tpmfront_exit(void)
434 {
435 	xenbus_unregister_driver(&tpmfront_driver);
436 }
437 module_exit(xen_tpmfront_exit);
438 
439 MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
440 MODULE_DESCRIPTION("Xen vTPM Driver");
441 MODULE_LICENSE("GPL");
442