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
20struct 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
33enum status_bits {
34	VTPM_STATUS_RUNNING  = 0x1,
35	VTPM_STATUS_IDLE     = 0x2,
36	VTPM_STATUS_RESULT   = 0x4,
37	VTPM_STATUS_CANCELED = 0x8,
38};
39
40static 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
55static 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) {
72again:
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
100static 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
116static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
117{
118	return status & VTPM_STATUS_CANCELED;
119}
120
121static 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
129static unsigned int shr_data_offset(struct vtpm_shared_page *shr)
130{
131	return sizeof(*shr) + sizeof(u32) * shr->nr_extra_pages;
132}
133
134static 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	unsigned int 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
176static 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	unsigned int 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
207static 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
217static 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
234static 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 */
251static 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	grant_ref_t gref;
257
258	priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
259	if (!priv->shr) {
260		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
261		return -ENOMEM;
262	}
263
264	rv = xenbus_grant_ring(dev, priv->shr, 1, &gref);
265	if (rv < 0)
266		return rv;
267
268	priv->ring_ref = gref;
269
270	rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
271	if (rv)
272		return rv;
273
274	rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
275				       "tpmif", priv);
276	if (rv <= 0) {
277		xenbus_dev_fatal(dev, rv, "allocating TPM irq");
278		return rv;
279	}
280	priv->irq = rv;
281
282 again:
283	rv = xenbus_transaction_start(&xbt);
284	if (rv) {
285		xenbus_dev_fatal(dev, rv, "starting transaction");
286		return rv;
287	}
288
289	rv = xenbus_printf(xbt, dev->nodename,
290			"ring-ref", "%u", priv->ring_ref);
291	if (rv) {
292		message = "writing ring-ref";
293		goto abort_transaction;
294	}
295
296	rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
297			priv->evtchn);
298	if (rv) {
299		message = "writing event-channel";
300		goto abort_transaction;
301	}
302
303	rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
304	if (rv) {
305		message = "writing feature-protocol-v2";
306		goto abort_transaction;
307	}
308
309	rv = xenbus_transaction_end(xbt, 0);
310	if (rv == -EAGAIN)
311		goto again;
312	if (rv) {
313		xenbus_dev_fatal(dev, rv, "completing transaction");
314		return rv;
315	}
316
317	xenbus_switch_state(dev, XenbusStateInitialised);
318
319	return 0;
320
321 abort_transaction:
322	xenbus_transaction_end(xbt, 1);
323	if (message)
324		xenbus_dev_error(dev, rv, "%s", message);
325
326	return rv;
327}
328
329static void ring_free(struct tpm_private *priv)
330{
331	if (!priv)
332		return;
333
334	if (priv->ring_ref)
335		gnttab_end_foreign_access(priv->ring_ref, 0,
336				(unsigned long)priv->shr);
337	else
338		free_page((unsigned long)priv->shr);
339
340	if (priv->irq)
341		unbind_from_irqhandler(priv->irq, priv);
342
343	kfree(priv);
344}
345
346static int tpmfront_probe(struct xenbus_device *dev,
347		const struct xenbus_device_id *id)
348{
349	struct tpm_private *priv;
350	int rv;
351
352	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
353	if (!priv) {
354		xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
355		return -ENOMEM;
356	}
357
358	rv = setup_chip(&dev->dev, priv);
359	if (rv) {
360		kfree(priv);
361		return rv;
362	}
363
364	rv = setup_ring(dev, priv);
365	if (rv) {
366		ring_free(priv);
367		return rv;
368	}
369
370	tpm_get_timeouts(priv->chip);
371
372	return tpm_chip_register(priv->chip);
373}
374
375static int tpmfront_remove(struct xenbus_device *dev)
376{
377	struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
378	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
379	tpm_chip_unregister(chip);
380	ring_free(priv);
381	dev_set_drvdata(&chip->dev, NULL);
382	return 0;
383}
384
385static int tpmfront_resume(struct xenbus_device *dev)
386{
387	/* A suspend/resume/migrate will interrupt a vTPM anyway */
388	tpmfront_remove(dev);
389	return tpmfront_probe(dev, NULL);
390}
391
392static void backend_changed(struct xenbus_device *dev,
393		enum xenbus_state backend_state)
394{
395	switch (backend_state) {
396	case XenbusStateInitialised:
397	case XenbusStateConnected:
398		if (dev->state == XenbusStateConnected)
399			break;
400
401		if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
402					  0)) {
403			xenbus_dev_fatal(dev, -EINVAL,
404					"vTPM protocol 2 required");
405			return;
406		}
407		xenbus_switch_state(dev, XenbusStateConnected);
408		break;
409
410	case XenbusStateClosing:
411	case XenbusStateClosed:
412		device_unregister(&dev->dev);
413		xenbus_frontend_closed(dev);
414		break;
415	default:
416		break;
417	}
418}
419
420static const struct xenbus_device_id tpmfront_ids[] = {
421	{ "vtpm" },
422	{ "" }
423};
424MODULE_ALIAS("xen:vtpm");
425
426static struct xenbus_driver tpmfront_driver = {
427	.ids = tpmfront_ids,
428	.probe = tpmfront_probe,
429	.remove = tpmfront_remove,
430	.resume = tpmfront_resume,
431	.otherend_changed = backend_changed,
432};
433
434static int __init xen_tpmfront_init(void)
435{
436	if (!xen_domain())
437		return -ENODEV;
438
439	if (!xen_has_pv_devices())
440		return -ENODEV;
441
442	return xenbus_register_frontend(&tpmfront_driver);
443}
444module_init(xen_tpmfront_init);
445
446static void __exit xen_tpmfront_exit(void)
447{
448	xenbus_unregister_driver(&tpmfront_driver);
449}
450module_exit(xen_tpmfront_exit);
451
452MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
453MODULE_DESCRIPTION("Xen vTPM Driver");
454MODULE_LICENSE("GPL");
455