summaryrefslogtreecommitdiffstats
path: root/drivers/char/tpm/xen-tpmfront.c
blob: 80cca3b83b226aa10918fc6e7a7468a43bd91996 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Implementation of the Xen vTPM device frontend
 *
 * Author:  Daniel De Graaf <dgdegra@tycho.nsa.gov>
 */
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/freezer.h>
#include <xen/xen.h>
#include <xen/events.h>
#include <xen/interface/io/tpmif.h>
#include <xen/grant_table.h>
#include <xen/xenbus.h>
#include <xen/page.h>
#include "tpm.h"
#include <xen/platform_pci.h>

struct tpm_private {
	struct tpm_chip *chip;
	struct xenbus_device *dev;

	struct vtpm_shared_page *shr;

	unsigned int evtchn;
	int ring_ref;
	domid_t backend_id;
	int irq;
	wait_queue_head_t read_queue;
};

enum status_bits {
	VTPM_STATUS_RUNNING  = 0x1,
	VTPM_STATUS_IDLE     = 0x2,
	VTPM_STATUS_RESULT   = 0x4,
	VTPM_STATUS_CANCELED = 0x8,
};

static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
					bool check_cancel, bool *canceled)
{
	u8 status = chip->ops->status(chip);

	*canceled = false;
	if ((status & mask) == mask)
		return true;
	if (check_cancel && chip->ops->req_canceled(chip, status)) {
		*canceled = true;
		return true;
	}
	return false;
}

static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
		unsigned long timeout, wait_queue_head_t *queue,
		bool check_cancel)
{
	unsigned long stop;
	long rc;
	u8 status;
	bool canceled = false;

	/* check current status */
	status = chip->ops->status(chip);
	if ((status & mask) == mask)
		return 0;

	stop = jiffies + timeout;

	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
again:
		timeout = stop - jiffies;
		if ((long)timeout <= 0)
			return -ETIME;
		rc = wait_event_interruptible_timeout(*queue,
			wait_for_tpm_stat_cond(chip, mask, check_cancel,
					       &canceled),
			timeout);
		if (rc > 0) {
			if (canceled)
				return -ECANCELED;
			return 0;
		}
		if (rc == -ERESTARTSYS && freezing(current)) {
			clear_thread_flag(TIF_SIGPENDING);
			goto again;
		}
	} else {
		do {
			tpm_msleep(TPM_TIMEOUT);
			status = chip->ops->status(chip);
			if ((status & mask) == mask)
				return 0;
		} while (time_before(jiffies, stop));
	}
	return -ETIME;
}

static u8 vtpm_status(struct tpm_chip *chip)
{
	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
	switch (priv->shr->state) {
	case VTPM_STATE_IDLE:
		return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED;
	case VTPM_STATE_FINISH:
		return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT;
	case VTPM_STATE_SUBMIT:
	case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */
		return VTPM_STATUS_RUNNING;
	default:
		return 0;
	}
}

static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
{
	return status & VTPM_STATUS_CANCELED;
}

static void vtpm_cancel(struct tpm_chip *chip)
{
	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
	priv->shr->state = VTPM_STATE_CANCEL;
	wmb();
	notify_remote_via_evtchn(priv->evtchn);
}

static size_t shr_data_offset(struct vtpm_shared_page *shr)
{
	return struct_size(shr, extra_pages, shr->nr_extra_pages);
}

static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
{
	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
	struct vtpm_shared_page *shr = priv->shr;
	size_t offset = shr_data_offset(shr);

	u32 ordinal;
	unsigned long duration;

	if (offset > PAGE_SIZE)
		return -EINVAL;

	if (offset + count > PAGE_SIZE)
		return -EINVAL;

	/* Wait for completion of any existing command or cancellation */
	if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->timeout_c,
			&priv->read_queue, true) < 0) {
		vtpm_cancel(chip);
		return -ETIME;
	}

	memcpy(offset + (u8 *)shr, buf, count);
	shr->length = count;
	barrier();
	shr->state = VTPM_STATE_SUBMIT;
	wmb();
	notify_remote_via_evtchn(priv->evtchn);

	ordinal = be32_to_cpu(((struct tpm_header *)buf)->ordinal);
	duration = tpm_calc_ordinal_duration(chip, ordinal);

	if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
			&priv->read_queue, true) < 0) {
		/* got a signal or timeout, try to cancel */
		vtpm_cancel(chip);
		return -ETIME;
	}

	return 0;
}

static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
	struct vtpm_shared_page *shr = priv->shr;
	size_t offset = shr_data_offset(shr);
	size_t length = shr->length;

	if (shr->state == VTPM_STATE_IDLE)
		return -ECANCELED;

	/* In theory the wait at the end of _send makes this one unnecessary */
	if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->timeout_c,
			&priv->read_queue, true) < 0) {
		vtpm_cancel(chip);
		return -ETIME;
	}

	if (offset > PAGE_SIZE)
		return -EIO;

	if (offset + length > PAGE_SIZE)
		length = PAGE_SIZE - offset;

	if (length > count)
		length = count;

	memcpy(buf, offset + (u8 *)shr, length);

	return length;
}

static const struct tpm_class_ops tpm_vtpm = {
	.status = vtpm_status,
	.recv = vtpm_recv,
	.send = vtpm_send,
	.cancel = vtpm_cancel,
	.req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
	.req_complete_val  = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
	.req_canceled      = vtpm_req_canceled,
};

static irqreturn_t tpmif_interrupt(int dummy, void *dev_id)
{
	struct tpm_private *priv = dev_id;

	switch (priv->shr->state) {
	case VTPM_STATE_IDLE:
	case VTPM_STATE_FINISH:
		wake_up_interruptible(&priv->read_queue);
		break;
	case VTPM_STATE_SUBMIT:
	case VTPM_STATE_CANCEL:
	default:
		break;
	}
	return IRQ_HANDLED;
}

static int setup_chip(struct device *dev, struct tpm_private *priv)
{
	struct tpm_chip *chip;

	chip = tpmm_chip_alloc(dev, &tpm_vtpm);
	if (IS_ERR(chip))
		return PTR_ERR(chip);

	init_waitqueue_head(&priv->read_queue);

	priv->chip = chip;
	dev_set_drvdata(&chip->dev, priv);

	return 0;
}

/* caller must clean up in case of errors */
static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
{
	struct xenbus_transaction xbt;
	const char *message = NULL;
	int rv;

	rv = xenbus_setup_ring(dev, GFP_KERNEL, (void **)&priv->shr, 1,
			       &priv->ring_ref);
	if (rv < 0)
		return rv;

	rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
	if (rv)
		return rv;

	rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
				       "tpmif", priv);
	if (rv <= 0) {
		xenbus_dev_fatal(dev, rv, "allocating TPM irq");
		return rv;
	}
	priv->irq = rv;

 again:
	rv = xenbus_transaction_start(&xbt);
	if (rv) {
		xenbus_dev_fatal(dev, rv, "starting transaction");
		return rv;
	}

	rv = xenbus_printf(xbt, dev->nodename,
			"ring-ref", "%u", priv->ring_ref);
	if (rv) {
		message = "writing ring-ref";
		goto abort_transaction;
	}

	rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
			priv->evtchn);
	if (rv) {
		message = "writing event-channel";
		goto abort_transaction;
	}

	rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
	if (rv) {
		message = "writing feature-protocol-v2";
		goto abort_transaction;
	}

	rv = xenbus_transaction_end(xbt, 0);
	if (rv == -EAGAIN)
		goto again;
	if (rv) {
		xenbus_dev_fatal(dev, rv, "completing transaction");
		return rv;
	}

	xenbus_switch_state(dev, XenbusStateInitialised);

	return 0;

 abort_transaction:
	xenbus_transaction_end(xbt, 1);
	if (message)
		xenbus_dev_error(dev, rv, "%s", message);

	return rv;
}

static void ring_free(struct tpm_private *priv)
{
	if (!priv)
		return;

	xenbus_teardown_ring((void **)&priv->shr, 1, &priv->ring_ref);

	if (priv->irq)
		unbind_from_irqhandler(priv->irq, priv);

	kfree(priv);
}

static int tpmfront_probe(struct xenbus_device *dev,
		const struct xenbus_device_id *id)
{
	struct tpm_private *priv;
	int rv;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv) {
		xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
		return -ENOMEM;
	}

	rv = setup_chip(&dev->dev, priv);
	if (rv) {
		kfree(priv);
		return rv;
	}

	rv = setup_ring(dev, priv);
	if (rv) {
		ring_free(priv);
		return rv;
	}

	tpm_get_timeouts(priv->chip);

	return tpm_chip_register(priv->chip);
}

static void tpmfront_remove(struct xenbus_device *dev)
{
	struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
	tpm_chip_unregister(chip);
	ring_free(priv);
	dev_set_drvdata(&chip->dev, NULL);
}

static int tpmfront_resume(struct xenbus_device *dev)
{
	/* A suspend/resume/migrate will interrupt a vTPM anyway */
	tpmfront_remove(dev);
	return tpmfront_probe(dev, NULL);
}

static void backend_changed(struct xenbus_device *dev,
		enum xenbus_state backend_state)
{
	switch (backend_state) {
	case XenbusStateInitialised:
	case XenbusStateConnected:
		if (dev->state == XenbusStateConnected)
			break;

		if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
					  0)) {
			xenbus_dev_fatal(dev, -EINVAL,
					"vTPM protocol 2 required");
			return;
		}
		xenbus_switch_state(dev, XenbusStateConnected);
		break;

	case XenbusStateClosing:
	case XenbusStateClosed:
		device_unregister(&dev->dev);
		xenbus_frontend_closed(dev);
		break;
	default:
		break;
	}
}

static const struct xenbus_device_id tpmfront_ids[] = {
	{ "vtpm" },
	{ "" }
};
MODULE_ALIAS("xen:vtpm");

static struct xenbus_driver tpmfront_driver = {
	.ids = tpmfront_ids,
	.probe = tpmfront_probe,
	.remove = tpmfront_remove,
	.resume = tpmfront_resume,
	.otherend_changed = backend_changed,
};

static int __init xen_tpmfront_init(void)
{
	if (!xen_domain())
		return -ENODEV;

	if (!xen_has_pv_devices())
		return -ENODEV;

	return xenbus_register_frontend(&tpmfront_driver);
}
module_init(xen_tpmfront_init);

static void __exit xen_tpmfront_exit(void)
{
	xenbus_unregister_driver(&tpmfront_driver);
}
module_exit(xen_tpmfront_exit);

MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
MODULE_DESCRIPTION("Xen vTPM Driver");
MODULE_LICENSE("GPL");