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