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(delay_msec: 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(dev: &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(dev: &chip->dev);
124 priv->shr->state = VTPM_STATE_CANCEL;
125 wmb();
126 notify_remote_via_evtchn(port: priv->evtchn);
127}
128
129static size_t shr_data_offset(struct vtpm_shared_page *shr)
130{
131 return struct_size(shr, extra_pages, 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(dev: &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, mask: VTPM_STATUS_IDLE, timeout: chip->timeout_c,
151 queue: &priv->read_queue, check_cancel: 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(port: 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, mask: VTPM_STATUS_IDLE, timeout: duration,
167 queue: &priv->read_queue, check_cancel: 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(dev: &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, mask: VTPM_STATUS_RESULT, timeout: chip->timeout_c,
188 queue: &priv->read_queue, check_cancel: 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(pdev: dev, ops: &tpm_vtpm);
239 if (IS_ERR(ptr: chip))
240 return PTR_ERR(ptr: chip);
241
242 init_waitqueue_head(&priv->read_queue);
243
244 priv->chip = chip;
245 dev_set_drvdata(dev: &chip->dev, data: 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
257 rv = xenbus_setup_ring(dev, GFP_KERNEL, vaddr: (void **)&priv->shr, nr_pages: 1,
258 grefs: &priv->ring_ref);
259 if (rv < 0)
260 return rv;
261
262 rv = xenbus_alloc_evtchn(dev, port: &priv->evtchn);
263 if (rv)
264 return rv;
265
266 rv = bind_evtchn_to_irqhandler(evtchn: priv->evtchn, handler: tpmif_interrupt, irqflags: 0,
267 devname: "tpmif", dev_id: priv);
268 if (rv <= 0) {
269 xenbus_dev_fatal(dev, err: rv, fmt: "allocating TPM irq");
270 return rv;
271 }
272 priv->irq = rv;
273
274 again:
275 rv = xenbus_transaction_start(t: &xbt);
276 if (rv) {
277 xenbus_dev_fatal(dev, err: rv, fmt: "starting transaction");
278 return rv;
279 }
280
281 rv = xenbus_printf(t: xbt, dir: dev->nodename,
282 node: "ring-ref", fmt: "%u", priv->ring_ref);
283 if (rv) {
284 message = "writing ring-ref";
285 goto abort_transaction;
286 }
287
288 rv = xenbus_printf(t: xbt, dir: dev->nodename, node: "event-channel", fmt: "%u",
289 priv->evtchn);
290 if (rv) {
291 message = "writing event-channel";
292 goto abort_transaction;
293 }
294
295 rv = xenbus_printf(t: xbt, dir: dev->nodename, node: "feature-protocol-v2", fmt: "1");
296 if (rv) {
297 message = "writing feature-protocol-v2";
298 goto abort_transaction;
299 }
300
301 rv = xenbus_transaction_end(t: xbt, abort: 0);
302 if (rv == -EAGAIN)
303 goto again;
304 if (rv) {
305 xenbus_dev_fatal(dev, err: rv, fmt: "completing transaction");
306 return rv;
307 }
308
309 xenbus_switch_state(dev, new_state: XenbusStateInitialised);
310
311 return 0;
312
313 abort_transaction:
314 xenbus_transaction_end(t: xbt, abort: 1);
315 if (message)
316 xenbus_dev_error(dev, err: rv, fmt: "%s", message);
317
318 return rv;
319}
320
321static void ring_free(struct tpm_private *priv)
322{
323 if (!priv)
324 return;
325
326 xenbus_teardown_ring(vaddr: (void **)&priv->shr, nr_pages: 1, grefs: &priv->ring_ref);
327
328 if (priv->irq)
329 unbind_from_irqhandler(irq: priv->irq, dev_id: priv);
330
331 kfree(objp: priv);
332}
333
334static 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(size: sizeof(*priv), GFP_KERNEL);
341 if (!priv) {
342 xenbus_dev_fatal(dev, err: -ENOMEM, fmt: "allocating priv structure");
343 return -ENOMEM;
344 }
345
346 rv = setup_chip(dev: &dev->dev, priv);
347 if (rv) {
348 kfree(objp: 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(chip: priv->chip);
361}
362
363static void tpmfront_remove(struct xenbus_device *dev)
364{
365 struct tpm_chip *chip = dev_get_drvdata(dev: &dev->dev);
366 struct tpm_private *priv = dev_get_drvdata(dev: &chip->dev);
367 tpm_chip_unregister(chip);
368 ring_free(priv);
369 dev_set_drvdata(dev: &chip->dev, NULL);
370}
371
372static 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
379static 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(dir: dev->otherend, node: "feature-protocol-v2",
389 default_val: 0)) {
390 xenbus_dev_fatal(dev, err: -EINVAL,
391 fmt: "vTPM protocol 2 required");
392 return;
393 }
394 xenbus_switch_state(dev, new_state: XenbusStateConnected);
395 break;
396
397 case XenbusStateClosing:
398 case XenbusStateClosed:
399 device_unregister(dev: &dev->dev);
400 xenbus_frontend_closed(dev);
401 break;
402 default:
403 break;
404 }
405}
406
407static const struct xenbus_device_id tpmfront_ids[] = {
408 { "vtpm" },
409 { "" }
410};
411MODULE_ALIAS("xen:vtpm");
412
413static 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
421static 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}
431module_init(xen_tpmfront_init);
432
433static void __exit xen_tpmfront_exit(void)
434{
435 xenbus_unregister_driver(drv: &tpmfront_driver);
436}
437module_exit(xen_tpmfront_exit);
438
439MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
440MODULE_DESCRIPTION("Xen vTPM Driver");
441MODULE_LICENSE("GPL");
442

source code of linux/drivers/char/tpm/xen-tpmfront.c