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