drivers/char/tpm/xen-tpmfront.c - kernel/msm-4.9 - Gitiles

 /*
  * Implementation of the Xen vTPM device frontend
  *
  * Author:  Daniel De Graaf <dgdegra@tycho.nsa.gov>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2,
  * as published by the Free Software Foundation.
  */
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/interrupt.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"

 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;
 };

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

 static u8 vtpm_status(struct tpm_chip *chip)
 {
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	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 = TPM_VPRIV(chip);
 	priv->shr->state = VTPM_STATE_CANCEL;
 	wmb();
 	notify_remote_via_evtchn(priv->evtchn);
 }

 static unsigned int shr_data_offset(struct vtpm_shared_page *shr)
 {
 	return sizeof(*shr) + sizeof(u32) * shr->nr_extra_pages;
 }

 static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	struct vtpm_shared_page *shr = priv->shr;
 	unsigned int 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->vendor.timeout_c,
 			&chip->vendor.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_input_header*)buf)->ordinal);
 	duration = tpm_calc_ordinal_duration(chip, ordinal);

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

 	return count;
 }

 static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	struct vtpm_shared_page *shr = priv->shr;
 	unsigned int 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->vendor.timeout_c,
 			&chip->vendor.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;
 }

 ssize_t tpm_show_locality(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
 	struct tpm_chip *chip = dev_get_drvdata(dev);
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	u8 locality = priv->shr->locality;

 	return sprintf(buf, "%d\n", locality);
 }

 ssize_t tpm_store_locality(struct device *dev, struct device_attribute *attr,
 			const char *buf, size_t len)
 {
 	struct tpm_chip *chip = dev_get_drvdata(dev);
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	u8 val;

 	int rv = kstrtou8(buf, 0, &val);
 	if (rv)
 		return rv;

 	priv->shr->locality = val;

 	return len;
 }

 static const struct file_operations vtpm_ops = {
 	.owner = THIS_MODULE,
 	.llseek = no_llseek,
 	.open = tpm_open,
 	.read = tpm_read,
 	.write = tpm_write,
 	.release = tpm_release,
 };

 static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL);
 static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL);
 static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL);
 static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL);
 static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL);
 static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated,
 		NULL);
 static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps, NULL);
 static DEVICE_ATTR(cancel, S_IWUSR | S_IWGRP, NULL, tpm_store_cancel);
 static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL);
 static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL);
 static DEVICE_ATTR(locality, S_IRUGO | S_IWUSR, tpm_show_locality,
 		tpm_store_locality);

 static struct attribute *vtpm_attrs[] = {
 	&dev_attr_pubek.attr,
 	&dev_attr_pcrs.attr,
 	&dev_attr_enabled.attr,
 	&dev_attr_active.attr,
 	&dev_attr_owned.attr,
 	&dev_attr_temp_deactivated.attr,
 	&dev_attr_caps.attr,
 	&dev_attr_cancel.attr,
 	&dev_attr_durations.attr,
 	&dev_attr_timeouts.attr,
 	&dev_attr_locality.attr,
 	NULL,
 };

 static struct attribute_group vtpm_attr_grp = {
 	.attrs = vtpm_attrs,
 };

 #define TPM_LONG_TIMEOUT   (10 * 60 * HZ)

 static const struct tpm_vendor_specific 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,
 	.attr_group = &vtpm_attr_grp,
 	.miscdev = {
 		.fops = &vtpm_ops,
 	},
 	.duration = {
 		TPM_LONG_TIMEOUT,
 		TPM_LONG_TIMEOUT,
 		TPM_LONG_TIMEOUT,
 	},
 };

 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->chip->vendor.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 = tpm_register_hardware(dev, &tpm_vtpm);
 	if (!chip)
 		return -ENODEV;

 	init_waitqueue_head(&chip->vendor.read_queue);

 	priv->chip = chip;
 	TPM_VPRIV(chip) = 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;

 	priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
 	if (!priv->shr) {
 		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 		return -ENOMEM;
 	}

 	rv = xenbus_grant_ring(dev, virt_to_mfn(priv->shr));
 	if (rv < 0)
 		return rv;

 	priv->ring_ref = 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->chip->vendor.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;

 	if (priv->ring_ref)
 		gnttab_end_foreign_access(priv->ring_ref, 0,
 				(unsigned long)priv->shr);
 	else
 		free_page((unsigned long)priv->shr);

 	if (priv->chip && priv->chip->vendor.irq)
 		unbind_from_irqhandler(priv->chip->vendor.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) {
 		tpm_remove_hardware(&dev->dev);
 		ring_free(priv);
 		return rv;
 	}

 	tpm_get_timeouts(priv->chip);

 	return rv;
 }

 static int tpmfront_remove(struct xenbus_device *dev)
 {
 	struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
 	struct tpm_private *priv = TPM_VPRIV(chip);
 	tpm_remove_hardware(&dev->dev);
 	ring_free(priv);
 	TPM_VPRIV(chip) = NULL;
 	return 0;
 }

 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)
 {
 	int val;

 	switch (backend_state) {
 	case XenbusStateInitialised:
 	case XenbusStateConnected:
 		if (dev->state == XenbusStateConnected)
 			break;

 		if (xenbus_scanf(XBT_NIL, dev->otherend,
 				"feature-protocol-v2", "%d", &val) < 0)
 			val = 0;
 		if (!val) {
 			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 DEFINE_XENBUS_DRIVER(tpmfront, ,
 		.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;

 	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");
	/*
	* Implementation of the Xen vTPM device frontend
	*
	* Author: Daniel De Graaf <dgdegra@tycho.nsa.gov>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2,
	* as published by the Free Software Foundation.
	*/
	#include <linux/errno.h>
	#include <linux/err.h>
	#include <linux/interrupt.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"

	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;
	};

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

	static u8 vtpm_status(struct tpm_chip *chip)
	{
	struct tpm_private *priv = TPM_VPRIV(chip);
	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 = TPM_VPRIV(chip);
	priv->shr->state = VTPM_STATE_CANCEL;
	wmb();
	notify_remote_via_evtchn(priv->evtchn);
	}

	static unsigned int shr_data_offset(struct vtpm_shared_page *shr)
	{
	return sizeof(shr) + sizeof(u32) shr->nr_extra_pages;
	}

	static int vtpm_send(struct tpm_chip chip, u8 buf, size_t count)
	{
	struct tpm_private *priv = TPM_VPRIV(chip);
	struct vtpm_shared_page *shr = priv->shr;
	unsigned int 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->vendor.timeout_c,
	&chip->vendor.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_input_header*)buf)->ordinal);
	duration = tpm_calc_ordinal_duration(chip, ordinal);

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

	return count;
	}

	static int vtpm_recv(struct tpm_chip chip, u8 buf, size_t count)
	{
	struct tpm_private *priv = TPM_VPRIV(chip);
	struct vtpm_shared_page *shr = priv->shr;
	unsigned int 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->vendor.timeout_c,
	&chip->vendor.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;
	}

	ssize_t tpm_show_locality(struct device dev, struct device_attribute attr,
	char *buf)
	{
	struct tpm_chip *chip = dev_get_drvdata(dev);
	struct tpm_private *priv = TPM_VPRIV(chip);
	u8 locality = priv->shr->locality;

	return sprintf(buf, "%d\n", locality);
	}

	ssize_t tpm_store_locality(struct device dev, struct device_attribute attr,
	const char *buf, size_t len)
	{
	struct tpm_chip *chip = dev_get_drvdata(dev);
	struct tpm_private *priv = TPM_VPRIV(chip);
	u8 val;

	int rv = kstrtou8(buf, 0, &val);
	if (rv)
	return rv;

	priv->shr->locality = val;

	return len;
	}

	static const struct file_operations vtpm_ops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.open = tpm_open,
	.read = tpm_read,
	.write = tpm_write,
	.release = tpm_release,
	};

	static DEVICE_ATTR(pubek, S_IRUGO, tpm_show_pubek, NULL);
	static DEVICE_ATTR(pcrs, S_IRUGO, tpm_show_pcrs, NULL);
	static DEVICE_ATTR(enabled, S_IRUGO, tpm_show_enabled, NULL);
	static DEVICE_ATTR(active, S_IRUGO, tpm_show_active, NULL);
	static DEVICE_ATTR(owned, S_IRUGO, tpm_show_owned, NULL);
	static DEVICE_ATTR(temp_deactivated, S_IRUGO, tpm_show_temp_deactivated,
	NULL);
	static DEVICE_ATTR(caps, S_IRUGO, tpm_show_caps, NULL);
	static DEVICE_ATTR(cancel, S_IWUSR \| S_IWGRP, NULL, tpm_store_cancel);
	static DEVICE_ATTR(durations, S_IRUGO, tpm_show_durations, NULL);
	static DEVICE_ATTR(timeouts, S_IRUGO, tpm_show_timeouts, NULL);
	static DEVICE_ATTR(locality, S_IRUGO \| S_IWUSR, tpm_show_locality,
	tpm_store_locality);

	static struct attribute *vtpm_attrs[] = {
	&dev_attr_pubek.attr,
	&dev_attr_pcrs.attr,
	&dev_attr_enabled.attr,
	&dev_attr_active.attr,
	&dev_attr_owned.attr,
	&dev_attr_temp_deactivated.attr,
	&dev_attr_caps.attr,
	&dev_attr_cancel.attr,
	&dev_attr_durations.attr,
	&dev_attr_timeouts.attr,
	&dev_attr_locality.attr,
	NULL,
	};

	static struct attribute_group vtpm_attr_grp = {
	.attrs = vtpm_attrs,
	};

	#define TPM_LONG_TIMEOUT (10 * 60 * HZ)

	static const struct tpm_vendor_specific 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,
	.attr_group = &vtpm_attr_grp,
	.miscdev = {
	.fops = &vtpm_ops,
	},
	.duration = {
	TPM_LONG_TIMEOUT,
	TPM_LONG_TIMEOUT,
	TPM_LONG_TIMEOUT,
	},
	};

	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->chip->vendor.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 = tpm_register_hardware(dev, &tpm_vtpm);
	if (!chip)
	return -ENODEV;

	init_waitqueue_head(&chip->vendor.read_queue);

	priv->chip = chip;
	TPM_VPRIV(chip) = 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;

	priv->shr = (void *)__get_free_page(GFP_KERNEL\|__GFP_ZERO);
	if (!priv->shr) {
	xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
	return -ENOMEM;
	}

	rv = xenbus_grant_ring(dev, virt_to_mfn(priv->shr));
	if (rv < 0)
	return rv;

	priv->ring_ref = 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->chip->vendor.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;

	if (priv->ring_ref)
	gnttab_end_foreign_access(priv->ring_ref, 0,
	(unsigned long)priv->shr);
	else
	free_page((unsigned long)priv->shr);

	if (priv->chip && priv->chip->vendor.irq)
	unbind_from_irqhandler(priv->chip->vendor.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) {
	tpm_remove_hardware(&dev->dev);
	ring_free(priv);
	return rv;
	}

	tpm_get_timeouts(priv->chip);

	return rv;
	}

	static int tpmfront_remove(struct xenbus_device *dev)
	{
	struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
	struct tpm_private *priv = TPM_VPRIV(chip);
	tpm_remove_hardware(&dev->dev);
	ring_free(priv);
	TPM_VPRIV(chip) = NULL;
	return 0;
	}

	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)
	{
	int val;

	switch (backend_state) {
	case XenbusStateInitialised:
	case XenbusStateConnected:
	if (dev->state == XenbusStateConnected)
	break;

	if (xenbus_scanf(XBT_NIL, dev->otherend,
	"feature-protocol-v2", "%d", &val) < 0)
	val = 0;
	if (!val) {
	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 DEFINE_XENBUS_DRIVER(tpmfront, ,
	.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;

	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");