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// 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 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 = dev_get_drvdata(&chip->dev);
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->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;
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->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;
grant_ref_t gref;
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, priv->shr, 1, &gref);
if (rv < 0)
return rv;
priv->ring_ref = gref;
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;
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->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 int 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);
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)
{
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");