diff options
Diffstat (limited to 'drivers/char/tpm/xen-tpmfront.c')
| -rw-r--r-- | drivers/char/tpm/xen-tpmfront.c | 441 |
1 files changed, 441 insertions, 0 deletions
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c new file mode 100644 index 0000000000..80cca3b83b --- /dev/null +++ b/drivers/char/tpm/xen-tpmfront.c @@ -0,0 +1,441 @@ +// 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 size_t shr_data_offset(struct vtpm_shared_page *shr) +{ + return struct_size(shr, extra_pages, 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; + size_t 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; + size_t 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; + + rv = xenbus_setup_ring(dev, GFP_KERNEL, (void **)&priv->shr, 1, + &priv->ring_ref); + if (rv < 0) + return 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->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; + + xenbus_teardown_ring((void **)&priv->shr, 1, &priv->ring_ref); + + 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 void 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); +} + +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"); |