drivers/tpm: add xen tpmfront interface

This is a complete rewrite of the Xen TPM frontend driver, taking
advantage of a simplified frontend/backend interface and adding support
for cancellation and timeouts.  The backend for this driver is provided
by a vTPM stub domain using the interface in Xen 4.3.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Matthew Fioravante <matthew.fioravante@jhuapl.edu>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Peter Huewe <peterhuewe@gmx.de>
Reviewed-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

3 files changed, 485 insertions, 0 deletions

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index dbfd56446c31..205ed35c1a31 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -91,4 +91,15 @@ config TCG_ST33_I2C
         To compile this driver as a module, choose M here; the module will be
         called tpm_stm_st33_i2c.
 
+config TCG_XEN
+        tristate "XEN TPM Interface"
+        depends on TCG_TPM && XEN
+        ---help---
+          If you want to make TPM support available to a Xen user domain,
+          say Yes and it will be accessible from within Linux. See
+          the manpages for xl, xl.conf, and docs/misc/vtpm.txt in
+          the Xen source repository for more details.
+          To compile this driver as a module, choose M here; the module
+          will be called xen-tpmfront.
+
 endif # TCG_TPM
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index a3736c97c65a..eb41ff97d0ad 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -18,3 +18,4 @@ obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o
 obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o
 obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
 obj-$(CONFIG_TCG_ST33_I2C) += tpm_i2c_stm_st33.o
+obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
new file mode 100644
index 000000000000..7a7929ba2658
--- /dev/null
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -0,0 +1,473 @@
+/*
+ * 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);
+
+        dev_set_drvdata(&dev->dev, 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");