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[Xen-devel] [PATCH RFC] 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.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---

This patch does not include the v1 interfaces from linux-2.6.18-xen.hg
in include/xen/interface/io/tpmif.h, since they do not pass checkpatch
due to their use of typedefs, are not 32/64-bit clean, and are not used
in this patch.

This patch relies on the mini-os patch to tpmback/front:

    [PATCH v5.1 01/12] mini-os/tpm{back,front}: Change shared page ABI

which should be sent as a reply.

 drivers/char/tpm/Kconfig         |  11 ++
 drivers/char/tpm/Makefile        |   1 +
 drivers/char/tpm/tpm.h           |  10 +
 drivers/char/tpm/xen-tpmfront.c  | 418 +++++++++++++++++++++++++++++++++++++++
 include/xen/interface/io/tpmif.h |  50 +++++
 5 files changed, 490 insertions(+)
 create mode 100644 drivers/char/tpm/xen-tpmfront.c
 create mode 100644 include/xen/interface/io/tpmif.h

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 915875e..23d272f 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -81,4 +81,15 @@ config TCG_IBMVTPM
          will be accessible from within Linux.  To compile this driver
          as a module, choose M here; the module will be called tpm_ibmvtpm.
 
+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 5b3fc8b..424ecaa 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -17,3 +17,4 @@ obj-$(CONFIG_TCG_NSC) += tpm_nsc.o
 obj-$(CONFIG_TCG_ATMEL) += tpm_atmel.o
 obj-$(CONFIG_TCG_INFINEON) += tpm_infineon.o
 obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
+obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 8ef7649..b575892 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -328,6 +328,16 @@ extern int tpm_pm_resume(struct device *);
 extern int wait_for_tpm_stat(struct tpm_chip *, u8, unsigned long,
                             wait_queue_head_t *);
 
+static inline void *chip_get_private(const struct tpm_chip *chip)
+{
+       return chip->vendor.data;
+}
+
+static inline void chip_set_private(struct tpm_chip *chip, void *priv)
+{
+       chip->vendor.data = priv;
+}
+
 #ifdef CONFIG_ACPI
 extern int tpm_add_ppi(struct kobject *);
 extern void tpm_remove_ppi(struct kobject *);
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
new file mode 100644
index 0000000..c02f172
--- /dev/null
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -0,0 +1,418 @@
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <xen/events.h>
+#include <xen/interface/grant_table.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 = chip_get_private(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:
+               return VTPM_STATUS_RUNNING;
+       default:
+               return 0;
+       }
+}
+
+static void vtpm_cancel(struct tpm_chip *chip)
+{
+       struct tpm_private *priv = chip_get_private(chip);
+       priv->shr->state = VTPM_STATE_CANCEL;
+       notify_remote_via_evtchn(priv->evtchn);
+}
+
+static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+       struct tpm_private *priv = chip_get_private(chip);
+       struct vtpm_shared_page *shr = priv->shr;
+       unsigned int offset = sizeof(*shr) + 4*shr->nr_extra_pages;
+
+       u32 ordinal;
+       unsigned long duration;
+
+       if (count < TPM_HEADER_SIZE)
+               return -EIO;
+
+       if (offset > PAGE_SIZE)
+               return -EIO;
+
+       if (offset + count > PAGE_SIZE)
+               return -EIO;
+
+       /* 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) < 0) {
+               vtpm_cancel(chip);
+               return -ETIME;
+       }
+
+       memcpy(offset + (u8 *)shr, buf, count);
+       shr->length = count;
+       barrier();
+       shr->state = VTPM_STATE_SUBMIT;
+       notify_remote_via_evtchn(priv->evtchn);
+
+       ordinal = be32_to_cpu(*((__be32 *) (buf + 6)));
+       duration = tpm_calc_ordinal_duration(chip, ordinal);
+
+       if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
+                       &chip->vendor.read_queue) < 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 = chip_get_private(chip);
+       struct vtpm_shared_page *shr = priv->shr;
+       unsigned int offset = sizeof(*shr) + 4*shr->nr_extra_pages;
+       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) < 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, count);
+
+       return length;
+}
+
+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 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,
+       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_STATUS_IDLE | VTPM_STATUS_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;
+       chip_set_private(chip, priv);
+
+       return 0;
+}
+
+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->ring_ref)
+               gnttab_end_foreign_access(priv->ring_ref, 0,
+                               (unsigned long)priv->shr);
+
+       if (priv->chip && priv->chip->vendor.irq)
+               unbind_from_irqhandler(priv->chip->vendor.irq, priv);
+
+       free_page((unsigned long)priv->shr);
+       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 = chip_get_private(chip);
+       tpm_remove_hardware(&dev->dev);
+       ring_free(priv);
+       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 (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_LICENSE("Dual BSD/GPL");
diff --git a/include/xen/interface/io/tpmif.h b/include/xen/interface/io/tpmif.h
new file mode 100644
index 0000000..92522a4
--- /dev/null
+++ b/include/xen/interface/io/tpmif.h
@@ -0,0 +1,50 @@
+/******************************************************************************
+ * tpmif.h
+ *
+ * TPM I/O interface for Xen guest OSes, v2
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __XEN_PUBLIC_IO_TPMIF_H__
+#define __XEN_PUBLIC_IO_TPMIF_H__
+
+enum vtpm_shared_page_state {
+       VTPM_STATE_IDLE,         /* no contents / vTPM idle / cancel complete */
+       VTPM_STATE_SUBMIT,       /* request ready / vTPM working */
+       VTPM_STATE_FINISH,       /* response ready / vTPM idle */
+       VTPM_STATE_CANCEL,       /* cancel requested / vTPM working */
+};
+/* The backend should only change state to IDLE or FINISH, while the
+ * frontend should only change to SUBMIT or CANCEL. */
+
+
+struct vtpm_shared_page {
+       uint32_t length;         /* request/response length in bytes */
+
+       uint8_t state;           /* enum vtpm_shared_page_state */
+       uint8_t locality;        /* for the current request */
+       uint8_t pad;
+
+       uint8_t nr_extra_pages;  /* extra pages for long packets; may be zero */
+       uint32_t extra_pages[0]; /* grant IDs; length in nr_extra_pages */
+};
+
+#endif
-- 
1.8.1.4


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