[v4,08/10] tpm: Driver for supporting multiple emulated TPMs

Commit Message

Stefan Berger Feb. 29, 2016, 5:29 p.m. UTC

This patch implements a driver for supporting multiple emulated TPMs in a
system.

The driver implements a device /dev/vtpmx that is used to created
a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side that
is accessed using a file descriptor returned by an ioctl.
The device /dev/tpmX is the usual TPM device created by the core TPM
driver. Applications or kernel subsystems can send TPM commands to it
and the corresponding server-side file descriptor receives these
commands and delivers them to an emulated TPM.

Signed-off-by: Stefan Berger <[e-mail]>
---
 drivers/char/tpm/Kconfig    |  10 +
 drivers/char/tpm/Makefile   |   1 +
 drivers/char/tpm/tpm-vtpm.c | 546 ++++++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/Kbuild   |   1 +
 include/uapi/linux/vtpm.h   |  41 ++++
 5 files changed, 599 insertions(+)
 create mode 100644 drivers/char/tpm/tpm-vtpm.c
 create mode 100644 include/uapi/linux/vtpm.h

Comments

Jarkko Sakkinen March 4, 2016, 8:29 p.m. UTC | #1

Hi

I noticed some glitches.

On Mon, Feb 29, 2016 at 12:29:54PM -0500, Stefan Berger wrote:
> This patch implements a driver for supporting multiple emulated TPMs in a
> system.
> 
> The driver implements a device /dev/vtpmx that is used to created
> a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side that
> is accessed using a file descriptor returned by an ioctl.
> The device /dev/tpmX is the usual TPM device created by the core TPM
> driver. Applications or kernel subsystems can send TPM commands to it
> and the corresponding server-side file descriptor receives these
> commands and delivers them to an emulated TPM.

Every other driver in the subsystem except xen-tpmfront uses
underscore instead of dash. For the sake of consistency this should be
renamed as tpm_vtpm.


> Signed-off-by: Stefan Berger <[e-mail]>
> ---
>  drivers/char/tpm/Kconfig    |  10 +
>  drivers/char/tpm/Makefile   |   1 +
>  drivers/char/tpm/tpm-vtpm.c | 546 ++++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/Kbuild   |   1 +
>  include/uapi/linux/vtpm.h   |  41 ++++
>  5 files changed, 599 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm-vtpm.c
>  create mode 100644 include/uapi/linux/vtpm.h
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 3b84a8b..4c4e843 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -122,5 +122,15 @@ config TCG_CRB
>  	  from within Linux.  To compile this driver as a module, choose
>  	  M here; the module will be called tpm_crb.
>  
> +config TCG_VTPM
> +	tristate "VTPM Interface"
> +	depends on TCG_TPM
> +	---help---
> +	  This driver supports an emulated TPM (vTPM) running in userspace.
> +	  A device /dev/vtpmx is provided that creates a device pair
> +	  /dev/vtpmX and a server-side file descriptor on which the vTPM
> +	  can receive commands.
> +
> +
>  source "drivers/char/tpm/st33zp24/Kconfig"
>  endif # TCG_TPM
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 56e8f1f..d947db2 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -23,3 +23,4 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
>  obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
>  obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
>  obj-$(CONFIG_TCG_CRB) += tpm_crb.o
> +obj-$(CONFIG_TCG_VTPM) += tpm-vtpm.o
> diff --git a/drivers/char/tpm/tpm-vtpm.c b/drivers/char/tpm/tpm-vtpm.c
> new file mode 100644
> index 0000000..2c69363
> --- /dev/null
> +++ b/drivers/char/tpm/tpm-vtpm.c
> @@ -0,0 +1,546 @@
> +/*
> + * Copyright (C) 2015, 2016 IBM Corporation
> + *
> + * Author: Stefan Berger <[e-mail]>
> + *
> + * Maintained by: <[e-mail]>
> + *
> + * Device driver for vTPM.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation, version 2 of the
> + * License.
> + *
> + */
> +
> +#include <linux/types.h>
> +#include <linux/spinlock.h>
> +#include <linux/uaccess.h>
> +#include <linux/wait.h>
> +#include <linux/miscdevice.h>
> +#include <linux/vtpm.h>
> +#include <linux/file.h>
> +#include <linux/anon_inodes.h>
> +#include <linux/poll.h>
> +#include <linux/compat.h>
> +
> +#include "tpm.h"
> +
> +#define VTPM_REQ_COMPLETE_FLAG  BIT(0)
> +
> +struct vtpm_dev {
> +	struct tpm_chip *chip;
> +
> +	u32 flags;                   /* public API flags */
> +
> +	wait_queue_head_t wq;
> +
> +	struct mutex buf_lock;       /* protect buffer and flag modifications */
> +
> +	long state;                  /* internal state */
> +#define STATE_OPENED_FLAG        BIT(0)
> +#define STATE_WAIT_RESPONSE_FLAG BIT(1)  /* waiting for emulator response */
> +
> +	size_t req_len;              /* length of queued TPM request */
> +	size_t resp_len;             /* length of queued TPM response */
> +	u8 buffer[TPM_BUFSIZE];      /* request/response buffer */
> +};
> +
> +
> +static void vtpm_delete_device_pair(struct vtpm_dev *vtpm_dev);
> +
> +/*
> + * Functions related to 'server side'
> + */
> +
> +/**
> + * vtpm_fops_read - Read TPM commands on 'server side'
> + *
> + * Return value:
> + *	Number of bytes read or negative error code
> + */
> +static ssize_t vtpm_fops_read(struct file *filp, char __user *buf,
> +			      size_t count, loff_t *off)
> +{
> +	struct vtpm_dev *vtpm_dev = filp->private_data;
> +	size_t len;
> +	int sig, rc;
> +
> +	sig = wait_event_interruptible(vtpm_dev->wq, vtpm_dev->req_len != 0);
> +	if (sig)
> +		return -EINTR;
> +
> +	mutex_lock(&vtpm_dev->buf_lock);
> +
> +	len = vtpm_dev->req_len;
> +
> +	if (count < len) {
> +		mutex_unlock(&vtpm_dev->buf_lock);
> +		pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n",
> +			 count, len);
> +		return -EIO;
> +	}
> +
> +	rc = copy_to_user(buf, vtpm_dev->buffer, len);
> +	memset(vtpm_dev->buffer, 0, len);
> +	vtpm_dev->req_len = 0;
> +
> +	if (!rc)
> +		vtpm_dev->state |= STATE_WAIT_RESPONSE_FLAG;
> +
> +	mutex_unlock(&vtpm_dev->buf_lock);
> +
> +	if (rc)
> +		return -EFAULT;
> +
> +	return len;
> +}
> +
> +/**
> + * vtpm_fops_write - Write TPM responses on 'server side'
> + *
> + * Return value:
> + *	Number of bytes read or negative error value
> + */
> +static ssize_t vtpm_fops_write(struct file *filp, const char __user *buf,
> +			       size_t count, loff_t *off)
> +{
> +	struct vtpm_dev *vtpm_dev = filp->private_data;
> +
> +	if (count > sizeof(vtpm_dev->buffer) ||
> +	    !(vtpm_dev->state & STATE_WAIT_RESPONSE_FLAG))
> +		return -EIO;

This is not atomic in any sense. You should move this statement after
taking buf_lock.

> +
> +	mutex_lock(&vtpm_dev->buf_lock);
> +
> +	vtpm_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;
> +
> +	vtpm_dev->req_len = 0;
> +
> +	if (copy_from_user(vtpm_dev->buffer, buf, count)) {
> +		mutex_unlock(&vtpm_dev->buf_lock);
> +		return -EFAULT;
> +	}
> +
> +	vtpm_dev->resp_len = count;
> +
> +	mutex_unlock(&vtpm_dev->buf_lock);
> +
> +	wake_up_interruptible(&vtpm_dev->wq);
> +
> +	return count;
> +}
> +
> +/*
> + * vtpm_fops_poll: Poll status on 'server side'
> + *
> + * Return value:
> + *      Poll flags
> + */
> +static unsigned int vtpm_fops_poll(struct file *filp, poll_table *wait)
> +{
> +	struct vtpm_dev *vtpm_dev = filp->private_data;
> +	unsigned ret;
> +
> +	poll_wait(filp, &vtpm_dev->wq, wait);
> +
> +	ret = POLLOUT;
> +	if (vtpm_dev->req_len)
> +		ret |= POLLIN | POLLRDNORM;
> +
> +	return ret;
> +}
> +
> +/*
> + * vtpm_fops_open - Open vTPM device on 'server side'
> + *
> + * Called when setting up the anonymous file descriptor
> + */
> +static void vtpm_fops_open(struct file *filp)
> +{
> +	struct vtpm_dev *vtpm_dev = filp->private_data;


mutex_lock(&vtpm_dev->buf_lock);

> +
> +	vtpm_dev->state |= STATE_OPENED_FLAG; /* locking not necessary */
> +
> +	mutex_unlock(&vtpm_dev->buf_lock);
> +}
> +
> +/**
> + * vtpm_fops_undo_open - counter-part to vtpm_fops_open
> + *
> + * Call to undo vtpm_fops_open
> + */
> +static void vtpm_fops_undo_open(struct vtpm_dev *vtpm_dev)
> +{
> +	vtpm_dev->state &= ~STATE_OPENED_FLAG; /* locking not necessary */
> +
> +	/* no more TPM responses -- wake up anyone waiting for them */
> +	wake_up_interruptible(&vtpm_dev->wq);
> +}
> +
> +/*
> + * vtpm_fops_release: Close 'server side'
> + *
> + * Return value:
> + *      Always returns 0.
> + */
> +static int vtpm_fops_release(struct inode *inode, struct file *filp)
> +{
> +	struct vtpm_dev *vtpm_dev = filp->private_data;
> +
> +	filp->private_data = NULL;
> +
> +	vtpm_delete_device_pair(vtpm_dev);
> +
> +	return 0;
> +}
> +
> +static const struct file_operations vtpm_fops = {
> +	.owner = THIS_MODULE,
> +	.llseek = no_llseek,
> +	.read = vtpm_fops_read,
> +	.write = vtpm_fops_write,
> +	.poll = vtpm_fops_poll,
> +	.release = vtpm_fops_release,
> +};
> +
> +/*
> + * Functions invoked by the core TPM driver to send TPM commands to
> + * 'server side' and receive responses from there.
> + */
> +
> +/*
> + * Called when core TPM driver reads TPM responses from 'server side'
> + *
> + * Return value:
> + *      Number of TPM response bytes read, negative error value otherwise
> + */
> +static int vtpm_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> +	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
> +	size_t len;
> +
> +	if (!vtpm_dev)
> +		return -EIO;
> +
> +	/* process gone ? */
> +	if (!(vtpm_dev->state & STATE_OPENED_FLAG))
> +		return -EPIPE;
> +
> +	mutex_lock(&vtpm_dev->buf_lock);
> +
> +	len = vtpm_dev->resp_len;
> +	if (count < len) {
> +		dev_err(&chip->dev,
> +			"Invalid size in recv: count=%zd, resp_len=%zd\n",
> +			count, len);
> +		len = -EIO;
> +		goto out;
> +	}
> +
> +	memcpy(buf, vtpm_dev->buffer, len);
> +	vtpm_dev->resp_len = 0;
> +
> +out:
> +	mutex_unlock(&vtpm_dev->buf_lock);
> +
> +	return len;
> +}
> +
> +/*
> + * Called when core TPM driver forwards TPM requests to 'server side'.
> + *
> + * Return value:
> + *      0 in case of success, negative error value otherwise.
> + */
> +static int vtpm_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t count)
> +{
> +	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
> +	int rc = 0;
> +
> +	if (!vtpm_dev)
> +		return -EIO;
> +
> +	if (!(vtpm_dev->state & STATE_OPENED_FLAG))
> +		return -EPIPE;
> +
> +	if (count > sizeof(vtpm_dev->buffer)) {
> +		dev_err(&chip->dev,
> +			"Invalid size in send: count=%zd, buffer size=%zd\n",
> +			count, sizeof(vtpm_dev->buffer));
> +		return -EIO;
> +	}
> +
> +	mutex_lock(&vtpm_dev->buf_lock);
> +
> +	vtpm_dev->resp_len = 0;
> +
> +	vtpm_dev->req_len = count;
> +	memcpy(vtpm_dev->buffer, buf, count);
> +
> +	vtpm_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;
> +
> +	mutex_unlock(&vtpm_dev->buf_lock);
> +
> +	wake_up_interruptible(&vtpm_dev->wq);
> +
> +	return rc;
> +}
> +
> +static void vtpm_tpm_op_cancel(struct tpm_chip *chip)
> +{
> +	/* not supported */
> +}
> +
> +static u8 vtpm_tpm_op_status(struct tpm_chip *chip)
> +{
> +	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
> +
> +	if (vtpm_dev->resp_len)
> +		return VTPM_REQ_COMPLETE_FLAG;
> +
> +	return 0;
> +}
> +
> +static bool vtpm_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
> +{
> +	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
> +
> +	return !(vtpm_dev->state & STATE_OPENED_FLAG);
> +}
> +
> +static const struct tpm_class_ops vtpm_tpm_ops = {
> +	.recv = vtpm_tpm_op_recv,
> +	.send = vtpm_tpm_op_send,
> +	.cancel = vtpm_tpm_op_cancel,
> +	.status = vtpm_tpm_op_status,
> +	.req_complete_mask = VTPM_REQ_COMPLETE_FLAG,
> +	.req_complete_val = VTPM_REQ_COMPLETE_FLAG,
> +	.req_canceled = vtpm_tpm_req_canceled,
> +};
> +
> +/*
> + * Code related to creation and deletion of device pairs
> + */
> +static struct vtpm_dev *vtpm_create_vtpm_dev(void)
> +{
> +	struct vtpm_dev *vtpm_dev;
> +	struct tpm_chip *chip;
> +	int err;
> +
> +	vtpm_dev = kzalloc(sizeof(*vtpm_dev), GFP_KERNEL);
> +	if (vtpm_dev == NULL)
> +		return ERR_PTR(-ENOMEM);
> +
> +	init_waitqueue_head(&vtpm_dev->wq);
> +	mutex_init(&vtpm_dev->buf_lock);
> +
> +	chip = tpm_chip_alloc(NULL, &vtpm_tpm_ops);
> +	if (IS_ERR(chip)) {
> +		err = PTR_ERR(chip);
> +		goto err_vtpm_dev_free;
> +	}
> +	chip->vendor.priv = vtpm_dev;
> +
> +	vtpm_dev->chip = chip;
> +
> +	return vtpm_dev;
> +
> +err_vtpm_dev_free:
> +	kfree(vtpm_dev);
> +
> +	return ERR_PTR(err);
> +}
> +
> +/*
> + * Undo what has been done in vtpm_create_vtpm_dev
> + */
> +static inline void vtpm_delete_vtpm_dev(struct vtpm_dev *vtpm_dev)
> +{
> +	put_device(&vtpm_dev->chip->dev); /* frees chip */
> +	kfree(vtpm_dev);
> +}
> +
> +/*
> + * Create a /dev/tpm%d and 'server side' file descriptor pair
> + *
> + * Return value:
> + *      Returns file pointer on success, an error value otherwise
> + */
> +static struct file *vtpm_create_device_pair(
> +				       struct vtpm_new_pair *vtpm_new_pair)
> +{
> +	struct vtpm_dev *vtpm_dev;
> +	int rc, fd;
> +	struct file *file;
> +
> +	if (vtpm_new_pair->flags & ~VTPM_FLAGS_ALL)
> +		return ERR_PTR(-EINVAL);
> +
> +	vtpm_dev = vtpm_create_vtpm_dev();
> +	if (IS_ERR(vtpm_dev))
> +		return ERR_CAST(vtpm_dev);
> +
> +	vtpm_dev->flags = vtpm_new_pair->flags;
> +
> +	/* setup an anonymous file for the server-side */
> +	fd = get_unused_fd_flags(O_RDWR);
> +	if (fd < 0) {
> +		rc = fd;
> +		goto err_delete_vtpm_dev;
> +	}
> +
> +	file = anon_inode_getfile("[vtpms]", &vtpm_fops, vtpm_dev, O_RDWR);
> +	if (IS_ERR(file)) {
> +		rc = PTR_ERR(file);
> +		goto err_put_unused_fd;
> +	}
> +
> +	/* from now on we can unwind with put_unused_fd() + fput() */
> +	/* simulate an open() on the server side */
> +	vtpm_fops_open(file);
> +
> +	if (vtpm_dev->flags & VTPM_FLAG_TPM2)
> +		vtpm_dev->chip->flags |= TPM_CHIP_FLAG_TPM2;
> +
> +	rc = tpm_chip_register(vtpm_dev->chip);
> +	if (rc)
> +		goto err_vtpm_fput;
> +
> +	vtpm_new_pair->fd = fd;
> +	vtpm_new_pair->major = MAJOR(vtpm_dev->chip->dev.devt);
> +	vtpm_new_pair->minor = MINOR(vtpm_dev->chip->dev.devt);
> +	vtpm_new_pair->tpm_dev_num = vtpm_dev->chip->dev_num;
> +
> +	return file;
> +
> +err_vtpm_fput:
> +	put_unused_fd(fd);
> +	fput(file);
> +
> +	return ERR_PTR(rc);
> +
> +err_put_unused_fd:
> +	put_unused_fd(fd);
> +
> +err_delete_vtpm_dev:
> +	vtpm_delete_vtpm_dev(vtpm_dev);
> +
> +	return ERR_PTR(rc);
> +}
> +
> +/*
> + * Counter part to vtpm_create_device_pair.
> + */
> +static void vtpm_delete_device_pair(struct vtpm_dev *vtpm_dev)
> +{
> +	tpm_chip_unregister(vtpm_dev->chip);
> +
> +	vtpm_fops_undo_open(vtpm_dev);
> +
> +	vtpm_delete_vtpm_dev(vtpm_dev);
> +}
> +
> +/*
> + * Code related to the control device /dev/vtpmx
> + */
> +
> +/*
> + * vtpmx_fops_ioctl: ioctl on /dev/vtpmx
> + *
> + * Return value:
> + *      Returns 0 on success, a negative error code otherwise.
> + */
> +static long vtpmx_fops_ioctl(struct file *f, unsigned int ioctl,
> +			    unsigned long arg)
> +{
> +	void __user *argp = (void __user *)arg;
> +	struct vtpm_new_pair *vtpm_new_pair_p;
> +	struct vtpm_new_pair vtpm_new_pair;
> +	struct file *file;
> +
> +	switch (ioctl) {
> +	case VTPM_NEW_DEV:
> +		if (!capable(CAP_SYS_ADMIN))
> +			return -EPERM;
> +		vtpm_new_pair_p = argp;
> +		if (copy_from_user(&vtpm_new_pair, vtpm_new_pair_p,
> +				   sizeof(vtpm_new_pair)))
> +			return -EFAULT;
> +		file = vtpm_create_device_pair(&vtpm_new_pair);
> +		if (IS_ERR(file))
> +			return PTR_ERR(file);
> +		if (copy_to_user(vtpm_new_pair_p, &vtpm_new_pair,
> +				 sizeof(vtpm_new_pair))) {
> +			put_unused_fd(vtpm_new_pair.fd);
> +			fput(file);
> +			return -EFAULT;
> +		}
> +
> +		fd_install(vtpm_new_pair.fd, file);
> +		return 0;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +#ifdef CONFIG_COMPAT
> +static long vtpmx_fops_compat_ioctl(struct file *f, unsigned int ioctl,
> +				    unsigned long arg)
> +{
> +	return vtpmx_fops_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
> +}
> +#endif
> +
> +static const struct file_operations vtpmx_fops = {
> +	.owner = THIS_MODULE,
> +	.unlocked_ioctl = vtpmx_fops_ioctl,
> +#ifdef CONFIG_COMPAT
> +	.compat_ioctl = vtpmx_fops_compat_ioctl,
> +#endif
> +	.llseek = noop_llseek,
> +};
> +
> +static struct miscdevice vtpmx_miscdev = {
> +	.minor = MISC_DYNAMIC_MINOR,
> +	.name = "vtpmx",
> +	.fops = &vtpmx_fops,
> +};
> +
> +static int vtpmx_init(void)
> +{
> +	return misc_register(&vtpmx_miscdev);
> +}
> +
> +static void vtpmx_cleanup(void)
> +{
> +	misc_deregister(&vtpmx_miscdev);
> +}
> +
> +static int __init vtpm_module_init(void)
> +{
> +	int rc;
> +
> +	rc = vtpmx_init();
> +	if (rc) {
> +		pr_err("couldn't create vtpmx device\n");
> +		return rc;
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit vtpm_module_exit(void)
> +{
> +	vtpmx_cleanup();
> +}
> +
> +module_init(vtpm_module_init);
> +module_exit(vtpm_module_exit);
> +
> +MODULE_AUTHOR("Stefan Berger ([e-mail])");
> +MODULE_DESCRIPTION("vTPM Driver");
> +MODULE_VERSION("0.1");
> +MODULE_LICENSE("GPL");
> diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
> index ebd10e6..3a602c9 100644
> --- a/include/uapi/linux/Kbuild
> +++ b/include/uapi/linux/Kbuild
> @@ -449,6 +449,7 @@ header-y += virtio_scsi.h
>  header-y += virtio_types.h
>  header-y += vm_sockets.h
>  header-y += vt.h
> +header-y += vtpm.h
>  header-y += wait.h
>  header-y += wanrouter.h
>  header-y += watchdog.h
> diff --git a/include/uapi/linux/vtpm.h b/include/uapi/linux/vtpm.h
> new file mode 100644
> index 0000000..978a849
> --- /dev/null
> +++ b/include/uapi/linux/vtpm.h
> @@ -0,0 +1,41 @@
> +/*
> + * Definitions for the VTPM interface
> + * Copyright (c) 2015, 2016, IBM Corporation
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + */
> +
> +#ifndef _UAPI_LINUX_VTPM_H
> +#define _UAPI_LINUX_VTPM_H
> +
> +#include <linux/types.h>
> +#include <linux/ioctl.h>
> +
> +/* ioctls */
> +
> +struct vtpm_new_pair {
> +	__u32 flags;         /* input */
> +	__u32 tpm_dev_num;   /* output */
> +	__u32 fd;            /* output */
> +	__u32 major;         /* output */
> +	__u32 minor;         /* output */
> +};
> +
> +/* above flags */
> +#define VTPM_FLAG_TPM2           1  /* emulator is TPM 2 */
> +
> +/* all supported flags */
> +#define VTPM_FLAGS_ALL  (VTPM_FLAG_TPM2)
> +
> +#define VTPM_TPM 0xa0
> +
> +#define VTPM_NEW_DEV         _IOW(VTPM_TPM, 0x00, struct vtpm_new_pair)
> +
> +#endif /* _UAPI_LINUX_VTPM_H */
> -- 
> 2.4.3

/Jarkko

------------------------------------------------------------------------------

Stefan Berger March 4, 2016, 9:16 p.m. UTC | #2

Jarkko Sakkinen <[e-mail]> wrote on 03/04/2016 
03:29:28 PM:
> 
> Hi
> 
> I noticed some glitches.
> 
> On Mon, Feb 29, 2016 at 12:29:54PM -0500, Stefan Berger wrote:
> > This patch implements a driver for supporting multiple emulated TPMs 
in a
> > system.
> > 
> > The driver implements a device /dev/vtpmx that is used to created
> > a client device pair /dev/tpmX (e.g., /dev/tpm10) and a server side 
that
> > is accessed using a file descriptor returned by an ioctl.
> > The device /dev/tpmX is the usual TPM device created by the core TPM
> > driver. Applications or kernel subsystems can send TPM commands to it
> > and the corresponding server-side file descriptor receives these
> > commands and delivers them to an emulated TPM.
> 
> Every other driver in the subsystem except xen-tpmfront uses
> underscore instead of dash. For the sake of consistency this should be
> renamed as tpm_vtpm.

fixed.


> 
> 
> > Signed-off-by: Stefan Berger <[e-mail]>
> > ---
> >  drivers/char/tpm/Kconfig    |  10 +
> >  drivers/char/tpm/Makefile   |   1 +
> >  drivers/char/tpm/tpm-vtpm.c | 546 +++++++++++++++++++++++++++++++
> +++++++++++++
> >  include/uapi/linux/Kbuild   |   1 +
> >  include/uapi/linux/vtpm.h   |  41 ++++
> >  5 files changed, 599 insertions(+)
> >  create mode 100644 drivers/char/tpm/tpm-vtpm.c
> >  create mode 100644 include/uapi/linux/vtpm.h
> > 
> > diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> > index 3b84a8b..4c4e843 100644
> > --- a/drivers/char/tpm/Kconfig
> > +++ b/drivers/char/tpm/Kconfig
> > @@ -122,5 +122,15 @@ config TCG_CRB
> >       from within Linux.  To compile this driver as a module, choose
> >       M here; the module will be called tpm_crb.
> > 
> > +config TCG_VTPM
> > +   tristate "VTPM Interface"
> > +   depends on TCG_TPM
> > +   ---help---
> > +     This driver supports an emulated TPM (vTPM) running in 
userspace.
> > +     A device /dev/vtpmx is provided that creates a device pair
> > +     /dev/vtpmX and a server-side file descriptor on which the vTPM
> > +     can receive commands.
> > +
> > +
> >  source "drivers/char/tpm/st33zp24/Kconfig"
> >  endif # TCG_TPM
> > diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> > index 56e8f1f..d947db2 100644
> > --- a/drivers/char/tpm/Makefile
> > +++ b/drivers/char/tpm/Makefile
> > @@ -23,3 +23,4 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
> >  obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
> >  obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
> >  obj-$(CONFIG_TCG_CRB) += tpm_crb.o
> > +obj-$(CONFIG_TCG_VTPM) += tpm-vtpm.o
> > diff --git a/drivers/char/tpm/tpm-vtpm.c b/drivers/char/tpm/tpm-vtpm.c
> > new file mode 100644
> > index 0000000..2c69363
> > --- /dev/null
> > +++ b/drivers/char/tpm/tpm-vtpm.c
> > @@ -0,0 +1,546 @@
> > +/*
> > + * Copyright (C) 2015, 2016 IBM Corporation
> > + *
> > + * Author: Stefan Berger <[e-mail]>
> > + *
> > + * Maintained by: <[e-mail]>
> > + *
> > + * Device driver for vTPM.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation, version 2 of the
> > + * License.
> > + *
> > + */
> > +
> > +#include <linux/types.h>
> > +#include <linux/spinlock.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/wait.h>
> > +#include <linux/miscdevice.h>
> > +#include <linux/vtpm.h>
> > +#include <linux/file.h>
> > +#include <linux/anon_inodes.h>
> > +#include <linux/poll.h>
> > +#include <linux/compat.h>
> > +
> > +#include "tpm.h"
> > +
> > +#define VTPM_REQ_COMPLETE_FLAG  BIT(0)
> > +
> > +struct vtpm_dev {
> > +   struct tpm_chip *chip;
> > +
> > +   u32 flags;                   /* public API flags */
> > +
> > +   wait_queue_head_t wq;
> > +
> > +   struct mutex buf_lock;       /* protect buffer and flag 
modifications */
> > +
> > +   long state;                  /* internal state */
> > +#define STATE_OPENED_FLAG        BIT(0)
> > +#define STATE_WAIT_RESPONSE_FLAG BIT(1)  /* waiting for emulator 
> response */
> > +
> > +   size_t req_len;              /* length of queued TPM request */
> > +   size_t resp_len;             /* length of queued TPM response */
> > +   u8 buffer[TPM_BUFSIZE];      /* request/response buffer */
> > +};
> > +
> > +
> > +static void vtpm_delete_device_pair(struct vtpm_dev *vtpm_dev);
> > +
> > +/*
> > + * Functions related to 'server side'
> > + */
> > +
> > +/**
> > + * vtpm_fops_read - Read TPM commands on 'server side'
> > + *
> > + * Return value:
> > + *   Number of bytes read or negative error code
> > + */
> > +static ssize_t vtpm_fops_read(struct file *filp, char __user *buf,
> > +               size_t count, loff_t *off)
> > +{
> > +   struct vtpm_dev *vtpm_dev = filp->private_data;
> > +   size_t len;
> > +   int sig, rc;
> > +
> > +   sig = wait_event_interruptible(vtpm_dev->wq, vtpm_dev->req_len != 
0);
> > +   if (sig)
> > +      return -EINTR;
> > +
> > +   mutex_lock(&vtpm_dev->buf_lock);
> > +
> > +   len = vtpm_dev->req_len;
> > +
> > +   if (count < len) {
> > +      mutex_unlock(&vtpm_dev->buf_lock);
> > +      pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n",
> > +          count, len);
> > +      return -EIO;
> > +   }
> > +
> > +   rc = copy_to_user(buf, vtpm_dev->buffer, len);
> > +   memset(vtpm_dev->buffer, 0, len);
> > +   vtpm_dev->req_len = 0;
> > +
> > +   if (!rc)
> > +      vtpm_dev->state |= STATE_WAIT_RESPONSE_FLAG;
> > +
> > +   mutex_unlock(&vtpm_dev->buf_lock);
> > +
> > +   if (rc)
> > +      return -EFAULT;
> > +
> > +   return len;
> > +}
> > +
> > +/**
> > + * vtpm_fops_write - Write TPM responses on 'server side'
> > + *
> > + * Return value:
> > + *   Number of bytes read or negative error value
> > + */
> > +static ssize_t vtpm_fops_write(struct file *filp, const char __user 
*buf,
> > +                size_t count, loff_t *off)
> > +{
> > +   struct vtpm_dev *vtpm_dev = filp->private_data;
> > +
> > +   if (count > sizeof(vtpm_dev->buffer) ||
> > +       !(vtpm_dev->state & STATE_WAIT_RESPONSE_FLAG))
> > +      return -EIO;
> 
> This is not atomic in any sense. You should move this statement after
> taking buf_lock.


set_bit and friends were all atomic. Now we need to put all of these into 
the mutex... ?

   Stefan
------------------------------------------------------------------------------

Jarkko Sakkinen March 4, 2016, 10:34 p.m. UTC | #3

On Fri, Mar 04, 2016 at 04:16:41PM -0500, Stefan Berger wrote:
>    > > +static ssize_t vtpm_fops_write(struct file *filp, const char __user
>    *buf,
>    > > +                size_t count, loff_t *off)
>    > > +{
>    > > +   struct vtpm_dev *vtpm_dev = filp->private_data;
>    > > +
>    > > +   if (count > sizeof(vtpm_dev->buffer) ||
>    > > +       !(vtpm_dev->state & STATE_WAIT_RESPONSE_FLAG))
>    > > +      return -EIO;
>    >
>    > This is not atomic in any sense. You should move this statement after
>    > taking buf_lock.
> 
>    set_bit and friends were all atomic. Now we need to put all of these into
>    the mutex... ?

Hmm... but you have other fields too in struct vtpm_dev so you anyway
need to use mutex for concurrent access to the file. In that statement
you are accessing two fields from that structure.

Lets say someone forks 100 processes that concurrently access this
same open file. How else you would keep the state of vtpm_dev coherent
than protecting with a mutex?

Maybe the problem is that you are only thinking a proper way to use
this infrastructure?

>       Stefan

/Jarkko

------------------------------------------------------------------------------

Stefan Berger March 5, 2016, 2:55 p.m. UTC | #4

Jarkko Sakkinen <[e-mail]> wrote on 03/04/2016 
05:34:10 PM:


> On Fri, Mar 04, 2016 at 04:16:41PM -0500, Stefan Berger wrote:
> >    > > +static ssize_t vtpm_fops_write(struct file *filp, const char 
__user
> >    *buf,
> >    > > +                size_t count, loff_t *off)
> >    > > +{
> >    > > +   struct vtpm_dev *vtpm_dev = filp->private_data;
> >    > > +
> >    > > +   if (count > sizeof(vtpm_dev->buffer) ||
> >    > > +       !(vtpm_dev->state & STATE_WAIT_RESPONSE_FLAG))
> >    > > +      return -EIO;
> >    >
> >    > This is not atomic in any sense. You should move this statement 
after
> >    > taking buf_lock.
> > 
> >    set_bit and friends were all atomic. Now we need to put all of 
these into
> >    the mutex... ?
> 
> Hmm... but you have other fields too in struct vtpm_dev so you anyway
> need to use mutex for concurrent access to the file. In that statement
> you are accessing two fields from that structure.
> 
> Lets say someone forks 100 processes that concurrently access this
> same open file. How else you would keep the state of vtpm_dev coherent
> than protecting with a mutex?

I moved the accesses to the flag now into the mutex where necessary, 
except for one place where it's done so early that there's no concurrency. 
The updated code is here:

https://github.com/stefanberger/linux/commits/vtpm-driver.v5

   Stefan
------------------------------------------------------------------------------

Patch

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 3b84a8b..4c4e843 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -122,5 +122,15 @@  config TCG_CRB
 	  from within Linux.  To compile this driver as a module, choose
 	  M here; the module will be called tpm_crb.
 
+config TCG_VTPM
+	tristate "VTPM Interface"
+	depends on TCG_TPM
+	---help---
+	  This driver supports an emulated TPM (vTPM) running in userspace.
+	  A device /dev/vtpmx is provided that creates a device pair
+	  /dev/vtpmX and a server-side file descriptor on which the vTPM
+	  can receive commands.
+
+
 source "drivers/char/tpm/st33zp24/Kconfig"
 endif # TCG_TPM
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 56e8f1f..d947db2 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -23,3 +23,4 @@  obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
 obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
 obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
 obj-$(CONFIG_TCG_CRB) += tpm_crb.o
+obj-$(CONFIG_TCG_VTPM) += tpm-vtpm.o
diff --git a/drivers/char/tpm/tpm-vtpm.c b/drivers/char/tpm/tpm-vtpm.c
new file mode 100644
index 0000000..2c69363
--- /dev/null
+++ b/drivers/char/tpm/tpm-vtpm.c
@@ -0,0 +1,546 @@ 
+/*
+ * Copyright (C) 2015, 2016 IBM Corporation
+ *
+ * Author: Stefan Berger <[e-mail]>
+ *
+ * Maintained by: <[e-mail]>
+ *
+ * Device driver for vTPM.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/wait.h>
+#include <linux/miscdevice.h>
+#include <linux/vtpm.h>
+#include <linux/file.h>
+#include <linux/anon_inodes.h>
+#include <linux/poll.h>
+#include <linux/compat.h>
+
+#include "tpm.h"
+
+#define VTPM_REQ_COMPLETE_FLAG  BIT(0)
+
+struct vtpm_dev {
+	struct tpm_chip *chip;
+
+	u32 flags;                   /* public API flags */
+
+	wait_queue_head_t wq;
+
+	struct mutex buf_lock;       /* protect buffer and flag modifications */
+
+	long state;                  /* internal state */
+#define STATE_OPENED_FLAG        BIT(0)
+#define STATE_WAIT_RESPONSE_FLAG BIT(1)  /* waiting for emulator response */
+
+	size_t req_len;              /* length of queued TPM request */
+	size_t resp_len;             /* length of queued TPM response */
+	u8 buffer[TPM_BUFSIZE];      /* request/response buffer */
+};
+
+
+static void vtpm_delete_device_pair(struct vtpm_dev *vtpm_dev);
+
+/*
+ * Functions related to 'server side'
+ */
+
+/**
+ * vtpm_fops_read - Read TPM commands on 'server side'
+ *
+ * Return value:
+ *	Number of bytes read or negative error code
+ */
+static ssize_t vtpm_fops_read(struct file *filp, char __user *buf,
+			      size_t count, loff_t *off)
+{
+	struct vtpm_dev *vtpm_dev = filp->private_data;
+	size_t len;
+	int sig, rc;
+
+	sig = wait_event_interruptible(vtpm_dev->wq, vtpm_dev->req_len != 0);
+	if (sig)
+		return -EINTR;
+
+	mutex_lock(&vtpm_dev->buf_lock);
+
+	len = vtpm_dev->req_len;
+
+	if (count < len) {
+		mutex_unlock(&vtpm_dev->buf_lock);
+		pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n",
+			 count, len);
+		return -EIO;
+	}
+
+	rc = copy_to_user(buf, vtpm_dev->buffer, len);
+	memset(vtpm_dev->buffer, 0, len);
+	vtpm_dev->req_len = 0;
+
+	if (!rc)
+		vtpm_dev->state |= STATE_WAIT_RESPONSE_FLAG;
+
+	mutex_unlock(&vtpm_dev->buf_lock);
+
+	if (rc)
+		return -EFAULT;
+
+	return len;
+}
+
+/**
+ * vtpm_fops_write - Write TPM responses on 'server side'
+ *
+ * Return value:
+ *	Number of bytes read or negative error value
+ */
+static ssize_t vtpm_fops_write(struct file *filp, const char __user *buf,
+			       size_t count, loff_t *off)
+{
+	struct vtpm_dev *vtpm_dev = filp->private_data;
+
+	if (count > sizeof(vtpm_dev->buffer) ||
+	    !(vtpm_dev->state & STATE_WAIT_RESPONSE_FLAG))
+		return -EIO;
+
+	mutex_lock(&vtpm_dev->buf_lock);
+
+	vtpm_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;
+
+	vtpm_dev->req_len = 0;
+
+	if (copy_from_user(vtpm_dev->buffer, buf, count)) {
+		mutex_unlock(&vtpm_dev->buf_lock);
+		return -EFAULT;
+	}
+
+	vtpm_dev->resp_len = count;
+
+	mutex_unlock(&vtpm_dev->buf_lock);
+
+	wake_up_interruptible(&vtpm_dev->wq);
+
+	return count;
+}
+
+/*
+ * vtpm_fops_poll: Poll status on 'server side'
+ *
+ * Return value:
+ *      Poll flags
+ */
+static unsigned int vtpm_fops_poll(struct file *filp, poll_table *wait)
+{
+	struct vtpm_dev *vtpm_dev = filp->private_data;
+	unsigned ret;
+
+	poll_wait(filp, &vtpm_dev->wq, wait);
+
+	ret = POLLOUT;
+	if (vtpm_dev->req_len)
+		ret |= POLLIN | POLLRDNORM;
+
+	return ret;
+}
+
+/*
+ * vtpm_fops_open - Open vTPM device on 'server side'
+ *
+ * Called when setting up the anonymous file descriptor
+ */
+static void vtpm_fops_open(struct file *filp)
+{
+	struct vtpm_dev *vtpm_dev = filp->private_data;
+
+	vtpm_dev->state |= STATE_OPENED_FLAG; /* locking not necessary */
+
+	mutex_unlock(&vtpm_dev->buf_lock);
+}
+
+/**
+ * vtpm_fops_undo_open - counter-part to vtpm_fops_open
+ *
+ * Call to undo vtpm_fops_open
+ */
+static void vtpm_fops_undo_open(struct vtpm_dev *vtpm_dev)
+{
+	vtpm_dev->state &= ~STATE_OPENED_FLAG; /* locking not necessary */
+
+	/* no more TPM responses -- wake up anyone waiting for them */
+	wake_up_interruptible(&vtpm_dev->wq);
+}
+
+/*
+ * vtpm_fops_release: Close 'server side'
+ *
+ * Return value:
+ *      Always returns 0.
+ */
+static int vtpm_fops_release(struct inode *inode, struct file *filp)
+{
+	struct vtpm_dev *vtpm_dev = filp->private_data;
+
+	filp->private_data = NULL;
+
+	vtpm_delete_device_pair(vtpm_dev);
+
+	return 0;
+}
+
+static const struct file_operations vtpm_fops = {
+	.owner = THIS_MODULE,
+	.llseek = no_llseek,
+	.read = vtpm_fops_read,
+	.write = vtpm_fops_write,
+	.poll = vtpm_fops_poll,
+	.release = vtpm_fops_release,
+};
+
+/*
+ * Functions invoked by the core TPM driver to send TPM commands to
+ * 'server side' and receive responses from there.
+ */
+
+/*
+ * Called when core TPM driver reads TPM responses from 'server side'
+ *
+ * Return value:
+ *      Number of TPM response bytes read, negative error value otherwise
+ */
+static int vtpm_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
+	size_t len;
+
+	if (!vtpm_dev)
+		return -EIO;
+
+	/* process gone ? */
+	if (!(vtpm_dev->state & STATE_OPENED_FLAG))
+		return -EPIPE;
+
+	mutex_lock(&vtpm_dev->buf_lock);
+
+	len = vtpm_dev->resp_len;
+	if (count < len) {
+		dev_err(&chip->dev,
+			"Invalid size in recv: count=%zd, resp_len=%zd\n",
+			count, len);
+		len = -EIO;
+		goto out;
+	}
+
+	memcpy(buf, vtpm_dev->buffer, len);
+	vtpm_dev->resp_len = 0;
+
+out:
+	mutex_unlock(&vtpm_dev->buf_lock);
+
+	return len;
+}
+
+/*
+ * Called when core TPM driver forwards TPM requests to 'server side'.
+ *
+ * Return value:
+ *      0 in case of success, negative error value otherwise.
+ */
+static int vtpm_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
+	int rc = 0;
+
+	if (!vtpm_dev)
+		return -EIO;
+
+	if (!(vtpm_dev->state & STATE_OPENED_FLAG))
+		return -EPIPE;
+
+	if (count > sizeof(vtpm_dev->buffer)) {
+		dev_err(&chip->dev,
+			"Invalid size in send: count=%zd, buffer size=%zd\n",
+			count, sizeof(vtpm_dev->buffer));
+		return -EIO;
+	}
+
+	mutex_lock(&vtpm_dev->buf_lock);
+
+	vtpm_dev->resp_len = 0;
+
+	vtpm_dev->req_len = count;
+	memcpy(vtpm_dev->buffer, buf, count);
+
+	vtpm_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;
+
+	mutex_unlock(&vtpm_dev->buf_lock);
+
+	wake_up_interruptible(&vtpm_dev->wq);
+
+	return rc;
+}
+
+static void vtpm_tpm_op_cancel(struct tpm_chip *chip)
+{
+	/* not supported */
+}
+
+static u8 vtpm_tpm_op_status(struct tpm_chip *chip)
+{
+	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
+
+	if (vtpm_dev->resp_len)
+		return VTPM_REQ_COMPLETE_FLAG;
+
+	return 0;
+}
+
+static bool vtpm_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
+{
+	struct vtpm_dev *vtpm_dev = chip->vendor.priv;
+
+	return !(vtpm_dev->state & STATE_OPENED_FLAG);
+}
+
+static const struct tpm_class_ops vtpm_tpm_ops = {
+	.recv = vtpm_tpm_op_recv,
+	.send = vtpm_tpm_op_send,
+	.cancel = vtpm_tpm_op_cancel,
+	.status = vtpm_tpm_op_status,
+	.req_complete_mask = VTPM_REQ_COMPLETE_FLAG,
+	.req_complete_val = VTPM_REQ_COMPLETE_FLAG,
+	.req_canceled = vtpm_tpm_req_canceled,
+};
+
+/*
+ * Code related to creation and deletion of device pairs
+ */
+static struct vtpm_dev *vtpm_create_vtpm_dev(void)
+{
+	struct vtpm_dev *vtpm_dev;
+	struct tpm_chip *chip;
+	int err;
+
+	vtpm_dev = kzalloc(sizeof(*vtpm_dev), GFP_KERNEL);
+	if (vtpm_dev == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	init_waitqueue_head(&vtpm_dev->wq);
+	mutex_init(&vtpm_dev->buf_lock);
+
+	chip = tpm_chip_alloc(NULL, &vtpm_tpm_ops);
+	if (IS_ERR(chip)) {
+		err = PTR_ERR(chip);
+		goto err_vtpm_dev_free;
+	}
+	chip->vendor.priv = vtpm_dev;
+
+	vtpm_dev->chip = chip;
+
+	return vtpm_dev;
+
+err_vtpm_dev_free:
+	kfree(vtpm_dev);
+
+	return ERR_PTR(err);
+}
+
+/*
+ * Undo what has been done in vtpm_create_vtpm_dev
+ */
+static inline void vtpm_delete_vtpm_dev(struct vtpm_dev *vtpm_dev)
+{
+	put_device(&vtpm_dev->chip->dev); /* frees chip */
+	kfree(vtpm_dev);
+}
+
+/*
+ * Create a /dev/tpm%d and 'server side' file descriptor pair
+ *
+ * Return value:
+ *      Returns file pointer on success, an error value otherwise
+ */
+static struct file *vtpm_create_device_pair(
+				       struct vtpm_new_pair *vtpm_new_pair)
+{
+	struct vtpm_dev *vtpm_dev;
+	int rc, fd;
+	struct file *file;
+
+	if (vtpm_new_pair->flags & ~VTPM_FLAGS_ALL)
+		return ERR_PTR(-EINVAL);
+
+	vtpm_dev = vtpm_create_vtpm_dev();
+	if (IS_ERR(vtpm_dev))
+		return ERR_CAST(vtpm_dev);
+
+	vtpm_dev->flags = vtpm_new_pair->flags;
+
+	/* setup an anonymous file for the server-side */
+	fd = get_unused_fd_flags(O_RDWR);
+	if (fd < 0) {
+		rc = fd;
+		goto err_delete_vtpm_dev;
+	}
+
+	file = anon_inode_getfile("[vtpms]", &vtpm_fops, vtpm_dev, O_RDWR);
+	if (IS_ERR(file)) {
+		rc = PTR_ERR(file);
+		goto err_put_unused_fd;
+	}
+
+	/* from now on we can unwind with put_unused_fd() + fput() */
+	/* simulate an open() on the server side */
+	vtpm_fops_open(file);
+
+	if (vtpm_dev->flags & VTPM_FLAG_TPM2)
+		vtpm_dev->chip->flags |= TPM_CHIP_FLAG_TPM2;
+
+	rc = tpm_chip_register(vtpm_dev->chip);
+	if (rc)
+		goto err_vtpm_fput;
+
+	vtpm_new_pair->fd = fd;
+	vtpm_new_pair->major = MAJOR(vtpm_dev->chip->dev.devt);
+	vtpm_new_pair->minor = MINOR(vtpm_dev->chip->dev.devt);
+	vtpm_new_pair->tpm_dev_num = vtpm_dev->chip->dev_num;
+
+	return file;
+
+err_vtpm_fput:
+	put_unused_fd(fd);
+	fput(file);
+
+	return ERR_PTR(rc);
+
+err_put_unused_fd:
+	put_unused_fd(fd);
+
+err_delete_vtpm_dev:
+	vtpm_delete_vtpm_dev(vtpm_dev);
+
+	return ERR_PTR(rc);
+}
+
+/*
+ * Counter part to vtpm_create_device_pair.
+ */
+static void vtpm_delete_device_pair(struct vtpm_dev *vtpm_dev)
+{
+	tpm_chip_unregister(vtpm_dev->chip);
+
+	vtpm_fops_undo_open(vtpm_dev);
+
+	vtpm_delete_vtpm_dev(vtpm_dev);
+}
+
+/*
+ * Code related to the control device /dev/vtpmx
+ */
+
+/*
+ * vtpmx_fops_ioctl: ioctl on /dev/vtpmx
+ *
+ * Return value:
+ *      Returns 0 on success, a negative error code otherwise.
+ */
+static long vtpmx_fops_ioctl(struct file *f, unsigned int ioctl,
+			    unsigned long arg)
+{
+	void __user *argp = (void __user *)arg;
+	struct vtpm_new_pair *vtpm_new_pair_p;
+	struct vtpm_new_pair vtpm_new_pair;
+	struct file *file;
+
+	switch (ioctl) {
+	case VTPM_NEW_DEV:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		vtpm_new_pair_p = argp;
+		if (copy_from_user(&vtpm_new_pair, vtpm_new_pair_p,
+				   sizeof(vtpm_new_pair)))
+			return -EFAULT;
+		file = vtpm_create_device_pair(&vtpm_new_pair);
+		if (IS_ERR(file))
+			return PTR_ERR(file);
+		if (copy_to_user(vtpm_new_pair_p, &vtpm_new_pair,
+				 sizeof(vtpm_new_pair))) {
+			put_unused_fd(vtpm_new_pair.fd);
+			fput(file);
+			return -EFAULT;
+		}
+
+		fd_install(vtpm_new_pair.fd, file);
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long vtpmx_fops_compat_ioctl(struct file *f, unsigned int ioctl,
+				    unsigned long arg)
+{
+	return vtpmx_fops_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct file_operations vtpmx_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = vtpmx_fops_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = vtpmx_fops_compat_ioctl,
+#endif
+	.llseek = noop_llseek,
+};
+
+static struct miscdevice vtpmx_miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "vtpmx",
+	.fops = &vtpmx_fops,
+};
+
+static int vtpmx_init(void)
+{
+	return misc_register(&vtpmx_miscdev);
+}
+
+static void vtpmx_cleanup(void)
+{
+	misc_deregister(&vtpmx_miscdev);
+}
+
+static int __init vtpm_module_init(void)
+{
+	int rc;
+
+	rc = vtpmx_init();
+	if (rc) {
+		pr_err("couldn't create vtpmx device\n");
+		return rc;
+	}
+
+	return 0;
+}
+
+static void __exit vtpm_module_exit(void)
+{
+	vtpmx_cleanup();
+}
+
+module_init(vtpm_module_init);
+module_exit(vtpm_module_exit);
+
+MODULE_AUTHOR("Stefan Berger ([e-mail])");
+MODULE_DESCRIPTION("vTPM Driver");
+MODULE_VERSION("0.1");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index ebd10e6..3a602c9 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -449,6 +449,7 @@  header-y += virtio_scsi.h
 header-y += virtio_types.h
 header-y += vm_sockets.h
 header-y += vt.h
+header-y += vtpm.h
 header-y += wait.h
 header-y += wanrouter.h
 header-y += watchdog.h
diff --git a/include/uapi/linux/vtpm.h b/include/uapi/linux/vtpm.h
new file mode 100644
index 0000000..978a849
--- /dev/null
+++ b/include/uapi/linux/vtpm.h
@@ -0,0 +1,41 @@ 
+/*
+ * Definitions for the VTPM interface
+ * Copyright (c) 2015, 2016, IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#ifndef _UAPI_LINUX_VTPM_H
+#define _UAPI_LINUX_VTPM_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+/* ioctls */
+
+struct vtpm_new_pair {
+	__u32 flags;         /* input */
+	__u32 tpm_dev_num;   /* output */
+	__u32 fd;            /* output */
+	__u32 major;         /* output */
+	__u32 minor;         /* output */
+};
+
+/* above flags */
+#define VTPM_FLAG_TPM2           1  /* emulator is TPM 2 */
+
+/* all supported flags */
+#define VTPM_FLAGS_ALL  (VTPM_FLAG_TPM2)
+
+#define VTPM_TPM 0xa0
+
+#define VTPM_NEW_DEV         _IOW(VTPM_TPM, 0x00, struct vtpm_new_pair)
+
+#endif /* _UAPI_LINUX_VTPM_H */