tpm: add support for nonblocking operation

Currently the TPM driver only supports blocking calls, which doesn't allow
asynchronous IO operations to the TPM hardware.
This patch changes it and adds support for nonblocking write and a new poll
function to enable applications, which want to take advantage of this.

Tested-by: Philip Tricca <philip.b.tricca@intel.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off--by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm-dev-common.c

@@ -17,29 +17,56 @@
  * License.
  *
  */
+#include <linux/poll.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/workqueue.h>
 #include "tpm.h"
 #include "tpm-dev.h"
 
+static struct workqueue_struct *tpm_dev_wq;
+static DEFINE_MUTEX(tpm_dev_wq_lock);
+
+static void tpm_async_work(struct work_struct *work)
+{
+	struct file_priv *priv =
+			container_of(work, struct file_priv, async_work);
+	ssize_t ret;
+
+	mutex_lock(&priv->buffer_mutex);
+	priv->command_enqueued = false;
+	ret = tpm_transmit(priv->chip, priv->space, priv->data_buffer,
+			   sizeof(priv->data_buffer), 0);
+
+	tpm_put_ops(priv->chip);
+	if (ret > 0) {
+		priv->data_pending = ret;
+		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
+	}
+	mutex_unlock(&priv->buffer_mutex);
+	wake_up_interruptible(&priv->async_wait);
+}
+
 static void user_reader_timeout(struct timer_list *t)
 {
 	struct file_priv *priv = from_timer(priv, t, user_read_timer);
 
 	pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
 		task_tgid_nr(current));
 
-	schedule_work(&priv->work);
+	schedule_work(&priv->timeout_work);
 }
 
-static void timeout_work(struct work_struct *work)
+static void tpm_timeout_work(struct work_struct *work)
 {
-	struct file_priv *priv = container_of(work, struct file_priv, work);
+	struct file_priv *priv = container_of(work, struct file_priv,
+					      timeout_work);
 
 	mutex_lock(&priv->buffer_mutex);
 	priv->data_pending = 0;
 	memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
 	mutex_unlock(&priv->buffer_mutex);
+	wake_up_interruptible(&priv->async_wait);
 }
 
 void tpm_common_open(struct file *file, struct tpm_chip *chip,
@@ -50,8 +77,9 @@ void tpm_common_open(struct file *file, struct tpm_chip *chip,
 
 	mutex_init(&priv->buffer_mutex);
 	timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
-	INIT_WORK(&priv->work, timeout_work);
-
+	INIT_WORK(&priv->timeout_work, tpm_timeout_work);
+	INIT_WORK(&priv->async_work, tpm_async_work);
+	init_waitqueue_head(&priv->async_wait);
 	file->private_data = priv;
 }
 
@@ -63,15 +91,17 @@ ssize_t tpm_common_read(struct file *file, char __user *buf,
 	int rc;
 
 	del_singleshot_timer_sync(&priv->user_read_timer);
-	flush_work(&priv->work);
+	flush_work(&priv->timeout_work);
 	mutex_lock(&priv->buffer_mutex);
 
 	if (priv->data_pending) {
 		ret_size = min_t(ssize_t, size, priv->data_pending);
-		rc = copy_to_user(buf, priv->data_buffer, ret_size);
-		memset(priv->data_buffer, 0, priv->data_pending);
-		if (rc)
-			ret_size = -EFAULT;
+		if (ret_size > 0) {
+			rc = copy_to_user(buf, priv->data_buffer, ret_size);
+			memset(priv->data_buffer, 0, priv->data_pending);
+			if (rc)
+				ret_size = -EFAULT;
+		}
 
 		priv->data_pending = 0;
 	}
@@ -84,10 +114,9 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
 			 size_t size, loff_t *off)
 {
 	struct file_priv *priv = file->private_data;
-	size_t in_size = size;
-	ssize_t out_size;
+	int ret = 0;
 
-	if (in_size > TPM_BUFSIZE)
+	if (size > TPM_BUFSIZE)
 		return -E2BIG;
 
 	mutex_lock(&priv->buffer_mutex);
@@ -96,56 +125,96 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
 	 * tpm_read or a user_read_timer timeout. This also prevents split
 	 * buffered writes from blocking here.
 	 */
-	if (priv->data_pending != 0) {
-		mutex_unlock(&priv->buffer_mutex);
-		return -EBUSY;
+	if (priv->data_pending != 0 || priv->command_enqueued) {
+		ret = -EBUSY;
+		goto out;
 	}
 
-	if (copy_from_user
-	    (priv->data_buffer, (void __user *) buf, in_size)) {
-		mutex_unlock(&priv->buffer_mutex);
-		return -EFAULT;
+	if (copy_from_user(priv->data_buffer, buf, size)) {
+		ret = -EFAULT;
+		goto out;
 	}
 
-	if (in_size < 6 ||
-	    in_size < be32_to_cpu(*((__be32 *) (priv->data_buffer + 2)))) {
-		mutex_unlock(&priv->buffer_mutex);
-		return -EINVAL;
+	if (size < 6 ||
+	    size < be32_to_cpu(*((__be32 *)(priv->data_buffer + 2)))) {
+		ret = -EINVAL;
+		goto out;
 	}
 
 	/* atomic tpm command send and result receive. We only hold the ops
 	 * lock during this period so that the tpm can be unregistered even if
 	 * the char dev is held open.
 	 */
 	if (tpm_try_get_ops(priv->chip)) {
-		mutex_unlock(&priv->buffer_mutex);
-		return -EPIPE;
+		ret = -EPIPE;
+		goto out;
 	}
-	out_size = tpm_transmit(priv->chip, priv->space, priv->data_buffer,
-				sizeof(priv->data_buffer), 0);
 
-	tpm_put_ops(priv->chip);
-	if (out_size < 0) {
+	/*
+	 * If in nonblocking mode schedule an async job to send
+	 * the command return the size.
+	 * In case of error the err code will be returned in
+	 * the subsequent read call.
+	 */
+	if (file->f_flags & O_NONBLOCK) {
+		priv->command_enqueued = true;
+		queue_work(tpm_dev_wq, &priv->async_work);
 		mutex_unlock(&priv->buffer_mutex);
-		return out_size;
+		return size;
 	}
 
-	priv->data_pending = out_size;
+	ret = tpm_transmit(priv->chip, priv->space, priv->data_buffer,
+			   sizeof(priv->data_buffer), 0);
+	tpm_put_ops(priv->chip);
+
+	if (ret > 0) {
+		priv->data_pending = ret;
+		mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
+		ret = size;
+	}
+out:
 	mutex_unlock(&priv->buffer_mutex);
+	return ret;
+}
+
+__poll_t tpm_common_poll(struct file *file, poll_table *wait)
+{
+	struct file_priv *priv = file->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(file, &priv->async_wait, wait);
 
-	/* Set a timeout by which the reader must come claim the result */
-	mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
+	if (priv->data_pending)
+		mask = EPOLLIN | EPOLLRDNORM;
+	else
+		mask = EPOLLOUT | EPOLLWRNORM;
 
-	return in_size;
+	return mask;
 }
 
 /*
  * Called on file close
  */
 void tpm_common_release(struct file *file, struct file_priv *priv)
 {
+	flush_work(&priv->async_work);
 	del_singleshot_timer_sync(&priv->user_read_timer);
-	flush_work(&priv->work);
+	flush_work(&priv->timeout_work);
 	file->private_data = NULL;
 	priv->data_pending = 0;
 }
+
+int __init tpm_dev_common_init(void)
+{
+	tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);
+
+	return !tpm_dev_wq ? -ENOMEM : 0;
+}
+
+void __exit tpm_dev_common_exit(void)
+{
+	if (tpm_dev_wq) {
+		destroy_workqueue(tpm_dev_wq);
+		tpm_dev_wq = NULL;
+	}
+}

drivers/char/tpm/tpm-dev.c

@@ -68,5 +68,6 @@ const struct file_operations tpm_fops = {
 	.open = tpm_open,
 	.read = tpm_common_read,
 	.write = tpm_common_write,
+	.poll = tpm_common_poll,
 	.release = tpm_release,
 };

drivers/char/tpm/tpm-dev.h

@@ -2,18 +2,22 @@
 #ifndef _TPM_DEV_H
 #define _TPM_DEV_H
 
+#include <linux/poll.h>
 #include "tpm.h"
 
 struct file_priv {
 	struct tpm_chip *chip;
 	struct tpm_space *space;
 
-	/* Data passed to and from the tpm via the read/write calls */
-	size_t data_pending;
+	/* Holds the amount of data passed or an error code from async op */
+	ssize_t data_pending;
 	struct mutex buffer_mutex;
 
 	struct timer_list user_read_timer;      /* user needs to claim result */
-	struct work_struct work;
+	struct work_struct timeout_work;
+	struct work_struct async_work;
+	wait_queue_head_t async_wait;
+	bool command_enqueued;
 
 	u8 data_buffer[TPM_BUFSIZE];
 };
@@ -24,6 +28,7 @@ ssize_t tpm_common_read(struct file *file, char __user *buf,
 			size_t size, loff_t *off);
 ssize_t tpm_common_write(struct file *file, const char __user *buf,
 			 size_t size, loff_t *off);
-void tpm_common_release(struct file *file, struct file_priv *priv);
+__poll_t tpm_common_poll(struct file *file, poll_table *wait);
 
+void tpm_common_release(struct file *file, struct file_priv *priv);
 #endif

drivers/char/tpm/tpm-interface.c

@@ -1409,19 +1409,32 @@ static int __init tpm_init(void)
 	tpmrm_class = class_create(THIS_MODULE, "tpmrm");
 	if (IS_ERR(tpmrm_class)) {
 		pr_err("couldn't create tpmrm class\n");
-		class_destroy(tpm_class);
-		return PTR_ERR(tpmrm_class);
+		rc = PTR_ERR(tpmrm_class);
+		goto out_destroy_tpm_class;
 	}
 
 	rc = alloc_chrdev_region(&tpm_devt, 0, 2*TPM_NUM_DEVICES, "tpm");
 	if (rc < 0) {
 		pr_err("tpm: failed to allocate char dev region\n");
-		class_destroy(tpmrm_class);
-		class_destroy(tpm_class);
-		return rc;
+		goto out_destroy_tpmrm_class;
+	}
+
+	rc = tpm_dev_common_init();
+	if (rc) {
+		pr_err("tpm: failed to allocate char dev region\n");
+		goto out_unreg_chrdev;
 	}
 
 	return 0;
+
+out_unreg_chrdev:
+	unregister_chrdev_region(tpm_devt, 2 * TPM_NUM_DEVICES);
+out_destroy_tpmrm_class:
+	class_destroy(tpmrm_class);
+out_destroy_tpm_class:
+	class_destroy(tpm_class);
+
+	return rc;
 }
 
 static void __exit tpm_exit(void)
@@ -1430,6 +1443,7 @@ static void __exit tpm_exit(void)
 	class_destroy(tpm_class);
 	class_destroy(tpmrm_class);
 	unregister_chrdev_region(tpm_devt, 2*TPM_NUM_DEVICES);
+	tpm_dev_common_exit();
 }
 
 subsys_initcall(tpm_init);

drivers/char/tpm/tpm.h

@@ -604,4 +604,6 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
 
 int tpm_bios_log_setup(struct tpm_chip *chip);
 void tpm_bios_log_teardown(struct tpm_chip *chip);
+int tpm_dev_common_init(void);
+void tpm_dev_common_exit(void);
 #endif

drivers/char/tpm/tpmrm-dev.c

@@ -51,5 +51,6 @@ const struct file_operations tpmrm_fops = {
 	.open = tpmrm_open,
 	.read = tpm_common_read,
 	.write = tpm_common_write,
+	.poll = tpm_common_poll,
 	.release = tpmrm_release,
 };