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>

1 files changed, 105 insertions, 36 deletions

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index f0c033b69b62..99b5133a9d05 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -17,11 +17,36 @@
  * 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);
@@ -29,17 +54,19 @@ static void user_reader_timeout(struct timer_list *t)
 	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);
@@ -96,21 +125,20 @@ 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
@@ -118,25 +146,50 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
 	 * 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;
 }
 
 /*
@@ -144,8 +197,24 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
  */
 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;
+	}
+}