[PATCH v6 2/2] tpm: add support for nonblocking operation

From: Tadeusz Struk
Date: Mon Sep 10 2018 - 13:18:37 EST

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@xxxxxxxxx>
Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxx>
---
drivers/char/tpm/tpm-dev-common.c | 141 ++++++++++++++++++++++++++++---------
drivers/char/tpm/tpm-dev.c | 1
drivers/char/tpm/tpm-dev.h | 13 ++-
drivers/char/tpm/tpm-interface.c | 24 +++++-
drivers/char/tpm/tpm.h | 2 +
drivers/char/tpm/tpmrm-dev.c | 1
6 files changed, 137 insertions(+), 45 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;
+ }
+}
diff --git a/drivers/char/tpm/tpm-dev.c b/drivers/char/tpm/tpm-dev.c
index 98b9630c3a36..32f9738f1cb2 100644
--- a/drivers/char/tpm/tpm-dev.c
+++ b/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,
};
diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h
index 4048677bbd78..a126b575cb8c 100644
--- a/drivers/char/tpm/tpm-dev.h
+++ b/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
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1a803b0cf980..69c8fb0115c4 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -1407,19 +1407,32 @@ 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)
@@ -1428,6 +1441,7 @@ 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);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index f3501d05264f..f20dc8ece348 100644
--- a/drivers/char/tpm/tpm.h
+++ b/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
diff --git a/drivers/char/tpm/tpmrm-dev.c b/drivers/char/tpm/tpmrm-dev.c
index 96006c6b9696..0c751a79bbed 100644
--- a/drivers/char/tpm/tpmrm-dev.c
+++ b/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,
};