Currently to read a response from the TPM device an application needs
provide big enough buffer for the whole response and read it in one go.
The application doesn't know how big the response it beforehand so it
always needs to maintain a 4K buffer and read the max (4K).
In case if the user of the TSS library doesn't provide big enough
buffer the TCTI spec says that the library should set the required
size and return TSS2_TCTI_RC_INSUFFICIENT_BUFFER error code so that the
application could allocate a bigger buffer and call receive again.
To make it possible in the TSS library, this requires being able to do
partial reads from the driver.
The library would read the 10 bytes header first to get the actual size
of the response from the header, and then read the rest of the response.
This patch adds support for partial reads, i.e. the user can read the
response in one or multiple reads, until the whole response is consumed.
The user can also read only part of the response and ignore
the rest by issuing a new write to send a new command.
Signed-off-by: Tadeusz Struk <[email protected]>
---
The usecase is implemented in this TSS commit:
https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c
Changes in v5:
- Merge the two patches back into one.
- Change variable 'partial_data' to a new flag 'response_read'.
- Update the logic around partial_data to reflect the new flag.
- Add a new variable response_length that keeps track of how much
of the response is left.
Changes in v4:
- Use unsigned type for response_pending as it will never be negative.
- Rebased on top of name change data_pending to transmit_result patch.
Changes in v3:
- Remove link to usecase implemented in TSS out of the commit message.
- Update the conddition in tpm_common_poll() to take into account
the partial_data also.
Changes in v2:
- Allow writes after only partial response is consumed to maintain
backwords compatibility.
---
drivers/char/tpm/tpm-dev-common.c | 51 +++++++++++++++++++++++++------------
drivers/char/tpm/tpm-dev.h | 7 +++--
2 files changed, 39 insertions(+), 19 deletions(-)
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 99b5133a9d05..344739223451 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -40,7 +40,7 @@ static void tpm_async_work(struct work_struct *work)
tpm_put_ops(priv->chip);
if (ret > 0) {
- priv->data_pending = ret;
+ priv->response_length = ret;
mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
}
mutex_unlock(&priv->buffer_mutex);
@@ -63,7 +63,8 @@ static void tpm_timeout_work(struct work_struct *work)
timeout_work);
mutex_lock(&priv->buffer_mutex);
- priv->data_pending = 0;
+ priv->response_read = true;
+ priv->response_length = 0;
memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
mutex_unlock(&priv->buffer_mutex);
wake_up_interruptible(&priv->async_wait);
@@ -74,6 +75,7 @@ void tpm_common_open(struct file *file, struct tpm_chip *chip,
{
priv->chip = chip;
priv->space = space;
+ priv->response_read = true;
mutex_init(&priv->buffer_mutex);
timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
@@ -90,22 +92,35 @@ ssize_t tpm_common_read(struct file *file, char __user *buf,
ssize_t ret_size = 0;
int rc;
- del_singleshot_timer_sync(&priv->user_read_timer);
- flush_work(&priv->timeout_work);
mutex_lock(&priv->buffer_mutex);
- if (priv->data_pending) {
- ret_size = min_t(ssize_t, size, priv->data_pending);
- 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;
+ if (priv->response_length) {
+ priv->response_read = true;
+
+ ret_size = min_t(ssize_t, size, priv->response_length);
+ if (!ret_size) {
+ priv->response_length = 0;
+ goto out;
}
- priv->data_pending = 0;
+ rc = copy_to_user(buf, priv->data_buffer + *off, ret_size);
+ if (rc) {
+ memset(priv->data_buffer, 0, TPM_BUFSIZE);
+ priv->response_length = 0;
+ ret_size = -EFAULT;
+ } else {
+ memset(priv->data_buffer + *off, 0, ret_size);
+ priv->response_length -= ret_size;
+ *off += ret_size;
+ }
}
+out:
+ if (!priv->response_length) {
+ *off = 0;
+ del_singleshot_timer_sync(&priv->user_read_timer);
+ flush_work(&priv->timeout_work);
+ }
mutex_unlock(&priv->buffer_mutex);
return ret_size;
}
@@ -125,7 +140,7 @@ 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 || priv->command_enqueued) {
+ if (!priv->response_read || priv->command_enqueued) {
ret = -EBUSY;
goto out;
}
@@ -150,6 +165,10 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
goto out;
}
+ priv->response_length = 0;
+ priv->response_read = false;
+ *off = 0;
+
/*
* If in nonblocking mode schedule an async job to send
* the command return the size.
@@ -168,7 +187,7 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
tpm_put_ops(priv->chip);
if (ret > 0) {
- priv->data_pending = ret;
+ priv->response_length = ret;
mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
ret = size;
}
@@ -184,7 +203,7 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait)
poll_wait(file, &priv->async_wait, wait);
- if (priv->data_pending)
+ if (!priv->response_read || priv->response_length)
mask = EPOLLIN | EPOLLRDNORM;
else
mask = EPOLLOUT | EPOLLWRNORM;
@@ -201,7 +220,7 @@ void tpm_common_release(struct file *file, struct file_priv *priv)
del_singleshot_timer_sync(&priv->user_read_timer);
flush_work(&priv->timeout_work);
file->private_data = NULL;
- priv->data_pending = 0;
+ priv->response_length = 0;
}
int __init tpm_dev_common_init(void)
diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h
index a126b575cb8c..a744d9bec7b6 100644
--- a/drivers/char/tpm/tpm-dev.h
+++ b/drivers/char/tpm/tpm-dev.h
@@ -9,14 +9,15 @@ struct file_priv {
struct tpm_chip *chip;
struct tpm_space *space;
- /* 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 timeout_work;
struct work_struct async_work;
wait_queue_head_t async_wait;
+ /* Holds the resul of the last successful call to tpm_transmit() */
+ size_t response_length;
+ /* Becomes true when the response (or part of it) is consumed */
+ bool response_read;
bool command_enqueued;
u8 data_buffer[TPM_BUFSIZE];
On Mon, Nov 19, 2018 at 10:55:15AM -0800, Tadeusz Struk wrote:
> Currently to read a response from the TPM device an application needs
> provide big enough buffer for the whole response and read it in one go.
> The application doesn't know how big the response it beforehand so it
> always needs to maintain a 4K buffer and read the max (4K).
> In case if the user of the TSS library doesn't provide big enough
> buffer the TCTI spec says that the library should set the required
> size and return TSS2_TCTI_RC_INSUFFICIENT_BUFFER error code so that the
> application could allocate a bigger buffer and call receive again.
> To make it possible in the TSS library, this requires being able to do
> partial reads from the driver.
> The library would read the 10 bytes header first to get the actual size
> of the response from the header, and then read the rest of the response.
>
> This patch adds support for partial reads, i.e. the user can read the
> response in one or multiple reads, until the whole response is consumed.
> The user can also read only part of the response and ignore
> the rest by issuing a new write to send a new command.
>
> Signed-off-by: Tadeusz Struk <[email protected]>
> ---
> The usecase is implemented in this TSS commit:
> https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c
Can you implement test for this to
https://github.com/jsakkine-intel/tpm2-scripts
?
Would make it easy to test and also to test in future kernel releases
that doesn't break.
>
> Changes in v5:
> - Merge the two patches back into one.
> - Change variable 'partial_data' to a new flag 'response_read'.
> - Update the logic around partial_data to reflect the new flag.
> - Add a new variable response_length that keeps track of how much
> of the response is left.
>
> Changes in v4:
> - Use unsigned type for response_pending as it will never be negative.
> - Rebased on top of name change data_pending to transmit_result patch.
>
> Changes in v3:
> - Remove link to usecase implemented in TSS out of the commit message.
> - Update the conddition in tpm_common_poll() to take into account
> the partial_data also.
>
> Changes in v2:
> - Allow writes after only partial response is consumed to maintain
> backwords compatibility.
> ---
> drivers/char/tpm/tpm-dev-common.c | 51 +++++++++++++++++++++++++------------
> drivers/char/tpm/tpm-dev.h | 7 +++--
> 2 files changed, 39 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index 99b5133a9d05..344739223451 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -40,7 +40,7 @@ static void tpm_async_work(struct work_struct *work)
>
> tpm_put_ops(priv->chip);
> if (ret > 0) {
> - priv->data_pending = ret;
> + priv->response_length = ret;
> mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
> }
> mutex_unlock(&priv->buffer_mutex);
> @@ -63,7 +63,8 @@ static void tpm_timeout_work(struct work_struct *work)
> timeout_work);
>
> mutex_lock(&priv->buffer_mutex);
> - priv->data_pending = 0;
> + priv->response_read = true;
> + priv->response_length = 0;
> memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
> mutex_unlock(&priv->buffer_mutex);
> wake_up_interruptible(&priv->async_wait);
> @@ -74,6 +75,7 @@ void tpm_common_open(struct file *file, struct tpm_chip *chip,
> {
> priv->chip = chip;
> priv->space = space;
> + priv->response_read = true;
>
> mutex_init(&priv->buffer_mutex);
> timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
> @@ -90,22 +92,35 @@ ssize_t tpm_common_read(struct file *file, char __user *buf,
> ssize_t ret_size = 0;
> int rc;
>
> - del_singleshot_timer_sync(&priv->user_read_timer);
> - flush_work(&priv->timeout_work);
> mutex_lock(&priv->buffer_mutex);
>
> - if (priv->data_pending) {
> - ret_size = min_t(ssize_t, size, priv->data_pending);
> - 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;
> + if (priv->response_length) {
> + priv->response_read = true;
> +
> + ret_size = min_t(ssize_t, size, priv->response_length);
> + if (!ret_size) {
> + priv->response_length = 0;
> + goto out;
> }
>
> - priv->data_pending = 0;
> + rc = copy_to_user(buf, priv->data_buffer + *off, ret_size);
> + if (rc) {
> + memset(priv->data_buffer, 0, TPM_BUFSIZE);
> + priv->response_length = 0;
> + ret_size = -EFAULT;
> + } else {
> + memset(priv->data_buffer + *off, 0, ret_size);
> + priv->response_length -= ret_size;
> + *off += ret_size;
> + }
> }
>
> +out:
> + if (!priv->response_length) {
> + *off = 0;
> + del_singleshot_timer_sync(&priv->user_read_timer);
> + flush_work(&priv->timeout_work);
> + }
> mutex_unlock(&priv->buffer_mutex);
> return ret_size;
> }
> @@ -125,7 +140,7 @@ 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 || priv->command_enqueued) {
> + if (!priv->response_read || priv->command_enqueued) {
> ret = -EBUSY;
> goto out;
> }
> @@ -150,6 +165,10 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
> goto out;
> }
>
> + priv->response_length = 0;
> + priv->response_read = false;
> + *off = 0;
> +
> /*
> * If in nonblocking mode schedule an async job to send
> * the command return the size.
> @@ -168,7 +187,7 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
> tpm_put_ops(priv->chip);
>
> if (ret > 0) {
> - priv->data_pending = ret;
> + priv->response_length = ret;
> mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
> ret = size;
> }
> @@ -184,7 +203,7 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait)
>
> poll_wait(file, &priv->async_wait, wait);
>
> - if (priv->data_pending)
> + if (!priv->response_read || priv->response_length)
> mask = EPOLLIN | EPOLLRDNORM;
> else
> mask = EPOLLOUT | EPOLLWRNORM;
> @@ -201,7 +220,7 @@ void tpm_common_release(struct file *file, struct file_priv *priv)
> del_singleshot_timer_sync(&priv->user_read_timer);
> flush_work(&priv->timeout_work);
> file->private_data = NULL;
> - priv->data_pending = 0;
> + priv->response_length = 0;
> }
>
> int __init tpm_dev_common_init(void)
> diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h
> index a126b575cb8c..a744d9bec7b6 100644
> --- a/drivers/char/tpm/tpm-dev.h
> +++ b/drivers/char/tpm/tpm-dev.h
> @@ -9,14 +9,15 @@ struct file_priv {
> struct tpm_chip *chip;
> struct tpm_space *space;
>
> - /* 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 timeout_work;
> struct work_struct async_work;
> wait_queue_head_t async_wait;
> + /* Holds the resul of the last successful call to tpm_transmit() */
This comment is cruft.
> + size_t response_length;
data_pending would be now perfectly fine name now that we concluded
that the original length is not needed to be stored. Better than this
as once you decrease it the variable name and contents mismatch.
> + /* Becomes true when the response (or part of it) is consumed */
> + bool response_read;
/* Tell whether response been consumed (read at least once). */
> bool command_enqueued;
>
> u8 data_buffer[TPM_BUFSIZE];
>
Otherwise, starts to look pretty much acceptable.
/Jarkko
On 11/20/18 4:48 AM, Jarkko Sakkinen wrote:
>> The usecase is implemented in this TSS commit:
>> https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c
> Can you implement test for this to
>
> https://github.com/jsakkine-intel/tpm2-scripts
Just created a PR for you
https://github.com/jsakkine-intel/tpm2-scripts/pull/4
--
Tadeusz
On 11/20/18 4:48 AM, Jarkko Sakkinen wrote:
>> + /* Holds the resul of the last successful call to tpm_transmit() */
> This comment is cruft.
Do you want me to remove it? This is the comment you proposed.
>
>> + size_t response_length;
> data_pending would be now perfectly fine name now that we concluded
> that the original length is not needed to be stored. Better than this
> as once you decrease it the variable name and contents mismatch.
>
Can we finally agree on something? We have changed three times already.
response_length is exactly what it is and data_pending is a bit vague.
>> + /* Becomes true when the response (or part of it) is consumed */
>> + bool response_read;
> /* Tell whether response been consumed (read at least once). */
>
Ok I'll update the comment.
--
Tadeusz
On 11/20/18 3:07 PM, Jarkko Sakkinen wrote:
>>>> + /* Holds the resul of the last successful call to tpm_transmit() */
>>> This comment is cruft.
>> Do you want me to remove it? This is the comment you proposed.
> As I explained before it made sense before you made the remark that
> it can only get positive values i.e. the length.
>
So what do you want me to do with this one?
--
Tadeusz
On Tue, Nov 20, 2018 at 10:30:32AM -0800, Tadeusz Struk wrote:
> On 11/20/18 4:48 AM, Jarkko Sakkinen wrote:
> >> The usecase is implemented in this TSS commit:
> >> https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c
> > Can you implement test for this to
> >
> > https://github.com/jsakkine-intel/tpm2-scripts
>
> Just created a PR for you
> https://github.com/jsakkine-intel/tpm2-scripts/pull/4
Great, thank you.
I'm wondering if Python scripts can be added to kselftests. Then a test
case could be part of a tpmdd change when required. Have to do research
on this...
/Jarkko
On Tue, Nov 20, 2018 at 10:36:14AM -0800, Tadeusz Struk wrote:
> On 11/20/18 4:48 AM, Jarkko Sakkinen wrote:
> >> + /* Holds the resul of the last successful call to tpm_transmit() */
> > This comment is cruft.
>
> Do you want me to remove it? This is the comment you proposed.
As I explained before it made sense before you made the remark that
it can only get positive values i.e. the length.
> > data_pending would be now perfectly fine name now that we concluded
> > that the original length is not needed to be stored. Better than this
> > as once you decrease it the variable name and contents mismatch.
> >
>
> Can we finally agree on something? We have changed three times already.
> response_length is exactly what it is and data_pending is a bit vague.
You are correct in this one. If I remember right, I finally proposed
'response_pending' because 'data_pending' is really vague. For me
'response_length' is just fine too.
If you see problem in my review comment or inconsistency or whatever,
please just state it. I will listen. When you multitask between patch
reviews etc. forgetting stuff is not unheard.
And seriously, 5th iteration is not alot. User space facing changes
need alot of consideration and as uncluttered code change as possible.
/Jarkko
On Tue, Nov 20, 2018 at 03:13:59PM -0800, Tadeusz Struk wrote:
> On 11/20/18 3:07 PM, Jarkko Sakkinen wrote:
> >>>> + /* Holds the resul of the last successful call to tpm_transmit() */
> >>> This comment is cruft.
> >> Do you want me to remove it? This is the comment you proposed.
> > As I explained before it made sense before you made the remark that
> > it can only get positive values i.e. the length.
> >
> So what do you want me to do with this one?
I don't think it needs now any comment because the variable describes
itself so well.
/Jarkko