On Fri, Nov 16, 2018 at 01:31:58AM +0200, Jarkko Sakkinen wrote: > On Thu, Nov 15, 2018 at 12:42:22PM -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 <tadeusz.st...@intel.com> > > --- > > The usecase is implemented in this TSS commit: > > https://github.com/tpm2-software/tpm2-tss/commit/ce982f67a67dc08e24683d30b05800648d8a264c > > > > 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 | 41 > > ++++++++++++++++++++++++++++--------- > > drivers/char/tpm/tpm-dev.h | 2 ++ > > 2 files changed, 33 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm-dev-common.c > > b/drivers/char/tpm/tpm-dev-common.c > > index 99b5133a9d05..5d43b0c28565 100644 > > --- a/drivers/char/tpm/tpm-dev-common.c > > +++ b/drivers/char/tpm/tpm-dev-common.c > > @@ -64,6 +64,7 @@ static void tpm_timeout_work(struct work_struct *work) > > > > mutex_lock(&priv->buffer_mutex); > > priv->data_pending = 0; > > + priv->partial_data = 0; > > memset(priv->data_buffer, 0, sizeof(priv->data_buffer)); > > mutex_unlock(&priv->buffer_mutex); > > wake_up_interruptible(&priv->async_wait); > > @@ -90,22 +91,39 @@ 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 || priv->partial_data) { > > + if (*off == 0) > > + priv->partial_data = priv->data_pending; > > + > > + ret_size = min_t(ssize_t, size, priv->partial_data); > > + if (ret_size <= 0) { > > + ret_size = 0; > > + priv->data_pending = 0; > > + priv->partial_data = 0; > > + goto out; > > + } > > > > - 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; > > + rc = copy_to_user(buf, priv->data_buffer + *off, ret_size); > > + if (rc) { > > + memset(priv->data_buffer, 0, TPM_BUFSIZE); > > + priv->partial_data = 0; > > + ret_size = -EFAULT; > > + } else { > > + memset(priv->data_buffer + *off, 0, ret_size); > > + priv->partial_data -= ret_size; > > + *off += ret_size; > > You could drop these memset() calls and also one from > tpm_timeout_work(). The call could be done once in the beginning of > tpm_common_write() instead of having three different call sites. > > Replacing two memsets with one could be a prepending commit. > > > } > > > > priv->data_pending = 0; > > } > > > > +out: > > + if (!priv->partial_data) { > > + *off = 0; > > + del_singleshot_timer_sync(&priv->user_read_timer); > > + flush_work(&priv->timeout_work); > > + } > > mutex_unlock(&priv->buffer_mutex); > > return ret_size; > > } > > @@ -150,6 +168,9 @@ ssize_t tpm_common_write(struct file *file, const char > > __user *buf, > > goto out; > > } > > > > + priv->partial_data = 0; > > + *off = 0; > > + > > /* > > * If in nonblocking mode schedule an async job to send > > * the command return the size. > > @@ -184,7 +205,7 @@ __poll_t tpm_common_poll(struct file *file, poll_table > > *wait) > > > > poll_wait(file, &priv->async_wait, wait); > > > > - if (priv->data_pending) > > + if (priv->data_pending || priv->partial_data) > > mask = EPOLLIN | EPOLLRDNORM; > > else > > mask = EPOLLOUT | EPOLLWRNORM; > > diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h > > index a126b575cb8c..a2ca6a7a06f1 100644 > > --- a/drivers/char/tpm/tpm-dev.h > > +++ b/drivers/char/tpm/tpm-dev.h > > @@ -11,6 +11,8 @@ struct file_priv { > > > > /* Holds the amount of data passed or an error code from async op */ > > ssize_t data_pending; > > + /* For partial reads, holds the reminder of a response */ > > + ssize_t partial_data; > > Naming becomes a mess and the comment for data_pending variable is > incorrect as it is also used for synchronous operation. > > Maybe add a prepending commit to rename it as > > /* Holds the resul of the tpm_transmit() last call. */ > ssize_t transmit_result; > > That is at least clear and obvious on what it contains. > > The comment for partial_data is incorrect as the variable does not > contain any data. > > We could use declare: > > /* Holds the count how much of the response is still unread. */ > size_t response_pending; > > Observe another remark from your commit: there is no reaso to ssize_t as > the type as the value should never be a negative number.
In order to correct amazing amount of typos in the last sentence I meant to say that there is no reason to use ssize_t as response_pending can hold only positive values. /Jarkko
