The current code waits for data to be available before attempting a
second read. However the second read would not be executed as the
while loop exits.
This fix does not wait if all data has been read and reads a second
time if only partial data was retrieved on the first read.
This fix also does not attempt to read if not data is requested.
Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
---
v2: tidy up the while loop to avoid reading when no data is requested
drivers/char/hw_random/optee-rng.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
index 5bc4700c4dae..a99d82949981 100644
--- a/drivers/char/hw_random/optee-rng.c
+++ b/drivers/char/hw_random/optee-rng.c
@@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
if (max > MAX_ENTROPY_REQ_SZ)
max = MAX_ENTROPY_REQ_SZ;
- while (read == 0) {
+ while (read < max) {
rng_size = get_optee_rng_data(pvt_data, data, (max - read));
data += rng_size;
read += rng_size;
if (wait && pvt_data->data_rate) {
- if (timeout-- == 0)
+ if ((timeout-- == 0) || (read == max))
return read;
msleep((1000 * (max - read)) / pvt_data->data_rate);
} else {
--
2.17.1
On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
>
> The current code waits for data to be available before attempting a
> second read. However the second read would not be executed as the
> while loop exits.
>
> This fix does not wait if all data has been read and reads a second
> time if only partial data was retrieved on the first read.
>
> This fix also does not attempt to read if not data is requested.
I am not sure how this is possible, can you elaborate?
>
> Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> ---
> v2: tidy up the while loop to avoid reading when no data is requested
>
> drivers/char/hw_random/optee-rng.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> index 5bc4700c4dae..a99d82949981 100644
> --- a/drivers/char/hw_random/optee-rng.c
> +++ b/drivers/char/hw_random/optee-rng.c
> @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> if (max > MAX_ENTROPY_REQ_SZ)
> max = MAX_ENTROPY_REQ_SZ;
>
> - while (read == 0) {
> + while (read < max) {
> rng_size = get_optee_rng_data(pvt_data, data, (max - read));
>
> data += rng_size;
> read += rng_size;
>
> if (wait && pvt_data->data_rate) {
> - if (timeout-- == 0)
> + if ((timeout-- == 0) || (read == max))
If read == max, would there be any sleep?
-Sumit
> return read;
> msleep((1000 * (max - read)) / pvt_data->data_rate);
> } else {
> --
> 2.17.1
>
On 24/07/20, Sumit Garg wrote:
> On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> >
> > The current code waits for data to be available before attempting a
> > second read. However the second read would not be executed as the
> > while loop exits.
> >
> > This fix does not wait if all data has been read and reads a second
> > time if only partial data was retrieved on the first read.
> >
> > This fix also does not attempt to read if not data is requested.
>
> I am not sure how this is possible, can you elaborate?
currently, if the user sets max 0, get_optee_rng_data will regardless
issuese a call to the secure world requesting 0 bytes from the RNG
with this patch, this request is avoided.
>
> >
> > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > ---
> > v2: tidy up the while loop to avoid reading when no data is requested
> >
> > drivers/char/hw_random/optee-rng.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > index 5bc4700c4dae..a99d82949981 100644
> > --- a/drivers/char/hw_random/optee-rng.c
> > +++ b/drivers/char/hw_random/optee-rng.c
> > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > if (max > MAX_ENTROPY_REQ_SZ)
> > max = MAX_ENTROPY_REQ_SZ;
> >
> > - while (read == 0) {
> > + while (read < max) {
> > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> >
> > data += rng_size;
> > read += rng_size;
> >
> > if (wait && pvt_data->data_rate) {
> > - if (timeout-- == 0)
> > + if ((timeout-- == 0) || (read == max))
>
> If read == max, would there be any sleep?
no but I see no reason why there should be a wait since we already have
all the data that we need; the msleep is only required when we need to
wait for the RNG to generate entropy for the number of bytes we are
requesting. if we are requesting 0 bytes, the entropy is already
available. at leat this is what makes sense to me.
>
> -Sumit
>
> > return read;
> > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > } else {
> > --
> > 2.17.1
> >
On 23/07/20, Jorge Ramirez-Ortiz wrote:
> The current code waits for data to be available before attempting a
> second read. However the second read would not be executed as the
> while loop exits.
>
> This fix does not wait if all data has been read and reads a second
> time if only partial data was retrieved on the first read.
>
> This fix also does not attempt to read if not data is requested.
>
> Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> ---
> v2: tidy up the while loop to avoid reading when no data is requested
>
> drivers/char/hw_random/optee-rng.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> index 5bc4700c4dae..a99d82949981 100644
> --- a/drivers/char/hw_random/optee-rng.c
> +++ b/drivers/char/hw_random/optee-rng.c
> @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> if (max > MAX_ENTROPY_REQ_SZ)
> max = MAX_ENTROPY_REQ_SZ;
>
> - while (read == 0) {
> + while (read < max) {
> rng_size = get_optee_rng_data(pvt_data, data, (max - read));
>
> data += rng_size;
> read += rng_size;
>
> if (wait && pvt_data->data_rate) {
> - if (timeout-- == 0)
> + if ((timeout-- == 0) || (read == max))
> return read;
> msleep((1000 * (max - read)) / pvt_data->data_rate);
> } else {
any comments please?
On 05/08/20, Sumit Garg wrote:
> Apologies for my delayed response as I was busy with some other tasks
> along with holidays.
no pb! was just making sure this wasnt falling through some cracks.
>
> On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> <[email protected]> wrote:
> >
> > On 24/07/20, Sumit Garg wrote:
> > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > >
> > > > The current code waits for data to be available before attempting a
> > > > second read. However the second read would not be executed as the
> > > > while loop exits.
> > > >
> > > > This fix does not wait if all data has been read and reads a second
> > > > time if only partial data was retrieved on the first read.
> > > >
> > > > This fix also does not attempt to read if not data is requested.
> > >
> > > I am not sure how this is possible, can you elaborate?
> >
> > currently, if the user sets max 0, get_optee_rng_data will regardless
> > issuese a call to the secure world requesting 0 bytes from the RNG
> >
>
> This case is already handled by core API: rng_dev_read().
ah ok good point, you are right
but yeah, there is no consequence to the actual patch.
>
> > with this patch, this request is avoided.
> >
> > >
> > > >
> > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > ---
> > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > >
> > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > index 5bc4700c4dae..a99d82949981 100644
> > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > max = MAX_ENTROPY_REQ_SZ;
> > > >
> > > > - while (read == 0) {
> > > > + while (read < max) {
> > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > >
> > > > data += rng_size;
> > > > read += rng_size;
> > > >
> > > > if (wait && pvt_data->data_rate) {
> > > > - if (timeout-- == 0)
> > > > + if ((timeout-- == 0) || (read == max))
> > >
> > > If read == max, would there be any sleep?
> >
> > no but I see no reason why there should be a wait since we already have
> > all the data that we need; the msleep is only required when we need to
> > wait for the RNG to generate entropy for the number of bytes we are
> > requesting. if we are requesting 0 bytes, the entropy is already
> > available. at leat this is what makes sense to me.
> >
>
> Wouldn't it lead to a call as msleep(0); that means no wait as well?
I dont understand: there is no reason to wait if read == max and this
patch will not wait: if read == max it calls 'return read'
am I misunderstanding your point?
>
> -Sumit
>
> >
> > >
> > > -Sumit
> > >
> > > > return read;
> > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > } else {
> > > > --
> > > > 2.17.1
> > > >
On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries
<[email protected]> wrote:
>
> On 05/08/20, Sumit Garg wrote:
> > Apologies for my delayed response as I was busy with some other tasks
> > along with holidays.
>
> no pb! was just making sure this wasnt falling through some cracks.
>
> >
> > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> > <[email protected]> wrote:
> > >
> > > On 24/07/20, Sumit Garg wrote:
> > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > > >
> > > > > The current code waits for data to be available before attempting a
> > > > > second read. However the second read would not be executed as the
> > > > > while loop exits.
> > > > >
> > > > > This fix does not wait if all data has been read and reads a second
> > > > > time if only partial data was retrieved on the first read.
> > > > >
> > > > > This fix also does not attempt to read if not data is requested.
> > > >
> > > > I am not sure how this is possible, can you elaborate?
> > >
> > > currently, if the user sets max 0, get_optee_rng_data will regardless
> > > issuese a call to the secure world requesting 0 bytes from the RNG
> > >
> >
> > This case is already handled by core API: rng_dev_read().
>
> ah ok good point, you are right
> but yeah, there is no consequence to the actual patch.
>
So, at least you could get rid of the corresponding text from commit message.
> >
> > > with this patch, this request is avoided.
> > >
> > > >
> > > > >
> > > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > > ---
> > > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > > >
> > > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > > index 5bc4700c4dae..a99d82949981 100644
> > > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > > max = MAX_ENTROPY_REQ_SZ;
> > > > >
> > > > > - while (read == 0) {
> > > > > + while (read < max) {
> > > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > > >
> > > > > data += rng_size;
> > > > > read += rng_size;
> > > > >
> > > > > if (wait && pvt_data->data_rate) {
> > > > > - if (timeout-- == 0)
> > > > > + if ((timeout-- == 0) || (read == max))
> > > >
> > > > If read == max, would there be any sleep?
> > >
> > > no but I see no reason why there should be a wait since we already have
> > > all the data that we need; the msleep is only required when we need to
> > > wait for the RNG to generate entropy for the number of bytes we are
> > > requesting. if we are requesting 0 bytes, the entropy is already
> > > available. at leat this is what makes sense to me.
> > >
> >
> > Wouldn't it lead to a call as msleep(0); that means no wait as well?
>
> I dont understand: there is no reason to wait if read == max and this
> patch will not wait: if read == max it calls 'return read'
>
> am I misunderstanding your point?
What I mean is that we shouldn't require this extra check here as
there wasn't any wait if read == max with existing implementation too.
-Sumit
>
> >
> > -Sumit
> >
> > >
> > > >
> > > > -Sumit
> > > >
> > > > > return read;
> > > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > > } else {
> > > > > --
> > > > > 2.17.1
> > > > >
On 06/08/20, Sumit Garg wrote:
> On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries
> <[email protected]> wrote:
> >
> > On 05/08/20, Sumit Garg wrote:
> > > Apologies for my delayed response as I was busy with some other tasks
> > > along with holidays.
> >
> > no pb! was just making sure this wasnt falling through some cracks.
> >
> > >
> > > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> > > <[email protected]> wrote:
> > > >
> > > > On 24/07/20, Sumit Garg wrote:
> > > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > > > >
> > > > > > The current code waits for data to be available before attempting a
> > > > > > second read. However the second read would not be executed as the
> > > > > > while loop exits.
> > > > > >
> > > > > > This fix does not wait if all data has been read and reads a second
> > > > > > time if only partial data was retrieved on the first read.
> > > > > >
> > > > > > This fix also does not attempt to read if not data is requested.
> > > > >
> > > > > I am not sure how this is possible, can you elaborate?
> > > >
> > > > currently, if the user sets max 0, get_optee_rng_data will regardless
> > > > issuese a call to the secure world requesting 0 bytes from the RNG
> > > >
> > >
> > > This case is already handled by core API: rng_dev_read().
> >
> > ah ok good point, you are right
> > but yeah, there is no consequence to the actual patch.
> >
>
> So, at least you could get rid of the corresponding text from commit message.
>
> > >
> > > > with this patch, this request is avoided.
> > > >
> > > > >
> > > > > >
> > > > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > > > ---
> > > > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > > > >
> > > > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > > > index 5bc4700c4dae..a99d82949981 100644
> > > > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > > > max = MAX_ENTROPY_REQ_SZ;
> > > > > >
> > > > > > - while (read == 0) {
> > > > > > + while (read < max) {
> > > > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > > > >
> > > > > > data += rng_size;
> > > > > > read += rng_size;
> > > > > >
> > > > > > if (wait && pvt_data->data_rate) {
> > > > > > - if (timeout-- == 0)
> > > > > > + if ((timeout-- == 0) || (read == max))
> > > > >
> > > > > If read == max, would there be any sleep?
> > > >
> > > > no but I see no reason why there should be a wait since we already have
> > > > all the data that we need; the msleep is only required when we need to
> > > > wait for the RNG to generate entropy for the number of bytes we are
> > > > requesting. if we are requesting 0 bytes, the entropy is already
> > > > available. at leat this is what makes sense to me.
> > > >
> > >
> > > Wouldn't it lead to a call as msleep(0); that means no wait as well?
> >
> > I dont understand: there is no reason to wait if read == max and this
> > patch will not wait: if read == max it calls 'return read'
> >
> > am I misunderstanding your point?
>
> What I mean is that we shouldn't require this extra check here as
> there wasn't any wait if read == max with existing implementation too.
um, I am getting confused Sumit
with the exisiting implementation (the one we aim to replace), if get_optee_rng_data reads all the values requested on the first call (ie, read = 0) with wait set to true, the call will wait with msleep(0). Which is unnecessary and waits for a jiffy (ie, the call to msleep 0 will schedule a one jiffy timeout interrruptible)
with this alternative implementation, msleep(0) does not get called.
are we in synch?
>
> -Sumit
>
> >
> > >
> > > -Sumit
> > >
> > > >
> > > > >
> > > > > -Sumit
> > > > >
> > > > > > return read;
> > > > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > > > } else {
> > > > > > --
> > > > > > 2.17.1
> > > > > >
On Thu, 6 Aug 2020 at 12:00, Jorge Ramirez-Ortiz, Foundries
<[email protected]> wrote:
>
> On 06/08/20, Sumit Garg wrote:
> > On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries
> > <[email protected]> wrote:
> > >
> > > On 05/08/20, Sumit Garg wrote:
> > > > Apologies for my delayed response as I was busy with some other tasks
> > > > along with holidays.
> > >
> > > no pb! was just making sure this wasnt falling through some cracks.
> > >
> > > >
> > > > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> > > > <[email protected]> wrote:
> > > > >
> > > > > On 24/07/20, Sumit Garg wrote:
> > > > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > > > > >
> > > > > > > The current code waits for data to be available before attempting a
> > > > > > > second read. However the second read would not be executed as the
> > > > > > > while loop exits.
> > > > > > >
> > > > > > > This fix does not wait if all data has been read and reads a second
> > > > > > > time if only partial data was retrieved on the first read.
> > > > > > >
> > > > > > > This fix also does not attempt to read if not data is requested.
> > > > > >
> > > > > > I am not sure how this is possible, can you elaborate?
> > > > >
> > > > > currently, if the user sets max 0, get_optee_rng_data will regardless
> > > > > issuese a call to the secure world requesting 0 bytes from the RNG
> > > > >
> > > >
> > > > This case is already handled by core API: rng_dev_read().
> > >
> > > ah ok good point, you are right
> > > but yeah, there is no consequence to the actual patch.
> > >
> >
> > So, at least you could get rid of the corresponding text from commit message.
> >
> > > >
> > > > > with this patch, this request is avoided.
> > > > >
> > > > > >
> > > > > > >
> > > > > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > > > > ---
> > > > > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > > > > >
> > > > > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > > > > index 5bc4700c4dae..a99d82949981 100644
> > > > > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > > > > max = MAX_ENTROPY_REQ_SZ;
> > > > > > >
> > > > > > > - while (read == 0) {
> > > > > > > + while (read < max) {
> > > > > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > > > > >
> > > > > > > data += rng_size;
> > > > > > > read += rng_size;
> > > > > > >
> > > > > > > if (wait && pvt_data->data_rate) {
> > > > > > > - if (timeout-- == 0)
> > > > > > > + if ((timeout-- == 0) || (read == max))
> > > > > >
> > > > > > If read == max, would there be any sleep?
> > > > >
> > > > > no but I see no reason why there should be a wait since we already have
> > > > > all the data that we need; the msleep is only required when we need to
> > > > > wait for the RNG to generate entropy for the number of bytes we are
> > > > > requesting. if we are requesting 0 bytes, the entropy is already
> > > > > available. at leat this is what makes sense to me.
> > > > >
> > > >
> > > > Wouldn't it lead to a call as msleep(0); that means no wait as well?
> > >
> > > I dont understand: there is no reason to wait if read == max and this
> > > patch will not wait: if read == max it calls 'return read'
> > >
> > > am I misunderstanding your point?
> >
> > What I mean is that we shouldn't require this extra check here as
> > there wasn't any wait if read == max with existing implementation too.
>
> um, I am getting confused Sumit
>
> with the exisiting implementation (the one we aim to replace), if get_optee_rng_data reads all the values requested on the first call (ie, read = 0) with wait set to true, the call will wait with msleep(0). Which is unnecessary and waits for a jiffy (ie, the call to msleep 0 will schedule a one jiffy timeout interrruptible)
>
> with this alternative implementation, msleep(0) does not get called.
>
> are we in synch?
Ah, I see msleep(0) also by default schedules timeout for 1 jiffy. So
we are in sync now. Probably you can clarify this in commit message as
well to avoid confusion.
-Sumit
>
> >
> > -Sumit
> >
> > >
> > > >
> > > > -Sumit
> > > >
> > > > >
> > > > > >
> > > > > > -Sumit
> > > > > >
> > > > > > > return read;
> > > > > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > > > > } else {
> > > > > > > --
> > > > > > > 2.17.1
> > > > > > >
On 06/08/20, Sumit Garg wrote:
> On Thu, 6 Aug 2020 at 12:00, Jorge Ramirez-Ortiz, Foundries
> <[email protected]> wrote:
> >
> > On 06/08/20, Sumit Garg wrote:
> > > On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries
> > > <[email protected]> wrote:
> > > >
> > > > On 05/08/20, Sumit Garg wrote:
> > > > > Apologies for my delayed response as I was busy with some other tasks
> > > > > along with holidays.
> > > >
> > > > no pb! was just making sure this wasnt falling through some cracks.
> > > >
> > > > >
> > > > > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> > > > > <[email protected]> wrote:
> > > > > >
> > > > > > On 24/07/20, Sumit Garg wrote:
> > > > > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > > > > > >
> > > > > > > > The current code waits for data to be available before attempting a
> > > > > > > > second read. However the second read would not be executed as the
> > > > > > > > while loop exits.
> > > > > > > >
> > > > > > > > This fix does not wait if all data has been read and reads a second
> > > > > > > > time if only partial data was retrieved on the first read.
> > > > > > > >
> > > > > > > > This fix also does not attempt to read if not data is requested.
> > > > > > >
> > > > > > > I am not sure how this is possible, can you elaborate?
> > > > > >
> > > > > > currently, if the user sets max 0, get_optee_rng_data will regardless
> > > > > > issuese a call to the secure world requesting 0 bytes from the RNG
> > > > > >
> > > > >
> > > > > This case is already handled by core API: rng_dev_read().
> > > >
> > > > ah ok good point, you are right
> > > > but yeah, there is no consequence to the actual patch.
> > > >
> > >
> > > So, at least you could get rid of the corresponding text from commit message.
> > >
> > > > >
> > > > > > with this patch, this request is avoided.
> > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > > > > > ---
> > > > > > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > > > > > >
> > > > > > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > > > > > index 5bc4700c4dae..a99d82949981 100644
> > > > > > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > > > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > > > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > > > > > max = MAX_ENTROPY_REQ_SZ;
> > > > > > > >
> > > > > > > > - while (read == 0) {
> > > > > > > > + while (read < max) {
> > > > > > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > > > > > >
> > > > > > > > data += rng_size;
> > > > > > > > read += rng_size;
> > > > > > > >
> > > > > > > > if (wait && pvt_data->data_rate) {
> > > > > > > > - if (timeout-- == 0)
> > > > > > > > + if ((timeout-- == 0) || (read == max))
> > > > > > >
> > > > > > > If read == max, would there be any sleep?
> > > > > >
> > > > > > no but I see no reason why there should be a wait since we already have
> > > > > > all the data that we need; the msleep is only required when we need to
> > > > > > wait for the RNG to generate entropy for the number of bytes we are
> > > > > > requesting. if we are requesting 0 bytes, the entropy is already
> > > > > > available. at leat this is what makes sense to me.
> > > > > >
> > > > >
> > > > > Wouldn't it lead to a call as msleep(0); that means no wait as well?
> > > >
> > > > I dont understand: there is no reason to wait if read == max and this
> > > > patch will not wait: if read == max it calls 'return read'
> > > >
> > > > am I misunderstanding your point?
> > >
> > > What I mean is that we shouldn't require this extra check here as
> > > there wasn't any wait if read == max with existing implementation too.
> >
> > um, I am getting confused Sumit
> >
> > with the exisiting implementation (the one we aim to replace), if get_optee_rng_data reads all the values requested on the first call (ie, read = 0) with wait set to true, the call will wait with msleep(0). Which is unnecessary and waits for a jiffy (ie, the call to msleep 0 will schedule a one jiffy timeout interrruptible)
> >
> > with this alternative implementation, msleep(0) does not get called.
> >
> > are we in synch?
>
> Ah, I see msleep(0) also by default schedules timeout for 1 jiffy. So
> we are in sync now. Probably you can clarify this in commit message as
> well to avoid confusion.
ok will do.
shall I add your reviewed-by line or just resend?
>
> -Sumit
>
> >
> > >
> > > -Sumit
> > >
> > > >
> > > > >
> > > > > -Sumit
> > > > >
> > > > > >
> > > > > > >
> > > > > > > -Sumit
> > > > > > >
> > > > > > > > return read;
> > > > > > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > > > > > } else {
> > > > > > > > --
> > > > > > > > 2.17.1
> > > > > > > >
On Thu, 6 Aug 2020 at 13:44, Jorge Ramirez-Ortiz, Foundries
<[email protected]> wrote:
>
> On 06/08/20, Sumit Garg wrote:
> > On Thu, 6 Aug 2020 at 12:00, Jorge Ramirez-Ortiz, Foundries
> > <[email protected]> wrote:
> > >
> > > On 06/08/20, Sumit Garg wrote:
> > > > On Thu, 6 Aug 2020 at 02:08, Jorge Ramirez-Ortiz, Foundries
> > > > <[email protected]> wrote:
> > > > >
> > > > > On 05/08/20, Sumit Garg wrote:
> > > > > > Apologies for my delayed response as I was busy with some other tasks
> > > > > > along with holidays.
> > > > >
> > > > > no pb! was just making sure this wasnt falling through some cracks.
> > > > >
> > > > > >
> > > > > > On Fri, 24 Jul 2020 at 19:53, Jorge Ramirez-Ortiz, Foundries
> > > > > > <[email protected]> wrote:
> > > > > > >
> > > > > > > On 24/07/20, Sumit Garg wrote:
> > > > > > > > On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz <[email protected]> wrote:
> > > > > > > > >
> > > > > > > > > The current code waits for data to be available before attempting a
> > > > > > > > > second read. However the second read would not be executed as the
> > > > > > > > > while loop exits.
> > > > > > > > >
> > > > > > > > > This fix does not wait if all data has been read and reads a second
> > > > > > > > > time if only partial data was retrieved on the first read.
> > > > > > > > >
> > > > > > > > > This fix also does not attempt to read if not data is requested.
> > > > > > > >
> > > > > > > > I am not sure how this is possible, can you elaborate?
> > > > > > >
> > > > > > > currently, if the user sets max 0, get_optee_rng_data will regardless
> > > > > > > issuese a call to the secure world requesting 0 bytes from the RNG
> > > > > > >
> > > > > >
> > > > > > This case is already handled by core API: rng_dev_read().
> > > > >
> > > > > ah ok good point, you are right
> > > > > but yeah, there is no consequence to the actual patch.
> > > > >
> > > >
> > > > So, at least you could get rid of the corresponding text from commit message.
> > > >
> > > > > >
> > > > > > > with this patch, this request is avoided.
> > > > > > >
> > > > > > > >
> > > > > > > > >
> > > > > > > > > Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> > > > > > > > > ---
> > > > > > > > > v2: tidy up the while loop to avoid reading when no data is requested
> > > > > > > > >
> > > > > > > > > drivers/char/hw_random/optee-rng.c | 4 ++--
> > > > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > > > >
> > > > > > > > > diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c
> > > > > > > > > index 5bc4700c4dae..a99d82949981 100644
> > > > > > > > > --- a/drivers/char/hw_random/optee-rng.c
> > > > > > > > > +++ b/drivers/char/hw_random/optee-rng.c
> > > > > > > > > @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> > > > > > > > > if (max > MAX_ENTROPY_REQ_SZ)
> > > > > > > > > max = MAX_ENTROPY_REQ_SZ;
> > > > > > > > >
> > > > > > > > > - while (read == 0) {
> > > > > > > > > + while (read < max) {
> > > > > > > > > rng_size = get_optee_rng_data(pvt_data, data, (max - read));
> > > > > > > > >
> > > > > > > > > data += rng_size;
> > > > > > > > > read += rng_size;
> > > > > > > > >
> > > > > > > > > if (wait && pvt_data->data_rate) {
> > > > > > > > > - if (timeout-- == 0)
> > > > > > > > > + if ((timeout-- == 0) || (read == max))
> > > > > > > >
> > > > > > > > If read == max, would there be any sleep?
> > > > > > >
> > > > > > > no but I see no reason why there should be a wait since we already have
> > > > > > > all the data that we need; the msleep is only required when we need to
> > > > > > > wait for the RNG to generate entropy for the number of bytes we are
> > > > > > > requesting. if we are requesting 0 bytes, the entropy is already
> > > > > > > available. at leat this is what makes sense to me.
> > > > > > >
> > > > > >
> > > > > > Wouldn't it lead to a call as msleep(0); that means no wait as well?
> > > > >
> > > > > I dont understand: there is no reason to wait if read == max and this
> > > > > patch will not wait: if read == max it calls 'return read'
> > > > >
> > > > > am I misunderstanding your point?
> > > >
> > > > What I mean is that we shouldn't require this extra check here as
> > > > there wasn't any wait if read == max with existing implementation too.
> > >
> > > um, I am getting confused Sumit
> > >
> > > with the exisiting implementation (the one we aim to replace), if get_optee_rng_data reads all the values requested on the first call (ie, read = 0) with wait set to true, the call will wait with msleep(0). Which is unnecessary and waits for a jiffy (ie, the call to msleep 0 will schedule a one jiffy timeout interrruptible)
> > >
> > > with this alternative implementation, msleep(0) does not get called.
> > >
> > > are we in synch?
> >
> > Ah, I see msleep(0) also by default schedules timeout for 1 jiffy. So
> > we are in sync now. Probably you can clarify this in commit message as
> > well to avoid confusion.
>
> ok will do.
> shall I add your reviewed-by line or just resend?
>
Yes it's fine with me to add mine reviewed-by.
> >
> > -Sumit
> >
> > >
> > > >
> > > > -Sumit
> > > >
> > > > >
> > > > > >
> > > > > > -Sumit
> > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > -Sumit
> > > > > > > >
> > > > > > > > > return read;
> > > > > > > > > msleep((1000 * (max - read)) / pvt_data->data_rate);
> > > > > > > > > } else {
> > > > > > > > > --
> > > > > > > > > 2.17.1
> > > > > > > > >