Re: [Tee-dev] [PATCHv8 1/3] optee: use uuid for sysfs driver entry

[Maxim Uvarov]

There was a comment about a new mailing list address in Documentation.
Which one I should specify now?

On Thu, 18 Jun 2020 at 09:57, Jerome Forissier <jerome@xxxxxxxxxxxxx> wrote:
>
> On 6/18/20 6:59 AM, Sumit Garg wrote:
> > Hi Jerome,
> >
> > On Wed, 17 Jun 2020 at 20:46, Jerome Forissier <jerome@xxxxxxxxxxxxx> wrote:
> >>
> >>
> >>
> >> On 6/17/20 3:58 PM, Sumit Garg wrote:
> >>> Hi Maxim,
> >>>
> >>> On Thu, 4 Jun 2020 at 23:28, Maxim Uvarov <maxim.uvarov@xxxxxxxxxx> wrote:
> >>>>
> >>>> With the evolving use-cases for TEE bus, now it's required to support
> >>>> multi-stage enumeration process. But using a simple index doesn't
> >>>> suffice this requirement and instead leads to duplicate sysfs entries.
> >>>> So instead switch to use more informative device UUID for sysfs entry
> >>>> like:
> >>>> /sys/bus/tee/devices/optee-ta-<uuid>
> >>>>
> >>>> Signed-off-by: Maxim Uvarov <maxim.uvarov@xxxxxxxxxx>
> >>>> Reviewed-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> >>>> ---
> >>>>  Documentation/ABI/testing/sysfs-bus-optee-devices | 8 ++++++++
> >>>>  MAINTAINERS                                       | 1 +
> >>>>  drivers/tee/optee/device.c                        | 9 ++++++---
> >>>>  3 files changed, 15 insertions(+), 3 deletions(-)
> >>>>  create mode 100644 Documentation/ABI/testing/sysfs-bus-optee-devices
> >>>>
> >>>> diff --git a/Documentation/ABI/testing/sysfs-bus-optee-devices b/Documentation/ABI/testing/sysfs-bus-optee-devices
> >>>> new file mode 100644
> >>>> index 000000000000..0ae04ae5374a
> >>>> --- /dev/null
> >>>> +++ b/Documentation/ABI/testing/sysfs-bus-optee-devices
> >>>> @@ -0,0 +1,8 @@
> >>>> +What:          /sys/bus/tee/devices/optee-ta-<uuid>/
> >>>> +Date:           May 2020
> >>>> +KernelVersion   5.7
> >>>> +Contact:        tee-dev@xxxxxxxxxxxxxxxx
> >>>> +Description:
> >>>> +               OP-TEE bus provides reference to registered drivers under this directory. The <uuid>
> >>>> +               matches Trusted Application (TA) driver and corresponding TA in secure OS. Drivers
> >>>> +               are free to create needed API under optee-ta-<uuid> directory.
> >>>> diff --git a/MAINTAINERS b/MAINTAINERS
> >>>> index ecc0749810b0..6717afef2de3 100644
> >>>> --- a/MAINTAINERS
> >>>> +++ b/MAINTAINERS
> >>>> @@ -12516,6 +12516,7 @@ OP-TEE DRIVER
> >>>>  M:     Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> >>>>  L:     tee-dev@xxxxxxxxxxxxxxxx
> >>>>  S:     Maintained
> >>>> +F:     Documentation/ABI/testing/sysfs-bus-optee-devices
> >>>>  F:     drivers/tee/optee/
> >>>>
> >>>>  OP-TEE RANDOM NUMBER GENERATOR (RNG) DRIVER
> >>>> diff --git a/drivers/tee/optee/device.c b/drivers/tee/optee/device.c
> >>>> index e3a148521ec1..23d264c8146e 100644
> >>>> --- a/drivers/tee/optee/device.c
> >>>> +++ b/drivers/tee/optee/device.c
> >>>> @@ -65,7 +65,7 @@ static int get_devices(struct tee_context *ctx, u32 session,
> >>>>         return 0;
> >>>>  }
> >>>>
> >>>> -static int optee_register_device(const uuid_t *device_uuid, u32 device_id)
> >>>> +static int optee_register_device(const uuid_t *device_uuid)
> >>>>  {
> >>>>         struct tee_client_device *optee_device = NULL;
> >>>>         int rc;
> >>>> @@ -75,7 +75,10 @@ static int optee_register_device(const uuid_t *device_uuid, u32 device_id)
> >>>>                 return -ENOMEM;
> >>>>
> >>>>         optee_device->dev.bus = &tee_bus_type;
> >>>> -       dev_set_name(&optee_device->dev, "optee-clnt%u", device_id);
> >>>> +       if (dev_set_name(&optee_device->dev, "optee-ta-%pUl", device_uuid)) {
> >>>
> >>> You should be using format specifier as: "%pUb" instead of "%pUl" as
> >>> UUID representation for TAs is in big endian format. See below:
> >>
> >> Where does device_uuid come from? If it comes directly from OP-TEE, then
> >> it should be a pointer to the following struct:
> >>
> >> typedef struct
> >> {
> >>         uint32_t timeLow;
> >>         uint16_t timeMid;
> >>         uint16_t timeHiAndVersion;
> >>         uint8_t clockSeqAndNode[8];
> >> } TEE_UUID;
> >>
> >> (GlobalPlatform TEE Internal Core API spec v1.2.1 section 3.2.4)
> >>
> >> - The spec does not mandate any particular endianness and simply warns
> >> about possible issues if secure and non-secure worlds differ in endianness.
> >> - OP-TEE uses %pUl assuming that host order is little endian (that is
> >> true for the Arm platforms that run OP-TEE currently). By the same logic
> >> %pUl should be fine in the kernel.
> >> - On the other hand, the UUID in a Trusted App header is always encoded
> >> big endian by the Python script that signs and optionally encrypts the
> >> TA. This should not have any visible impact on UUIDs exchanged between
> >> the secure and non-secure world though.
> >>
> >> So I am wondering why you had to use %pUb. There must be some
> >> inconsistency somewhere :-/
> >
> > Yes there is. Linux stores UUID in big endian format (16 byte octets)
> > and OP-TEE stores UUID in little endian format (in form of struct you
> > referenced above).
> >
> > And format conversion APIs [1] in OP-TEE OS are used while passing
> > UUID among Linux and OP-TEE.
> >
> > So we need to use %pUb in case of Linux and %pUl in case of OP-TEE.
> >
> > [1] https://github.com/OP-TEE/optee_os/blob/master/core/tee/uuid.c
>
>
> Got it now. The TA enumeration function in OP-TEE performs  the
> conversion here:
> https://github.com/OP-TEE/optee_os/blob/3.9.0/core/pta/device.c#L34
>
> Thanks for clarifying.
>
> --
> Jerome