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

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Message-ID: <CAFA6WYNVk1RcaqnL0FGyYkB+hGkgyqeOMsSKyySL=zfCdNUZXA@mail.gmail.com>
Date:   Wed, 17 Jun 2020 19:28:16 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Maxim Uvarov <maxim.uvarov@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>,
        peterhuewe@....de,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        linux-integrity@...r.kernel.org, Arnd Bergmann <arnd@...aro.org>
Subject: Re: [PATCHv8 1/3] optee: use uuid for sysfs driver entry

Hi Maxim,

On Thu, 4 Jun 2020 at 23:28, Maxim Uvarov <maxim.uvarov@...aro.org> 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@...aro.org>
> Reviewed-by: Sumit Garg <sumit.garg@...aro.org>
> ---
>  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@...ts.linaro.org
> +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@...aro.org>
>  L:     tee-dev@...ts.linaro.org
>  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:

# ls /sys/bus/tee/devices/
optee-ta-405b6ad9-e5c3-e321-8794-1002a5d5c61b
optee-ta-71d950bc-c9d4-c442-82cb-343fb7f37896
optee-ta-e70f4af0-5d1f-9b4b-abf7-619b85b4ce8c

While UUID for fTPM TA is in big endian format:
bc50d971-d4c9-42c4-82cb-343fb7f37896

Sorry that I missed it during review and noticed this while testing.

With the above fix included, I tested this series using fTPM early TA
on Qemu for aarch64 and used basic random number generation test using
tpm2-tools. So feel free to add:

Tested-by: Sumit Garg <sumit.garg@...aro.org>

-Sumit

> +               kfree(optee_device);
> +               return -ENOMEM;
> +       }
>         uuid_copy(&optee_device->id.uuid, device_uuid);
>
>         rc = device_register(&optee_device->dev);
> @@ -144,7 +147,7 @@ int optee_enumerate_devices(void)
>         num_devices = shm_size / sizeof(uuid_t);
>
>         for (idx = 0; idx < num_devices; idx++) {
> -               rc = optee_register_device(&device_uuid[idx], idx);
> +               rc = optee_register_device(&device_uuid[idx]);
>                 if (rc)
>                         goto out_shm;
>         }
> --
> 2.17.1
>