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Message-ID: <f3131cf1-d2a5-60df-fa3c-0613fd8f416c@forissier.org>
Date: Wed, 17 Jun 2020 22:45:46 +0200
From: Jerome Forissier <jerome@...issier.org>
To: Maxim Uvarov <maxim.uvarov@...aro.org>
Cc: Sumit Garg <sumit.garg@...aro.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
Arnd Bergmann <arnd@...aro.org>,
"tee-dev @ lists . linaro . org" <tee-dev@...ts.linaro.org>,
Jason Gunthorpe <jgg@...pe.ca>,
linux-integrity@...r.kernel.org, peterhuewe@....de
Subject: Re: [Tee-dev] [PATCHv8 1/3] optee: use uuid for sysfs driver entry
On 6/17/20 9:52 PM, Maxim Uvarov wrote:
> On Wed, 17 Jun 2020 at 18:16, Jerome Forissier <jerome@...issier.org> 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@...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:
>>
>> 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 :-/
>>
>> --
>> Jerome
>
> From linux side it is for example:
>
> static const struct tee_client_device_id optee_ftpm_id_table[] = {
> {UUID_INIT(0xbc50d971, 0xd4c9, 0x42c4,
> 0x82, 0xcb, 0x34, 0x3f, 0xb7, 0xf3, 0x78, 0x96)},
> {}
> };
>
> static struct tee_client_driver ftpm_tee_driver = {
> .id_table = optee_ftpm_id_table,
> .driver = {
>
> So sysfs name has to be the same as the driver has. And UUD is simple
> 16 bytes:#define UUID_SIZE 16
> typedef struct {
> __u8 b[UUID_SIZE];
> } uuid_t;
>
> From TA it also:
> #define TA_UUID { 0xBC50D971, 0xD4C9, 0x42C4, \
> {0x82, 0xCB, 0x34, 0x3F, 0xB7, 0xF3, 0x78, 0x96}}
>
> Compare uuid from optee and kernel driver version is simple:
> static inline bool uuid_equal(const uuid_t *u1, const uuid_t *u2)
> {
> return memcmp(u1, u2, sizeof(uuid_t)) == 0;
> }
>
> So to support better code navigation. For example grep sources for
> 0xBC50D971, or find in sysfs "*bc50d971-*" I would say we need to use
> BE format.
> optee might also need to switch to BE prints for the same reason.
Sorry but this does not make much sense to me :-/
All I want to say is, if you ever need to use %pUb for things to work as
expected then it is *very* suspect and you should try to understand why,
because as I said and as far as I can tell OP-TEE stores all it's UUIDs
in memory in little endian format (more precisely, host endian with all
platforms being little endian currently), and %pUb is not even
implemented in OP-TEE.
--
Jerome
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