Re: [PATCH RFC 0/3] Implement Qualcomm TEE IPC and ioctl calls

[neil.armstrong@linaro.org]

On 03/07/2024 13:36, Dmitry Baryshkov wrote:
> On Tue, Jul 02, 2024 at 10:57:35PM GMT, Amirreza Zarrabi wrote:

<snip>

> 
>>
>> Can we use TEE subsystem?
>> -------------------------
>> There are workarounds for some of the issues above. The question is if we
>> should define our own UAPI or try to use a hack-y way of fitting into
>> the TEE subsystem. I am using word hack-y, as most of the workaround
>> involves:
>>
>> - "diverging from the definition". For instance, ignoring the session
>>    open and close ioctl calls or use file descriptors for all remote
>> resources (as, fd is the closet to capability) which undermines the
>> isolation provided by the contexts,
>>
>> - "overloading the variables". For instance, passing object ID as file
>>    descriptors in a place of session ID, or
>>
>> - "bypass TEE subsystem". For instance, extensively rely on meta
>>    parameters or push everything (e.g. kernel services) to the back-end
>> driver, which means leaving almost all TEE subsystem unused.

Why can't you extend the TEE subsystem with those features ?

>>
>> We cannot take the full benefits of TEE subsystem and may need to
>> implement most of the requirements in the back-end driver. Also, as
>> discussed above, the UAPI is not suitable for capability-based use cases.
>> We proposed a new set of ioctl calls for SMC-Invoke driver.
>>
>> In this series we posted three patches. We implemented a transport
>> driver that provides qcom_tee_object. Any object on secure side is
>> represented with an instance of qcom_tee_object and any struct exposed
>> to TEE should embed an instance of qcom_tee_object. Any, support for new
>> services, e.g. memory object, RPMB, userspace clients or supplicants are
>> implemented independently from the driver.
>>
>> We have a simple memory object and a user driver that uses
>> qcom_tee_object.
> 
> Could you please point out any user for the uAPI? I'd like to understand
> how does it from from the userspace point of view.

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