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| 4 | ==================================================
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| 5 | TEE (Trusted Execution Environment) Userspace API
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| 6 | ==================================================
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| 7 |
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| 8 | include/uapi/linux/tee.h defines the generic interface to a TEE.
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| 9 |
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| 10 | User space (the client) connects to the driver by opening /dev/tee[0-9]* or
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| 11 | /dev/teepriv[0-9]*.
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| 12 |
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| 13 | - TEE_IOC_SHM_ALLOC allocates shared memory and returns a file descriptor
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| 14 | which user space can mmap. When user space doesn't need the file
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| 15 | descriptor any more, it should be closed. When shared memory isn't needed
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| 16 | any longer it should be unmapped with munmap() to allow the reuse of
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| 17 | memory.
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| 18 |
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| 19 | - TEE_IOC_VERSION lets user space know which TEE this driver handles and
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| 20 | its capabilities.
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| 21 |
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| 22 | - TEE_IOC_OPEN_SESSION opens a new session to a Trusted Application.
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| 23 |
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| 24 | - TEE_IOC_INVOKE invokes a function in a Trusted Application.
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| 25 |
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| 26 | - TEE_IOC_CANCEL may cancel an ongoing TEE_IOC_OPEN_SESSION or TEE_IOC_INVOKE.
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| 27 |
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| 28 | - TEE_IOC_CLOSE_SESSION closes a session to a Trusted Application.
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| 29 |
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| 30 | There are two classes of clients, normal clients and supplicants. The latter is
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| 31 | a helper process for the TEE to access resources in Linux, for example file
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| 32 | system access. A normal client opens /dev/tee[0-9]* and a supplicant opens
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| 33 | /dev/teepriv[0-9].
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| 34 |
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| 35 | Much of the communication between clients and the TEE is opaque to the
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| 36 | driver. The main job for the driver is to receive requests from the
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| 37 | clients, forward them to the TEE and send back the results. In the case of
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| 38 | supplicants the communication goes in the other direction, the TEE sends
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| 39 | requests to the supplicant which then sends back the result.
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