mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-01 00:49:43 +00:00
113 lines
4 KiB
Text
113 lines
4 KiB
Text
|
=============
|
||
|
|
TEE uclass
|
||
|
|
=============
|
||
|
|
|
||
|
|
This document describes the TEE uclass in U-Boot
|
||
|
|
|
||
|
|
A TEE (Trusted Execution Environment) is a trusted OS running in some
|
||
|
|
secure environment, for example, TrustZone on ARM CPUs, or a separate
|
||
|
|
secure co-processor etc. A TEE driver handles the details needed to
|
||
|
|
communicate with the TEE.
|
||
|
|
|
||
|
|
This uclass deals with:
|
||
|
|
|
||
|
|
- Registration of TEE drivers
|
||
|
|
|
||
|
|
- Managing shared memory between U-Boot and the TEE
|
||
|
|
|
||
|
|
- Providing a generic API to the TEE
|
||
|
|
|
||
|
|
The TEE interface
|
||
|
|
=================
|
||
|
|
|
||
|
|
include/tee.h defines the generic interface to a TEE.
|
||
|
|
|
||
|
|
A client finds the TEE device via tee_find_device(). Other important functions
|
||
|
|
when interfacing with a TEE are:
|
||
|
|
|
||
|
|
- tee_shm_alloc(), tee_shm_register() and tee_shm_free() to manage shared
|
||
|
|
memory objects often needed when communicating with the TEE.
|
||
|
|
|
||
|
|
- tee_get_version() lets the client know which the capabilities of the TEE
|
||
|
|
device.
|
||
|
|
|
||
|
|
- tee_open_session() opens a session to a Trusted Application
|
||
|
|
|
||
|
|
- tee_invoke_func() invokes a function in a Trusted Application
|
||
|
|
|
||
|
|
- tee_close_session() closes a session to a Trusted Application
|
||
|
|
|
||
|
|
Much of the communication between clients and the TEE is opaque to the
|
||
|
|
driver. The main job for the driver is to receive requests from the
|
||
|
|
clients, forward them to the TEE and send back the results.
|
||
|
|
|
||
|
|
OP-TEE driver
|
||
|
|
=============
|
||
|
|
|
||
|
|
The OP-TEE driver handles OP-TEE [1] based TEEs. Currently it is only the ARM
|
||
|
|
TrustZone based OP-TEE solution that is supported.
|
||
|
|
|
||
|
|
Lowest level of communication with OP-TEE builds on ARM SMC Calling
|
||
|
|
Convention (SMCCC) [2], which is the foundation for OP-TEE's SMC interface
|
||
|
|
[3] used internally by the driver. Stacked on top of that is OP-TEE Message
|
||
|
|
Protocol [4].
|
||
|
|
|
||
|
|
OP-TEE SMC interface provides the basic functions required by SMCCC and some
|
||
|
|
additional functions specific for OP-TEE. The most interesting functions are:
|
||
|
|
|
||
|
|
- OPTEE_SMC_FUNCID_CALLS_UID (part of SMCCC) returns the version information
|
||
|
|
which is then returned by TEE_IOC_VERSION
|
||
|
|
|
||
|
|
- OPTEE_SMC_CALL_GET_OS_UUID returns the particular OP-TEE implementation, used
|
||
|
|
to tell, for instance, a TrustZone OP-TEE apart from an OP-TEE running on a
|
||
|
|
separate secure co-processor.
|
||
|
|
|
||
|
|
- OPTEE_SMC_CALL_WITH_ARG drives the OP-TEE message protocol
|
||
|
|
|
||
|
|
- OPTEE_SMC_GET_SHM_CONFIG lets the driver and OP-TEE agree on which memory
|
||
|
|
range to used for shared memory between Linux and OP-TEE.
|
||
|
|
|
||
|
|
The GlobalPlatform TEE Client API [5] is implemented on top of the generic
|
||
|
|
TEE API.
|
||
|
|
|
||
|
|
Picture of the relationship between the different components in the
|
||
|
|
OP-TEE architecture:
|
||
|
|
|
||
|
|
U-Boot Secure world
|
||
|
|
~~~~~~ ~~~~~~~~~~~~
|
||
|
|
+------------+ +-------------+
|
||
|
|
| Client | | Trusted |
|
||
|
|
| | | Application |
|
||
|
|
+------------+ +-------------+
|
||
|
|
/\ /\
|
||
|
|
|| ||
|
||
|
|
\/ \/
|
||
|
|
+------------+ +-------------+
|
||
|
|
| TEE | | TEE Internal|
|
||
|
|
| uclass | | API |
|
||
|
|
+------------+ +-------------+
|
||
|
|
| OP-TEE | | OP-TEE |
|
||
|
|
| driver | | Trusted OS |
|
||
|
|
+------------+-----------+-------------+
|
||
|
|
| OP-TEE MSG |
|
||
|
|
| SMCCC (OPTEE_SMC_CALL_*) |
|
||
|
|
+--------------------------------------+
|
||
|
|
|
||
|
|
RPC (Remote Procedure Call) are requests from secure world to the driver.
|
||
|
|
An RPC is identified by a special range of SMCCC return values from
|
||
|
|
OPTEE_SMC_CALL_WITH_ARG.
|
||
|
|
|
||
|
|
References
|
||
|
|
==========
|
||
|
|
|
||
|
|
[1] https://github.com/OP-TEE/optee_os
|
||
|
|
|
||
|
|
[2] http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html
|
||
|
|
|
||
|
|
[3] drivers/tee/optee/optee_smc.h
|
||
|
|
|
||
|
|
[4] drivers/tee/optee/optee_msg.h
|
||
|
|
|
||
|
|
[5] http://www.globalplatform.org/specificationsdevice.asp look for
|
||
|
|
"TEE Client API Specification v1.0" and click download.
|