Lines Matching +full:secure +full:- +full:firmware
1 .. SPDX-License-Identifier: GPL-2.0
4 OP-TEE (Open Portable Trusted Execution Environment)
7 The OP-TEE driver handles OP-TEE [1] based TEEs. Currently it is only the ARM
8 TrustZone based OP-TEE solution that is supported.
10 Lowest level of communication with OP-TEE builds on ARM SMC Calling
11 Convention (SMCCC) [2], which is the foundation for OP-TEE's SMC interface
12 [3] used internally by the driver. Stacked on top of that is OP-TEE Message
15 OP-TEE SMC interface provides the basic functions required by SMCCC and some
16 additional functions specific for OP-TEE. The most interesting functions are:
18 - OPTEE_SMC_FUNCID_CALLS_UID (part of SMCCC) returns the version information
21 - OPTEE_SMC_CALL_GET_OS_UUID returns the particular OP-TEE implementation, used
22 to tell, for instance, a TrustZone OP-TEE apart from an OP-TEE running on a
23 separate secure co-processor.
25 - OPTEE_SMC_CALL_WITH_ARG drives the OP-TEE message protocol
27 - OPTEE_SMC_GET_SHM_CONFIG lets the driver and OP-TEE agree on which memory
28 range to used for shared memory between Linux and OP-TEE.
34 OP-TEE architecture::
36 User space Kernel Secure world
38 +--------+ +-------------+
40 +--------+ | Application |
41 /\ +-------------+
42 || +----------+ /\
43 || |tee- | ||
45 || +----------+ +-------------+
47 +-------+ || | API |
48 + TEE | || +--------+--------+ +-------------+
49 | Client| || | TEE | OP-TEE | | OP-TEE |
51 +-------+----------------+----+-------+----+-----------+-------------+
52 | Generic TEE API | | OP-TEE MSG |
54 +-----------------------------+ +------------------------------+
56 RPC (Remote Procedure Call) are requests from secure world to kernel driver
57 or tee-supplicant. An RPC is identified by a special range of SMCCC return
60 tee-supplicant without further involvement of the driver, except switching
63 OP-TEE device enumeration
64 -------------------------
66 OP-TEE provides a pseudo Trusted Application: drivers/tee/optee/device.c in
67 order to support device enumeration. In other words, OP-TEE driver invokes this
71 OP-TEE notifications
72 --------------------
74 There are two kinds of notifications that secure world can use to make
79 2. Asynchronous notifications delivered with a combination of a non-secure
80 edge-triggered interrupt and a fast call from the non-secure interrupt
84 this is only usable when secure world is entered with a yielding call via
85 ``OPTEE_SMC_CALL_WITH_ARG``. This excludes such notifications from secure
88 An asynchronous notification is delivered via a non-secure edge-triggered
89 interrupt to an interrupt handler registered in the OP-TEE driver. The
98 building block for OP-TEE OS in secure world to implement the top half and
102 ----------------------------------------
105 BL32 OP-TEE image from the kernel after the kernel boots, rather than loading
106 it from the firmware before the kernel boots. This also requires enabling the
107 corresponding option in Trusted Firmware for Arm. The Trusted Firmware for Arm
109 well as mitigations at the firmware and platform level.
116 * Attack vector: Replace the OP-TEE OS image in the rootfs to gain control of
120 rootfs, otherwise an attacker can modify the loaded OP-TEE binary by
126 OP-TEE driver isn't loaded, leaving the SMC hole open.
135 OP-TEE can be exploited to then load an alternate OS image.
137 * Mitigation: The OP-TEE driver must be loaded before any potential attack
142 4. Blocking SMC call to load OP-TEE.
145 load OP-TEE isn't executed when desired, leaving it open to being executed
148 * Mitigation: It is recommended to build the OP-TEE driver as builtin driver
155 [1] https://github.com/OP-TEE/optee_os
166 [6] https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html