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3c789bfccc
For a feature to be used at lower ELs, EL3 generally needs to disable
the trap so that lower ELs can access the system registers associated
with the feature. Lower ELs generally check ID registers to dynamically
detect if a feature is present (in HW) or not while EL3 Firmware relies
statically on feature build macros to enable a feature.
If a lower EL accesses a system register for a feature that EL3 FW is
unaware of, EL3 traps the access and panics. This happens mostly with
EL2 but sometimes VMs can also cause EL3 panic.
To provide platforms with capability to mitigate this problem, UNDEF
injection support has been introduced which injects a synchronous
exception into the lower EL which is supposed to handle the
synchronous exception.
The current support is only provided for aarch64.
The implementation does the following on encountering sys reg trap
- Get the target EL, which can be either EL2 or EL1
- Update ELR_ELx with ELR_EL3, so that after UNDEF handling in lower EL
control returns to original location.
- ESR_ELx with EC_UNKNOWN
- Update ELR_EL3 with vector address of sync exception handler with
following possible causes
- Current EL with SP0
- Current EL with SPx
- Lower EL using AArch64
- Re-create SPSR_EL3 which will be used to generate PSTATE at ERET
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I1b7bf6c043ce7aec1ee4fc1121c389b490b7bfb7
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Trusted Firmware-A ================== Trusted Firmware-A (TF-A) is a reference implementation of secure world software for `Arm A-Profile architectures`_ (Armv8-A and Armv7-A), including an Exception Level 3 (EL3) `Secure Monitor`_. It provides a suitable starting point for productization of secure world boot and runtime firmware, in either the AArch32 or AArch64 execution states. TF-A implements Arm interface standards, including: - `Power State Coordination Interface (PSCI)`_ - `Trusted Board Boot Requirements CLIENT (TBBR-CLIENT)`_ - `SMC Calling Convention`_ - `System Control and Management Interface (SCMI)`_ - `Software Delegated Exception Interface (SDEI)`_ The code is designed to be portable and reusable across hardware platforms and software models that are based on the Armv8-A and Armv7-A architectures. In collaboration with interested parties, we will continue to enhance TF-A with reference implementations of Arm standards to benefit developers working with Armv7-A and Armv8-A TrustZone technology. Users are encouraged to do their own security validation, including penetration testing, on any secure world code derived from TF-A. More Info and Documentation --------------------------- To find out more about Trusted Firmware-A, please `view the full documentation`_ that is available through `trustedfirmware.org`_. -------------- *Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.* .. _Armv7-A and Armv8-A: https://developer.arm.com/products/architecture/a-profile .. _Secure Monitor: http://www.arm.com/products/processors/technologies/trustzone/tee-smc.php .. _Power State Coordination Interface (PSCI): PSCI_ .. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf .. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT): https://developer.arm.com/docs/den0006/latest .. _SMC Calling Convention: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf .. _System Control and Management Interface (SCMI): SCMI_ .. _SCMI: http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/DEN0056A_System_Control_and_Management_Interface.pdf .. _Software Delegated Exception Interface (SDEI): SDEI_ .. _SDEI: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf .. _Arm A-Profile architectures: https://developer.arm.com/architectures/cpu-architecture/a-profile .. _view the full documentation: https://www.trustedfirmware.org/docs/tf-a .. _trustedfirmware.org: http://www.trustedfirmware.org