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Vector entries in EL3 from lower ELs, first check for any pending async EAs from lower EL before handling the original exception. This happens when there is an error (EA) in the system which is not yet signaled to PE while executing at lower EL. During entry into EL3 the errors (EA) are synchronized causing async EA to pend at EL3. On detecting the pending EA (via ISR_EL1.A) EL3 either reflects it back to lower EL (KFH) or handles it in EL3 (FFH) based on EA routing model. In case of Firmware First handling mode (FFH), EL3 handles the pended EA first before returing back to handle the original exception. While in case of Kernel First handling mode (KFH), EL3 will return back to lower EL without handling the original exception. On returing to lower EL, EA will be pended. In KFH mode there is a risk of back and forth between EL3 and lower EL if the EA is masked at lower EL or priority of EA is lower than that of original exception. This is a limitation in current architecture but can be solved in future if EL3 gets a capability to inject virtual SError. Signed-off-by: Manish Pandey <manish.pandey2@arm.com> Change-Id: I3a2a31de7cf454d9d690b1ef769432a5b24f6c11 |
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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/trusted-board-boot-requirements-client-tbbr-client-armv8-a .. _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