Architectures and Processors

Cortex-M33 Unprivileged Mode Stack Corruption and Register Zeroing in Secure State When running an unprivileged application in the secure state on the Cortex-M33 processor (specifically on the STM32U5 microcontroller with TrustZone enabled), a critical issue arises. The system exhibits unexpected behavior during context switching and exception handling. Specifically, when the Link Register (LR) is set…

ARM Cortex Cache Line Faults and Their Impact on System Reliability Cache memory in ARM processors is a critical component that significantly impacts system performance and reliability. However, like any other hardware component, cache memory is susceptible to manufacturing defects, aging, or environmental factors that can introduce faulty bits. These faulty bits, often referred to…

ARM Cortex-M3 Event Register Behavior During WFE and SEV Operations The ARM Cortex-M3 processor includes a 1-bit Event Register (ER) that plays a critical role in managing low-power modes and synchronization between threads or interrupts. The Event Register is closely tied to the Wait For Event (WFE) and Send Event (SEV) instructions, which are used…

Cache Contents Mismatch with Main TLB After Enabling MMU and Configuring Memory Attributes The core issue revolves around a mismatch between the contents of the L1 data cache and the main TLB after enabling the MMU and configuring memory attributes for a specific SRAM region (0x30000000-0x30200000). The user observed that the L1 data cache only…

ARM Cortex-A65 MPIDR Core ID Issue: PE1 Not Responding The ARM Cortex-A65 is a high-performance processor designed for multi-core implementations, often used in scenarios requiring high throughput and scalability. One of the key features of multi-core ARM processors is the ability to identify each Processing Element (PE) using the Multiprocessor Affinity Register (MPIDR). The MPIDR…

ARM Cortex-A72 Branch Prediction Mechanism and Disabling Implications The ARM Cortex-A72 is a high-performance out-of-order execution core designed for advanced applications requiring both power efficiency and computational throughput. One of its key features is the branch predictor, which speculatively executes instructions based on predicted branch outcomes to minimize pipeline stalls. Disabling the branch predictor on…

ARM Cortex-M33 BASEPRI_NS Configuration and Secure Hard Fault The ARM Cortex-M33 processor, like other Cortex-M series processors, utilizes a priority-based interrupt handling mechanism. This mechanism is governed by several key registers, including BASEPRI and PRIGROUP, which control the masking of interrupts based on their priority levels. In this scenario, the user is encountering a secure…

ARM Cortex-A CPUACTLR_EL1 Debug Bits and Their Impact on Execution Predictability The ARM Cortex-A series of processors, particularly those implementing the ARMv8-A architecture, include a system register known as CPUACTLR_EL1 (CPU Auxiliary Control Register, EL1). This register is designed to control various microarchitectural features of the processor, many of which are optimization mechanisms aimed at…

ARM Cortex-M3 MPU Access Permissions and Memory Protection Overview The ARM Cortex-M3 Memory Protection Unit (MPU) is a critical component for ensuring secure and reliable operation in embedded systems. The MPU allows developers to define memory regions with specific access permissions, enabling the separation of software into privileged and unprivileged execution contexts. This separation is…

ARM Cortex-A53 Boot Process and ATF BL2 Initialization Challenges The ARM Cortex-A53 processor is a widely used 64-bit core in embedded systems, often integrated into custom System-on-Chips (SoCs) for applications requiring high performance and energy efficiency. The ARM Trusted Firmware (ATF) provides a reference implementation of secure world software, including Boot Loader stages BL1 and…