Architectures and Processors

ARM System Control Registers and Their Role in Alignment Checking The ARM architecture, particularly in its ARMv8-A implementation, employs a hierarchical system of control registers to manage various aspects of processor behavior. Among these, the System Control Registers (SCTLR) play a pivotal role in configuring system-level features, including memory management, cache behavior, and alignment checking….

ARM Cortex-A53 System Control Register Access Errors in AArch64 and AArch32 Modes The ARM Cortex-A53 processor, a popular choice for embedded systems, supports both AArch64 (64-bit) and AArch32 (32-bit) execution states. Accessing system control registers, such as the System Control Register (SCTLR), is a common task for low-level firmware development. However, developers often encounter errors…

ARMv8-M TrustZone Secure State to Non-Secure State Branching Faults In ARMv8-M architectures, the TrustZone security extension provides a robust mechanism for isolating secure and non-secure worlds. This isolation is critical for ensuring that sensitive operations and data in the secure world are protected from potential vulnerabilities in the non-secure world. However, this isolation also introduces…

Cortex-M7 Boot Process and Initialization Challenges The Cortex-M7 processor, part of ARM’s Cortex-M series, is a high-performance microcontroller core designed for embedded systems requiring significant computational power. When creating a program for the Cortex-M7 from scratch, developers must handle several low-level tasks, including writing the startup code, configuring the linker script, initializing the system, and…

Undefined Instruction Exception and Data Abort During CP15 System Control Register Access The core issue revolves around the AM3352 Cortex-A8 processor experiencing a hang-up during the execution of a specific sequence involving the CP15 system control register. The hang-up is consistently observed after a sequence of events: an undefined instruction exception related to the VFP…

ARM Trusted Firmware-M Boot Process and BL2 Bypass Requirements The ARM Trusted Firmware-M (TF-M) is a secure firmware solution designed for ARM Cortex-M processors, providing a secure boot process and runtime services. The boot process typically involves multiple stages, including Bootloader Stage 1 (BL1) and Bootloader Stage 2 (BL2). BL2 is responsible for loading and…

Mixed-Mode Translation in AArch64 Kernel with AArch32 User Space The core issue revolves around the complexities of mixed-mode translation in an ARMv8 architecture, where an AArch64 kernel (running at EL1) needs to manage AArch32 user-space applications (running at EL0). Specifically, the challenge lies in configuring the translation tables to allow the AArch64 kernel to access…

ARM Cortex-A53 PC Corruption During NEON Register Operations with O2/O3 Optimization The issue at hand involves a program running on an ARM Cortex-A53 processor that fails to execute correctly when compiled with optimization levels O2 and O3. The program works as expected with optimization levels O0 and O1. The failure manifests as Program Counter (PC)…

ARM Cortex-A5 Normal/Non-shareable/Non-cacheable Memory Access and L1 Cache Bypass The Cortex-A5 processor, like many ARM cores, provides a sophisticated memory system that allows developers to configure memory regions with different attributes to optimize performance and ensure correct behavior in multi-core or multi-master systems. One such configuration is the use of Normal/Non-shareable/Non-cacheable memory attributes. The Technical…

ARMv8M Secure Function Calls in Handler Mode: Architectural Intent and Use Cases The ARMv8-M architecture introduces a robust security model that partitions software execution into secure and non-secure states. This partitioning is critical for modern embedded systems, where security-sensitive operations must be isolated from less trusted code. One of the key design decisions in ARMv8-M…