BLAS Library Integration Challenges on Cortex-A9 Baremetal Systems Integrating the Basic Linear Algebra Subprograms (BLAS) library into a baremetal system based on the ARM Cortex-A9 processor presents a unique set of challenges. The Cortex-A9, known for its dual-core configuration and advanced features like out-of-order execution and NEON SIMD capabilities, is a powerful processor for embedded…
ARMv9 FEAT_DoPD: Debug Power Domain Reconfiguration and Its Implications The introduction of FEAT_DoPD (Debug Power Domain) in ARMv9 architecture marks a significant shift in how debug resources are managed within DynamIQ-based cores. Historically, DynamIQ cores utilized a separate DebugBlock, which allowed for the isolation of debugging logic into its own power domain. This separation was…
ARM Cortex-A Series and the Absence of Nested Virtualization (FEAT_NV, FEAT_NV2) Nested Virtualization, a feature that allows a hypervisor to run within another hypervisor, has been a topic of significant interest in the ARM ecosystem. The ARM architecture has introduced features like FEAT_NV and FEAT_NV2 to support nested virtualization, but as of the latest CPU…
Cortex-A55 IMPDEF System Registers and Their Undocumented Behavior The Cortex-A55, a highly efficient mid-range ARM Cortex-A series processor, implements a variety of system registers that are critical for its operation. Among these, some registers fall under the IMPDEF (Implementation Defined) category, meaning their functionality is specific to the Cortex-A55 implementation and not architecturally defined by…
ARM Cortex TLB Invalidation: Broadcast vs. Local Operation Serialization In ARM architectures, the Translation Lookaside Buffer (TLB) is a critical component for virtual-to-physical address translation. The TLB caches recently used translations to reduce latency in memory access. However, maintaining TLB coherency across multiple cores or masters in a system is a complex task, especially when…
Cortex-A53 Write-Streaming Mode and BUS_ACCESS_LD Anomalies The Cortex-A53 processor, a widely used ARM core in embedded systems, is known for its efficiency and performance in applications ranging from mobile devices to embedded controllers. However, when operating in write-streaming mode, particularly during memory operations such as memset, unexpected behavior in Performance Monitoring Unit (PMU) counters, specifically…
ARMv8 Core Dump Triggering via Illegal Vector Table Fetch and PSTATE Manipulation The process of triggering a core dump in ARMv8 architectures can be a critical debugging tool, especially when diagnosing complex system failures or unexpected behavior. However, the methods employed to force a core dump, such as manipulating the PSTATE flags or instigating an…
ARM Cortex-M4F SMLAxy Instruction Behavior and Sign Bit Handling The ARM Cortex-M4F processor, a member of the Cortex-M family, is widely used in embedded systems for its balance of performance and power efficiency. One of its key features is the support for DSP (Digital Signal Processing) instructions, which include the SMLAxy family of instructions. These…
ARM Cortex-M55 Helium Vector Extension and Neon VEXT Instruction Compatibility The ARM Cortex-M55 processor, featuring the Helium vector extension, represents a significant evolution in the ARM architecture for microcontrollers. Helium, also known as M-Profile Vector Extension (MVE), is designed to bring enhanced vector processing capabilities to the Cortex-M series, targeting applications requiring digital signal processing…
Understanding Worst-Case Execution Time (WCET) Analysis on ARM Cortex-M4F Worst-case execution time (WCET) analysis is a critical aspect of real-time embedded systems design, particularly for safety-critical applications where timing guarantees are paramount. The ARM Cortex-M4F, with its floating-point unit and efficient Thumb-2 instruction set, is widely used in such systems. However, determining the WCET of…