ARM Cortex-A72 Performance Counter Access in EL0 (User Mode) The core issue revolves around accessing the ARM Cortex-A72 cycle counter (PMCCNTR_EL0) from user mode (EL0) on a Linux-based system. The user attempted to read the cycle counter using the MRS instruction in a C program but encountered an "Illegal Instruction" error. This error indicates that…
ARM A-15 Performance Register Emulation Challenges on x86 Host Emulating ARM A-15 performance registers on an x86-based system, such as an Intel i5 laptop, presents a unique set of challenges. The primary goal is to compile a C program into ARM A-15 assembly code to accurately measure performance metrics like instruction count, CPU cycles, bus…
ARM Cortex-M33 Hard Fault During VLDR Execution The issue at hand involves a HardFault triggered by the execution of the vldr d16, [r7, #200] instruction on an ARM Cortex-M33 processor, specifically the LPC55S69 (CM33_Core0) with DSP extensions. The fault occurs during the execution of a floating-point unit (FPU) instruction, suggesting potential misconfigurations or memory access…
ARMv8-A 64-bit Processors and Volatile Execution Timing When working with ARMv8-A 64-bit processors, one of the most common challenges developers face is accurately measuring the execution time of programs. This issue is particularly pronounced when using high-resolution clocks, such as std::chrono in C++, which are commonly used on Intel processors. On ARMv8-A architectures, the execution…
Cortex-A9 Core Lockup and Debugger Inability to Halt Execution When working with ARM Cortex-A9 processors, particularly in a dual-core configuration such as the Cyclone V SoC, one of the most frustrating issues that can arise during debugging is the inability to stop one of the cores. This issue manifests when using debugging tools like ARM…
ARM Cortex-M4 Frame Pointer Behavior with -fno-omit-frame-pointer The issue at hand revolves around the unexpected behavior of the frame pointer (FP) when compiling code for the ARM Cortex-M4 processor using the -fno-omit-frame-pointer compiler flag. The user expects the frame pointer to be present in the call stack, similar to how it appears in the ARM…
ARM Cortex-R4F FPU Internal Precision Behavior for Single-Precision Operations The ARM Cortex-R4F Floating-Point Unit (FPU) is designed to handle single-precision (32-bit) and double-precision (64-bit) floating-point operations. A key question arises regarding how the FPU manages intermediate results during single-precision calculations. Specifically, does the FPU internally use higher precision (e.g., double precision) to store intermediate results…
ARM Cortex Processor Limitations for Multi-OS Implementations The ARM Cortex family of processors is widely used in embedded systems due to its efficiency, scalability, and performance. However, running multiple operating systems (OS) on a single ARM Cortex processor presents significant challenges, particularly when considering the differences between Cortex-M and Cortex-A series processors. The Cortex-M series,…
ARM Cortex-M7 INVSTATE Fault During Assembly Function Execution The ARM Cortex-M7 processor is a high-performance embedded processor designed for real-time applications. It is based on the ARMv7-M architecture, which supports both Thumb and ARM instruction sets. However, the Cortex-M7 primarily operates in Thumb mode, which is a more compact instruction set designed for efficiency in…
Understanding ARM Cortex-M4 Load/Store Latency in Zero Wait State Memory When working with ARM Cortex-M4 processors, one of the most critical performance metrics is the cycle count for load and store operations, especially when accessing zero wait state memory. Zero wait state memory, such as internal RAM, is typically designed to operate at the same…