ARM Cortex-A53 MMU Translation Fault on Virt Board During Bootloader Execution The core issue revolves around a Memory Management Unit (MMU) configuration that works flawlessly on a Raspberry Pi 3B (Cortex-A53) but fails on a QEMU virt board (also Cortex-A53) with an "Instruction Abort" exception. The fault occurs immediately after enabling the MMU, specifically during…
ARM Cortex-M Thumb Mode B Instruction PC Calculation Discrepancy The ARM Cortex-M architecture, particularly in Thumb mode, exhibits a discrepancy in the Program Counter (PC) calculation for the B (Branch) instruction. According to the ARMv7-M Architecture Reference Manual (ARM DDI 0403E.e), the expected behavior is that the PC should be incremented by the immediate value…
ARM Cortex-A32 AArch32 HYP Mode to SVC Mode Transition Issue The ARM Cortex-A32 processor, operating in AArch32 state, supports multiple privilege levels, including Hypervisor (HYP) mode (EL2) and Supervisor (SVC) mode (EL1). Transitioning between these modes is a critical operation during system initialization, particularly when moving from a higher privilege level (HYP mode) to a…
GICA Frame INTID Range Violations and Expected Behavior The Generic Interrupt Controller Architecture (GICA) frames in ARM’s GIC600AE are designed to handle message-based interrupts, such as those generated by PCIe controllers using Message Signaled Interrupts (MSIs). Each GICA frame is assigned a specific range of Shared Peripheral Interrupts (SPIs), defined by the INTID field (bits…
ARM Cortex-A9 MMU Translation Table Structure and 1MB Granularity Limitation The ARM Cortex-A9 processor, based on the ARMv7-A architecture, utilizes a Memory Management Unit (MMU) to handle virtual-to-physical address translation. The MMU supports multiple levels of translation tables, enabling flexible memory management with varying granularities. By default, many implementations, including the one described in the…
ARM Cortex-A78 Cache Performance Metrics: L3D_CACHE_REFILL and LL_CACHE_MISS_RD L3D_CACHE_REFILL and LL_CACHE_MISS_RD Event Definitions and Discrepancies In the ARM Cortex-A78 architecture, cache performance metrics are critical for understanding system behavior, particularly in high-performance computing environments. Two key metrics, L3D_CACHE_REFILL and LL_CACHE_MISS_RD, often cause confusion due to their seemingly overlapping definitions but differing behaviors in practice. The…
ARM Cortex-A55 Cache Coherency and Snoop Protocol Overview The ARM Cortex-A55 processor, part of the ARMv8-A architecture, implements a sophisticated cache coherency mechanism to ensure data consistency across multiple cores and system components. This mechanism is critical in systems where multiple agents, such as CPUs, GPUs, and DMA controllers, access shared memory. The Cortex-A55 employs…
Realm EL1/0 Stage 2 Translation and Non-Secure PAS Access The core issue revolves around the sharing of memory pages between the Realm EL1/0 and the Non-Secure Physical Address Space (PAS) in ARM’s Realm Management Extension (RME). The problem arises from the interpretation of the ARM RME specification, particularly section 5.1.2.3, which discusses Realm EL1&0 stage…
ARMv8-A CPU Feature Detection and HWCAP Misconfiguration The issue at hand revolves around the runtime detection of ARMv8-A CPU features, specifically the Scalable Vector Extension 2 (SVE2) and its associated matrix multiplication extensions (SVEF32MM and SVEF64MM). The user attempted to detect these features using the getauxval system call in conjunction with the AT_HWCAP and AT_HWCAP2…
ARMv7 and ARMv8 Firmware Analysis: Choosing the Right Architecture Variant in Ghidra When reverse-engineering ARM firmware, one of the most critical steps is selecting the appropriate architecture variant for disassembly and analysis in tools like Ghidra. This decision directly impacts the accuracy of the disassembled code, the recognition of processor-specific instructions, and the overall success…