NEON Instruction Execution Failure in NSEL1 with HCR_EL2.ID and HCR_EL2.CD Set to 1 The core issue revolves around the failure of NEON instructions to execute in Non-Secure EL1 (NSEL1) when the HCR_EL2 register’s ID (Instruction Cache Disable) and CD (Data Cache Disable) bits are both set to 1. Specifically, the NEON instruction str q0, [x1,…
Cortex-A9 MPCore IRQ Vector Misdirection During Local Timer Interrupt The Cortex-A9 MPCore processor, when configured to handle interrupts via the Generic Interrupt Controller (GIC), is experiencing a misdirection of the interrupt vector. Specifically, when a local timer interrupt (vector 29) is triggered, the processor incorrectly jumps to the Supervisor Call (SVC) exception handler instead of…
ARMv8-M Secure Stack Pointer Vulnerability Overview (CVE-2020-16273) The ARMv8-M architecture introduces a security extension known as TrustZone for ARM Cortex-M processors, which partitions the system into Secure and Non-secure worlds. This partitioning is designed to isolate sensitive code and data in the Secure world from potentially malicious or untrusted code in the Non-secure world. A…
Identifying ARM CPU Cores on Die: Feasibility and Techniques Reverse engineering an ARM CPU core on a die is a complex but feasible task for skilled engineers with access to advanced tools and techniques. The process involves decapsulating the integrated circuit (IC), imaging the die using high-resolution microscopy, and analyzing the physical layout to identify…
ARM Cortex-A7 SMP CPU0 Boot Dependency and Offlining Constraints In ARM Cortex-A7-based symmetric multiprocessing (SMP) systems running Linux, CPU0 is designated as the boot CPU and is inherently required to remain active throughout the system’s operation. This design choice stems from the architecture’s reliance on CPU0 for critical system tasks, such as interrupt routing, kernel…
ARM Cortex-A78 Atomic Instruction Execution Failure During Kernel Boot The issue at hand involves the ARM Cortex-A78 CPU failing to execute atomic instructions, specifically Load-Exclusive (LDXR) and Store-Exclusive (STXR), during the Linux kernel boot process. The kernel version in use is 5.10.39, and the bootloader is U-Boot 2021.10-rc2. The problem manifests when the kernel attempts…
ARM STM32 GPIO Bit Assignment Challenges in Hex-to-Binary Conversion When working with ARM-based microcontrollers like the STM32 series, a common task is to manipulate individual GPIO pins to reflect the binary representation of a hexadecimal value. This involves converting a hexadecimal value to its binary equivalent and then assigning each bit of the binary representation…
AXI Write Data Preceding Write Address: The Realignment Challenge In the ARM AMBA AXI protocol, one of the most nuanced aspects of the write transaction mechanism is the potential for write data (W channel) to precede the corresponding write address (AW channel). This scenario, while permitted by the protocol, introduces a significant challenge for the…
Cortex-M0 Debugging Instability Due to XIP Flash Mapping at Address 0 The instability observed during debugging of the Cortex-M0 DesignStart FPGA implementation, particularly when using the Keil debugger with the Arty A7-35T board and DAPLink interface, is primarily caused by the mapping of XIP (Execute-In-Place) Flash at address 0. This configuration leads to slow execution…
Understanding the Impact of Bit Width and Depth on SMIC28 Memory Area When designing memory structures such as DPRAM (Dual-Port RAM), Two-Port RAM, SPRAM (Single-Port RAM), and ROM in SMIC28 technology, understanding the relationship between bit width, depth, and area is crucial. The area of a memory block is influenced by both the bit width…