Port meniOS to ARM64/AArch64 architecture

Open pbalduino opened this issue 4 months ago • 2 comments

Goal

Port meniOS to ARM64/AArch64 architecture, creating a complete second architecture implementation for the operating system.

Context

ARM64 is a modern, clean 64-bit architecture widely used in mobile devices, servers, and embedded systems. Porting to ARM64 will demonstrate the portability of meniOS and provide access to a huge ecosystem of ARM-based hardware.

Definition of Done

Complete ARM64 port: Full meniOS functionality on ARM64 hardware
Boot support: Boot from standard ARM64 bootloaders (U-Boot, GRUB)
Hardware drivers: Essential ARM64 platform drivers
SMP support: Multi-core ARM64 CPU support
Performance: Performance comparable to x86_64 implementation
Testing: Comprehensive testing on real hardware and emulation
Documentation: ARM64-specific documentation and build instructions

Prerequisites

✅ Architecture abstraction layer (Issue #97)
✅ Clean separation of x86_64-specific code
✅ Standard architecture interfaces defined
✅ Multi-architecture build system

Target Platforms

Primary: QEMU ARM64 (virt machine) for development
Secondary: Raspberry Pi 4/5 for real hardware testing
Tertiary: ARM64 cloud instances for CI/testing
Future: Apple Silicon Macs, ARM64 servers

Implementation Phases

Phase 1: Basic Bring-up (6-8 weeks)

Boot and Early Initialization

ARM64 boot protocol implementation
Device tree parsing and hardware discovery
Early console output (UART/serial)
Memory layout and kernel mapping
Exception vector setup

Memory Management

ARM64 page table format implementation
Virtual memory layout design
MMU initialization and setup
Cache management operations
Memory barriers and ordering

Core Infrastructure

ARM64 interrupt handling (GIC)
Timer implementation (ARM Generic Timer)
Basic context switching
System call entry/exit
CPU identification and features

Phase 2: Core Functionality (8-10 weeks)

Process Management

ARM64 context switching optimization
Signal handling implementation
Process creation and management
Thread scheduling adaptation
SMP processor startup

System Services

System call implementation
Virtual file system adaptation
Device driver framework
Interrupt controller (GIC-400/500)
Power management basics

Memory Allocator

ARM64-specific memory allocator optimizations
DMA coherency handling
NUMA awareness (for multi-socket systems)
Performance tuning

Phase 3: Hardware Support (6-8 weeks)

Essential Drivers

UART/serial console drivers
Timer drivers (ARM Generic Timer)
Interrupt controller (GIC) drivers
GPIO and pin control
I2C and SPI buses

Platform Support

Raspberry Pi 4/5 specific support
Device tree integration
Framebuffer/display support
USB controller support
Network interface drivers

Storage and I/O

SDHCI/MMC controller
PCIe support (where available)
Block device drivers
DMA engine support

Phase 4: Optimization and Polish (4-6 weeks)

Performance Optimization

ARM64-specific optimizations
NEON/SIMD utilization
Cache optimization
Branch prediction optimization
Memory access patterns

Testing and Validation

Comprehensive hardware testing
Performance benchmarking
Compatibility validation
Stress testing
Real-world application testing

Technical Implementation

ARM64-Specific Code Structure

src/kernel/arch/aarch64/
├── boot/
│   ├── head.S              # Boot entry point
│   ├── setup.c             # Early initialization
│   └── devicetree.c        # Device tree parsing
├── mm/
│   ├── pgtable.c           # Page table management
│   ├── mmu.c               # MMU setup and management
│   └── cache.c             # Cache management
├── kernel/
│   ├── entry.S             # Exception vectors
│   ├── irq.c               # Interrupt handling
│   ├── smp.c               # SMP support
│   ├── syscall.c           # System call handling
│   └── process.c           # Process/thread management
├── drivers/
│   ├── gic.c               # Generic Interrupt Controller
│   ├── timer.c             # ARM Generic Timer
│   ├── uart.c              # UART drivers
│   └── gpio.c              # GPIO support
└── include/
    └── asm/                # ARM64-specific headers

Key ARM64 Features to Implement

Exception Levels: EL0 (user), EL1 (kernel), EL2 (hypervisor)
Virtual Memory: 48-bit virtual addresses, 4KB/64KB pages
NEON/SIMD: Vector processing unit integration
Pointer Authentication: Security feature support
Memory Tagging: MTE (Memory Tagging Extensions)
SVE: Scalable Vector Extensions (future)

Hardware Abstraction

ARM64 Architecture Operations

struct aarch64_arch_ops {
    // Memory management
    void (*setup_mmu)(void);
    void (*flush_tlb_all)(void);
    void (*flush_tlb_page)(unsigned long addr);
    
    // Interrupt handling
    void (*gic_init)(void);
    void (*enable_irq)(int irq);
    void (*disable_irq)(int irq);
    
    // Timer operations
    void (*timer_init)(void);
    uint64_t (*read_cntpct)(void);
    void (*set_timer_interrupt)(uint64_t cycles);
    
    // CPU operations
    void (*cpu_relax)(void);
    void (*cpu_halt)(void);
    int (*smp_boot_cpu)(int cpu);
};

Testing Strategy

Emulation Testing

QEMU ARM64 virt machine testing
Automated CI/CD on emulated hardware
Performance regression testing
Compatibility validation

Real Hardware Testing

Raspberry Pi 4/5 validation
ARM64 development boards
Cloud instance testing
Multi-core validation

Application Testing

Port and test essential applications
Shell functionality validation
Network stack testing
File system operations
Graphics and audio (where supported)

Build System Integration

Cross-Compilation Setup

ARM64 cross-compiler toolchain
Architecture-specific build flags
Kernel image format (Image, zImage)
Device tree compilation
Boot image creation

Configuration

ARCH=aarch64
CROSS_COMPILE=aarch64-linux-gnu-
KERNEL_IMAGE_FORMAT=Image
DEVICE_TREE_SUPPORT=y

Documentation Deliverables

ARM64 Port Guide
Hardware Support Matrix
Performance Comparison Report
Build and Deployment Instructions
Debugging Guide for ARM64

Performance Goals

Boot time < 5 seconds on Raspberry Pi 4
Context switch overhead < x86_64 + 10%
Memory management performance within 5% of x86_64
Network and I/O performance competitive with Linux
Power efficiency optimized for ARM64 characteristics

Risk Mitigation

Start with QEMU for easier debugging
Incremental implementation and testing
Maintain x86_64 compatibility throughout
Regular testing on real hardware
Community feedback and testing

Dependencies

Architecture abstraction layer (Issue #97)
ARM64 cross-compilation toolchain
QEMU ARM64 support for development
ARM64 hardware for testing
Device tree understanding and tools

Related Issues

Validates architecture abstraction design
Enables broader hardware support
Demonstrates meniOS portability
Opens ARM64 ecosystem for meniOS
Educational value for different architectures

Success Metrics

Complete meniOS functionality on ARM64
Successful boot and operation on multiple ARM64 platforms
Performance within 10% of x86_64 implementation
All major applications working (shell, networking, etc.)
Stable multi-core operation
Community adoption and testing

Timeline

Total estimated effort: 6-8 months part-time or 3-4 months full-time
Milestone 1: Basic boot and console (2 months)
Milestone 2: Core functionality (4 months)
Milestone 3: Hardware support (6 months)
Milestone 4: Optimization and release (8 months)

Sep 27 '25 02:09 pbalduino