Operating Systems Design and Implementation

64-bit unix-like kernel for Raspberry Pi 3B+ (CPU: Arm Cortex A53)

NYCU, Operating System Capstone, Spring 2021

Author

Student ID	GitHub Account	Name	Email
0856167	Yunyung	許振揚	[email protected]

About this Repository

• This is the repository for the labs in NCTU CS Operating Systems Capstone(OSC, or OSDI) Spring 2021 class.
• We are going to design some important part in the OS implementation.
• The hardware we use is Raspberry Pi 3 Model B+.

How to Use This Repository

• Lab instruction is in here.
• You can download different labs in branch and release.
• Here are some references we use in each lab.

Labs

• Lab 0: Environment Setup
  • Branch
• Lab 1: Hello World
  • Branch
• Lab 2: Bootloader
  • Branch
• Lab 3: Allocator
  • Branch
• Lab 4: Exception and Interrupt
  • Branch
• Lab 5: Thread and User Process
  • Branch
• Lab 6: Virtual File System
  • Branch
• Lab 7: File System Meets Hardware
  • Branch
• Lab 8: Virtual Memory
  • Branch

Progress Overview

• Lab0: Environment Setup
• Lab1: Hello World
• Lab2: Booting
• Lab3: Allocator
• Lab4: Exception and Interrupt Handling
• Lab5: Multitasking
• Lab6: Virtual Filesystem
• Lab7: Filesystem Meets Hardware
• Lab8: Virtual Memory

Kernel Features

• Initialize rpi3 (Clear bss segment, set stack pointer...)
• Set up mini UART
• Kernel shell

Booting

• UART bootloader
• Loading cpio archive
• Bootloader Self Relocation
• Parsing Devicetree

Exception & Interrupt

• Synchronous exception handling
• Asynchronous interrupts (i.e. Hardware interrupt) handling. (Including core timer, mini uart I/O)
• MiniUART I/O - supports sync/async I/O
• Timer Multiplexing
• Concurrent I/O Devices Handling

Multitasking

• Create kernel/user thread
• Context switch
• Task Scheduler
• System call. (fork / exec / wait / exit...)
• User / Kernel threads
• Wait queues
• User preeption
• Kernel preemption - protect critical sections
• POSIX Signals - kill(), signal(), sigreturn()

Memory allocator

• Buddy Memory Allocator
• Slab Allocator
• Startup Allocator

Vitual Memory

• Kernel/User virtual address space
• Page fault handler
• mmap
• Demand paging
• ELF Loader
• Copy on Write

Virtual File System

• Virtual filesystem (VFS)
• VFS APIs and interfaces - open / read / write / close / mount ...
• VFS System calls
• Multi-levels VFS
• Memory-based file system, tmpfs. And mount the tmpfs as the root file system.
• Component name cache mechanism for faster pathname lookup
• Read a directory
• System-wide opened file table, Per-process file descriptor tables
• Populate the root file system with initramfs
• Mount Another File System
• /proc file system

File System & Interact with sdcard

• Fat32 file system - read / write / open / close ...
• Read/write data from an SD card hardware
• Access hardware devices by the VFS
• Mount the FAT32 File System
• Parse MBR (Master Boot Record)
• FAT32 with LFN (Long File Name) support
• Device File
• Memory as cache for external storage