📂
build a OS
  • Learn OS with me
  • OS Interfaces
    • OS interfaces
    • I/O and File descriptors
    • Process and Memory
    • Pipes
    • File
  • OS Organization
    • OS Organization
    • Challenge yourself
  • Memory Management
    • XV6 Virtual Memory
    • Page Table
      • Part 1: How to translate address
      • Part 2: Create an Address Space
      • Part 3: How Page Table is used
      • Part 4: Page Fault and Swap
      • Part 5: How to operate on page tables
    • xv6 buddy allocator
      • How to display physical memory
    • Memory Management Walk Through
  • Traps and Interrupts
    • Trap Home Page
      • 系统调用的核心原理
    • What is trapframe
    • What is trampoline
    • Traps from kernel space
    • How fork() works
    • How system calls get into/out of the kernel
    • How exec() works
  • Scheduling
    • XV6 CPU Scheduling
    • How unix pipes work?
    • How does wait(), exit(), kill() work?
  • File System
    • Overview and Disk Layout
    • Buffer Cache
    • Design Inode Layer
    • Inode Content
    • Block Allocator
    • Design a log system for crash recovery
    • Directory Layer
    • Path names
    • File Descriptor Layer
    • FS System Calls
    • XV6 VS Real World
    • Make Xv6 File disk management system
    • Write FS simulator in python
    • How Redirect Shell command works
  • Concurrency
    • Spinlock
    • How linux select work
    • Hardware Support Locking
    • Exercise: Implement atomic counter
    • Locking in Xv6
    • Concurrency in Xv6
    • Exercise: Socket Programming with Event loop
  • Labs
    • Lab 1 Xv6 and Unix utilities
    • Lab 2 Shell
    • Lab 3 Buddy Allocator
    • Lab 4 Lazy
    • Lab 5 Copy-on-Write Fork for xv6
    • Lab 6 RISC-V assembly
    • Lab 6 Uthread: switching between threads
    • Lab 6 Alarm
    • Lab 7 Lock
    • Lab 8 File System: Large Files
    • Lab 8 File System: Symbolic links
    • Lab 9 mmap
    • Lab 10 Networking Part 1
    • Lab 10 Networking Part 2
  • Hardware, Device, Assembly
    • RISC-V assembly
    • Assembly: Access and Store information in Memory
    • Start xv6 and the first process
    • Why first user process loads another program?
    • What does kernel.ld do in XV6?
    • XV6 Device Driver
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  1. File System

Make Xv6 File disk management system

QEMU presents a “legacy” virtio interface and has a virtue disk device. Xv6 implements a driver for this disk device. virtio_disk.c

QEMU command qemu … -drive file=fs.img,if=none,format=raw,id=x0 -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0

The fs.img is actually another xv6 problem built, and ask QEMU to treat it as file system.

Who builds fs.img?

A program called mkfs.c does.

It builds disk layout as: [ boot block | sb block | log | inode blocks | free bit map | data blocks ]

The program calls Real OS (not xv6, not QEMU) create system call to create a file named fs.img. It set all data to this file! mkfs writes all the disk layout content, including superblock, inode, bitmaps, etc.

This program runs before kernel starts.

When kernel starts, it will contains this virtual file system already (supported by QEMU)!

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Last updated 5 years ago

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