OS Kernel

Writing an OS Kernel from Scratch – Part 9: User Program Loading — ELF Parsing and Simple Filesystem “Your OS can fork/exec, but where do programs come from? Today, we build the first filesystem, letting the kernel load user programs from ‘disk’!” In the previous post, we implemented fork and exec, but user programs still... » read more

Writing an OS Kernel from Scratch – Part 20: User Toolchain — Implementing ls, cat, mkdir and Other Basic Commands “No matter how powerful the kernel, without user tools, it’s just an island. Today, we write the first user-mode shell toolset, making your OS truly usable!” In the previous 19 posts, we built a complete... » read more

Writing an OS Kernel from Scratch – Part 32: Integrating LVGL — Text Editor with Open Source GUI Framework “Building wheels from scratch is fun, but industrial-grade GUI needs mature frameworks. Today, we port LVGL (Light and Versatile Graphics Library) to our OS, implementing a professional text editor!” In previous posts, we built from scratch:... » read more

Writing an OS Kernel from Scratch – Part 26: User-Mode Display Server and Client — A True Graphics System Architecture “An in-kernel Display Server is controllable but violates the microkernel philosophy; a real graphics system should be in userspace! Today, we move the Display Server and Client entirely to userspace, communicating via Unix domain sockets!”... » read more

Writing an OS Kernel from Scratch | Keyboard — How Keystrokes Become Characters Have you ever wondered about this process: you press a key → a character appears on screen. What does the OS experience in between? How do keyboard scan codes become scancodes? What’s the difference between USB HID and PS/2? From the mechanical... » read more

#233 Conntrack: High-Performance Connection Tracking and NAT Implementation Preface In the previous two articles, we thoroughly understood Netfilter’s HOOK mechanism (Article 231) and iptables’ rule table-chain system (Article 232). However, there’s one system hiding between them, omnipresent yet not yet detailed — Connection Tracking (conntrack). Conntrack is the cornerstone of Linux stateful firewalls. It’s because... » read more

Writing an OS Kernel from Scratch | #345: USB Protocol — From HID to High-Speed Devices Abstract: USB is essentially the “universal serial bus” for all peripherals, but many only know “plug and play.” This article takes you from physical layer topology, transfer types, xHCI controller, to practical lsusb usage, thoroughly understanding USB’s design philosophy... » read more

Writing an OS Kernel from Scratch – Part 7: User-Mode Processes and System Calls — Make Your OS Truly Usable! “No matter how powerful the kernel, if it can’t run user programs, it’s just a fancy bare-metal toy. Today, we embrace user mode, taking the decisive step toward becoming a true OS!” In the previous... » read more

Writing an OS Kernel from Scratch | The Last Jump from BIOS to Kernel — What the CPU Thinks After POST You press the power button, the screen lights up, the fan spins, BIOS POST completes, GRUB countdown ends — then what? How does the kernel actually start running? What state is the CPU in... » read more

Writing an OS Kernel from Scratch | How BIOS/UEFI/GRUB Hand Control to the OS After Boot Have you ever wondered: in the instant you press the power button, where does the CPU’s CS:IP register point? Who set it to that value? Why does the screen light up showing a selection menu instead of black? This... » read more

Writing an OS Kernel from Scratch | Physical Memory Management — The Buddy System A 64KB memory request, but the smallest free block you have is 128KB — do you split it in half and use half, or allocate the whole thing? That’s the core problem the Buddy System solves. Physical memory management is one... » read more

Writing an OS Kernel from Scratch – Part 6: First Look at Multitasking — From Single-Core Loops to Process Switching “A kernel that can only do one thing? That’s a bare-metal program. A real OS must be able to ‘simultaneously’ do multiple things!” In the previous five posts, we completed kernel boot, entering protected mode,... » read more

Writing an OS Kernel from Scratch – Part 15: Slab Allocator — Efficiently Managing Kernel Small Objects “The Buddy system is great at allocating large memory blocks, but what about the kernel’s frequent 32-byte, 128-byte small object allocations? Today, we implement the Slab allocator, making kernel memory allocation lightning fast!” In the previous post, we... » read more

Writing an OS Kernel from Scratch | VFS — The Virtual File System: How Linux’s “Everything is a File” Works You use cat /proc/cpuinfo, ls /dev/null, echo "hello" > /tmp/a.txt — three different operations, all using the same open/read/write system calls. Why? The answer is VFS (Virtual File System Switch) — an abstraction layer that... » read more

从零开始写一个操作系统kernel-Part 1: 不只是”Hello World” 🌱 从零开始写一个操作系统kernel-Part 1: 不只是”Hello World”! 你是否曾好奇: ✅ Windows, Linux, macOS 这些操作系统是怎么”从无到有”启动的? ✅ kernel到底长什么样? 能不能自己写一个? ✅ 为什么kernel代码不能用 printf , 却能直接显示文字? 🛠️ 第一步: 准备开发环境 我们要构建一个 32位 x86 kernel , 通过 GRUB 引导 , 并在 QEMU 中运行 — 这样既安全又快捷! 你需要安装: ⚠️ 为了规范编译, 推荐使用 交叉编译器 i686-elf-gcc (避免宿主系统库干扰) . 教程可Reference: OSDev Wiki – GCC Cross-Compiler 🚀... » read more

Writing an OS Kernel from Scratch | Windows MBR+BIOS Boot: What Happens Before BOOTMGR and How to Fix It Have you noticed a phenomenon: You assemble a computer, install Windows 10, the System Reserved partition takes up 100MB, and the C: drive takes everything else. This 100MB partition is usually invisible in File Explorer. Only... » read more

Writing an OS Kernel from Scratch | Interrupt and Exception Handling — How the CPU Gets “Interrupted” by Peripherals Your program is running, and suddenly you press a key on the keyboard — how does the operating system know about it? How does the CPU instantly switch from executing code to handling keyboard input? The... » read more

Writing an OS Kernel from Scratch | Audio Subsystem — How ALSA Plays Sound Have you ever wondered about this process: When playing a song, how does the CPU turn digital signals into vibrations from the speaker? From WAV/MP3 files to music in your headphones, there’s sampling rate, bit depth, alsa-lib, the ALSA driver, HDA... » read more

title: [Writing an OS Kernel from Scratch] 337 – DRAM Training: From Principles to Debugging category: os tag: [dram, ddr, embedded, signal-integrity] source: https://github.com/golang12306/os-kernel-from-scratch [Writing an OS Kernel from Scratch] 337 – DRAM Training: From Principles to Debugging 1. What Is DRAM Training? DRAM Training is the process where the DDR controller automatically adjusts signal... » read more

Writing an OS Kernel from Scratch | Virtual Memory — The Complete Journey of Paging and Linear Addresses You write int *p = (int*)0x00401000; *p = 42; — is this address a real physical address? How does the operating system ensure every process feels it has 4GB of memory when there’s actually only 8GB of... » read more