X-Git-Url: https://scm.lunaixsky.com/lunaix-os.git/blobdiff_plain/bffa3430fbbaaad29bec0b5bee9c1f0bfc7fd068..9e622bd093f8e106b7e8a00f55620f13cc5cd87f:/README.md

diff --git a/README.md b/README.md
index 2fce0e9..fe73edc 100644
--- a/README.md
+++ b/README.md
@@ -3,247 +3,323 @@
 </p>
 
 <p align="center">
-  <a href="#lunaixos-project">简体中文</a> | <a href="docs/README_en.md">English</a>
+  <a href="docs/README.cn.md">简体中文</a> | <a href="#the-lunaixos-project">English</a>
 </p>
 
-# The LunaixOS Project
+# The Lunaix Project
+
+The Lunaix kernel (or soon-to-be LunaixOS) is a hobby kernel, written entirely from scratch. Designed to be POSIX-compliance, performance critical and modern, with some independent thoughts being applied in architectural design.
+
+
+This project is built entirely from first principles - meaning no code was copy-pasted or recycled from other OS projects or tutorials. Lunaix didn't begin as an attempt to outperform anything; it started as a personal challenge to learn OS theory and explore advanced kernel features through original design and implementation. Everything you see here was developed solo, part-time, with only hardware specs and my beloved **Modern Operating Systems** as guidance.
+
+If you're a kernel hobbyist looking for a fresh take or tired of mass-produced projects, then welcome, you're in the right place!
+
+
+| ![showcase_lunaix-over-serial.png](docs/img/showcase_lunaix-over-serial.png) |
+|:--:|
+| *Lunaix over serial* (`console=/dev/ttyS0`) |
+
+| ![showcase_lunaix-over-serial.png](docs/img/showcase_lunaix-over-vga-text.png) |
+|:--:|
+| *Lunaix over VGA text mode* (`console=/dev/ttyVCON0`) |
+
+> By the way, do you know there is an online video course  by the author on the design of lunaix? [Check it out](https://space.bilibili.com/12995787/channel/collectiondetail?sid=196337) (although it is in Chinese!)
+
+## Features
+
+Lunaix is a multi-architecture, general-purpose kernel built with performance, modularity, and robustness in mind. Its design emphasizes advanced abstractions, proactive error detection, and subsystem isolation. Lunaix is
+
++ **Fully-preemptive** for responsive multi-tasking
++ **Modular** with compile-time configurable components and extensible subsystems
++ **High-performance**, leveraging modern caching strategies and efficient infrastructures.
++ **Fault-tolerant**, with built-in error handling and stack backtracing
++ **Robust by design**, using mechanisms like proactive deadlock detection and driver isolation
+
+A significant amount of effort has gone into crafting clean abstractions, implementing advanced kernel features, and applying performance optimizations throughout the system.
+
+To better illustrate the scope of work already done, the following non-exhaustive list outlines currently supported features in Lunaix:
+
+<details>
+
+<summary>List of all features implemented</summary>
+
++ Multi-ISA
+  + x86_32
+  + x86_64
+  + Aarch64 (WIP)
++ Boot protocol
+  + abstraction for different protocol
+  + configurable kernel boot-time parameters
++ Platform resource management and definition
+  + read-only ACPI table interpretation
+  + full devicetree implementation
++ Memory management
+  + architecture-neutral abstraction
+  + highmem
+  + copy-on-write
+  + page sharing
+  + explicit huge page
+  + on-demand paging
+  + compound page
+  + reverse mapping (rmap)
+  + memory compaction (WIP)
+  + slab-style object allocator
+  + inter-process address space access
++ Multi-tasking
+  + fully preemptive
+  + protection levels
+  + process isolation
+  + native threading
+  + signal mechanism
+  + round-robin scheduler (for now)
+  + kernel level multi-tasking (i.e. kernel threads)
+  + taskfs: file system interface to process and threads
++ File system
+  + POSIX-compliant interface
+  + virtual file system framework
+  + file system mounting mechanism
+  + page cache for file IO
+  + inode/dnode caching
+  + ext2 (rev.0, rev.1)
+  + iso9660 (rock-ridge)
+  + twifs: kernel state fs interface.
++ Device management and interrupt handling
+  + unified IRQ framework
+  + unified driver framework for heterogenous devices
+  + modular driver model allow compiled-time toggling
+  + asynchronous operation model supported
+  + devfs: device fs interface.
++ Block I/O (blkio)
+  + unified block IO interface
+  + IO request packets caching
+  + asynchronous IO operation
++ Serial I/O
+  + POSIX-compliant serial IO model
++ Caching Infrastructure
+  + LRU replacement policy and pooling
+  + kernel daemon for dynamic and transparent cache managements
++ Error handling and detection
+  + stack backtracing with symbol resolution
+  + stack unwinding for nested exception
+  + CPU state dumping
+  + deadlock/hung-up detection
+
+</details>
+
+<details>
+
+<summary>List of currently supported device</summary>
+
++ Architecture Neutral
+  + UART 16650-compatible driver
+  + Serial ATA AHCI
+  + PCI 3.0
+  + PCIe 1.1
+  + Standard VGA
++ Intel x86
+  + RTC (Intel PCH)
+  + IOAPIC IRQ controller
+  + APIC Timer
+  + Legacy i8042 keyboard controller
++ ARM
+  + GICv3
+  + PL011 (WIP)
+</details>
+
+## Project Structure
+
+| Path | Description |
+|-----|------|
+| [lunaix-os](../lunaix-os/) | LunaixOS source code |
+| [slides](../slides/) | Slides used in my videos |
+| [reference-material](../reference-material/)| References |
+
+## Compile and Build
+
+Building lunaix is simple, no more bloated dependencies to install, basic `build-essentials` installation plus a python are sufficient.
+
++ gcc (recommend v12+)
++ binutils
++ make
++ python (recommend v3.11+)
 
-LunaixOS - 一个简单的，详细的，POSIX兼容的（但愿！），带有浓重个人风格的操作系统，由 Lunaix 内核驱动。开发过程以视频教程形式在Bilibili呈现：[《从零开始自制操作系统系列》](https://space.bilibili.com/12995787/channel/collectiondetail?sid=196337)。
+And also one should have environment variable `ARCH=<arch>` exported, where `<arch>` is one of the supported arhcitecture (`x86_32`, `x86_64`, `aarch64`).
 
-## 1. 一些实用资源
+For cross compilation, also export `CX_PREFIX` to the gcc prefix for the corresponding `<arch>`.
 
-如果有意研读 Lunaix 内核代码和其中的设计，或欲开始属于自己的OS开发之道，以下资料可能会对此有用。
+The following `make` actions are then available to use.
 
-+ [内核文档（Luna's Tour）](docs/lunaix-internal.md)
-+ [LunaixOS源代码分析教程](docs/tutorial/0-教程介绍和环境搭建.md)
-+ [作者修改的QEMU](https://github.com/Minep/qemu) (添加了一些额外用于调试的功能)
+| Make command | Usage |
+| ---- | ---- |
+| `make all`               | Build the kernel bin |
+| `make rootfs`            | Build the stock rootfs |
+| `make clean`             | clean |
+| `make config`            | menuconfig |
 
-## 2. 当前进度以及支持的功能
+A successful build will give `build/bin/kernel.bin`.
 
-Lunaix内核具有支持多种不同的指令集架构的能力，目前支持如下：
+**Please note: this is the kernel, not a bootable image, it require a bootloader to boot and specify the rootfs.**
 
-+ x86_32
-+ x86_64
+## Get Started
 
-Lunaix全部特性一览：
+If you are impatient, or just want something to run and don't want to went through tedious process of configuring rootfs and tweak kernel parameters. You can use the `live_debug.sh` provided in the lunaix root directory to quickly bring up the system with default parameters (also used by the author for debugging).
 
-+ 使用Multiboot进行引导启动
-  + Multiboot 1
-  + Multiboot 2 (WIP)
-+ APIC/IOAPIC作为中断管理器和计时器
-+ ACPI
-+ 虚拟内存
-  + 架构中性设计
-  + 按需分页
-  + Copy-on-Write
-+ 内存管理
-+ 进程模型
-+ 61个常见的Linux/POSIX系统调用（[附录1](#appendix1)）
-+ 用户/内核态隔离
-+ 信号机制
-+ PCI 3.0
-+ PCIe 1.1 (WIP)
-+ 块设备IO与驱动
-  + 块IO通用缓存池
-  + Serial ATA AHCI
-    + ATA设备
-    + ATAPI封装的SCSI协议
-+ 文件系统（POSIX.1-2008, section 5 & 10）
-  + 虚拟文件系统
-  + 内核态文件系统（twifs, Lunaix自己的sysfs）
-  + 设备文件系统（devfs, Lunaix自己的udev）
-  + 进程文件系统（procfs）
-  + ISO9660
-    + ECMA-119
-    + IEEE P1282（Rock Ridge拓展）
-  + ext2
-    + Revision 0
-    + Revision 1 （额外特性不支持）
-+ 远程GDB串口调试 (COM1@9600Bd)
-+ 用户程序加载与执行
-+ 通用设备抽象层
-  + 架构中性的设备支持位于：`lunaix-os/hal`
-    + 16550 UART
-    + ACPI （不完全实现）
-  + 架构耦合的设备支持位于：`lunaix-os/arch/<ARCH>/hal`
-    + x86
-      + APIC/IOAPIC 组合
-      + MC146818 RTC
-      + i8042 PS/2
-      + RNG（使用`rdrand`）
-  + [Devicetree](https://www.devicetree.org/)
-+ 通用图形设备抽象层 (Draft)
-  + 参考：`lunaix-os/hal/gfxa`
-+ 虚拟终端设备接口（POSIX.1-2008, section 11）
-  + 参考：`lunaix-os/hal/term`
-+ 线程模型
-  + 用户线程支持（pthread系列）
-  + 内核线程支持
-+ 抢占式内核设计
-  + 内核态上下文切换
-  + 内核态异常挂起/死锁自动检测机制
-
-## 3. 目录结构
-
-|                                           |                              |
-| ----------------------------------------- | ---------------------------- |
-| [lunaix-os](lunaix-os/)                   | LunaixOS源代码               |
-| [slides](slides/)                         | 视频中所用的幻灯片和补充材料 |
-| [reference-material](reference-material/) | 标准，技术文档和参考文献     |
-
-## 4. 编译与构建
-
-**！如果想要立刻构建并运行，请参考4.7！**
-
-构建该项目需要满足以下条件：
-
-+ gcc 工具链
-+ make
-+ xorriso
-+ grub-mkrescue
+### Quick Start
 
-### 4.1 使用 GNU CC 工具链
+This will get you up and running real quick. We will use `x86_64` as example.
 
-正如同大多数内核一样，Lunaix 是一个混合了 C 和汇编的产物。这就意味着你得要使用一些标准的C编译器来构建Lunaix。在这里，我推荐使用 GNU CC 工具链来进行构建。因为Lunaix 在编写时使用了大量的GNU CC 相关编译器属性修饰 (`__attribute__`) 。假若使用其他工具链，如LLVM，我对此就不能做出任何保证了。
+Assuming a Linux or other Unix-like shell environment.
 
-如果你使用的是基于 x86 指令集的Linux系统，不论是64位还是32位，**其本机自带的gcc就足以编译Lunaix**。 当然了，如果说你的平台是其他非x86的，你也可以指定使用某个针对x86_32的gcc套件来进行交叉编译——在`make`时通过`CX_PREFIX`变量来指定gcc套件的前缀。如下例所示，我们可以在任意平台上，如risc-v，单独使用一个面向x86_32的gcc来进行交叉编译：
-
-```
-make CX_PREFIX=i686-linux-gnu- all
+#### Select your target
+```sh
+$ export ARCH=x86_64
 ```
 
-### 4.2 Docker镜像
-
-对于开发环境，本项目也提供了Docker镜像封装。开箱即用，无需配置，非常适合懒人或惜时者。详细使用方法请转到：[Lunaix OSDK项目](https://github.com/Minep/os-devkit)。
-
-### 4.3 构建选项
+#### Check Python
+```sh
+$ python --version
+```
 
-本项目支持的make命令：
-| 命令                     | 用途                                            |
-| ------------------------ | ----------------------------------------------- |
-| `make all`               | 构建内核ELF镜像 |
-| `make rootfs`            | 构建根文件系统镜像，将会封装`usr/`下的程序        |
-| `make clean`             | 删除构建缓存，用于重新构建               |
-| `make config`            | 配置Lunaix                                   |
+Ensure at least `3.11`
 
-与make命令配套的环境变量，Lunaix的makefile会自动检测这些环境变量，以更改构建行为
+#### Check compiler
+```sh
+$ gcc -dumpmachine
+```
 
-+ `MODE={debug|release}` 使用debug模式构建（-Og）或者release模式（-O2）
-+ `ARCH=<isa>` 为指定的指令集架构编译Lunaix。 所使用的配置选项均为选定架构默认，该环境变量
-  存在的目的就是方便用户进行快速编译，而无需钻研Lunaix的种种配置项。
+Ensure `x86_64-linux-gnu` or anything resemble `x86_64`
 
-### 4.4 Lunaix的功能配置
+#### Check QEMU
+```sh
+$ which qemu-system-x86_64
+```
 
-Lunaix是一个可配置的内核，允许用户在编译前选择应当包含或移除的功能。
+Should display a valid installation path
 
-使用`make config`来进行基于命令行的交互配置。采用TUI呈现，效果类似于menuconfig.
+#### Optional: Setting up Cross-Compiler
+```sh
+$ export CX_PREFIX=x86_64-linux-gnu-
+```
 
-如果因为某种原因，TUI界面无法呈现，那么将会默认使用shell形式的呈现：
+#### Run Configuration
+```sh
+make config
+```
 
-所有的配置项按照类似于文件树的形式组织，如单个配置项为一个“文件”，多个配置项组成的配置组为一个目录，呈现形式为方括号`[]`包裹起来的项目。在提示符中输入`usage`并回车可以查看具体的使用方法。
+Then hitting `q` in the interactive shell to save and quit
 
-一个最常用的配置可能就是`architecture_support/arch`了，也就是配置Lunaix所面向的指令集。比如，编译一个在x86_64平台上运行的Lunaix，在提示符中输入（**注意等号两侧的空格，这是不能省略的**）：
+#### Build stock rootfs
 
-```
-/architecture_support/arch = x86_64
+```sh
+make rootfs
 ```
 
-之后输入`exit`保存并退出。而后正常编译。
-
-### 4.5 设置内核参数
-
-在 make 的时候通过`CMDLINE`变量可以设置内核启动参数列表。该列表可以包含多个参数，通过一个或多个空格来分割。每个参数可以为键值对 `<key>=<val>` 或者是开关标志位 `<flag>`。目前 Lunaix 支持以下参数：
+#### Build & Run
+```sh
+./live_debug.sh
+```
 
-+ `console=<dev>` 设置系统终端的输入输出设备（tty设备）。其中 `<dev>` 是设备文件路径 （注意，这里的设备文件路径是针对Lunaix，而非Linux）。关于LunaixOS设备文件系统的介绍可参考 Lunaix Wiki（WIP）
-+ （参考 4.6）
+you should see gdb now take control of your shell
 
-如果`CMDLINE`未指定，则将会载入默认参数：
+#### Connect to serial via telnet
 
-```
-console=/dev/ttyFB0
+Open up another window or session
+```sh
+telnet localhost 12345
 ```
 
-其中，`/dev/ttyFB0` 指向基于VGA文本模式的tty设备，也就是平时启动QEMU时看到的黑色窗口。
+#### Commence simulation
 
-当然，读者也可以使用 `/dev/ttyS0` 来作为默认tty设备，来验证 Lunaix 的灵活性与兼容性。该路径指向第一个串口设备。可以通过telnet协议在`12345`端口上进行访问——端口号可以自行修改QEMU启动参数（位于：`makeinc/qemu.mkinc`）来变更。
+Back to the gdb session and type `c` to countine
 
-**注意：** 根据操作系统和键盘布局的不同，telnet客户端对一些关键键位的映射（如退格，回车）可能有所差别（如某些版本的Linux会将退格键映射为`0x7f`，也就是ASCII的`<DEL>`字符，而非我们熟知`0x08`）。如果读者想要通过串口方式把玩Lunaix，请修改`usr/init/init.c`里面的终端初始化代码，将`VERASE`设置为正确的映射（修改方式可以参考 POSIX termios 的使用方式。由于Lunaix的终端接口的实现是完全兼容POSIX的，读者可以直接去查阅Linux自带的帮助`man termios`，无需作任何的转换）
 
+#### Watch Lunaix booting!
 
-### 4.6 Lunaix的启动
+Congrats, enjoy your lunaix! (or submit an issue)
 
-由于 Lunaix 的定位是内核。为了避免太多的编译时的前置要求，同时为了提高灵活性，我们移除了iso文件的封装功能。目前的 Lunaix 将只会编译出一个 ELF 格式的二进制文件。用户可以根据自己的喜好，使用的不同的方式，不同的 bootloader 来引导 Lunaix. 
 
-为了能够使得 Lunaix 能够正确的启动，用户必须设置以下内核参数：
+### Not so Quick Start
 
-+ `rootfs=` 指明根目录设备，值为设备文件路径，指向包含根文件系统的磁盘设备，如`/dev/block/sda`。 Lunaix将会在启动之后自动挂在该文件系统到根目录。缺少此选项 Lunaix 将会拒绝启动，并进入 kernel panic （在 Lunaix 的世界里，这个被称之为 Nightmare Moon arrival ）
-+ `init=` 指明 init 程序的位置，该程序必须放在 `rootfs` 中。改选项为可选设置，其默认值为 `/init`。  init 程序是 Lunaix 在启动后所运行的第一个程序。
+Here is a slower and yet more verbose steps:
 
-### 4.7 测试与体验 Lunaix
+1. Select an architecture `<arch>`
+2. Check the compilation prerequisites and presence of `qemu-system-<arch>`
+3. Optionally export `CX_PREFIX` if you are building for another architecture.
+4. Run `make ARCH=<arch> rootfs` to build stock rootfs image, require support of `dd`，`mkfs.ext2`, `mount -o loop`, `mktemp`.
+5. Run `ARCH=<arch> live_debug.sh` to boot in QEMU with gdb hooked (one should see a gdb session)
+6. telnet to `localhost:12345`, this is QEMU emulated serial port
+7. type `c` in the active gdb session and commence emulation.
+8. Congrats, enjoy your lunaix!
+(or submit an issue)
 
 
-想要快速体验，请跟随以下步骤：
+## Booting the kernel
 
-1. 决定一个你想要体验的架构，如 `x86_64`。 （支持：`x86_64`, `i386`）为了叙述方便，这个架构在下文被指代为`<arch>`
-2. 检查你是否安装了： `qemu-system-<arch>`，`gdb`，`python3`，`telnet`，`gcc`
-3. 运行 `make ARCH=<arch> user` 来编译自带的用户程序
-4. 运行 `make ARCH=<arch> rootfs` 来打包根文件系统镜像。（需要本机系统支持 `dd`，`mkfs.ext2`, `mount -o loop`, `mktemp`）
-5. 运行 `ARCH=<arch> live_debug.sh` 来启动
+Since lunaix is a kernel, much like linux. It requires additional setup to do the magic. And, as in "much like linux", methods to make linux kernel boot can also apply to lunaix without or with little translation, as we will discuss below.
 
-该脚本自动按照默认的选项构建Lunaix，而后调用 `scripts/qemu.py` 根据配置文件生成QEMU启动参数（配置文件位于`scripts/qemus/`）
+The bootloader part is generic, any bootloader, for example GRUB will work (not tested for UEFI, but I expect this would be an exception), or booting up in QEMU using `-kernel` option
 
-由于该脚本的主要用途是方便作者进行调试，所以在QEMU窗口打开后还需要进行以下动作：
+The kernel command line, is however, a bit differentiated.
+The syntax is similar, both takes form of space-separated array of `<key>=<val>` pairs or boolean `<flag>`.
 
-1. 使用telnet连接到`localhost:12345`，这里是Lunaix进行标准输入输出所使用的UART映射（QEMU为guest提供UART实现，并将其利用telnet协议重定向到宿主机）
-2. 在GDB窗口中输入`c`然后回车，此时Lunaix开始运行。这样做的目的是允许在QEMU进行模拟前，事先打好感兴趣的断点。
+Currently, lunaix support the following options
 
-## 5. 运行，分支以及 Issue
+| Option | Default Value | Optional | Usage |
+| ------ | ----          |  -----   | ----  |
+| console | `/dev/ttyS0`   | No | Specify the system console device, path within lunaix's devfs |
+| rootfs | `/dev/block/sda` | No | Specify the device contain rootfs image, path within lunaix's devfs |
+| init | `/init` | Yes | Path within rootfs of the `init` |
 
-### 5.1 代码稳定性
 
-主分支一般是稳定的。因为在大多数情况下，我都会尽量保证本机运行无误后，push到该分支中。所有正在开发的功能请参考当前活跃的Pull Request。
+## Submit an Issue
 
-如果主分支的运行出现了此问题，欢迎提issue。请参考[附录3：Issue的提交](#appendix3)
+If one ran into bug, one can submit an issue by filling up the following template
 
-## 6. 调试 Lunaix 内核
+```
+1. Describe the problem
+    "How does it look like, anything descriptive: visual, sonic, emotional experience"
 
-除了[附录4：串口GDB远程调试](#appendix4)描述的一种用于实机调试的方式以外。LunaixOS还提供了LunaDBG调试套件。这是一个GDB客户端插件，包含了对GDB原生命令集的一些扩充，主要用于改善与简化内核调试的过程。目前包含以下几个命令：
+2. Steps to reproduce
+    "How you ran into this mess?"
 
-+ `vmrs [pid]` 列举进程`<pid>`的内存区域图（Memory Regions），如果`<pid>`未指定，则默认为正在运行的进程（smp=1）。
-+ `proc [pid]` 打印进程`<pid>`的进程控制块状态，如果`<pid>`未指定，则默认为正在运行的进程（smp=1）。
-+ `sched <threads | procs> [-l]` 查看调度器信息，接受两个参数：
-  + `threads` 打印所有依然在调度器中有注册的线程
-  + `procs` 打印所有依然在调度器中有注册的进程
-  + 可选开关 `-l` 决定是否以长列表打印（更详细的信息）
+3. Expected behaviour
+    "What do you intended/expected to achieve/to be"
 
-该插件可以通过运行以下命令来进行安装：
+4. Lunaix's panic trace (if applicable)
 
-```shell
-./scripts/gdb/install_lunadbg
+5. Other clues that you think might be helpful
 ```
 
-## 7. 参考教程
 
-#### 没有！！
+## Limitations
+
+The development process is still in motion, any limitation can be categorised as a feature yet to be. However, some features that the author considered to be the most urgent and wish the matters to be discussed.
 
-本教程以及该操作系统的所有的架构设计与实现**均为原创**。
+Lunaix is under impression of uniprocessor and not capable of running in SMP environment. This is major held back of being a modern operating system. It has the highest priority among all other tasks
 
-对此，作者可以保证，该项目是做到了三个 “没有”：
+Lunaix do not have a mature (or even, an infant) user space ecosystem, mainly because the lack of a proper and sophisticated libc. Efforts need to be done for porting one to the target. However, given the author's tight schedule, this task is unfortunately still beyond the horizon.
 
-+ **没有** 参考任何现行的，关于操作系统开发的，教程或书籍。
-+ **没有** 参考任何开源内核的源代码（包括Linux）
-+ **没有** 基于任何开源内核的二次开发行为。
+## Acknowledgement
 
-为了制作LunaixOS，作者耗费大量时间和精力钻研技术文档，手册，理论书籍以及现行工业标准，从而尽量保证了知识的一手性。（这样一来，读者和听众们也算是拿到了二手的知识，而不是三手，四手，甚至n手的知识）。
+Albeit one must realise that the author has mentioned it in the very beginning, the author would like to emphaise **again** on the nature of this project.
 
-大部分的文档和标准可以在上述的[reference-material](reference-material/)中找到。
+As a personal challenge, this project is independently developed by the author single-handly, which means:
 
-当然，您也可以参考以下列表来了解现阶段的LunaixOS都使用了哪些资料（本列表会随着开发进度更新）：
++ No reference to existing tutorials, books, online courses or any open source project that might provide any example, hint or working prototype on the design and implementation of kernel, subsystems or anythings that can be contributed towards a working prototype.
++ The author has no prior knowledge on Linux kernel through out 90% of the project time.
++ All knowledge on the kernel design is coming from the basic textbook on operating system theory, that is, *Modern Operating System* by Tanenbaum.
++ All knowledge on the system programming is coming from the basic textbook, that is, *Computer System - A Programmer's Perspective Third Edition*
++ All knowledge on the generic framework design and driver development are ingested from various technical specifications gathered across the Internet.
 
-#### 手册，标准，技术文档
+## References
 
-+ [Intel 64 and IA-32 Architecture Software Developer's Manual (Full Volume Bundle)](https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html)
-+ [ACPI Specification (version 6.4)](https://uefi.org/sites/default/files/resources/ACPI_Spec_6_4_Jan22.pdf)
++ Intel 64 and IA-32 Architecture Software Developer's Manual (Full Volume Bundle)
++ ACPI Specification (version 6.4)
++ Devicetree Specification
++ ARM® Generic Interrupt Controller (v3)
++ Arm® Architecture Reference Manual (Profile-A)
++ Procedure Call Standard for the Arm® 64-bit Architecture (AArch64)
 + IBM PC/AT Technical Reference
 + IBM VGA/XGA Technical Reference
 + 82093AA I/O Advanced Programmable Controller (IOAPIC) (Datasheet)
@@ -256,32 +332,20 @@ console=/dev/ttyFB0
 + Serial ATA: High Speed Serialized AT Attachment, Revision 3.2
 + SCSI Command Reference Manual
 + ATA/ATAPI Command Set - 3 (ACS-3)
-+ [ECMA-119 (ISO9660)](https://www.ecma-international.org/publications-and-standards/standards/ecma-119/)
++ ECMA-119 (ISO9660)
 + Rock Ridge Interchange Protocol (RRIP: IEEE P1282)
 + System Use Sharing Protocol (SUSP: IEEE P1281)
 + Tool Interface Standard (TIS) Portable Formats Specification (Version 1.1)
-
-**免责声明：PCI相关的标准最终解释权归PCI-SIG所有。此处提供的副本仅供个人学习使用。任何商用目的须向PCI-SIG购买。**
-
-#### 理论书籍
-
-+ *Computer System - A Programmer's Perspective Third Edition (CS:APP)* (Bryant, R & O'Hallaron, D)
++ *Computer System - A Programmer's Perspective Third Edition* (Bryant, R & O'Hallaron, D), a.k.a. CS:APP
 + *Modern Operating System* (Tanenbaum, A)
++ Free VGA, http://www.osdever.net/FreeVGA/home.htm 
++ GNU CC & LD online documentation.
++ PCI Lookup, https://www.pcilookup.com/
++ Linux man pages
 
-#### 网站
-
-+ [OSDev](https://wiki.osdev.org/Main_Page) - 适合快速入门，和一些文档手册的总结。
-+ [FreeVGA](http://www.osdever.net/FreeVGA/home.htm) - 98年的资源！关于VGA编程技术的宝藏网站。
-+ GNU CC 和 GNU LD 的官方文档。
-+ [PCI Lookup](https://www.pcilookup.com/) - PCI设备编号查询
-
-#### 其他
-
-+ Linux Manual - 用于查询*nix API的一些具体行为。
-
-## 附录1：实现的 POSIX 系统接口 <a id="appendix1"></a>
+## Appendix 1: Supported System Call<a id="appendix1"></a>
 
-LunaixOS 提供对以下POSIX的系统接口的实现。内核定义的系统调用号可以参考 [LunaixOS系统调用表](docs/lunaix-syscall-table.md) 。
+**Unix/Linux/POSIX**
 
 1. `sleep(3)`
 1. `wait(2)`
@@ -296,7 +360,7 @@ LunaixOS 提供对以下POSIX的系统接口的实现。内核定义的系统调
 1. `_exit(2)`
 1. `sigreturn(2)`
 1. `sigprocmask(2)`
-1. `sigaction(2)`
+1. `signal(2)`
 1. `kill(2)`
 1. `sigpending(2)`
 1. `sigsuspend(2)`
@@ -312,7 +376,7 @@ LunaixOS 提供对以下POSIX的系统接口的实现。内核定义的系统调
 2. `rmdir(2)`
 2. `unlink(2)`
 2. `unlinkat(2)`
-2. `link(2)`※
+2. `link(2)`
 2. `fsync(2)`
 2. `dup(2)`
 2. `dup2(2)`
@@ -322,7 +386,7 @@ LunaixOS 提供对以下POSIX的系统接口的实现。内核定义的系统调
 2. `getcwd(2)`
 2. `rename(2)`※
 2. `mount(2)`
-2. `unmount` (a.k.a `umount(2)`)※
+2. `unmount` (a.k.a `umount(2)`)
 2. `getxattr(2)`※
 2. `setxattr(2)`※
 2. `fgetxattr(2)`※
@@ -344,28 +408,43 @@ LunaixOS 提供对以下POSIX的系统接口的实现。内核定义的系统调
 4. `pthread_kill`
 4. `pthread_detach`
 4. `pthread_sigmask`
+4. `getuid`
+4. `getgid`
+4. `geteuid`
+4. `getegid`
+4. `getgroups`
+4. `setuid`
+4. `setgid`
+4. `seteuid`
+4. `setegid`
+4. `setgroups`
+4. `chroot`
+4. `fchmodat`
+4. `fchownat`
+4. `faccessat`
 
+**LunaixOS**
 
-( **※**：该系统调用暂未经过测试 )
+1. `yield`
+2. `geterrno`
+3. `realpathat`
 
-## 附录2：Issue的提交<a id="appendix3"></a>
+( **※**：Indicate syscall is not tested )
 
-假若Lunaix的运行出现任何问题，还请按照以下的描述，在Issue里面提供详细的信息。
+## Appendix 2: Debugging with GDB remotely via UART
 
-+ 可用于复现问题的描述和指引（如Lunaix运行平台的软硬件配置）
-+ 错误症状描述
-+ LunaixOS在panic时打印的调试信息（如无法复制，可以截图）
+**(((( Broken after a refactoring years ago, need rework ))))**
 
-## 附录3：串口GDB远程调试<a id="appendix4"></a>
+The LunaixOS kernel comes with a built-in GDB debugging server, which runs on COM1@9600Bd. However, LunaixOS must be in debug mode before involving GDB.
 
-**（该功能正在重构，目前不可用）**
+One could trigger the debug mode by writing a byte sequence `0x40` `0x63` `0x6D` `0x63`, to the same serial port. A text "DEBUG MODE" with magenta-coloured background shall be present at the bottom of the screen.
 
-LunaixOS内核集成了最基本的GDB远程调试服务器。可通过串口COM1在9600波特率上与之建立链接。但是，在将GDB与内核链接起来之前，还需要让内核处在调试模式下。
+Note that, whenever the text appears, the LunaixOS always halt all activities other than the debugging server, which means no scheduling and no external interrupt servicing. Users are now recommended to attach their GDB and drive the kernel with the debugging workflow.
 
-要进入调试模式，需要往串口（波特率如上）写入字节串 `0x40` `0x63` `0x6D` `0x63`。此时，如果屏幕底部出现一条品红色背景的`DEBUG` 字样，那么就说明LunaixOS已处在调试模式下。
+Currently, LunaixOS implements the required minimal server-side command subset required by GDB Remote Protocol, namely, `g`, `G`, `p`, `P`, `Q`, `S`, `k`, `?`, `m`, `M`, `X`. Which should be enough to cover most debugging activities.
 
-注意，在这个时候，LunaixOS会开始在`COM1`上监听GDB协议信息，并且暂停一切的活动（如调度，以及对外部中断的一切响应）。用户此时需要将GDB与其挂载，并使用GDB的工作流来指示内核下一步的动作。
+When debugging is finished, one shall disconnect with `kill` command. This command will not force LunaixOS to power down the computer, instead it just resume the execution (identical behavior as `c` command). However, disconnecting does not means exiting of debug mode. The debug mode is still actived and any subsequent GDB attaching request shall remain the highest priority amongst all other activity. One shall deactivate the debug mode by writing byte sequence `0x40` `0x79` `0x61` `0x79` to the port, after GDB detached.
 
-在目前，为了防止代码过于臃肿，LunaixOS实现的是GDB远程协议要求的最小服务端命令子集：`g`, `G`, `p`, `P`, `Q`, `S`, `k`, `?`, `m`, `M`, `X`。足以满足大部分的调试需求。
+### Limitations
 
-当结束调试的时候，请使用GDB的`kill`指令进行连接的断开。注意，这个指令会使得LunaixOS恢复所有暂停的活动，进入正常的运行序列，但并不会退出调试模式。GDB的挂载请求依然在LunaixOS中享有最高优先权。如果需要退出调试模式，需要往串口写入字节串：`0x40` `0x79` `0x61` `0x79`。
+Currently, one should avoid the use of `info stack`, `bt` or any other command that involves stack unwinding or stack backtracing. As it will somehow corrupt the stack layout and result in undefined behaviour. This issue should be addressed in future releases.