Chapter 4:淺談Linux 核心
背景知識
1991年 當Linus Torvalds 還是赫爾辛基大學的學生時，發表了最初的Linux,並在同年8月在 comp.os.unix上發了一篇公告
From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds)
Newsgroups: comp.os.minix
Subject: What would you like to see most in minix?
Summary: small poll for my new operating system
Message-ID: <1991Aug25.205708.9541@klaava.Helsinki.FI>
Date: 25 Aug 91 20:57:08 GMT
Organization: University of Helsinki
Hello everybody out there using minix –
I’m doing a (free) operating system (just a hobby, won’t be big and
professional like gnu) for 386(486) AT clones. This has been brewing
since april, and is starting to get ready. I’d like any feedback on
things people like/dislike in minix, as my OS resembles it somewhat
(same physical layout of the file-system (due to practical reasons)
among other things).
I’ve currently ported bash(1.08) and gcc(1.40), and things seem to work.
This implies that I’ll get something practical within a few months, and
I’d like to know what features most people would want. Any suggestions
are welcome, but I won’t promise I’ll implement them 🙂
Linus (torvalds@kruuna.helsinki.fi)
PS. Yes – it’s free of any minix code, and it has a multi-threaded fs.
It is NOT protable (uses 386 task switching etc), and it probably never
will support anything other than AT-harddisks, as that’s all I have :-(.
出處:http://www.thelinuxdaily.com/2010/04/the-first-linux-announcement-from-linus-torvalds/
Linux source code
Linux 的source code 的官方網站是https://www.kernel.org/ 可以用git或wget下載原始碼 現在就讓我們開始吧~ 實驗環境:
ubuntuDistributor ID: Ubuntu
Description: Ubuntu 16.04.1 LTS
Release: 16.04
Codename: xenial
kernel version:4.4.0-45-generic
下載source code
首先先安裝必要的package
sudo apt-get install libncurses5-dev gcc make git exuberant-ctags bc libssl-dev
下載source code The latest stable
git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
下載好了之後我們先來看看 directory 裡有什麼東西吧
cd linux
ls
| 文件 | 說明 |
|---|---|
| arch | 包含各種處理器架構的程式碼 |
| block | holds code for block-device drivers |
| certs | |
| crypto | Linux kernel的加密API |
| Documentation | Linux kernel的說明文件 |
| drivers | 驅動程式 |
| firmware | |
| fs | filesystem code |
| include | 標頭檔 |
| init | 核心初始化 |
| ipc | Inter-Process Communication |
| kernel | Kernel level code 和system call code |
| lib | 函式庫 |
| mm | High level memory management code |
| net | The high-level networking code |
| scripts | 建立kerenel 會用到的scripts |
| security | Code for different Linux security models |
| sound | 音效卡 |
| tools | kernel tools |
| usr |
編譯核心
安裝cross compile tool
$ sudo apt-get install binutils-arm-linux-gnueabi
設定.config
可以自己設定或選擇預設的設定
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- <defconfig>
defconfig 的內容可以利用 make ARCH=arm help 查看
自己設定.config
make menuconfig
make xconfig # QTK圖形界面
make gconfig # GTK圖形界面
make defconfig # 使用預設的config
config 設定好了後就來compile linux kernel
編譯linux
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- V=1 zImage
把V=1 打開是為了可以觀察詳細的指令輸出情形
然後稍待片刻:tea: 當所有中間檔、函式庫、都編譯建構好後，他們會被集合起來放進一隻ELF檔，叫做vmlinux。 vmlinux 是一個真正的kernel proper是可獨立運作且一體成形的完整ELF映像檔。
待補: a. uImage: 給 uboot 用的 binary format b. dtbs: 編譯 device tree c. 針對make target解釋