背景

这两天读《UNIX传奇：历史与回忆》这本书，重新唤起了我对 Linux 开发的向往。

事不迟疑，赶紧动手干点儿什么。再说，万一这次真坚持下去了呢？

不知道为什么，“构建并替换内核”这件事在曾经的我眼中好似“活人换心脏”，让我打了退堂鼓，但如今看来不过是一连串命令，应该没有任何难度。

机器参数

我这次用的是一台大概 2011 年左右买的一台宏碁（Acer）笔记本，早就没人用了，后来我装了 Ubuntu 和 CentOS 双系统（参见：安装 Ubuntu 和 CentOS 双系统），但装完没两天也不用了。

大致看一下 CPU 和内存：

~/Downloads$ lscpu
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  2
Core(s) per socket:  2
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               42
Model name:          Intel(R) Core(TM) i3-2348M CPU @ 2.30GHz
Stepping:            7

~/Downloads$ free -m
              total        used        free      shared  buff/cache   available
Mem:           3773        1602         529         187        1640        1715
Swap:             0           0           0

参考链接

以下步骤参考这篇文章：How to Build Linux Kernel From Scratch {Step-By-Step Guide}

操作流程

开始之前，首先查看一下当前的内核版本：

~/Downloads$ uname -mrs
Linux 5.3.0-46-generic x86_64

嗯，用的是 5.3.0-46。

步骤1：下载 Linux 内核源码

截至写稿时，Linux 内核官网上的最新版本是 5.13.1，比参考文章上的又高了几个小版本。
在这里插入图片描述
使用 wget 下载源码：

$ wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.13.1.tar.xz
--2021-07-14 21:30:10--  https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.13.1.tar.xz
Resolving cdn.kernel.org (cdn.kernel.org)... 2a04:4e42:1a::432, 151.101.229.176
Connecting to cdn.kernel.org (cdn.kernel.org)|2a04:4e42:1a::432|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 119286316 (114M) [application/x-xz]
Saving to: ‘linux-5.13.1.tar.xz’

linux-5.13.1.tar.xz 100%[===================>] 113.76M  90.4KB/s    in 18m 11s 

2021-07-14 21:48:22 (107 KB/s) - ‘linux-5.13.1.tar.xz’ saved [119286316/119286316]

步骤 2：解压源码

这一步也没啥说的。

$ tar xvf linux-5.13.1.tar.xz
# ...
# 中间太长，略
# ...
linux-5.13.1/virt/kvm/Kconfig
linux-5.13.1/virt/kvm/async_pf.c
linux-5.13.1/virt/kvm/async_pf.h
linux-5.13.1/virt/kvm/coalesced_mmio.c
linux-5.13.1/virt/kvm/coalesced_mmio.h
linux-5.13.1/virt/kvm/dirty_ring.c
linux-5.13.1/virt/kvm/eventfd.c
linux-5.13.1/virt/kvm/irqchip.c
linux-5.13.1/virt/kvm/kvm_main.c
linux-5.13.1/virt/kvm/mmu_lock.h
linux-5.13.1/virt/kvm/vfio.c
linux-5.13.1/virt/kvm/vfio.h
linux-5.13.1/virt/lib/
linux-5.13.1/virt/lib/Kconfig
linux-5.13.1/virt/lib/Makefile
linux-5.13.1/virt/lib/irqbypass.c

步骤 3：下载所需软件包

回头再研究这些软件包，先按参考文章来吧：

~/Downloads$ sudo apt-get install git fakeroot build-essential ncurses-dev xz-utils libssl-dev bc flex libelf-dev bison
[sudo] password for doudou: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
# 中间太长，略
3 upgraded, 8 newly installed, 0 to remove and 518 not upgraded.
Need to get 8,035 kB of archives.
After this operation, 4,734 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://mirrors.aliyun.com/ubuntu bionic/main amd64 flex amd64 2.6.4-6 [316 kB]
Get:2 http://mirrors.aliyun.com/ubuntu bionic-security/main amd64 libssl-dev amd64 1.1.1-1ubuntu2.1~18.04.9 [1,566 kB]
Get:3 http://mirrors.aliyun.com/ubuntu bionic-security/main amd64 libssl1.1 amd64 1.1.1-1ubuntu2.1~18.04.9 [1,301 kB]
# 中间太长，略
update-alternatives: using /usr/bin/bison.yacc to provide /usr/bin/yacc (yacc) in auto mode
Setting up git (1:2.17.1-1ubuntu0.8) ...
Setting up libssl-dev:amd64 (1.1.1-1ubuntu2.1~18.04.9) ...
Setting up libfl-dev:amd64 (2.6.4-6) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for install-info (6.5.0.dfsg.1-2) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...

参考文章中简单描述了一下这些软件包：链接

步骤 4：内核配置

这一步也没啥好说的，把系统当前版本内核的配置文件，拿过来直接用。

~/Downloads$ cd linux-5.13.1/
~/Downloads/linux-5.13.1$ cp -v /boot/config-$(uname -r) .config
'/boot/config-5.3.0-46-generic' -> '.config'

步骤 5：开始构建！

这一步就很有意思了，输入 make 之后弹出来一堆选项，都标着 (NEW) 的字样，估计是之前版本内核配置里没有包括的新参数吧。

一开始我还想看看这些配置都是啥意思，选一选，后来发现要选的参数实在太多了，怎么也得有几千个吧，我就一路都按回车了，按了也有半天！

$ make
Makefile:656: include/config/auto.conf: No such file or directory
Makefile:701: include/config/auto.conf.cmd: No such file or directory
  SYNC    include/config/auto.conf.cmd
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/conf.o
# 中间太长，略
.config:10171:warning: symbol value '1' invalid for KASAN_STACK
*
* Restart config...
*
*
* General setup
*
Compile also drivers which will not load (COMPILE_TEST) [N/y/?] n
Local version - append to kernel release (LOCALVERSION) [] 
Automatically append version information to the version string (LOCALVERSION_AUTO) [N/y/?] n
Build ID Salt (BUILD_SALT) [] 
Kernel compression mode
> 1. Gzip (KERNEL_GZIP)
  2. Bzip2 (KERNEL_BZIP2)
  3. LZMA (KERNEL_LZMA)
  4. XZ (KERNEL_XZ)
  5. LZO (KERNEL_LZO)
  6. LZ4 (KERNEL_LZ4)
  7. ZSTD (KERNEL_ZSTD) (NEW)
choice[1-7?]: 

# 中间巨长无比，略

  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_32.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_64.h
  SYSHDR  arch/x86/include/generated/uapi/asm/unistd_x32.h
  SYSTBL  arch/x86/include/generated/asm/syscalls_32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_32_ia32.h
  SYSHDR  arch/x86/include/generated/asm/unistd_64_x32.h
  SYSTBL  arch/x86/include/generated/asm/syscalls_64.h
  HYPERCALLS arch/x86/include/generated/asm/xen-hypercalls.h
  HOSTCC  arch/x86/tools/relocs_32.o
  HOSTCC  arch/x86/tools/relocs_64.o
  HOSTCC  arch/x86/tools/relocs_common.o
  HOSTLD  arch/x86/tools/relocs
  HOSTCC  scripts/selinux/genheaders/genheaders
  HOSTCC  scripts/selinux/mdp/mdp
  HOSTCC  scripts/bin2c

截至写稿时 make 还在跑，估计要跑一晚上了，明天再来看。

第二天早上发现，终于跑完啦：

CC [M]  sound/usb/snd-usbmidi-lib.mod.o
  LD [M]  sound/usb/snd-usbmidi-lib.ko
  CC [M]  sound/usb/usx2y/snd-usb-us122l.mod.o
  LD [M]  sound/usb/usx2y/snd-usb-us122l.ko
  CC [M]  sound/usb/usx2y/snd-usb-usx2y.mod.o
  LD [M]  sound/usb/usx2y/snd-usb-usx2y.ko
  CC [M]  sound/x86/snd-hdmi-lpe-audio.mod.o
  LD [M]  sound/x86/snd-hdmi-lpe-audio.ko
  CC [M]  sound/xen/snd_xen_front.mod.o
  LD [M]  sound/xen/snd_xen_front.ko
  CC [M]  virt/lib/irqbypass.mod.o
  LD [M]  virt/lib/irqbypass.ko
  GEN     scripts/gdb/linux/constants.py