体验rust-for-linux

编译x86 kernel + 构建文件系统

1. Rust依赖安装

   1. 参考：Rust for linux: Quick Start
   2. 使用用cargo/rustup安装rustc + rust-src + bindgen
   3. 安装LLVM-14
      1. 参考https://apt.llvm.org/
      2. bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)"

2. x86生成配置+编译内核

   1. 需要注意的选项

      1. CONFIG_SYSTEM_TRUSTED_KEYS 设置为空
      2. CONFIG_SYSTEM_REVOCATION_KEYS 设置为空
      3. MODVERSIONS + GCC_PLUGINS 这两个配置默认是y，需要关闭才能打开CONFIG_RUST

   2. 编译内核+模块

      make LLVM=-14   O=../rust-kernel-build/amd64 -j 64

   3. 安装内核模块

      INSTALL_MOD_PATH 是相对于内核编译路径设置的，不是当前内核源码路径

      sudo make LLVM=-14  O=../rust-kernel-build/amd64  INSTALL_MOD_PATH=../../../debian11-amd64-rootfs  modules_install

3. 编译独立的内核模块

   1. rust-out-of-tree-module repo

   2. 改一下Makefile，加上modules_install 内容

      ❯ cat Makefile
      # SPDX-License-Identifier: GPL-2.0
      
      KDIR ?= /lib/modules/`uname -r`/build
      INSTALL_MOD_PATH ?= /
      default:
      	$(MAKE) -C $(KDIR) M=$$PWD
      modules_install:
      	$(MAKE) -C $(KDIR) M=$$PWD  modules_install

   3. 编译独立的模块，并安装

      make LLVM=-14 KDIR=../rust-kernel-build/amd64
      make LLVM=-14 KDIR=../rust-kernel-build/amd64 INSTALL_MOD_PATH=../../../debian11-arm64-rootfs modules_install

4. 构建文件系统

   dd  if=/dev/zero of=./debian11-amd64-rootfs.img bs=1M count=10240
   mkfs -t ext4 ./debian11-amd64-rootfs.img
   sudo mkdir debian11-amd64-rootfs
   sudo mount debian11-amd64-rootfs.img debian11-amd64-rootfs
   # 下载debian 11 rootfs
   sudo debootstrap --arch amd64 stable debian11-amd64-rootfs http://ftp.debian.org/debian
   # 根据自己习惯配置一下rootfs
   sudo chroot debian11-amd64-rootfs
   
   apt-get update
   apt-get install sudo vim bash-completion -y
   apt-get install net-tools ethtool ifupdown network-manager iputils-ping -y
   apt-get install rsyslog resolvconf udev -y
   apt-get install vim net-tools openssh-server curl git build-essential -y
   echo "debian" >/etc/hostname
   echo "127.0.0.1 localhost" >/etc/hosts
   
   dpkg-reconfigure resolvconf
   dpkg-reconfigure tzdata
   exit

5. Qemu启动脚本

   #!/bin/bash
   
   KRNL_IMGE=<kernel-build-dir>/amd64/arch/x86_64/boot/bzImage
   ROOT_FILE=debian11-amd64-rootfs.img
   QEMU_BINY=./x86_64-qemu/qemu-system-x86_64
   
   sudo ${QEMU_BINY} \
       -name "rust-for-linux-VM" \
       -enable-kvm \
       -cpu host \
       -smp 4 \
       -m 16G \
       -kernel ${KRNL_IMGE} \
       -hda ${ROOT_FILE} -append "console=ttyS0 root=/dev/sda rw"  \
       -serial mon:stdio \
       -net user,hostfwd=tcp::38080-:22 \
       -net nic,model=virtio \
       -nographic \
       -qmp unix:./qmp-amd64-sock,server,nowait

6. 测试独立的模块

   用新编译的内核+文件系统启动qemu

   root@debian:~# modprobe rust_out_of_tree
   [  149.540799] rust_out_of_tree: loading out-of-tree module taints kernel.
   [  149.548570] rust_out_of_tree: Rust out-of-tree sample (init)
   root@debian:~# modinfo  rust_out_of_tree
   filename:       /lib/modules/5.19.0-rc1-156671-gabd32d188969/extra/rust_out_of_tree.ko
   author:         Rust for Linux Contributors
   description:    Rust out-of-tree sample
   license:        GPL v2
   vermagic:       5.19.0-rc1-156671-gabd32d188969 SMP preempt mod_unload aarch64
   name:           rust_out_of_tree
   depends:
   root@debian:~# rmmod rust_out_of_tree
   [  210.345721] rust_out_of_tree: My message is on the heap!
   [  210.345961] rust_out_of_tree: Rust out-of-tree sample (exit)

交叉编译Arm64 kernel

对于LLVM交叉编译而言，不需要像gcc一样安装不同架构的工具链，仅是需要给clang传递-target=<triple> 参数，所以执行编译内核时，设置ARCH变量即可，不需要设置CROSS_COMPILE 变量，详细的LLVM编译内核文档可以参考：Building Linux with Clang/LLVM

1. config中打开 CONFIG_RUST 相关选项

   make LLVM=-14  ARCH=arm64  O=../rust-kernel-build/arm64  menuconfig

2. 编译内核/内核模块

   make LLVM=-14  ARCH=arm64  O=../rust-kernel-build/arm64  -j 64

3. 安装内核模块，需要指定根文件目录

   安装完成后，内核模块会被安装到 ../../debian11-arm64-rootfs/lib/modules/ 目录下

   sudo make LLVM=-14  ARCH=arm64  O=../rust-kernel-build/arm64 INSTALL_MOD_PATH=../../../debian11-arm64-rootfs  modules_install