[QEMU][BusyBox] MainLine Kernel Emulation(arm64)

목적

• MainLine Kernel(=Vanilla)를 가상머신에서 구동
• Cross Compile 및 HW 가상화 사용 (Host:Ubuntu x64, Target:arm64)
• QEMU 및 BusyBox 사용

 

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Kernel Build

 

Build Dependency 설치

 

Kernel Build Dependency 설치 및 CrossComplier 설치

sudo apt-get build-dep linux linux-image-$(uname -r)
sudo apt-get install libncurses-dev gawk flex bison openssl libssl-dev dkms libelf-dev libudev-dev libpci-dev libiberty-dev autoconf llvm
sudo apt-get install gcc-aarch64-linux-gnu
sudo apt-get install g++-aarch64-linux-gnu

 

Kernel Source Code Download

git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
git tag  | grep 5.19
git checkout v5.19

 

Kernel Configuration 설정

cd linux
make ARCH=arm64 mrproper
make ARCH=arm64 O=../out defconfig -j$(nproc) CROSS_COMPILE=aarch64-linux-gnu-
make ARCH=arm64 O=../out menuconfig -j$(nproc) CROSS_COMPILE=aarch64-linux-gnu-

 

menuconfig 화면에서 RAM Disk 지원 기능(CONFIG_BLK_DEV_RAM) 활성화 

• Device Drivers
  • Block devices
    • RAM block device support

 

Kernel Image Build

make ARCH=arm64 O=../out -j$(nproc) CROSS_COMPILE=aarch64-linux-gnu-

 

 

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Booting Image 준비

 

BusyBox를 이용해서 부팅 가능한 RAM Disk Image 준비

 

BusyBox 설치

git clone git://busybox.net/busybox.git
cd busybox/
git branch  -a --sort=-committerdate | grep stable
git checkout 1_36_stable

 

BusyBox Configuration 설정

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

각종 library를 static build하도록 설정

• Settings
  • Build static library (no shared libs)

 

BusyBox Build

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j$(nproc)
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- install

성공적으로 완료되었다면 _install 폴더 생성

(만약 _install 폴더가 없으면 menuconfig에서 "Settings→Destination path for 'make install'"에서 산출물 생성 폴더 이름 확인 가능)

 

RamDisk 준비 작업

cd _install
mkdir -p dev etc/init.d home/root lib mnt proc root sys tmp usr/lib var
cp -v /usr/aarch64-linux-gnu/lib/* ./lib/

cat > etc/init.d/rcS << EOF
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys
/sbin/mdev -s
[ ! -h /etc/mtab ]  && ln -s /proc/mounts /etc/mtab
[ ! -f /etc/resolv.conf ] && cat /proc/net/pnp > /etc/resolv.conf
EOF

chmod +x etc/init.d/rcS
find . | cpio -o --format=newc > ../initramfs
cd ..
gzip -vc initramfs > initramfs.gz

생성된 Image를 통해서 Booting후, /etc/init.d/rcS를 실행하게 된다.

이제 initramfs.gz를 RamDisk에 올려서 가상머신이 Booting할 수 있다.

 

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QEMU 설치

 

arm machine emulator 설치

sudo apt install qemu-system-arm qemu-efi-aarch64

(source coe : https://gitlab.com/qemu-project/qemu.git)

 

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QEMU 가상머신 실행

 

qemu-system-aarch64 \
-machine virt \
-cpu cortex-a57 \
-smp 4 \
-m 2048 \
-kernel out/arch/arm64/boot/Image \
-initrd busybox/initramfs.gz \
-append "rdinit=/sbin/init root=/dev/ram rootfstype=ramfs rw nokaslr" \
-nographic

 

사용한 Option

• -machine virt
  • HW 종류
• -cpu cortex-a57
  • architecture 종류
• -smp 4
  • core 갯수
• -m 2048
  • 메모리 사이즈 (단위 KB)
• -kernel out/arch/arm64/boot/Image
  • Kernel Image (Build 완료된 Kernel 경로)
• -initrd busybox/initramfs.gz
  • Booting Image (BusyBox를 통해서 생성한 Image)
• -append "rdinit=/sbin/init root=/dev/ram rootfstype=ramfs rw"
  • Kernel Command Line
  • rdinit : 최초로 실행되는 Process
  • oot=/dev/ram rootfstype=ramfs rw : root file system 설정
• -nographic
  • graphical 출력을 끄고, shell 입출력을 console에서 수행

 

실행 결과

• Ctrl+a, x 입력하여 종료
• Ctrl+a, c 입력하여 qemu console로 Switch 가능

 

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사용한 Tool Version

• Kernel : v5.19
• BusyBox : v1.36
• QEMU : v7.0.0

 

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참고 및 출처

 

https://elinux.org/QEMU

QEMU - eLinux.org

https://velog.io/@pikamon/Linux-Kernel-3

[Linux] Aarch64 Busybox 크로스 컴파일 방법

https://www.css-techhelp.com/post/build-the-linux-kernel-and-busybox-and-run-them-on-qemu

Build the Linux Kernel and Busybox and run them on QEMU

https://www.jianshu.com/p/0d94898300d2

qemu-ubuntu-arm64 kernel

https://elinux.org/QEMU

QEMU - eLinux.org

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