Build a basic Linux kernel and ramdisk that can start in QEMU.

.gitignore

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+old/
+tmp/
+artifacts/

docker/Dockerfile.kernel

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+FROM fedora:latest
+ENV KERNEL_VERSION=5.10.3
+
+RUN dnf install -y \
+  bc \
+  bison \
+  clang \
+  cpio \
+  curl \
+  diffutils \
+  elfutils-libelf-devel \
+  findutils \
+  flex \
+  hostname \
+  make \
+  ncurses-devel \
+  patch \
+  xz
+
+RUN mkdir -p /build/ramfs
+RUN curl https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-${KERNEL_VERSION}.tar.xz | tar xJC /build
+RUN mv /build/linux* /build/kernel
+COPY buildramfs.sh /build/ramfs/buildramfs.sh
+COPY lam.config /build/kernel/.config

docker/buildramfs.sh

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+#!/bin/bash
+ 
+ARCH="x86_64"
+BB_VER="1.31.0"
+ 
+# Dirs
+mkdir -p root
+cd root
+mkdir -p bin dev etc lib mnt proc sbin sys tmp var
+cd -
+ 
+# Utils
+if [ ! -f "root/bin/busybox" ]; then
+    curl -L "https://www.busybox.net/downloads/binaries/${BB_VER}-defconfig-multiarch-musl/busybox-${ARCH}" >root/bin/busybox
+fi
+cd root/bin
+chmod +x busybox
+ln -s busybox mount
+ln -s busybox sh
+cd -
+ 
+# Init process
+ 
+cat >>root/init << EOF
+#!/bin/busybox sh
+/bin/busybox --install -s /bin
+mount -t devtmpfs  devtmpfs  /dev
+mount -t proc      proc      /proc
+mount -t sysfs     sysfs     /sys
+mount -t tmpfs     tmpfs     /tmp
+setsid cttyhack sh
+exec /bin/sh
+EOF
+chmod +x root/init
+ 
+# initramfs creation
+ 
+cd root
+find . | cpio -ov --format=newc | gzip -9 >../initramfs
+cd -

scripts/build-kernel.sh

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+#!/bin/sh
+
+mkdir -p artifacts/kernel
+docker run --rm -v "$(pwd)/artifacts/kernel:/build/artifacts" lam-kernel bash -c "make -j2 -C /build/kernel && cp /build/kernel/arch/x86/boot/bzImage /build/artifacts/"

scripts/build-ramfs.sh

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+#!/bin/sh
+
+mkdir -p artifacts/ramdisk
+docker run --rm -v "$(pwd)/artifacts/ramdisk:/build/artifacts" lam-kernel bash -c "cd /build/ramfs && ./buildramfs.sh && cp initramfs /build/artifacts/initramfs.cpio.gz"

scripts/run.sh

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+#!/bin/sh
+
+qemu-system-x86_64 \
+  -kernel artifacts/kernel/bzImage \
+  -initrd artifacts/ramdisk/initramfs.cpio.gz \
+  -nographic \
+  -serial mon:stdio \
+  -no-reboot \
+  -append "console=ttyS0"