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-rw-r--r--content/2019-10-27-kernel-debugging-qemu/Dockerfile32
-rw-r--r--content/2019-10-27-kernel-debugging-qemu/Makefile12
-rwxr-xr-xcontent/2019-10-27-kernel-debugging-qemu/build_initrd.sh54
-rwxr-xr-xcontent/2019-10-27-kernel-debugging-qemu/build_kernel.sh38
-rwxr-xr-xcontent/2019-10-27-kernel-debugging-qemu/run.sh24
5 files changed, 160 insertions, 0 deletions
diff --git a/content/2019-10-27-kernel-debugging-qemu/Dockerfile b/content/2019-10-27-kernel-debugging-qemu/Dockerfile
new file mode 100644
index 0000000..42e1f05
--- /dev/null
+++ b/content/2019-10-27-kernel-debugging-qemu/Dockerfile
@@ -0,0 +1,32 @@
+FROM ubuntu:20.04
+MAINTAINER Johannes Stoelp <johannes.stoelp@gmail.edu>
+
+RUN apt update \
+ && DEBIAN_FRONTEND=noninteractive \
+ apt install \
+ --yes \
+ --no-install-recommends \
+ # Download & unpack.
+ wget \
+ ca-certificates \
+ xz-utils \
+ # Build tools & deps (kernel).
+ make \
+ bc \
+ gcc g++ \
+ flex bison \
+ libelf-dev \
+ # Build tools & deps (initrd).
+ cpio \
+ # Run & debug.
+ qemu-system-x86 \
+ gdb \
+ telnet \
+ # Convenience.
+ ripgrep \
+ fd-find \
+ neovim \
+ && rm -rf /var/lib/apt/lists/* \
+ && apt-get clean
+
+WORKDIR /develop
diff --git a/content/2019-10-27-kernel-debugging-qemu/Makefile b/content/2019-10-27-kernel-debugging-qemu/Makefile
new file mode 100644
index 0000000..11e7c7b
--- /dev/null
+++ b/content/2019-10-27-kernel-debugging-qemu/Makefile
@@ -0,0 +1,12 @@
+build:
+ scripts/build_kernel.sh
+ scripts/build_initrd.sh
+
+clean:
+ $(RM) -r linux-*
+ $(RM) -r busybox-*
+ $(RM) initramfs.cpio.gz
+
+docker:
+ DOCKER_BUILDKIT=1 docker build -t kernel-dev .
+ docker run -it --rm -v $(PWD):/develop/scripts -v $(PWD)/Makefile:/develop/Makefile kernel-dev
diff --git a/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh b/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh
new file mode 100755
index 0000000..fd82990
--- /dev/null
+++ b/content/2019-10-27-kernel-debugging-qemu/build_initrd.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+
+if test $(id -u) -ne 0; then
+ SUDO=sudo
+fi
+
+set -e
+
+BUSYBOX=busybox-1.33.1
+INITRD=$PWD/initramfs.cpio.gz
+
+## Build busybox
+
+echo "[+] configure & build $BUSYBOX ..."
+[[ ! -d $BUSYBOX ]] && {
+ wget https://busybox.net/downloads/$BUSYBOX.tar.bz2
+ bunzip2 $BUSYBOX.tar.bz2 && tar xf $BUSYBOX.tar
+}
+
+cd $BUSYBOX
+make defconfig
+sed -i 's/# CONFIG_STATIC .*/CONFIG_STATIC=y/' .config
+make -j4 busybox
+make install
+
+## Create initrd
+
+echo "[+] create initrd $INITRD ..."
+
+cd _install
+
+# 1. create initrd folder structure
+mkdir -p bin sbin etc proc sys usr/bin usr/sbin dev
+
+# 2. create init process
+cat <<EOF > init
+#!/bin/sh
+
+mount -t proc none /proc
+mount -t sysfs none /sys
+
+exec setsid cttyhack sh
+EOF
+chmod +x init
+
+# 3. create device nodes
+$SUDO mknod dev/tty c 5 0
+$SUDO mknod dev/tty0 c 4 0
+$SUDO mknod dev/ttyS0 c 4 64
+
+# 4. created compressed initrd
+find . -print0 \
+ | cpio --null -ov --format=newc \
+ | gzip -9 > $INITRD
diff --git a/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh b/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh
new file mode 100755
index 0000000..7ae3014
--- /dev/null
+++ b/content/2019-10-27-kernel-debugging-qemu/build_kernel.sh
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+set -e
+
+LINUX=linux-5.13.2
+wget https://cdn.kernel.org/pub/linux/kernel/v5.x/$LINUX.tar.xz
+unxz $LINUX.tar.xz && tar xf $LINUX.tar
+
+cd $LINUX
+
+cat <<EOF > kernel_fragment.config
+# 64bit kernel
+CONFIG_64BIT=y
+# enable support for compressed initrd (gzip)
+CONFIG_BLK_DEV_INITRD=y
+CONFIG_RD_GZIP=y
+# support for ELF and #! binary format
+CONFIG_BINFMT_ELF=y
+CONFIG_BINFMT_SCRIPT=y
+# /dev
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
+# tty & console
+CONFIG_TTY=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+# pseudo fs
+CONFIG_PROC_FS=y
+CONFIG_SYSFS=y
+# debugging
+CONFIG_DEBUG_INFO=y
+CONFIG_PRINTK=y
+CONFIG_EARLY_PRINTK=y
+EOF
+
+make tinyconfig
+./scripts/kconfig/merge_config.sh -n ./kernel_fragment.config
+make -j4
diff --git a/content/2019-10-27-kernel-debugging-qemu/run.sh b/content/2019-10-27-kernel-debugging-qemu/run.sh
new file mode 100755
index 0000000..b0a84ae
--- /dev/null
+++ b/content/2019-10-27-kernel-debugging-qemu/run.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+VER=5.13.2
+
+# Launch the emulator with our kernel.
+qemu-system-x86_64 \
+ -kernel ./linux-$VER/arch/x86/boot/bzImage \
+ -nographic \
+ -append "earlyprintk=ttyS0 console=ttyS0 nokaslr init=/init debug" \
+ -initrd ./initramfs.cpio.gz \
+ -serial telnet:localhost:12345,server,nowait \
+ -monitor none \
+ -gdb tcp::1234 \
+ -S &
+
+# Kill qemu when we exit.
+QEMU_PID=$!
+trap "kill $QEMU_PID" EXIT
+
+# Give qemu some time to come up.
+sleep 0.5
+
+# Attach debugger to qemu and load the kernel symbols.
+gdb -ex 'target remote :1234' ./linux-$VER/vmlinux