Makefile for pwn-kernel chal building

Makefile.kernel

# Kernel Pwn-Chal Build @TheFlash2k
.ONESHELL:
KERN_VERSION  := 6.6.85
KERN_BASE_VER := 6
BUSYBOX_VER   := 1.32.1
KERNEL_NAME   := bzImage
ROOTFS_NAME   := rootfs.cpio
ROOTFS_DIR    := root
KERNEL_DRIVER := kernel101
KERNEL_DIR    := $(PWD)/linux-$(KERN_VERSION)
CHAL_DIR      := chal
# required when building the ko
obj-m         += $(KERNEL_DRIVER).o

all: kernel rootfs driver

kernel:
ifneq ("$(wildcard $(KERNEL_NAME))", "")
	@echo "[*] Kernel $(KERNEL_NAME) already exists!"
	exit
endif
ifneq ("$(wildcard $(KERNEL_DIR))", "")
	@echo "[*] Kernel folder linux-$(KERN_VERSION) already found."
else
	wget https://cdn.kernel.org/pub/linux/kernel/v$(KERN_BASE_VER).x/linux-$(KERN_VERSION).tar.xz
	tar -xvf "linux-$(KERN_VERSION).tar.xz"
	rm -f "linux-$(KERN_VERSION).tar.xz"
	cd linux-$(KERN_VERSION)
	@echo "Building the kernel v$(KERN_VERSION)"
	make defconfig && make -j `nproc`
	cp ./arch/x86_64/boot/bzImage "$(CURR_DIR)"
endif

rootfs:
ifneq ("$(wildcard $(ROOTFS_NAME))", "")
	@echo "[*] Rootfs $(ROOTFS_NAME) already exists!"
else
	mkdir $(ROOTFS_DIR) && cd $(ROOTFS_DIR)
	wget https://busybox.net/downloads/busybox-$(BUSYBOX_VER).tar.bz2
	tar xvf ./busybox-$(BUSYBOX_VER).tar.bz2
	rm -f ./busybox-$(BUSYBOX_VER).tar.bz2
	cd busybox-$(BUSYBOX_VER)
	@read -p "Settings-> Build Options-> Build static binary (no shared libs) [For static binaries]. Press enter to continue." cont;
	make menuconfig
	make -j`nproc`
	make install
	cd _install
	mkdir -p proc sys dev etc
	touch init
	chmod +x init
	find . | cpio -o --format=newc > "../../../$(ROOTFS_NAME)"
endif

driver:
ifneq ("$(wildcard $(KERNEL_DRIVER))", "")
	@echo "[*] Kernel Driver already exists!"
else
	make -C $(KERNEL_DIR) M=$(PWD) modules
endif

chal:
	mkdir -p "$(CHAL_DIR)"
	cp "$(KERNEL_NAME)" "$(ROOTFS_NAME)" "$(CHAL_DIR)"
	cd "$(CHAL_DIR)"
	wget https://raw.githubusercontent.com/TheFlash2k/pwn-chal/refs/heads/master/samples/kernel/Makefile
	wget https://raw.githubusercontent.com/TheFlash2k/pwn-chal/refs/heads/master/samples/kernel/Dockerfile
	sed -i 's/initramfs.cpio.gz/$(ROOTFS_NAME)/g' Dockerfile
	sed -i 's/bzImage/$(KERNEL_NAME)/g' Dockerfile

clean_all: clean
# 	It will just clean the directories and not the actual bzImage/rootfs
	@read -p "Do you want to clean the Kernel Directory? (y/n) " clean_kern; \
	if [ "$$clean_kern" != "y" ]; then \
		echo "Skipping kernel cleaning"; \
	else \
		echo "Cleaning Kernel Directory..."; \
		rm -f "linux-$(KERN_VERSION).tar.xz"
		rm -rf "linux-$(KERN_VERSION)"
	fi

	@read -p "Do you want to clean the Root Filesystem? (y/n) " clean_rootfs; \
	if [ "$$clean_rootfs" != "y" ]; then \
		echo "Skipping rootfs cleaning"; \
	else \
		echo "Cleaning Rootfs Directory..."; \
		rm -rf "$(ROOTFS_DIR)"
	fi

clean:
# 	We don't clean the FS and everything else. Just challenge.
	make -C $(KERNEL_DIR) M=$(PWD) clean
	rm -rf *.o *.mod.* *.symvers *.order