MAKE := make
MAKEFLAGS += -j8

ARCH := aarch64
GNU := $(ARCH)-linux-gnu
GDB := $(GNU)-gdb

QEMU := qemu-system-$(ARCH)
QEMUFLAGS += -M raspi3b -display none -serial null

CC := $(GNU)-gcc
CCFLAGS += -Wall -Wextra -O0 \
					 -mcpu=cortex-a53+nofp+nosimd \
					 -nostdinc -nostdlib -nostartfiles -nodefaultlibs \
					 -Wno-unused-parameter -Wno-unused-value -Wno-main -g
LD := $(GNU)-ld
LDFLAGS += -g -nostdlib -no-pie
OBJCOPY := $(GNU)-objcopy
OBJDUMP := $(GNU)-objdump

MISC_DIR := misc
QEMUFLAGS += -dtb $(MISC_DIR)/bcm2710-rpi-3-b-plus.dtb

LIB_DIR := lib
INCLUDE := -Iinclude

#TARGET := kernel8
#TARGET_DIR := ./kernel
ELF := $(TARGET).elf
IMG := $(TARGET).img

LD_SCRIPT := $(TARGET_DIR)/linker.ld
INCLUDE += -I$(TARGET_DIR)/include
TARGET_LIB_DIR := $(TARGET_DIR)/lib

BOOTLOADER_DIR := ./bootloader

# initramfs
ROOTFS_DIR := ./rootfs
CPIO := initramfs.cpio
QEMUFLAGS += -initrd $(CPIO)

TARGET_SRCS := $(shell find $(TARGET_DIR) -maxdepth 1 -name '*.[cS]') \
							 $(shell find $(TARGET_LIB_DIR) -name '*.[cS]')
TARGET_OBJS := $(TARGET_SRCS:%=%.o)
SRCS := $(shell find $(LIB_DIR) -name '*.c')
OBJS := $(SRCS:%=%.o)

.PHONY: all build clean clean_target run \
        kernel bootloader userprog debug gdb objdump

all: $(CPIO)
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=kernel TARGET=kernel8
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=bootloader TARGET=bootloader

build: $(IMG)

$(CPIO): $(shell find $(ROOTFS_DIR)) userprog
	cp userprog/userprog $(ROOTFS_DIR)/userprog
	cd $(ROOTFS_DIR) && find . | cpio -o -H newc > ../$@

$(IMG): $(ELF)
	$(OBJCOPY) -O binary $< $@

$(ELF): $(LD_SCRIPT) $(TARGET_OBJS) $(OBJS)
	$(LD) -o $@ -T $(LD_SCRIPT) $(TARGET_OBJS) $(OBJS) $(LDFLAGS)

%.S.o: %.S
	mkdir -p $(dir $@)
	$(CC) -c $< -o $@ $(INCLUDE) $(CCFLAGS)

%.c.o: %.c
	mkdir -p $(dir $@)
	$(CC) -c $< -o $@ $(INCLUDE) $(CCFLAGS)

clean:
	-rm $(OBJS) $(CPIO) $(ROOTFS_DIR)/userprog
	$(MAKE) $(MAKEFLAGS) -C userprog clean
	$(MAKE) $(MAKEFLAGS) clean_target TARGET_DIR=kernel TARGET=kernel8
	$(MAKE) $(MAKEFLAGS) clean_target TARGET_DIR=bootloader TARGET=bootloader

clean_target:
	-rm $(TARGET_OBJS) $(ELF) $(IMG)

run: all $(CPIO)
	$(QEMU) -kernel bootloader.img $(QEMUFLAGS) -serial pty

kernel: $(CPIO)
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=kernel TARGET=kernel8
	$(QEMU) -kernel kernel8.img $(QEMUFLAGS) -serial stdio

bootloader: $(CPIO)
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=bootloader TARGET=bootloader
	$(QEMU) -kernel bootloader.img $(QEMUFLAGS) -serial stdio

userprog:
	$(MAKE) $(MAKEFLAGS) -C userprog

debug: $(CPIO)
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=kernel TARGET=kernel8
	$(QEMU) -kernel kernel8.img $(QEMUFLAGS) -serial stdio -S -s

gdb:
	$(GDB)

objdump:
	$(MAKE) $(MAKEFLAGS) build TARGET_DIR=kernel TARGET=kernel8
	$(OBJDUMP) -D kernel8.elf