.POSIX:
.SUFFIXES:
.PHONY: clean run

RPI_VERSION ?= 3

# Compiler.
AS      := aarch64-elf-as
CC      := aarch64-elf-gcc
LD      := aarch64-elf-ld
OBJCOPY := aarch64-elf-objcopy

# Paths.
SRC_DIR   := src
BUILD_DIR := build

# Output files.
ELF := $(BUILD_DIR)/kernel8.elf
IMG := $(BUILD_DIR)/kernel8.img

# Bootstrapping files.
OBJ_START = $(BUILD_DIR)/start.o
OBJ_MAIN = $(BUILD_DIR)/main.o
SRC_LINK = $(SRC_DIR)/linker.ld

CFLAGS := -Wall -ffreestanding -nostartfiles -O2 -nostdlib -lgcc -mgeneral-regs-only -fno-stack-protector
CFLAGS += -DRPI_VERSION=$(RPI_VERSION)
AFLAGS :=
LDFLAGS :=

default: $(IMG)

$(BUILD_DIR)/%.o: $(SRC_DIR)/%.s
	$(AS) $(AFLAGS) -o $@ -c $<

$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c
	$(CC) $(CFLAGS) -o $@ -c $<

$(IMG): $(BUILD_DIR) $(ELF)
	$(OBJCOPY) $(ELF) -O binary $(IMG)

$(ELF): $(OBJ_START) $(OBJ_MAIN)
	$(LD) $(LDFLAGS) -T $(SRC_LINK) -o $(ELF) $(OBJ_START) $(OBJ_MAIN)

clean:
	rm -rf $(BUILD_DIR)

$(BUILD_DIR):
	mkdir -p $(BUILD_DIR)

run: $(IMG)
	qemu-system-aarch64 -M raspi3 -kernel $(IMG) -serial null -serial stdio