moved stuff around

makefile

@@ -5,38 +5,51 @@ OBJCOPY = i686-elf-objcopy
 CFLAGS = -m32 -ffreestanding -O2 -Wall -Wextra -nostdlib
 ASFLAGS = -m32
 
+BOOT_DIR   := boot
+KERNEL_DIR := kernel
+BUILD_DIR  := build
+
+BOOT_BIN   := $(BUILD_DIR)/boot.bin
+KERNEL_BIN := $(BUILD_DIR)/kernel.bin
+IMAGE      := os.img
+
 .PHONY: all clean run
 
-all: os.img
+all: $(IMAGE)
 
-boot.o: boot.s 
-	$(CC) $(ASFLAGS) -c boot.s -o boot.o
+$(BUILD_DIR)/%.o: $(BOOT_DIR)/%.s | $(BUILD_DIR)
+	$(CC) $(ASFLAGS) -c $< -o $@
 
-boot.elf: boot.o boot.ld 
-	$(LD) -T boot.ld -o boot.elf boot.o
+$(BUILD_DIR)/%.o: $(KERNEL_DIR)/%.s | $(BUILD_DIR)
+	$(CC) $(ASFLAGS) -c $< -o $@
 
-boot.bin: boot.elf 
-	$(OBJCOPY) -O binary boot.elf boot.bin
+$(BUILD_DIR)/%.o: $(KERNEL_DIR)/%.c | $(BUILD_DIR)
+	$(CC) $(CFLAGS) -c $< -o $@
 
-prekernel.o: prekernel.s
-	$(CC) $(ASFLAGS) -c prekernel.s -o prekernel.o
+$(BUILD_DIR)/boot.elf: $(BUILD_DIR)/boot.o $(BOOT_DIR)/boot.ld
+	$(LD) -T $(BOOT_DIR)/boot.ld -o $@ $(BUILD_DIR)/boot.o
 
-kmain.o: kmain.c
-	$(CC) $(CFLAGS) -c kmain.c -o kmain.o
+$(BOOT_BIN): $(BUILD_DIR)/boot.elf
+	$(OBJCOPY) -O binary $< $@
 
-kernel.elf: prekernel.o kmain.o kernel.ld
-	$(LD) -T kernel.ld -o kernel.elf prekernel.o kmain.o
+KERNEL_OBJS := $(BUILD_DIR)/prekernel.o $(BUILD_DIR)/kmain.o
 
-kernel.bin: kernel.elf
-	$(OBJCOPY) -O binary kernel.elf kernel.bin
+$(BUILD_DIR)/kernel.elf: $(KERNEL_OBJS) $(KERNEL_DIR)/kernel.ld
+	$(LD) -T $(KERNEL_DIR)/kernel.ld -o $@ $(KERNEL_OBJS)
 
-os.img: boot.bin kernel.bin
-	dd if=boot.bin of=os.img bs=512 count=1
-	dd if=kernel.bin of=os.img bs=512 seek=1
-	truncate -s 1440k os.img
+$(KERNEL_BIN): $(BUILD_DIR)/kernel.elf
+	$(OBJCOPY) -O binary $< $@
 
-run: os.img
-	qemu-system-i386 -drive format=raw,file=os.img
+$(BUILD_DIR):
+	mkdir -p $(BUILD_DIR)
+
+$(IMAGE): $(BOOT_BIN) $(KERNEL_BIN)
+	dd if=$(BOOT_BIN) of=$@ bs=512 count=1
+	dd if=$(KERNEL_BIN) of=$@ bs=512 seek=1
+	truncate -s 1440k $@
+
+run: $(IMAGE)
+	qemu-system-i386 -drive format=raw,file=$(IMAGE)
 
 clean: 
-	rm -f *.o *.elf *.bin os.img
+	rm -rf $(BUILD_DIR) $(IMAGE)