improve makefile

Makefile

@@ -1,4 +1,5 @@
-#CROSS=aarch64-none-elf-
+# Used to generated .d file that deal with header dependencies
+CPPFLAGS = -MMD
 CROSS=aarch64-linux-gnu-
 CC=$(CROSS)gcc
 LD=$(CROSS)ld
@@ -6,18 +7,28 @@ CFLAGS=-Wall -Wextra -ffreestanding -march=armv8-a+crc -mcpu=cortex-a53
 LDSCRIPT=rpi3.ld
 
 OBJS=crt0.o uart.o hello.o
+gasmsrc=$(wildcard *.S)
+gasmobj=$(gasmsrc:%.S=%.o)
+csrc=$(wildcard *.c)
+cobj=$(csrc:%.c=%.o)
+deps=$(csrc:%.c=%.d) $(gasmsrc:%.S=%.d)
 
 all:kernel.bin
 
-kernel.elf: $(OBJS) $(LDSCRIPT)
-	$(LD) -o $@ $(OBJS) -T$(LDSCRIPT) -Map kernel.map
+kernel.elf: $(cobj) $(gasmobj) $(LDSCRIPT)
+	$(LD) $(LDFLAGS) -o $@ $(cobj) $(gasmobj) -T$(LDSCRIPT) -Map kernel.map
 
 kernel.bin: kernel.elf
-	$(CROSS)objcopy -O binay -B aarch64 $< $@
+	$(CROSS)objcopy -O binary $< $@
 
 clean:
-	rm -rf $(OBJS) *.bin *.elf *.map
+	rm -rf $(cobj) $(gasmobj) $(deps) *.bin *.elf *.map
 
 run: kernel.bin
 	qemu-system-aarch64 -machine raspi3b -kernel $<
 
+
+
+ifneq ($(MAKECMDGOALS),clean)
+-include $(deps)
+endif