C_SOURCES = $(wildcard kernel/*.c drivers/*.c)
HEADERS = $(wildcard kernel/*.h drivers/*.h)
# Nice syntax for file extension replacement
OBJ = ${C_SOURCES:.c=.o}

# Change this if your cross-compiler is somewhere else
CC = /usr/bin/gcc
GDB = /usr/bin/gdb
# -g: Use debugging symbols in gcc
CFLAGS = -g -m32 -fno-pie -ffreestanding

# First rule is run by default
all: run

# concatanate the binary files to make kernel image
os-image.bin: boot/bootsect.bin kernel.bin
	cat $^ > os-image.bin

# '--oformat binary' deletes all symbols as a collateral, so we don't need
# to 'strip' them manually on this case
kernel.bin: boot/kernel_entry.o ${OBJ}
	/usr/bin/ld -m elf_i386 -o $@ -Ttext 0x1000 $^ --oformat binary

# Used for debugging purposes
kernel.elf: boot/kernel_entry.o ${OBJ}
	/usr/bin/ld -m elf_i386 -o $@ -Ttext 0x1000 $^ 

run: os-image.bin
	qemu-system-i386 -vga std -drive file=$<,index=0,if=floppy,format=raw

curses: os-image.bin
	qemu-system-i386 -curses -drive file=$<,index=0,if=floppy,format=raw

# Open the connection to qemu and load our kernel-object file with symbols
debug: os-image.bin kernel.elf
	qemu-system-i386 -curses -s -drive file=os-image.bin,index=0,if=floppy,format=raw &
	${GDB} -ex "target remote localhost:1234" -ex "symbol-file kernel.elf"

# Generic rules for wildcards
# To make an object, always compile from its .c
%.o: %.c ${HEADERS}
	${CC} ${CFLAGS} -c $< -o $@

%.o: %.asm
	nasm $< -f elf -o $@

%.bin: %.asm
	nasm $< -f bin -o $@

clean:
	rm -rf *.bin *.dis *.o os-image.bin *.elf
	rm -rf kernel/*.o boot/*.bin drivers/*.o boot/*.o