Makefile

CC      = gcc
AS      = gcc
LD      = ld
QEMU    = qemu-system-i386

CFLAGS  = -m32 -ffreestanding -O2 -Wall -Wextra
ASFLAGS = -m32
LDFLAGS = -m elf_i386 -T linker.ld

KERNEL  = kernel.bin
ISO     = myos.iso
OBJ     = boot.o kernel.o

.PHONY: all clean iso verify run

all: $(ISO)

$(KERNEL): $(OBJ)
	$(LD) $(LDFLAGS) -o $(KERNEL) $(OBJ)

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

%.o: %.S
	$(AS) $(ASFLAGS) -c $< -o $@

verify: $(KERNEL)
	@if grub-file --is-x86-multiboot2 $(KERNEL); then \
		echo "MB2 Check: OK"; \
	else \
		echo "MB2 Check: FAILED (Not a valid Multiboot2 kernel)"; \
		exit 1; \
	fi

$(ISO): verify grub.cfg
	@mkdir -p isodir/boot/grub
	cp $(KERNEL) isodir/boot/
	cp grub.cfg isodir/boot/grub/
	grub-mkrescue -o $(ISO) isodir

run: $(ISO)
	$(QEMU) -cdrom $(ISO)

clean:
	rm -rf *.o $(KERNEL) $(ISO) isodir