# This compiles our bootloader as a static library,
# and wraps it in a multistage loader.


BUILD = ./build


.PHONY: all
all: $(BUILD)/mbr.bin $(BUILD)/512.bin $(BUILD)/stage2.bin

.PHONY: clean
clean:
	rm -drf $(BUILD)
	cd bootloader; cargo clean

# Compile bootloader as library
LIB_SRC = ./bootloader/Cargo.toml ./bootloader/Cargo.lock $(shell find ./bootloader/src -type f)
$(BUILD)/bootloader.lib: $(LIB_SRC)
	@mkdir -p $(BUILD)
	cd bootloader && \
		env RUSTFLAGS="-C soft-float" \
		cargo rustc \
			--manifest-path="./Cargo.toml" \
			-Z build-std=core,alloc \
			-Z build-std-features=compiler-builtins-mem \
			--target "./targets/x86-unknown-none.json" \
			--lib \
			--release \
			-- \
			--emit link="$(CURDIR)/$@"

# Link bootloader
BIOS_LD = ./bootloader/linkers/x86-unknown-none.ld
$(BUILD)/bootloader.elf: $(BUILD)/bootloader.lib $(BIOS_LD)
	ld \
		-m elf_i386 \
		--gc-sections \
		-z max-page-size=0x1000 \
		-T "$(BIOS_LD)" \
		-o "$@" \
		"$<"

	objcopy --only-keep-debug "$@" "$@.sym"
	objcopy --strip-debug "$@"

# Wrap bootloader in three-stage BIOS loader
# Parameters:
# - BIOS_SRC: source directory of bios assembly
# - STAGE3: path to linked stage 3 binary
# - STAGE2_SECTOR: the index of the first sector of the stage 2 binary on the disk
BIOS_SRC = ./bios
STAGE2_SECTOR = 5
STAGE3 = $(BUILD)/bootloader.elf 
$(BUILD)/bios.bin: $(wildcard $(BIOS_SRC)/*.asm) $(STAGE3)
	@mkdir -p "$(BUILD)"
	nasm \
		-f bin \
		-D STAGE3=$(STAGE3) \
		-D STAGE2_SECTOR=$(STAGE2_SECTOR) \
		-o "$@" \
		-l "$@.lst" \
		-i "$(BIOS_SRC)" \
		"$(BIOS_SRC)/main.asm"

# Extract MBR code (first 440 bytes)
# This can be used to embed this mbr in gpt-partitioned disks
$(BUILD)/mbr.bin: $(BUILD)/bios.bin
	@mkdir -p "$(BUILD)"
	@echo ""
	dd if="$<" bs=440 count=1 of="$@"

# Extract full mbr (first 512 bytes)
# This can be used to make raw boot disks
$(BUILD)/512.bin: $(BUILD)/bios.bin
	@mkdir -p "$(BUILD)"
	@echo ""
	dd if="$<" bs=512 count=1 of="$@"

# Extract stage 2 (rest of file)
$(BUILD)/stage2.bin: $(BUILD)/bios.bin
	@mkdir -p "$(BUILD)"
	@echo ""
	dd if="$<" bs=512 skip=1 of="$@"