Added stage 1 bootloader

bootloader/Makefile

@@ -0,0 +1,83 @@
+# 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="$<" bs=512 skip=1 of="$@"