diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index e33a24d..51cb6ca 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -1,13 +1,16 @@
-all: build-all
+CURRENT_MAKEFILE := $(realpath $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST)))
+SRC_DIR := $(dir $(CURRENT_MAKEFILE))
+TOPSRC_DIR := $(SRC_DIR)/../..
+VPATH = $(SRC_DIR)
+
+all: multiboot.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
 # Dummy command so that make thinks it has done something
 	@true
 
 include ../../config-host.mak
-include $(SRC_PATH)/rules.mak
-
-$(call set-vpath, $(SRC_PATH)/pc-bios/optionrom)
 
-.PHONY : all clean build-all
+quiet-command = $(if $(V),$1,$(if $(2),@printf "  %-7s %s\n" $2 $3 && $1, @$1))
+cc-option = $(if $(shell $(CC) $1 -S -o /dev/null -xc /dev/null >/dev/null 2>&1 && echo OK), $1, $2)
 
 # Compiling with no optimization creates ROMs that are too large
 ifeq ($(lastword $(filter -O%, -O0 $(CFLAGS))),-O0)
@@ -15,48 +18,60 @@ override CFLAGS += -O2
 endif
 override CFLAGS += -march=i486
 
-# Drop -fstack-protector and the like
-QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS)) $(CFLAGS_NOPIE) -ffreestanding
-QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
-QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -m16)
-ifeq ($(filter -m16, $(QEMU_CFLAGS)),)
+# Flags for dependency generation
+override CPPFLAGS += -MMD -MP -MT $@ -MF $(@D)/$(*F).d
+
+override CFLAGS += $(filter -W%, $(QEMU_CFLAGS))
+override CFLAGS += $(CFLAGS_NOPIE) -ffreestanding -I$(TOPSRC_DIR)/include
+override CFLAGS += $(call cc-option, -fno-stack-protector)
+override CFLAGS += $(call cc-option, -m16)
+
+ifeq ($(filter -m16, $(CFLAGS)),)
 # Attempt to work around compilers that lack -m16 (GCC <= 4.8, clang <= ??)
 # On GCC we add -fno-toplevel-reorder to keep the order of asm blocks with
 # respect to the rest of the code.  clang does not have -fno-toplevel-reorder,
 # but it places all asm blocks at the beginning and we're relying on it for
 # the option ROM header.  So just force clang not to use the integrated
 # assembler, which doesn't support .code16gcc.
-QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-toplevel-reorder)
-QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -no-integrated-as)
-QEMU_CFLAGS += -m32 -include $(SRC_PATH)/pc-bios/optionrom/code16gcc.h
+override CFLAGS += $(call cc-option, -fno-toplevel-reorder)
+override CFLAGS += $(call cc-option, -no-integrated-as)
+override CFLAGS += -m32 -include $(SRC_DIR)/code16gcc.h
 endif
 
-QEMU_INCLUDES += -I$(SRC_PATH)
-
 Wa = -Wa,
-ASFLAGS += -32
-QEMU_CFLAGS += $(call cc-c-option, $(QEMU_CFLAGS), $(Wa)-32)
+override ASFLAGS += -32
+override CFLAGS += $(call cc-option, $(Wa)-32)
 
-build-all: multiboot.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
 
-# suppress auto-removal of intermediate files
-.SECONDARY:
+LD_I386_EMULATION ?= elf_i386
+override LDFLAGS = -m $(LD_I386_EMULATION) -T $(SRC_DIR)/flat.lds
+override LDFLAGS += $(LDFLAGS_NOPIE)
 
+all: multiboot.bin linuxboot.bin linuxboot_dma.bin kvmvapic.bin pvh.bin
+
+pvh.img: pvh.o pvh_main.o
 
 %.o: %.S
-	$(call quiet-command,$(CPP) $(QEMU_INCLUDES) $(QEMU_DGFLAGS) -c -o - $< | $(AS) $(ASFLAGS) -o $@,"AS","$(TARGET_DIR)$@")
+	$(call quiet-command,$(CPP) $(CPPFLAGS) -c -o - $< | $(AS) $(ASFLAGS) -o $@,"AS","$@")
 
-pvh.img: pvh.o pvh_main.o
-	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -m $(LD_I386_EMULATION) -T $(SRC_PATH)/pc-bios/optionrom/flat.lds -s -o $@ $^,"BUILD","$(TARGET_DIR)$@")
+%.o: %.c
+	$(call quiet-command,$(CC) $(CPPFLAGS) $(CFLAGS) -c $< -o $@,"CC","$@")
 
 %.img: %.o
-	$(call quiet-command,$(LD) $(LDFLAGS_NOPIE) -m $(LD_I386_EMULATION) -T $(SRC_PATH)/pc-bios/optionrom/flat.lds -s -o $@ $<,"BUILD","$(TARGET_DIR)$@")
+	$(call quiet-command,$(LD) $(LDFLAGS) -s -o $@ $^,"BUILD","$@")
 
 %.raw: %.img
-	$(call quiet-command,$(OBJCOPY) -O binary -j .text $< $@,"BUILD","$(TARGET_DIR)$@")
+	$(call quiet-command,$(OBJCOPY) -O binary -j .text $< $@,"BUILD","$@")
 
 %.bin: %.raw
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/signrom.py $< $@,"SIGN","$(TARGET_DIR)$@")
+	$(call quiet-command,$(PYTHON) $(TOPSRC_DIR)/scripts/signrom.py $< $@,"SIGN","$@")
+
+include $(wildcard *.d)
 
 clean:
 	rm -f *.o *.d *.raw *.img *.bin *~
+
+# suppress auto-removal of intermediate files
+.SECONDARY:
+
+.PHONY: all clean
