esp-idf/components/bootloader/Makefile.projbuild

#
# Bootloader component
#
# The bootloader is not a real component that gets linked into the project.
# Instead it is an entire standalone project ( in src/) that gets built in 
# the upper projects build directory. This Makefile.projbuild provides the 
# glue to  build the bootloader project from the original project. It 
# basically runs Make in the src/ directory but it needs to zero some variables
# the ESP-IDF project.mk makefile exports first, to not let them interfere.
#
ifndef IS_BOOTLOADER_BUILD

BOOTLOADER_COMPONENT_PATH := $(COMPONENT_PATH)
BOOTLOADER_BUILD_DIR=$(abspath $(BUILD_DIR_BASE)/bootloader)
BOOTLOADER_BIN=$(BOOTLOADER_BUILD_DIR)/bootloader.bin

# signing key path is resolved relative to the project directory
SECURE_BOOT_SIGNING_KEY=$(abspath $(call dequote,$(CONFIG_SECURE_BOOT_SIGNING_KEY)))
export SECURE_BOOT_SIGNING_KEY  # used by bootloader_support component

# Has a matching value in bootloader_support esp_flash_partitions.h
BOOTLOADER_OFFSET := 0x1000

# Custom recursive make for bootloader sub-project
BOOTLOADER_MAKE=+$(MAKE) -C $(BOOTLOADER_COMPONENT_PATH)/src \
	V=$(V) BUILD_DIR_BASE=$(BOOTLOADER_BUILD_DIR) TEST_COMPONENTS=

.PHONY: bootloader-clean bootloader-flash bootloader $(BOOTLOADER_BIN)

$(BOOTLOADER_BIN): $(SDKCONFIG_MAKEFILE)
	$(BOOTLOADER_MAKE) $@

clean: bootloader-clean

ifndef CONFIG_SECURE_BOOT_ENABLED
# If secure boot disabled, bootloader flashing is integrated
# with 'make flash' and no warnings are printed.

bootloader: $(BOOTLOADER_BIN)
	@echo $(SEPARATOR)
	@echo "Bootloader built. Default flash command is:"
	@echo "$(ESPTOOLPY_WRITE_FLASH) $(BOOTLOADER_OFFSET) $^"

ESPTOOL_ALL_FLASH_ARGS += $(BOOTLOADER_OFFSET) $(BOOTLOADER_BIN)

bootloader-flash: $(BOOTLOADER_BIN)
	$(ESPTOOLPY_WRITE_FLASH) 0x1000 $^

else ifdef CONFIG_SECURE_BOOTLOADER_ONE_TIME_FLASH

# One time flashing requires user to run esptool.py command themselves,
# and warning is printed about inability to reflash.

bootloader: $(BOOTLOADER_BIN)
	@echo $(SEPARATOR)
	@echo "Bootloader built. One-time flash command is:"
	@echo "$(ESPTOOLPY_WRITE_FLASH) $(BOOTLOADER_OFFSET) $(BOOTLOADER_BIN)"
	@echo $(SEPARATOR)
	@echo "* IMPORTANT: After first boot, BOOTLOADER CANNOT BE RE-FLASHED on same device"

else ifdef CONFIG_SECURE_BOOTLOADER_REFLASHABLE
# Reflashable secure bootloader
# generates a digest binary (bootloader + digest)

BOOTLOADER_DIGEST_BIN := $(BOOTLOADER_BUILD_DIR)/bootloader-reflash-digest.bin
SECURE_BOOTLOADER_KEY := $(BOOTLOADER_BUILD_DIR)/secure-bootloader-key.bin

$(SECURE_BOOTLOADER_KEY): $(SECURE_BOOT_SIGNING_KEY)
	$(Q) $(ESPSECUREPY) digest_private_key -k $< $@

bootloader: $(BOOTLOADER_DIGEST_BIN)
	@echo $(SEPARATOR)
	@echo "Bootloader built and secure digest generated. First time flash command is:"
	@echo "$(ESPEFUSEPY) burn_key secure_boot $(SECURE_BOOTLOADER_KEY)"
	@echo "$(ESPTOOLPY_WRITE_FLASH) $(BOOTLOADER_OFFSET) $(BOOTLOADER_BIN)"
	@echo $(SEPARATOR)
	@echo "To reflash the bootloader after initial flash:"
	@echo "$(ESPTOOLPY_WRITE_FLASH) 0x0 $(BOOTLOADER_DIGEST_BIN)"
	@echo $(SEPARATOR)
	@echo "* After first boot, only re-flashes of this kind (with same key) will be accepted."
	@echo "* Not recommended to re-use the same secure boot keyfile on multiple production devices."

$(BOOTLOADER_DIGEST_BIN): $(BOOTLOADER_BIN) $(SECURE_BOOTLOADER_KEY)
	@echo "DIGEST $(notdir $@)"
	$(Q) $(ESPSECUREPY) digest_secure_bootloader -k $(SECURE_BOOTLOADER_KEY) -o $@ $<

else
bootloader:
	@echo "Invalid bootloader target: bad sdkconfig?"
	@exit 1
endif

ifndef CONFIG_SECURE_BOOT_ENABLED
# don't build bootloader by default is secure boot is enabled
all_binaries: $(BOOTLOADER_BIN)
endif

bootloader-clean:
	$(BOOTLOADER_MAKE) app-clean
	rm -f $(SECURE_BOOTLOADER_KEY) $(BOOTLOADER_DIGEST_BIN)

$(BOOTLOADER_BUILD_DIR):
	mkdir -p $@

else
CFLAGS += -D BOOTLOADER_BUILD=1 -I $(IDF_PATH)/components/esp32/include

endif