Embed a binary blob into a C program with CMake

embed.cmake

set(EMBEDDED_FILE "" CACHE PATH "Path to the file to embed (optional)")
if (EMBEDDED_FILE)
	file(SIZE ${EMBEDDED_FILE} EMBEDDED_FILE_SIZE)

	file(GENERATE OUTPUT ${CMAKE_BINARY_DIR}/empty.c CONTENT "")
	set_source_files_properties(${CMAKE_BINARY_DIR}/empty.c PROPERTIES GENERATED TRUE)
	add_library(empty OBJECT ${CMAKE_BINARY_DIR}/empty.c)

	add_custom_command(OUTPUT payload.o
		WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
		COMMAND ${CMAKE_OBJCOPY}
			--add-section=.image=${EMBEDDED_FILE}
			--set-section-flags=.image=contents,alloc,load,readonly,data
			--add-symbol=__start_image=.image:0
			--add-symbol=__end_image=.image:${EMBEDDED_FILE_SIZE}
			$<TARGET_OBJECTS:empty> payload.o
		DEPENDS empty
	)

	set_source_files_properties(payload.o PROPERTIES GENERATED TRUE)
	target_sources(${PROJECT_NAME} PRIVATE payload.o)
endif ()

Would you mind showing an example of this is used and how to access the blob in your application?

@3flares https://github.com/OpenDingux/odbootd/blob/master/odboot-client.c#L459-L461

(void *) &__start_image will get you a pointer to the blob. (void *) &__end_image will point to the end, and by doing some pointer arithmetic you can get the blob size.

@pcercuei That's great! Thanks for the quick response.