a question about btfixupprep

Hi, in arch/sparc/boot/Makefile, there is a rule below. $(obj)/btfix.S: $(obj)/btfixupprep vmlinux FORCE $(call if_changed,btfix) This makes btfix.S file using btfixupprep executable. and from the definition below, quiet_cmd_btfix = BTFIX $@ cmd_btfix = $(OBJDUMP) -x vmlinux | $(obj)/btfixupprep > $@ I can see to make the btfix.S, the make runs objdump -x vmlinux | btfixupprep > btfix.S What does btfixupprep do? maybe relocations? or function name substitution(for sub architecture)? Regards, Chan