This paper presents FIT, a Flexible open-source binary code
Instrumentation Toolkit. Unlike existing tools, FIT is truly portable,
with existing backends for the Alpha, x86 and ARM architectures and
the Tru64Unix, Linux and ARM Firmware execution environments. This
paper focuses on some of the problems that needed to be addressed for
providing this degree of portability. It also discusses the trade-off
between instrumentation precision and low overhead.