Hook Functions - Dynamic Instrumentation and Monitoring

Hi guys. I want to write a code (or library) which it used AFL and QEMU in order to monitor functions which called by an executable. I have worked with AFL for binary instrumentation and fuzzing. Also, I could find out multiple vulnerabilities in third-party libraries but I can't realize how is it possible I do the task - hooking functions and monitoring the behavior of a program with AFL and Qemu. Any ideas?