Learn a higher-level "rehosting" approach to emulating embedded Linux systems in this 38-minute DEF CON 33 conference talk. Discover how to avoid modifying userspace or firmware images by building patched Linux kernels and using modified QEMU machines to model system terrain as closely as possible to what userspace firmware expects. Explore the reverse-engineering process of userspace binaries and libraries, examine GPL code analysis techniques, and understand how to write kernel patches and dummy drivers while making reactive QEMU changes. Master the methodology for creating rehosting environments that appear nearly identical to real systems from a userspace perspective, enabling firmware to run essentially unimpeded through this hybrid emulation framework.