> The catch is that a process can only have one tracer attached at a time, so it's not possible emulate a foreign operating system while also debugging that pro

> The catch is that a process can only have one tracer attached at a time, so it's not possible emulate a foreign operating system while also debugging that process with, say, GDB. This is actually possible. How? The obvious way... You intercept and emulate ptrace calls with ptrace. https://robert.ocallahan.org/2016/04/using-rr-to-debug-rr.html https://robert.ocallahan.org/2016/04/using-rr-to-debug-rr.ht... explains how this works in practice.