One (more) thing that is conspicuously glossed over is non-ELF executables. We've seen Win32 programs invoking ELF64 binaries demonstrated. And of course the Windows NT Linux subsystem already "knows" that it's a Linux subsystem process when a program comes to exec() a script, and doesn't have to worry about checking binary formats over fork() because the program image doesn't change. But missing so far has been Win32 programs invoking Linux executable scripts, that have #! lines.