Another is the build infrastructure. Right now, you can only use Rust on platforms that the official Rust compiler compiles for, which is a lot narrower set tha

Another is the build infrastructure. Right now, you can only use Rust on platforms that the official Rust compiler compiles for, which is a lot narrower set than where Linux runs. The long-term solution for this are the various GCC Rust projects, but those are still ways out. Correspondingly, there are a lot of kernel subsystems where Rust is not welcome until those projects mature.