There is an almost all-Smalltalk bare metal system for X86, CogNOS. It runs on top of NopSys, about 3500 lines of C and 600 lines of assembler for booting, accessing device registers, and responding to interrupts. But the file system etc. are in Smalltalk.
Do you know anything about the status of this project? I started following it on Github a couple of years ago when it appeared but it does not seem like anyone is working on it