Within the context of security and user freedom, firmware is often regarded as a necessary evil - an inescapable gatekeeper whose involvement and even permission is required before the software you actually want to run can start. While open source bootloaders and firmware have been written for some platforms and even the notion of Linux as a bootloader is not unprecedented, there is almost always some other code open or not that runs first and so at least one more thing to understand and trust.

This begs the question: could a highly specialized embedded Linux kernel be prepared such that it itself can act as the target of the CPU's reset vector - in other words: can the first instruction my CPU executes be from Linux?

Certainly a very open and well documented hardware platform would be required, as would customizing and minimizing the footprint of the kernel to the max, but even so trying to answer that question led me definitively into the unknown, off the beaten path, and down a wild goose chase through some of the most obscure, unexplored, and tricky corners of the Linux kernel, the RISC-V specification, and the SiFive FU540-C000 platform.

This talk will try to tell the whole story, shedding light on hardware bringup, emulation vs reality, the Linux kernel development process, and what your CPU and firmware are really doing.