.Bx has a new article on boot loaders:
As a teaser here’s the first paragraph:
Welcome neighbors. In this blog I will be publishing notes I have taken on UEFI, BIOS, bootloading, ELF, and other technical topics that interest me and seem to lack documentation or explanation. I will also be keeping a list of UEFI, bootloading, and other resources I have found useful on my resources page. The rest of this post will be a whirlwind toure of bootloading and thus fairly introductory, so if you are already familiar with the world of bootloaders you might as well move on and read something else (although I would like to encourage you to look at the section where I propose new general bootloader terminology). In case you want to stick around for the full blog post I will be discussing: my motivations behind studying bootloading, bootloader terminology, how to navigate the plethora of bootloader implementations, specifications that relate to bootloading, BIOS, UEFI, and how they came to be, and how to write a simple boot sector.