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Learning about the miracle of boot
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pantonshire ae2720c826 library-ify nasm helper 9 months ago
boot1 print to vga on panic 1 year ago
buildtools library-ify nasm helper 9 months ago
elf fix hexdump alignment for non-multiple-of-16 size 1 year ago
include refactor + wip bios call from protected mode 1 year ago
memregion_merge memory region merge algorithm 12 months ago
patches add seabios as submodule 1 year ago
seabios@e5f2e4c696 add seabios as submodule 1 year ago
.gitignore start elf parser 1 year ago
.gitmodules add seabios as submodule 1 year ago
boot0.s refactor + wip bios call from protected mode 1 year ago
boot1.s enter unreal mode 1 year ago
justfile enable a20 in stage 2 prelude 1 year ago
readme.md enable a20 1 year ago
resources.md update resources 1 year ago

readme.md

Overview

Currently we boot from BIOS on a GPT-partitioned disk.

boot0.s is the first-stage bootloader. It lives in the MBR bootstrap field, and must therefore fit into 440 bytes. Its tasks are:

  • Set up a stack etc.
  • Get the boot drive geometry
  • Load and parse the GPT
  • Find the partition of the second stage
  • Load and jump to the first sector of the second stage

boot1.s is the second-stage bootloader. Its tasks are:

  • Load its own sectors not loaded by the first stage
  • Enable A20
  • Detect available memory
  • Enter unreal mode
  • Read the kernel ELF from disk (don't have to parse the ELF just yet)
  • Get all the useful information we can from the BIOS before we leave unreal mode
  • Enter long mode (possibly via protected mode?)
  • Load the kernel ELF
  • Initialise stack etc. for the kernel
  • Jump to kernel