Operating Systems · Cluster
Boot and Firmware
Firmware handoff, init, and early boot.
- 01 The Reset Vector and the First Instruction Executed Why an x86 processor begins executing at 0xFFFFFFF0 in real mode, how that address reaches the firmware ROM, and what the sixteen bytes at the top of memory must contain.
- 02 How Firmware Describes Physical Memory to the Kernel The E820 and UEFI memory map formats, why reserved ranges outnumber usable ones, and how the kernel turns a list of address ranges into its own page allocator.
- 03 Why Boot Loaders Are Split Into Stages The 512-byte first sector, the real-mode address space that constrains where a second stage can live, and how chainloading hands control from firmware to a loader to a kernel.
- 04 Entering Long Mode From a Boot Loader The exact register sequence that turns on 64-bit addressing on x86-64, why paging must be enabled in the same instruction that commits to long mode, and the page tables that must exist beforehand.
- 05 Kernel Decompression and Physical Relocation Why a compressed kernel image relocates itself before decompressing, how the position-independent stub finds free memory, and what has to change in the page tables when the kernel moves.
- 06 Early Console Output Before Drivers Exist How a kernel prints messages before it has a driver for any display or serial device, why the framebuffer left by firmware is the usual answer, and what early output costs when it is a polling loop.
- 07 From the First Kernel Thread to PID 1 How the kernel creates its initial task, what changes when that task returns to user mode, and why the first user-space process must be a single-threaded, privileged program that never exits.
- 08 Unpacking an Initramfs and Switching to the Real Root How the kernel unpacks a compressed cpio archive into a temporary filesystem, what pivot_root and switch_root change, and why the old root cannot simply be unmounted.
- 09 Measured Boot and the Chain of Trust From Firmware to Kernel How each boot stage hashes the next into a TPM before executing it, why the measurements go into append-only PCRs, and what an attestation actually proves about a running system.
- 10 Kexec: Booting a Second Kernel Without Firmware How a running kernel loads a replacement image into reserved memory, what the relocation blob does during the jump, and why the crash kernel needs its own reservation and its own devices.