How to Use This Section

Every convention this section uses, with a live example of each. The prose explaining the folder ladder and the learning paths lands with the rest of folder 00; what follows is the component gallery, which exists from the first day so that the conventions are visible while the section is being written.

Every page ends with a facts card

Four fixed rows, always in this order. The structure that matters and where it is defined, the code path in a few hops, the command that shows the mechanism on a live system, and the single most common wrong belief about the topic.

Structure

struct vm_area_struct — include/linux/mm_types.h

Pathdo_page_fault() → handle_mm_fault() → handle_pte_fault() → do_anonymous_page()

Observeperf trace -e 'exceptions:page_fault_user' -p $(pgrep -n bash)

TrapA major fault is not a fault that is worse. It is a fault that needed I/O. Most faults your process takes are minor, and minor faults are how ordinary memory allocation works.

Source references are pinned

Every reference into the kernel source names a file and a symbol and never a line number, because line numbers rot within one release. Path resolution happens in fs/namei.c:path_openat(), the allocator lives in mm/page_alloc.c, and handle_mm_fault() is where a fault is resolved.

Labs state where they run

Every lab carries a host badge. QEMU lab needs the virtual machine from Setting Up a Lab; Any Linux runs anywhere; WSL2 OK is explicitly confirmed to work under WSL2. Every lab shows expected output, not just commands.

QEMU labConfirm your lab kernel is the pinned version2 min

1. Boot the lab VM and run:

   uname -r

2. Expected output — the version string starts with the pinned release:

   6.18.0

If it fails: you booted the distribution's kernel rather than the one you built. Check the -kernel argument in your QEMU invocation.

Videos are linked, never stored

Where a talk develops an idea better than a page can, it is embedded. The video stays on its own host; nothing is committed to this repository.

Terminal sessions are replayable

Tool pages carry recorded sessions you can scrub through. They are text, not video — a few kilobytes each — and the decisive output always appears as a code block too, because the player does not render without JavaScript and the offline search cannot index it.

Checking the running kernel version in the lab VM

$ uname -r
6.18.0

Pages end with annotated references

Two to six entries, each saying why you would click it. Never a bare URL.

• Docusaurus admonitions — the five callout types this section uses, and nothing beyond them.
• asciinema player — options and keyboard controls for the recorded terminal sessions above.
• Bootlin Elixir cross-referencer — where every <Src> link in this section points, pinned to v6.18.