doc/paging.9

.\" Kernel paging docs, largely as a reference for myself.
.TH paging 9 "18 February 2021" "1" "Paging"
.SH NAME
Paging - kernel memory paging overview
.SH SYNOPSIS
Paging allows the kernel to map arbitrary virtual memory addresses to
locations in physical memory.
.SH DESCRIPTION
On x86 each page is fixed at 4kb.  Mapping each 4kb page for the
entire memory takes a lot of space, so instead,
.B
page directories
.NB
and
.B
page tables
.NB
are used.  The kernel stores one or more page directories, each of
which contains 1024 pointers to page tables (which may be null), each
of which in turn contains 1024
.B
page table entries
.NB

Each page table entry contains the upper 20 bits of the physical
memory location it maps to
.B
(frame).
.NB
It also contains several flags describing if the page is readable or
writable in user mode, as well as flags set by the CPU: such as if the
page has been accessed or modified.
.SH SEE ALSO
src/paging.c, src/paging.h, Intel manual volume 4, Figure 4-4.