mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-11 12:28:41 +08:00
lguest: documentation I: Preparation
The netfilter code had very good documentation: the Netfilter Hacking HOWTO. Noone ever read it. So this time I'm trying something different, using a bit of Knuthiness. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
dfb68689bf
commit
f938d2c892
58
Documentation/lguest/extract
Normal file
58
Documentation/lguest/extract
Normal file
@ -0,0 +1,58 @@
|
||||
#! /bin/sh
|
||||
|
||||
set -e
|
||||
|
||||
PREFIX=$1
|
||||
shift
|
||||
|
||||
trap 'rm -r $TMPDIR' 0
|
||||
TMPDIR=`mktemp -d`
|
||||
|
||||
exec 3>/dev/null
|
||||
for f; do
|
||||
while IFS="
|
||||
" read -r LINE; do
|
||||
case "$LINE" in
|
||||
*$PREFIX:[0-9]*:\**)
|
||||
NUM=`echo "$LINE" | sed "s/.*$PREFIX:\([0-9]*\).*/\1/"`
|
||||
if [ -f $TMPDIR/$NUM ]; then
|
||||
echo "$TMPDIR/$NUM already exits prior to $f"
|
||||
exit 1
|
||||
fi
|
||||
exec 3>>$TMPDIR/$NUM
|
||||
echo $f | sed 's,\.\./,,g' > $TMPDIR/.$NUM
|
||||
/bin/echo "$LINE" | sed -e "s/$PREFIX:[0-9]*//" -e "s/:\*/*/" >&3
|
||||
;;
|
||||
*$PREFIX:[0-9]*)
|
||||
NUM=`echo "$LINE" | sed "s/.*$PREFIX:\([0-9]*\).*/\1/"`
|
||||
if [ -f $TMPDIR/$NUM ]; then
|
||||
echo "$TMPDIR/$NUM already exits prior to $f"
|
||||
exit 1
|
||||
fi
|
||||
exec 3>>$TMPDIR/$NUM
|
||||
echo $f | sed 's,\.\./,,g' > $TMPDIR/.$NUM
|
||||
/bin/echo "$LINE" | sed "s/$PREFIX:[0-9]*//" >&3
|
||||
;;
|
||||
*:\**)
|
||||
/bin/echo "$LINE" | sed -e "s/:\*/*/" -e "s,/\*\*/,," >&3
|
||||
echo >&3
|
||||
exec 3>/dev/null
|
||||
;;
|
||||
*)
|
||||
/bin/echo "$LINE" >&3
|
||||
;;
|
||||
esac
|
||||
done < $f
|
||||
echo >&3
|
||||
exec 3>/dev/null
|
||||
done
|
||||
|
||||
LASTFILE=""
|
||||
for f in $TMPDIR/*; do
|
||||
if [ "$LASTFILE" != $(cat $TMPDIR/.$(basename $f) ) ]; then
|
||||
LASTFILE=$(cat $TMPDIR/.$(basename $f) )
|
||||
echo "[ $LASTFILE ]"
|
||||
fi
|
||||
cat $f
|
||||
done
|
||||
|
@ -1,5 +1,10 @@
|
||||
/* Simple program to layout "physical" memory for new lguest guest.
|
||||
* Linked high to avoid likely physical memory. */
|
||||
/*P:100 This is the Launcher code, a simple program which lays out the
|
||||
* "physical" memory for the new Guest by mapping the kernel image and the
|
||||
* virtual devices, then reads repeatedly from /dev/lguest to run the Guest.
|
||||
*
|
||||
* The only trick: the Makefile links it at a high address so it will be clear
|
||||
* of the guest memory region. It means that each Guest cannot have more than
|
||||
* about 2.5G of memory on a normally configured Host. :*/
|
||||
#define _LARGEFILE64_SOURCE
|
||||
#define _GNU_SOURCE
|
||||
#include <stdio.h>
|
||||
|
@ -5,3 +5,15 @@ obj-$(CONFIG_LGUEST_GUEST) += lguest.o lguest_asm.o lguest_bus.o
|
||||
obj-$(CONFIG_LGUEST) += lg.o
|
||||
lg-y := core.o hypercalls.o page_tables.o interrupts_and_traps.o \
|
||||
segments.o io.o lguest_user.o switcher.o
|
||||
|
||||
Preparation Preparation!: PREFIX=P
|
||||
Guest: PREFIX=G
|
||||
Drivers: PREFIX=D
|
||||
Launcher: PREFIX=L
|
||||
Host: PREFIX=H
|
||||
Switcher: PREFIX=S
|
||||
Mastery: PREFIX=M
|
||||
Beer:
|
||||
@for f in Preparation Guest Drivers Launcher Host Switcher Mastery; do echo "{==- $$f -==}"; make -s $$f; done; echo "{==-==}"
|
||||
Preparation Preparation! Guest Drivers Launcher Host Switcher Mastery:
|
||||
@sh ../../Documentation/lguest/extract $(PREFIX) `find ../../* -name '*.[chS]' -wholename '*lguest*'`
|
||||
|
47
drivers/lguest/README
Normal file
47
drivers/lguest/README
Normal file
@ -0,0 +1,47 @@
|
||||
Welcome, friend reader, to lguest.
|
||||
|
||||
Lguest is an adventure, with you, the reader, as Hero. I can't think of many
|
||||
5000-line projects which offer both such capability and glimpses of future
|
||||
potential; it is an exciting time to be delving into the source!
|
||||
|
||||
But be warned; this is an arduous journey of several hours or more! And as we
|
||||
know, all true Heroes are driven by a Noble Goal. Thus I offer a Beer (or
|
||||
equivalent) to anyone I meet who has completed this documentation.
|
||||
|
||||
So get comfortable and keep your wits about you (both quick and humorous).
|
||||
Along your way to the Noble Goal, you will also gain masterly insight into
|
||||
lguest, and hypervisors and x86 virtualization in general.
|
||||
|
||||
Our Quest is in seven parts: (best read with C highlighting turned on)
|
||||
|
||||
I) Preparation
|
||||
- In which our potential hero is flown quickly over the landscape for a
|
||||
taste of its scope. Suitable for the armchair coders and other such
|
||||
persons of faint constitution.
|
||||
|
||||
II) Guest
|
||||
- Where we encounter the first tantalising wisps of code, and come to
|
||||
understand the details of the life of a Guest kernel.
|
||||
|
||||
III) Drivers
|
||||
- Whereby the Guest finds its voice and become useful, and our
|
||||
understanding of the Guest is completed.
|
||||
|
||||
IV) Launcher
|
||||
- Where we trace back to the creation of the Guest, and thus begin our
|
||||
understanding of the Host.
|
||||
|
||||
V) Host
|
||||
- Where we master the Host code, through a long and tortuous journey.
|
||||
Indeed, it is here that our hero is tested in the Bit of Despair.
|
||||
|
||||
VI) Switcher
|
||||
- Where our understanding of the intertwined nature of Guests and Hosts
|
||||
is completed.
|
||||
|
||||
VII) Mastery
|
||||
- Where our fully fledged hero grapples with the Great Question:
|
||||
"What next?"
|
||||
|
||||
make Preparation!
|
||||
Rusty Russell.
|
@ -1,5 +1,8 @@
|
||||
/* World's simplest hypervisor, to test paravirt_ops and show
|
||||
* unbelievers that virtualization is the future. Plus, it's fun! */
|
||||
/*P:400 This contains run_guest() which actually calls into the Host<->Guest
|
||||
* Switcher and analyzes the return, such as determining if the Guest wants the
|
||||
* Host to do something. This file also contains useful helper routines, and a
|
||||
* couple of non-obvious setup and teardown pieces which were implemented after
|
||||
* days of debugging pain. :*/
|
||||
#include <linux/module.h>
|
||||
#include <linux/stringify.h>
|
||||
#include <linux/stddef.h>
|
||||
|
@ -1,5 +1,10 @@
|
||||
/* Actual hypercalls, which allow guests to actually do something.
|
||||
Copyright (C) 2006 Rusty Russell IBM Corporation
|
||||
/*P:500 Just as userspace programs request kernel operations through a system
|
||||
* call, the Guest requests Host operations through a "hypercall". You might
|
||||
* notice this nomenclature doesn't really follow any logic, but the name has
|
||||
* been around for long enough that we're stuck with it. As you'd expect, this
|
||||
* code is basically a one big switch statement. :*/
|
||||
|
||||
/* Copyright (C) 2006 Rusty Russell IBM Corporation
|
||||
|
||||
This program is free software; you can redistribute it and/or modify
|
||||
it under the terms of the GNU General Public License as published by
|
||||
|
@ -1,3 +1,16 @@
|
||||
/*P:800 Interrupts (traps) are complicated enough to earn their own file.
|
||||
* There are three classes of interrupts:
|
||||
*
|
||||
* 1) Real hardware interrupts which occur while we're running the Guest,
|
||||
* 2) Interrupts for virtual devices attached to the Guest, and
|
||||
* 3) Traps and faults from the Guest.
|
||||
*
|
||||
* Real hardware interrupts must be delivered to the Host, not the Guest.
|
||||
* Virtual interrupts must be delivered to the Guest, but we make them look
|
||||
* just like real hardware would deliver them. Traps from the Guest can be set
|
||||
* up to go directly back into the Guest, but sometimes the Host wants to see
|
||||
* them first, so we also have a way of "reflecting" them into the Guest as if
|
||||
* they had been delivered to it directly. :*/
|
||||
#include <linux/uaccess.h>
|
||||
#include "lg.h"
|
||||
|
||||
|
@ -1,5 +1,9 @@
|
||||
/* Simple I/O model for guests, based on shared memory.
|
||||
* Copyright (C) 2006 Rusty Russell IBM Corporation
|
||||
/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest
|
||||
* to talk to the Launcher or directly to another Guest. It uses familiar
|
||||
* concepts of DMA and interrupts, plus some neat code stolen from
|
||||
* futexes... :*/
|
||||
|
||||
/* Copyright (C) 2006 Rusty Russell IBM Corporation
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License as published by
|
||||
|
@ -1,6 +1,32 @@
|
||||
/*
|
||||
* Lguest specific paravirt-ops implementation
|
||||
/*P:010
|
||||
* A hypervisor allows multiple Operating Systems to run on a single machine.
|
||||
* To quote David Wheeler: "Any problem in computer science can be solved with
|
||||
* another layer of indirection."
|
||||
*
|
||||
* We keep things simple in two ways. First, we start with a normal Linux
|
||||
* kernel and insert a module (lg.ko) which allows us to run other Linux
|
||||
* kernels the same way we'd run processes. We call the first kernel the Host,
|
||||
* and the others the Guests. The program which sets up and configures Guests
|
||||
* (such as the example in Documentation/lguest/lguest.c) is called the
|
||||
* Launcher.
|
||||
*
|
||||
* Secondly, we only run specially modified Guests, not normal kernels. When
|
||||
* you set CONFIG_LGUEST to 'y' or 'm', this automatically sets
|
||||
* CONFIG_LGUEST_GUEST=y, which compiles this file into the kernel so it knows
|
||||
* how to be a Guest. This means that you can use the same kernel you boot
|
||||
* normally (ie. as a Host) as a Guest.
|
||||
*
|
||||
* These Guests know that they cannot do privileged operations, such as disable
|
||||
* interrupts, and that they have to ask the Host to do such things explicitly.
|
||||
* This file consists of all the replacements for such low-level native
|
||||
* hardware operations: these special Guest versions call the Host.
|
||||
*
|
||||
* So how does the kernel know it's a Guest? The Guest starts at a special
|
||||
* entry point marked with a magic string, which sets up a few things then
|
||||
* calls here. We replace the native functions in "struct paravirt_ops"
|
||||
* with our Guest versions, then boot like normal. :*/
|
||||
|
||||
/*
|
||||
* Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
|
@ -1,3 +1,6 @@
|
||||
/*P:050 Lguest guests use a very simple bus for devices. It's a simple array
|
||||
* of device descriptors contained just above the top of normal memory. The
|
||||
* lguest bus is 80% tedious boilerplate code. :*/
|
||||
#include <linux/init.h>
|
||||
#include <linux/bootmem.h>
|
||||
#include <linux/lguest_bus.h>
|
||||
|
@ -1,4 +1,9 @@
|
||||
/* Userspace control of the guest, via /dev/lguest. */
|
||||
/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
|
||||
* controls and communicates with the Guest. For example, the first write will
|
||||
* tell us the memory size, pagetable, entry point and kernel address offset.
|
||||
* A read will run the Guest until a signal is pending (-EINTR), or the Guest
|
||||
* does a DMA out to the Launcher. Writes are also used to get a DMA buffer
|
||||
* registered by the Guest and to send the Guest an interrupt. :*/
|
||||
#include <linux/uaccess.h>
|
||||
#include <linux/miscdevice.h>
|
||||
#include <linux/fs.h>
|
||||
|
@ -1,5 +1,11 @@
|
||||
/* Shadow page table operations.
|
||||
* Copyright (C) Rusty Russell IBM Corporation 2006.
|
||||
/*P:700 The pagetable code, on the other hand, still shows the scars of
|
||||
* previous encounters. It's functional, and as neat as it can be in the
|
||||
* circumstances, but be wary, for these things are subtle and break easily.
|
||||
* The Guest provides a virtual to physical mapping, but we can neither trust
|
||||
* it nor use it: we verify and convert it here to point the hardware to the
|
||||
* actual Guest pages when running the Guest. :*/
|
||||
|
||||
/* Copyright (C) Rusty Russell IBM Corporation 2006.
|
||||
* GPL v2 and any later version */
|
||||
#include <linux/mm.h>
|
||||
#include <linux/types.h>
|
||||
|
@ -1,3 +1,14 @@
|
||||
/*P:600 The x86 architecture has segments, which involve a table of descriptors
|
||||
* which can be used to do funky things with virtual address interpretation.
|
||||
* We originally used to use segments so the Guest couldn't alter the
|
||||
* Guest<->Host Switcher, and then we had to trim Guest segments, and restore
|
||||
* for userspace per-thread segments, but trim again for on userspace->kernel
|
||||
* transitions... This nightmarish creation was contained within this file,
|
||||
* where we knew not to tread without heavy armament and a change of underwear.
|
||||
*
|
||||
* In these modern times, the segment handling code consists of simple sanity
|
||||
* checks, and the worst you'll experience reading this code is butterfly-rash
|
||||
* from frolicking through its parklike serenity. :*/
|
||||
#include "lg.h"
|
||||
|
||||
static int desc_ok(const struct desc_struct *gdt)
|
||||
|
@ -1,10 +1,11 @@
|
||||
/* This code sits at 0xFFC00000 to do the low-level guest<->host switch.
|
||||
/*P:900 This is the Switcher: code which sits at 0xFFC00000 to do the low-level
|
||||
* Guest<->Host switch. It is as simple as it can be made, but it's naturally
|
||||
* very specific to x86.
|
||||
*
|
||||
* You have now completed Preparation. If this has whet your appetite; if you
|
||||
* are feeling invigorated and refreshed then the next, more challenging stage
|
||||
* can be found in "make Guest". :*/
|
||||
|
||||
There is are two pages above us for this CPU (struct lguest_pages).
|
||||
The second page (struct lguest_ro_state) becomes read-only after the
|
||||
context switch. The first page (the stack for traps) remains writable,
|
||||
but while we're in here, the guest cannot be running.
|
||||
*/
|
||||
#include <linux/linkage.h>
|
||||
#include <asm/asm-offsets.h>
|
||||
#include "lg.h"
|
||||
|
Loading…
Reference in New Issue
Block a user