freebsd-dev/sys/boot/forth/loader.4th
Roger Pau Monné ca49b3342d loader: implement multiboot support for Xen Dom0
Implement a subset of the multiboot specification in order to boot Xen
and a FreeBSD Dom0 from the FreeBSD bootloader. This multiboot
implementation is tailored to boot Xen and FreeBSD Dom0, and it will
most surely fail to boot any other multiboot compilant kernel.

In order to detect and boot the Xen microkernel, two new file formats
are added to the bootloader, multiboot and multiboot_obj. Multiboot
support must be tested before regular ELF support, since Xen is a
multiboot kernel that also uses ELF. After a multiboot kernel is
detected, all the other loaded kernels/modules are parsed by the
multiboot_obj format.

The layout of the loaded objects in memory is the following; first the
Xen kernel is loaded as a 32bit ELF into memory (Xen will switch to
long mode by itself), after that the FreeBSD kernel is loaded as a RAW
file (Xen will parse and load it using it's internal ELF loader), and
finally the metadata and the modules are loaded using the native
FreeBSD way. After everything is loaded we jump into Xen's entry point
using a small trampoline. The order of the multiboot modules passed to
Xen is the following, the first module is the RAW FreeBSD kernel, and
the second module is the metadata and the FreeBSD modules.

Since Xen will relocate the memory position of the second
multiboot module (the one that contains the metadata and native
FreeBSD modules), we need to stash the original modulep address inside
of the metadata itself in order to recalculate its position once
booted. This also means the metadata must come before the loaded
modules, so after loading the FreeBSD kernel a portion of memory is
reserved in order to place the metadata before booting.

In order to tell the loader to boot Xen and then the FreeBSD kernel the
following has to be added to the /boot/loader.conf file:

xen_cmdline="dom0_mem=1024M dom0_max_vcpus=2 dom0pvh=1 console=com1,vga"
xen_kernel="/boot/xen"

The first argument contains the command line that will be passed to the Xen
kernel, while the second argument is the path to the Xen kernel itself. This
can also be done manually from the loader command line, by for example
typing the following set of commands:

OK unload
OK load /boot/xen dom0_mem=1024M dom0_max_vcpus=2 dom0pvh=1 console=com1,vga
OK load kernel
OK load zfs
OK load if_tap
OK load ...
OK boot

Sponsored by: Citrix Systems R&D
Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D517

For the Forth bits:
Submitted by: Julien Grall <julien.grall AT citrix.com>
2015-01-15 16:27:20 +00:00

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\ Copyright (c) 1999 Daniel C. Sobral <dcs@freebsd.org>
\ All rights reserved.
\
\ Redistribution and use in source and binary forms, with or without
\ modification, are permitted provided that the following conditions
\ are met:
\ 1. Redistributions of source code must retain the above copyright
\ notice, this list of conditions and the following disclaimer.
\ 2. Redistributions in binary form must reproduce the above copyright
\ notice, this list of conditions and the following disclaimer in the
\ documentation and/or other materials provided with the distribution.
\
\ THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
\ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
\ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
\ ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
\ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
\ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
\ OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
\ HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
\ LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
\ OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
\ SUCH DAMAGE.
\
\ $FreeBSD$
s" arch-i386" environment? [if] [if]
s" loader_version" environment? [if]
11 < [if]
.( Loader version 1.1+ required) cr
abort
[then]
[else]
.( Could not get loader version!) cr
abort
[then]
[then] [then]
256 dictthreshold ! \ 256 cells minimum free space
2048 dictincrease ! \ 2048 additional cells each time
include /boot/support.4th
include /boot/color.4th
include /boot/delay.4th
only forth also support-functions also builtins definitions
: bootmsg ( -- )
loader_color? if
." Booting..." cr
else
." Booting..." cr
then
;
: try-menu-unset
\ menu-unset may not be present
s" beastie_disable" getenv
dup -1 <> if
s" YES" compare-insensitive 0= if
exit
then
else
drop
then
s" menu-unset"
sfind if
execute
else
drop
then
s" menusets-unset"
sfind if
execute
else
drop
then
;
: boot
0= if ( interpreted ) get_arguments then
\ Unload only if a path was passed
dup if
>r over r> swap
c@ [char] - <> if
0 1 unload drop
else
s" kernelname" getenv? if ( a kernel has been loaded )
try-menu-unset
bootmsg 1 boot exit
then
load_kernel_and_modules
?dup if exit then
try-menu-unset
bootmsg 0 1 boot exit
then
else
s" kernelname" getenv? if ( a kernel has been loaded )
try-menu-unset
bootmsg 1 boot exit
then
load_kernel_and_modules
?dup if exit then
try-menu-unset
bootmsg 0 1 boot exit
then
load_kernel_and_modules
?dup 0= if bootmsg 0 1 boot then
;
\ ***** boot-conf
\
\ Prepares to boot as specified by loaded configuration files.
: boot-conf
0= if ( interpreted ) get_arguments then
0 1 unload drop
load_kernel_and_modules
?dup 0= if 0 1 autoboot then
;
also forth definitions also builtins
builtin: boot
builtin: boot-conf
only forth definitions also support-functions
include /boot/check-password.4th
\ ***** start
\
\ Initializes support.4th global variables, sets loader_conf_files,
\ processes conf files, and, if any one such file was succesfully
\ read to the end, loads kernel and modules.
: start ( -- ) ( throws: abort & user-defined )
s" /boot/defaults/loader.conf" initialize
include_conf_files
include_nextboot_file
\ Will *NOT* try to load kernel and modules if no configuration file
\ was succesfully loaded!
any_conf_read? if
s" loader_delay" getenv -1 = if
load_xen_throw
load_kernel
load_modules
else
drop
." Loading Kernel and Modules (Ctrl-C to Abort)" cr
s" also support-functions" evaluate
s" set delay_command='load_xen_throw load_kernel load_modules'" evaluate
s" set delay_showdots" evaluate
delay_execute
then
then
;
\ ***** initialize
\
\ Overrides support.4th initialization word with one that does
\ everything start one does, short of loading the kernel and
\ modules. Returns a flag
: initialize ( -- flag )
s" /boot/defaults/loader.conf" initialize
include_conf_files
include_nextboot_file
any_conf_read?
;
\ ***** read-conf
\
\ Read a configuration file, whose name was specified on the command
\ line, if interpreted, or given on the stack, if compiled in.
: (read-conf) ( addr len -- )
conf_files string=
include_conf_files \ Will recurse on new loader_conf_files definitions
;
: read-conf ( <filename> | addr len -- ) ( throws: abort & user-defined )
state @ if
\ Compiling
postpone (read-conf)
else
\ Interpreting
bl parse (read-conf)
then
; immediate
\ show, enable, disable, toggle module loading. They all take module from
\ the next word
: set-module-flag ( module_addr val -- ) \ set and print flag
over module.flag !
dup module.name strtype
module.flag @ if ." will be loaded" else ." will not be loaded" then cr
;
: enable-module find-module ?dup if true set-module-flag then ;
: disable-module find-module ?dup if false set-module-flag then ;
: toggle-module find-module ?dup if dup module.flag @ 0= set-module-flag then ;
\ ***** show-module
\
\ Show loading information about a module.
: show-module ( <module> -- ) find-module ?dup if show-one-module then ;
\ Words to be used inside configuration files
: retry false ; \ For use in load error commands
: ignore true ; \ For use in load error commands
\ Return to strict forth vocabulary
: #type
over - >r
type
r> spaces
;
: .? 2 spaces 2swap 15 #type 2 spaces type cr ;
: ?
['] ? execute
s" boot-conf" s" load kernel and modules, then autoboot" .?
s" read-conf" s" read a configuration file" .?
s" enable-module" s" enable loading of a module" .?
s" disable-module" s" disable loading of a module" .?
s" toggle-module" s" toggle loading of a module" .?
s" show-module" s" show module load data" .?
s" try-include" s" try to load/interpret files" .?
;
: try-include ( -- ) \ see loader.4th(8)
['] include ( -- xt ) \ get the execution token of `include'
catch ( xt -- exception# | 0 ) if \ failed
LF parse ( c -- s-addr/u ) 2drop \ advance >in to EOL (drop data)
\ ... prevents words unused by `include' from being interpreted
then
; immediate \ interpret immediately for access to `source' (aka tib)
only forth also