Alpha Miniloader Howto
David A. Rusling, david.rusling@reo.mts.dec.com
v0.84, 6 December 1996
This document describes the Miniloader, a program for Alpha based sys�
tems that can be used to initialize the machine and load Linux. The
Alpha Linux Miniloader (to give it it's full name) is also known as
MILO.
1. Introduction
This document describes the Miniloader for Linux on Alpha AXP (MILO).
This firmware is used to initialize Alpha AXP based systems, load and
start Linux and, finally, provide PALcode for Linux.
1.1. Copyright
The Alpha Miniloader (MILO) HOWTO is copyright (C) 1995, 1996 David A
Rusling.
Copyright. Like all Linux HOWTO documents, it may be reproduced and
distributed in whole or in part, in any medium, physical or
electronic, so long as this copyright notice is retained on all
copies. Commercial redistribution is allowed and encouraged; however
the author would like to be notified of such distributions. You may
translate this HOWTO into any language whatsover provided that you
leave this copyright statement and disclaimer intact, and that you
append a notice stating who translated the document.
Disclaimer. While I have tried to include the most correct and up to
date information available to me, I cannot guarantee that usage of
information in this document does not result in loss of data or
equipment. I provide NO WARRENTY about the information in the HOWTO
and I cannot be made liable for any consequences resulting from using
the information in this HOWTO.
1.2. New Versions of this Document
The latest version of this document can be found in
<ftp://gatekeeper.dec.com/pub/Digital/Linux-Alpha/Miniloader/docs> and
David Mosberger-Tang is kind enough to include the html form of it in
his excellent Linux Alpha FAQ site
<http://www.azstarnet.com/~axplinux>.
2. What is MILO?
On Intel based PC systems, the BIOS firmware sets up the system and
then loads the image to be run from the boot block of a DOS file
system. This is more or less what MILO does on an Alpha based system,
however there are several interesting differences between BIOS
firmware and MILO, not least of which is that MILO includes and uses
standard Linux device drivers unmodified. MILO is firmware, unlike
LILO, which relies on the BIOS firmware to get itself loaded. The
main functional parts of MILO are:
1. PALcode,
2. Memory set up code (builds page tables and turns on virtual
addressing),
3. Video code (BIOS emulation code and TGA (21030)),
4. Linux kernel code. This includes real Linux kernel code (for
example, the interrupt handling) and ersatz or mock Linux kernel,
5. Linux block device drivers (for example, the floppy driver),
6. File system support (ext2, MS-DOS and ISO9660),
7. User inteface code (MILO),
8. Kernel interface code (sets up the HWRPB and memory map for linux),
9. NVRAM code for managing environment variables.
The following paragraphs describe these functional parts in more
detail.
PALcode can be thought of as a tiny software layer that tailors the
chip to a particular operating system. It runs in a special mode
(PALmode) which has certain restrictions but it uses the standard
Alpha instruction set with just five extra instructions. In this way,
the Alpha chip can run such diverse operating systems as Windows NT,
OpenVMS, Digital Unix and, of course, Linux. The PALcode that MILO
uses (and therefore Linux itself) is, like the rest of MILO, freeware.
It is derived from Digital's Evaluation Board software example Digital
Unix PALcode.. The differences between the different PALcodes are
because of differences in address mapping and interrupt handling that
exist between the Alpha chips (21066 based systems have a different
I/O map to 21064+2107x systems) and different Alpha based systems.
For MILO to operate properly it needs to know what memory is
available, where Linux will eventually be running from and it must be
able to allocate temporary memory for the Linux device drivers. The
code maintains a memory map that has entries for permanent and
temporary allocated pages. As it boots, MILO uncompresses itself into
the correct place in physical memory. When it passes control to the
Linux kernel, it reserves memory for the compressed version of itself,
the PALcode (which the kernel needs) and some data structures. This
leaves most of the memory in the system for Linux itself.
The final act of the memory code is to set up and turn on virtual
addressing so that the data structures that Linux expects to see are
at the correct place in virtual memory.
MILO contains video code that initialises and uses the video device
for the system. It will detect and use a VGA device if there is one,
otherwise it will try to use a TGA (21030) video device. Failing
that, it will assume that there is no graphics device. The BIOS
emulation that the standard, pre-built, images include is Digital's
own BIOS emulation which supports most, if not all, of the standard
graphics devices available.
Linux device drivers live within the kernel and expect certain
services from the kernel. Some of these services are provided
directly by Linux kernel code, for example the interrupt handling and
some is provided by kernel look-alike routines.
MILO's most powerful feature is that you can embed unaltered Linux
device drivers into it. This gives it the potential to support every
device that Linux does. MILO includes all of the block devices that
are configured into the Linux kernel that it is built against as well
as a lot of the block device code (for example, ll_rw_blk()).
MILO loads the Linux kernel from real file systems rather than from
boot blocks and other strange places. It understands MSDOS, EXT2 and
ISO9660 filesystems. Gzip'd files are supported and these are
recommended, particularly if you are loading from floppy which is
rather slow. MILO recognises these by their .gz suffix.
Built into MILO is a simple keyboard driver which, together with an
equally simple video driver allows it to have a simple user interface.
That interface allows you to list file systems on configured devices,
boot Linux or run flash update utilities and set environment variables
that control the system's booting. Like LILO, you can pass arguments
to the Kernel.
MILO must tell the Linux kernel what sort of system this is, how much
memory there is and which of that memory is free. It does this using
the HWRPB (Hardware Restart Parameter Block) data structure and
associated memory cluster descriptions. These are placed at the
appropriate place in virtual memory just before control is passed to
the Linux kernel.
3. Pre-Built Standard MILO Images.
If you are planning to run Linux on a standard Alpha based system,
then there are pre-built "standard" MILO images that you might use.
These (along with the sources and other interesting stuff) can be
found in <ftp://gatekeeper.dec.com/pub/Digital/Linux-
Alpha/Miniloader>.
The images subdirectory contains a directory per standard system (eg
AlphaPC64) with MILO images having the following naming convention:
1. MILO - Miniloader executable image, this image can be loaded in a
variety of ways,
2. fmu.gz - Flash management utility,
3. MILO.dd - Boot block floppy disk image. These should be written
using rawrite.exe or dd on Linux.
The test-images, like the images subdirectory contains a directory per
standard system. These images are somewhat experimental but tend to
contain all the latest features.
4. How To Build MILO
You build MILO seperately from the Kernel. As MILO requires parts of
the kernel to function (for example interrupt handling) you must first
configure and build the kernel that matches with MILO that you want to
build. Mostly this means building the kernel with the same version
number. So, MILO-2.0.25.tar.gz will build against
linux-2.0.25.tar.gz. MILO may build against a higher version of the
kernel, but there again it may not. Also, now that ELF shared
libraries are fully supported, there are two versions of the MILO
sources. To build under an ELF system you must first unpack the
standard MILO sources and then patch those sources with the same
version numbered ELF patch. In the remainder of this discussion, I
assume that your kernel sources and object files are stored in the
subtree at /usr/src/linux and that the linux kernel has been fully
built with the command make boot
To build MILO, change your working directory to the MILO source
directory and invoke make with:
$ make KSRC=/usr/src/linux config
Just like the Linux kernel, you will be asked a series of questions
Echo output to the serial port (MINI_SERIAL_ECHO) [y]
It's a good idea to echo kernel printk to /dev/ttyS0 if you can. If
you can (and want to), then type "y", otherwise "n". All of the
standard, pre-built, MILO images include serial port I/O using COM1.
Use Digital's BIOS emulation code (not free) (MINI_DIGITAL_BIOS_EMU) [y]
This code is included as a library which is freely distributable so
long as it is used on an Alpha based system. The sources are not
available. If you answer n then the freeware alternative BIOS
emulation will be built. It's sources are included with MILO. Note
that you cannot right now build choose Digital's BIOS emulation code
in an ELF system (the library is not yet ready) and so you must answer
no to this question.
Build PALcode from sources (Warning this is dangerous) (MINI_BUILD_PALCODE_FROM_SOURCES) [n]
You should only do this if you have changed the PALcode sources,
otherwise use the standard, pre-built PALcode included with MILO.
You are now all set to build the MILO image itself:
$ make KSRC=/usr/src/linux
When the build has successfully completed, the MILO image is in the
file called milo. There are a lot of images called milo.*, these
should be ignored.
5. How To Load MILO
The most commonly supported method of loading MILO is from the Windows
NT ARC firmware as most shipping systems support this. However, there
are a wide variety of loading MILO. It may be loaded from:
� a failsafe boot block floppy,
� the Windows NT ARC firmware,
� Digital's SRM console,
� an Alpha Evaluation Board Debug Monitor,
� flash/ROM.
5.1. Loading MILO from the Windows NT ARC firmware
Most, if not all, Alpha AXP based systems include the Windows NT ARC
firmware and this is the prefered method of booting MILO and thus
Linux. Once the Windows NT firmware is running and you have the
correct MILO image for your system, this method is completely generic.
The Windows NT ARC firmware is an environment in which programs can
run and make callbacks into the firmware to perform actions. The
Windows NT OSLoader is a program that does exactly this. Linload.exe
is a much simpler program which does just enough to load and execute
MILO. It loads the appropriate image file into memory at 0x00000000
and then makes a swap-PAL PALcall to it. MILO, like Linux, uses a
different PALcode to Windows NT which is why the swap has to happen.
MILO relocates itself to 0x200000 and continues on through the PALcode
reset entry point as before.
Before you add a Linux boot option, you will need to copy linload.exe
and the appropriate MILO that you wish to load to someplace that the
Windows NT ARC firmware can read from. In the following example, I
assume that you are booting from a DOS format floppy disk:
1. At the boot menu, select "Supplementary menu..."
2. At the "Supplementary menu", select "Set up the system..."
3. At the "Setup menu", select "Manage boot selection menu..."
4. In the "Boot selections menu", choose "Add a boot selection"
5. Choose "Floppy Disk 0"
6. Enter "linload.exe" as the osloader directory and name
7. Say "yes" to the operating system being on the same partition as
the osloader
8. Enter "
9. I usually enter "Linux" as the name for this boot selection
10.
Say "No" you do not want to initialise the debugger at boot time
11.
You should now be back in the "Boot selections menu", choose the
"Change a boot selection option" and pick the selection you just
created as the one to edit
12.
Use the down arrow to get "OSLOADFILENAME" up and then type in the
name of the MILO image that you wish to use, for example
"noname.arc" followed by return.
13.
Press ESC to get back to the "Boot Selections menu"
14.
Choose "Setup Menu" (or hit ESC again) and choose "Supplementary
menu, and save changes" option
15.
ESC will get you back to the "Boot menu" and you can attempt to
boot MILO. If you do not want Linux as the first boot option, then
you can alter the order of the boot options in the "Boot selections
menu".
At the end of all this, you should have a boot selection that looks
something like:
LOADIDENTIFIER=Linux
SYSTEMPARTITION=multi(0)disk(0)fdisk(0)
OSLOADER=multi(0)disk(0)fdisk(0)\linload.exe
OSLOADPARTITION=multi(0)disk(0)fdisk(0)
OSLOADFILENAME=\noname.arc
OSLOADOPTIONS=
You can now boot MILO (and then Linux). You can load linload.exe and
MILO directly from a file system that Windows NT understands such as
NTFS or DOS on a hard disk.
The contents OSLOADOPTIONS are passed to MILO which interprets it as a
command. So, in order to boot Linux directly from Windows NT without
pausing in MILO, you could pass the following in OSLOADOPTIONS:
boot sda2:vmlinux.gz root=/dev/sda2
See ``MILO's User Interface'' for more information on the commands
available.
Another (rather sneaky) way of loading of loading MILO via the WNT ARC
firmware is to put MILO onto an MS-DOS floppy and call it fwupdate.exe
and then choose the "Upgrade Firmware" option.
5.2. Loading MILO from the Evaluation Board Debug Monitor
Evaluation boards (and often designs cloned from them) include support
for the Alpha Evaluation Board Debug Monitor. Consult your system
document before considering this method of booting MILO. The
following systems are known to include Debug Monitor support:
� AlphaPC64 (Section ``AlphaPC64'')
� EB64+ (Section ``EB64+'')
� EB66+ (Section ``EB66+'')
� EB164 (Section ``EB164'')
� PC164 (Section ``PC164'')
Before you consider this method, you should note that the early
versions of the Evaluation Board Debug Monitor did not include video
or keyboard drivers and so you must be prepared to connect another
system via the serial port so that you can use the Debug Monitor. Its
interface is very simple and typing help shows a whole heap of
commands. The ones that are most interesting include the word boot or
load in them.
The Evaluation Board Debug Monitor can load an image either via the
network (netboot) or via a floppy (flboot). In either case, set the
boot address to 0x200000 (> bootadr 200000) before booting the image.
If the image is on floppy (and note that only DOS formatted floppies
are supported), then you will need to type the following command:
AlphaPC64> flboot <MILO-image-name>
5.3. Loading MILO from a Failsafe Boot Block Floppy
Only the AxpPCI33 is known to include failsafe boot block floppy
support (Section < id="noname-section" name="Noname">).
If you do not have a standard pre-built MILO .dd image, then you may
need to build an SRM boot block floppy. Once you have built MILO, you
need to do the following on Digital Unix box:
fddisk -fmt /dev/rfd0a
cat mboot bootm > /dev/rfd0a
disklabel -rw rfd0a 'rx23' mboot bootm
Or on a Linux box:
cat mboot bootm > /dev/fd0
If you have a standard MILO image available (say MILO.dd) then you
would build a boot block floppy using the following command:
dd if=MILO.dd of=/dev/fd0
5.4. Loading MILO from Flash
There are a number of systems where MILO can be blown into flash and
booted directly (instead of via the Windows NT ARC firmware):
� AlphaPC64 (Section ``AlphaPC64'')
� Noname (Section ``Noname'')
� EB66+ (Section ``EB66+'')
� EB164 (Section ``EB164'')
� PC164 (Section ``PC164'')
5.5. Loading MILO from the SRM Console
The SRM (short for System Reference Manual) Console knows nothing
about filesystems or disk-partitions, it simply expects that the
secondary bootstrap loader occupies a consecutive range of physical
disk sectors starting from a given offset. The information
describing the secondary bootstrap loader (its size and offset) is
given in the first 512 byte block. To load MILO via the SRM you must
generate that structure on a device which the SRM can access (such as
a floppy disk). This is what mboot and bootm, mboot is the first
block (or boot description) and mboot is the MILO image rounded up to
a 512 byte boundary.
To load MILO from a boot block device, either build mboot and bootm
and push them onto the boot device using the following command:
$ cat mboot bootm > /dev/fd0
Or, grab the appropriate MILO.dd from a web site and write it onto the
boot device using either RAWRITE.EXE or dd.
Once you have done that you can boot the SRM console and use one of
its many commands to boot MILO. For example, to boot MILO from a
boot block floppy you would use the following command:
>>>boot dva0
(boot dva0.0.0.0.1 -flags 0)
block 0 of dva0.0.0.0.1 is a valid boot block
reading 621 blocks from dva0.0.0.0.1
bootstrap code read in
base = 112000, image_start = 0, image_bytes = 4da00
initializing HWRPB at 2000
initializing page table at 104000
initializing machine state
setting affinity to the primary CPU
jumping to bootstrap code
MILO Stub: V1.1
Unzipping MILO into position
Allocating memory for unzip
####...
The following systems are known to have SRM Console support:
� Noname (Section ``Noname'')
� AlphaPC64 (Section ``AlphaPC64'')
� EB164 (Section ``EB164'')
� PC164 (Section ``PC164'')
5.6. System Specific Information
5.6.1. AxpPCI33 (Noname)
The Noname board can load MILO from the Windows NT ARC firmware
(Section ``booting from Windows NT ARC firmware''), from the SRM
Console (Section ``Loading MILO from the SRM Console''). and from a
failsafe boot block floppy (Section ``Loading from a Failsafe Boot
Block Floppy''). A flash management utility, runnable from MILO is
available so that once MILO is running, it can be blown into flash
(Section ``running the flash management utility''). However, be
warned that once you have done this you will lose the previous image
held there as there is only room for one image.
The way that Noname boots is controlled by a set of jumpers on the
board, J29 and J28. These look like:
4
J29 2 x x x 6
1 x x x 5
J28 2 x x x 6
1 x x x 5
3
The two options that we're interested in are J28, pins 1-3 which boots
the console/loader from flash and J29, pins 1-3 which boots the
console/loader from a boot block floppy. The second option is the one
that you need to first boot MILO on the Noname board.
Once you've selected the boot from floppy option via the jumpers, put
the SRM boot block floppy containing MILO into the floppy and reboot.
In a few seconds (after the floppy light goes out) you should see the
screen blank to white and MILO telling you what's going on.
If you are really interested in technical stuff, the Noname loads
images off of the floppy into physical address 0x104000 and images
from flash into 0x100000. For this reason, MILO is built with it's
PALcode starting at 0x200000. When it is first loaded, it moves
itself to the correct location (see relocate.S).
5.6.2. AlphaPC64 (Cabriolet)
The AlphaPC64 includes the Windows NT ARC firmware (Section ``booting
from Windows NT ARC firmware''), the SRM Console (Section ``Loading
MILO from the SRM Console'') and the Evaluation Debug Monitor (Section
``Loading from the Debug Monitor''). These images are in flash and
there is room to add MILO so that you can boot MILO directly from
flash. A flash management utility, runnable from MILO is available so
that once MILO is running, it can be blown into flash (Section
``running the flash management utility''). This system supports MILO
environment variables.
You select between the boot options (and MILO when it is been put into
flash) using a combination of jumpers and a boot option which is saved
in the NVRAM of the TOY clock.
The jumper is J2, SP bits 6 and 7 have the following meanings:
� SP bit 6 should always be out. If this jumper is set then the SROM
mini-debugger gets booted,
� SP bit 7 in is boot image selected by the boot option byte in the
TOY clock,
� SP bit 7 out is boot first image in flash.
So, with bit 7 out, the Debug Monitor will be booted as it is always
the first image in flash. With bit 7 in, the image selected by the
boot option in the TOY clock will be selected. The Debug Monitor, the
Windows NT ARC firmware and MILO all support setting this boot option
byte but you must be very careful using it. In particular, you cannot
set the boot option so that next time the system boots MILO when you
are running the Windows NT ARC firmware, it only allows you to set
Debug Monitor or Windows NT ARC as boot options.
To get MILO into flash via the Evaluation Board Debug Monitor, you
will need a flashable image. The build proceedures make MILO.rom, but
you can also make a rom image using the makerom tool in the Debug
Monitor software that comes with the board:
> makerom -v -i7 -l200000 MILO -o mini.flash
(type makerom to find out what the arguments mean, but 7 is a flash
image id used by the srom and -l200000 gives the load address for the
image as 0x200000).
Load that image into memory (via the Debug Monitor commands flload,
netload, and so on) at 0x200000 and then blow the image into flash:
AlphaPC64> flash 200000 8
(200000 is where the image to be blown is in memory and 8 is the
segment number where you put the image. There are 16 1024*64 byte
segments in the flash and the Debug Monitor is at seg 0 and the
Windows NT ARC firmware is at seg 4).
Set up the image that the srom will boot by writing the number of the
image into the TOY clock.
AlphaPC64> bootopt 131
(131 means boot the 3rd image, 129 = 1st, 130 = 2nd and so on).
Power off, put jumper 7 on and power on and you should see the MILO
burst into life. If you don't then take jumper 7 back off and reboot
the Debug Monitor.
5.6.3. EB66+
The EB66+, like all of the Alpha Evaluation Boards built by Digital
contains the Evaluation Board Debug Monitor and so this is available
to load MILO (Section ``Loading from the Debug Monitor''). Quite
often (although not always) boards whose design is derived from these
include the Debug Monitor also. Usually, these boards include the
Windows NT ARC firmware (Section ``booting from Windows NT ARC
firmware''). A flash management utility, runnable from MILO is
available so that once MILO is running, it can be blown into flash
(Section ``running the flash management utility''). This system
supports MILO environment variables.
These systems have several boot images in flash controlled by jumpers.
The two jumper banks are J18 and J16 and are located at the bottom of
the board in the middle (if the Alpha chip is at the top). You select
between the boot options (and MILO when it is been put into flash)
using a combination of jumpers and a boot option which is saved in the
NVRAM of the TOY clock.
Jumper 7-8 of J18 in means boot the image described by the boot
option. Jumper 7-8 of J18 out means boot the Evaluation Board Debug
Monitor.
Blowing an image into flash via the Evaluation Board Debug Monitor is
exactly the same proceedure as for the AlphaPC64 (Section
``AlphaPC64'').
5.6.4. EB64+/Aspen Alpine
This system is quite like the AlphaPC64 except that it does not
contain flash which MILO can be loaded from. The EB64+ has two ROMs,
one of which contains the Windows NT ARC firmware (Section ``booting
from Windows NT ARC firmware''). and the other contains the
Evaluation Board Debug Monitor (Section ``Loading from the Debug
Monitor'').
The Aspen Alpine is a little different in that it only has one ROM;
this contains the Windows NT ARC firmware.
5.6.5. Universal Desktop Box (Multia)
This is a very compact pre-packaged 21066 based system that includes a
TGA (21030) graphics device. Although you can just fit a half height
PCI graphics card in the box you are better off waiting for full TGA
support in XFree86. It includes the Windows NT ARC firmware and so
booting from that is the prefered method (Section ``Loading from
Windows NT'').
5.6.6. EB164
The EB164, like all of the Alpha Evaluation Boards built by Digital
contains the Evaluation Board Debug Monitor and so this is available
to load MILO (Section ``Loading from the Debug Monitor''). Quite
often (although not always) boards whose design is derived from these
include the Debug Monitor also. Usually, these boards include the
Windows NT ARC firmware (Section ``booting from Windows NT ARC
firmware''). The SRM console is also available (Section ``Loading
MILO from the SRM Console''). A flash management utility, runnable
from MILO is available so that once MILO is running, it can be blown
into flash (Section ``running the flash management utility''). This
system supports MILO environment variables.
These systems have several boot images in flash controlled by jumpers.
The two jumper bank is J1 and is located at the bottom of the board on
the left (if the Alpha chip is at the top). You select between the
boot options (and MILO when it is been put into flash) using a
combination of jumpers and a boot option which is saved in the NVRAM
of the TOY clock.
Jumper SP-11 of J1 in means boot the image described by the boot
option. Jumper SP-11 of J1 out means boot the Evaluation Board Debug
Monitor.
Blowing an image into flash via the Evaluation Board Debug Monitor is
exactly the same proceedure as for the AlphaPC64 (Section
``AlphaPC64'').
5.6.7. PC164
The PC164, like all of the Alpha Evaluation Boards built by Digital
contains the Evaluation Board Debug Monitor and so this is available
to load MILO (Section ``Loading from the Debug Monitor''). Quite
often (although not always) boards whose design is derived from these
include the Debug Monitor also. Usually, these boards include the
Windows NT ARC firmware (Section ``booting from Windows NT ARC
firmware''). The SRM console is also available (Section ``Loading
MILO from the SRM Console''). A flash management utility, runnable
from MILO is available so that once MILO is running, it can be blown
into flash (Section ``running the flash management utility''). This
system supports MILO environment variables.
These systems have several boot images in flash controlled by jumpers.
The main jumper block, J30, contains the system configuration jumpers
and jumper CF6 in means that the system will boot the Debug Monitor,
the default is out.
Blowing an image into flash via the Evaluation Board Debug Monitor is
exactly the same proceedure as for the AlphaPC64 (Section
``AlphaPC64'').
5.6.8. XL266
The XL266 is one of a family of systems that are known as Avanti. It
has a riser card containing the Alpha chip and cache which plugs into
the main board at right angles. This board can replace the
equivalent Pentium board.
Some of these systems ship with the SRM console but others, notably
the XL266 ship with only the Windows NT ARC firmware (Section
``booting from Windows NT ARC firmware'').
Here is my list of compatible systems:
� AlphaStation 400 (Avanti),
� AlphaStation 250,
� AlphaStation 200 (Mustang),
� XL. There are two flavours, XL266 and XL233 with the only
difference being in processor speed and cache size.
Note The system that I use to develop and test MILO is an XL266 and so
this is the only one that I can guarentee will work. However,
technically, all of the above systems are equivalent; they have the
same support chipsets and the same interrupt handling mechanisms.
5.6.9. Platform2000
This is a 233Mhz 21066 based system.
6. MILO's User Interface
Once you have correctly installed/loaded/run MILO you will see the
MILO (for MIniLOader) prompt displayed on your screen. There is a
very simple interface that you must use in order to boot a particular
Linux kernel image. Typing "help" is a good idea as it gives a useful
summary of the commands.
6.1. The ''help'' Command
Probably the most useful command that MILO has:
MILO> help
MILO command summary:
ls [-t fs] [dev:[dir]]
- List files in directory on device
boot [-t fs] [dev:file] [boot string]
- Boot Linux from the specified device and file
run [-t fs] dev:file
- Run the standalone program dev:file
show - Display all known devices and file systems
set VAR VALUE - Set the variable VAR to the specified VALUE
unset VAR - Delete the specified variable
reset - Delete all variables
print - Display current variable settings
help [var] - Print this help text
Devices are specified as: fd0, hda1, hda2, sda1...
Use the '-t filesystem-name' option if you want to use
anything but the default filesystem ('ext2').
Use the 'show' command to show known devices and filesystems.
Type 'help var' for a list of variables.
Note that the bootopt command only appears on AlphaPC64 (and similar)
systems. Refer to the board's dcoumentation to find out just what it
means.
Devices. Until you use a command that needs to make use of a device,
no device inititalisation will take place. The first show, ls, boot
or run commands all cause the devices within MILO to be initialised.
Devices are named in the same way (exactly) that Linux itself will
name them. So, the first IDE disk will be called 'hda' and it's first
partition will be 'hda1'. Use the show command to show what devices
are available.
File Systems. MILO supports three file systems, MSDOS, EXT2 and
ISO9660. So long as a device is available to it, MILO can listboot or
run an image stored on one of these file systems. MILO's default file
system is EXT2 and so you have tell MILO that the file system is
something other than that. All of the commands that use filenames
allow you to pass the file system using the -t [filesystem]option.
So, if you wanted to list the contents of a SCSI CD ROM, you might
type the following:
MILO> ls -t iso9660 scd0:
Variables. MILO contains some settable variables that help the boot
process. If you are loading via the Windows NT ARC firmware, then
MILO makes use of the boot option environment variables set up by that
firmware. For some systems, MILO (for example, the AlphaPC64)
maintains its own set of environment variables that do not change from
boot to boot. These variables are:
MILO> help var
Variables that MILO cares about:
MEMORY_SIZE - System memory size in megabytes
BOOT_DEV - Specifies the default boot device
BOOT_FILE - Specifies the default boot file
BOOT_STRING - Specifies the boot string to pass to the kernel
SCSIn_HOSTID - Specifies the host id of the n-th SCSI controller.
AUTOBOOT - If set, MILO attempts to boot on powerup
and enters command loop only on failure.
AUTOBOOT_TIMEOUT - Seconds to wait before auto-booting on powerup.
6.2. Booting Linux
The boot command boots a linux kernel from a device. You will need to
have a linux kernel image on an EXT2 formated disk (SCSI, IDE or
floppy) or an ISO9660 formatted CD available to MILO. The image can
be gzip'd and in this case MILO will recognise that it is gzip'd by
the .gz suffix.
You should note that the version of MILO does not usually have to
match the version of the Linux kernel that you are loading. You boot
Linux using the following command syntax:
MILO> boot [-t file-system] device-name:file-name [[boot-option] [boot-option] ...]
Where device-name is the name of the device that you wish to use and
file-name is the name of the file containing the Linux kernel. All
arguments supplied after the file name are passed directly to the
Linux kernel.
If you are installing Red Hat, then you will need to specify a root
device and so on. So you would use:
MILO> boot fd0:vmlinux.gz root=/dev/fd0 load_ramdisk=1
MILO will automatically contain the block devices that you configure
into your vmlinux. I have tested the floppy driver, the IDE driver
and a number of SCSI drivers (for example, the NCR 810), and these
work fine. Also, it is important to set the host id of the SCSI
controller to a reasonable value. By default, MILO will initialize it
to the highest possible value (7) which should normally work just
fine. However, if you wish, you can explicitly set the host id of the
n-th SCSI controller in the system by setting environment variable
SCSIn_HOSTID to the appropriate value. For example, to set the hostid
of the first SCSI controller to 7, you can issue the following command
at the MILO prompt:
setenv SCSI0_HOSTID 7
6.3. Rebooting Linux
You may want to reboot a running Linux system using the shutdown -r
now command. In this case, the Linux kernel returns control to MILO
(via the HALT CallPAL entrypoint). MILO leaves a compressed copy of
itself in memory for just this reason and detects that the system is
being rebooted from information held in the HWRPB (Hardware Restart
Parameter Block). In this case it starts to reboot using exactly the
same command that was used to boot the Linux kernel the last time.
There is a 30 second timeout that allows you to interrupt this process
and boot whatever kernel you wish in whatever way you wish.
6.4. The ''bootopt'' command
For flash based systems such as the AlphaPC64, EB164 and the EB66+,
there are a number of possible boot options and these are changed
using the bootopt command. This has one argument, a decimal number
which is the type of the image to be booted the next time the system
is power cycled or reset:
0 Boot the Evaluation Board Debug Monitor,
1 Boot the Windows NT ARC firmware.
In order to tell the boot code to boot the MILO firmware from flash
then you need a boot option that means boot the N'th image. For this,
you need to 128 plus N, so if MILO is the third image, you would use
the command:
MILO> bootopt 131
Note: Be very careful with this command. A good rule is never to set
bootopt to 0 (the Evaluation Board Debug Monitor), but instead use the
system's jumpers to achieve the same thing.
7. Running the Flash Management Utility
The run command is used to run the flash management utility. Before
you start you will need a device available to MILO that contains the
updateflash program. This (like vmlinux) can be gzip'd. You need to
run the flash management utility program from the MILO using the
(run) command:
MILO> run fd0:fmu.gz
Once it has loaded and initialised, the flash management utility will
tell you some information about the flash device and give you a
command prompt. Again the help command is most useful.
Linux MILO Flash Management Utility V1.0
Flash device is an Intel 28f008SA
16 segments, each of 0x10000 (65536) bytes
Scanning Flash blocks for usage
Block 12 contains the environment variables
FMU>
Note that on systems where environment variables may be stored and
where there is more than one flash block (for example, the AlphaPC64)
the flash management utility will look for a block to hold MILO's
environment variables. If such a block already exists, the flash
management utility will tell you where it is. Otherwise, you must use
the environment command to set a block and initialise it. In the
above example, flash block 12 contains MILO's environment variables.
7.1. The ''help'' command
FMU> help
FMU command summary:
list - List the contents of flash
program - program an image into flash
quit - Quit
environment - Set which block should contain the environment variables
bootopt num - Select firmware type to use on next power up
help - Print this help text
FMU>
Note that the environment and bootopt commands are only available on
the EB66+, the AlphaPC64, EB164 and PC164 systems (and their clones).
7.2. The ''list'' command
The ''list'' command shows the current usage of the flash memory.
Where there is more than one flash block, the usage of each flash
block is shown. In the example below you can see that Windows NT ARC
is using blocks 4:7 and block 15.
FMU> list
Flash blocks: 0:DBM 1:DBM 2:DBM 3:WNT 4:WNT 5:WNT 6:WNT 7:WNT 8:MILO
9:MILO 10:MILO 11:MILO 12:MILO 13:U 14:U 15:WNT
Listing flash Images
Flash image starting at block 0:
Firmware Id: 0 (Alpha Evaluation Board Debug Monitor)
Image size is 191248 bytes (3 blocks)
Executing at 0x300000
Flash image starting at block 3:
Firmware Id: 1 (Windows NT ARC)
Image size is 277664 bytes (5 blocks)
Executing at 0x300000
Flash image starting at block 8:
Firmware Id: 7 (MILO/Linux)
Image size is 217896 bytes (4 blocks)
Executing at 0x200000
FMU>
7.3. The ''program'' command
The flash management utility contains a compressed copy of a flash
image of MILO. The ''program'' command allows you to blow this image
into flash. The command allows you to back out, but before you run it
you should use the ''list'' command to see where to put MILO. If MILO
is already in flash, then the flash management utility will offer to
overwrite it.
FMU> program
Image is:
Firmware Id: 7 (MILO/Linux)
Image size is 217896 bytes (4 blocks)
Executing at 0x200000
Found existing image at block 8
Overwrite existing image? (N/y)? y
Do you really want to do this (y/N)? y
Deleting blocks ready to program: 8 9 10 11
Programming image into flash
Scanning Flash blocks for usage
FMU>
Wait until it has completed before powering off your system.
Note: I cannot emphasise just how careful you must be here not to
overwrite an existing flash image that you might need or render your
system useless. A very good rule is never to overwrite the Debug
Monitor.
7.4. The ''environment'' command
This selects a flash block to contain MILO's environment variables.
7.5. The ''bootopt'' command
This is just the same as MILO's ''bootopt'' command, see (Section
``The ''bootopt'' command'').
7.6. The ''quit'' command
This is really pretty meaningless. The only way back to MILO (or
anything else) once the flash management utility has run is to reboot
the system.
8. Restrictions.
Unfortunately this is not a perfect world and there, as always, some
restrictions that you should be aware of.
MILO is not meant to load operating systems other than Linux, although
it can load images linked to run at the same place in memory as Linux
(which is 0xFFFFFC0000310000). This is how the flash management
utilities can be run.
The PALcode sources included in miniboot/palcode/blah are correct,
however there are problems when they are built using the latest gas.
They do build if you use the ancient a.out gas that's supplied in the
Alpha Evaluation Board toolset (and that's how they were built). I'm
trying to get someone to fix the new gas. Meanwhile, as a workaround,
I have provided pre-built PALcode for the supported boards and David
Mosberger-Tang has a fixed gas on his ftp site.
9. Problem Solving.
Here are some common problems that people have seen, together with the
solutions.
Reading MS-DOS floppies from the Evaluation Board Debug Monitor.
Some of the older versions of the Evaluation Board Debug Monitor (pre-
version 2.0) have a problem with DOS format flopies generated from
Linux. Usually, the Debug Monitor can load the first few sectors all
right, but then goes into an endless loop complaining about "bad
sectors." Apparently, there is an incompatibility between the DOS
file system as expected by the Debug Monitor and the Linux
implementation of DOSFS. To make the long story short: if you run
into this problem, try using DOS to write the floppy disk. For
example, if loading the file MILO.cab doesn't work, use a DOS machine,
insert the floppy and then do:
copy a:MILO.cab c:
copy c:MILO.cab a:
del c:MILO.cab
Then try booting from that floppy again. This normally solves the
problem.
MILO displays a long sequence of O> and does not accept input.
This usually happens when MILO was built to use COM1 as a secondary
console device. In such a case, MILO echo output to COM1 and accepts
input from there also. This is great for debugging but not so great
if you have a device other than a terminal connected. If this
happens, disconnect the device or power it down until the Linux kernel
has booted. Once Linux is up and running, everything will work as
expected.
MILO complains that the kernel image has the wrong magic number
Older versions of MILO did not support the ELF object file format and
so could not recognise an ELF image and this might be your problem.
If this is reported, upgrade to the latest MILO that you can find.
All 2.0.20 and beyond MILOs support ELF. On the other hand it could
be that the image is indeed damaged. You should also note that MILO
does not yet automatically distinquish between GZIP'd and non-GZIP'd
images; you need to add the ".gz" suffix to the file name.
MILO prints "...turning on virtual addressing and jumping to the Linux
Kernel" and nothing else happens
One obvious problem is that the kernel image is wrongly built or is
built for another Alpha system altogether. Another is that the video
board is a TGA (Zlxp) device and the kernel has been built for a VGA
device (or vice versa). It is worth building the kernel to echo to
COM1 and then connecting a terminal to that serial port or retrying
the kernel that came with the Linux distribution that you installed.
MILO does not recognise the SCSI device
The standard MILO images include as many device drivers as are known
to be stable for Alpha (as of now that includes the NCR 810, QLOGIC
ISP, Buslogic and Adaptec 2940s and 3940 cards). If your card is not
included, it may be that the driver is not stable enough on an Alpha
system yet. Again, the latest MILO images are worth trying. You can
tell which SCSI devices a MILO image has built into it by using the
"show" command.
10. Acknowledgements.
I would like to thank:
� Eric Rasmussen and Eilleen Samberg the authors of the PALcode,
� Jim Paradis for the keyboard driver and the original MILO
interface,
� Jay Estabrook for his help and bugfixes,
� David Mosberger-Tang for the freeware BIOS emulation and his
support and encouragement,
� Last (and not least) Linus Torvalds for the timer code and his
kernel.
There are a number of things that still need doing to MILO, if you
want to add something yourself, then do let me know
david.rusling@reo.mts.dec.com <mailto:david.rusling@reo.mts.dec.com>
so that we do not duplicate our efforts.
Finally, a big thank you to Digital for producing such a wonderful
chip (and paying me to do this).