ADLO

What is ADLO?

ADLO is a glue layer which bonds LinuxBIOS to the 16-bit PC BIOS of the Bochs project.

It was originally written by Adam Sulmicki.

See the following url:

http://www.missl.cs.umd.edu/sebos_phase2.html

Since the Bochs BIOS provides many of legacy BIOS services it allows you to boot some OS's that depend on those services.

What bios services does ADLO provide and when would I need them.

The full gory details for XP are at:

http://www.missl.cs.umd.edu/winint/index2.html

The full gory details for W2K are at:

http://www.missl.cs.umd.edu/winint/index1.html

What bootloaders work with ADLO?

Currently known to work are:

LILO
Windows 2000

Where is ADLO?

ADLO currently only exists the linuxBIOS V1 tree. It should work fine with V2 since its just an ELF image but to date nobody has needed it in V2.

How do I get LinuxBIOS to boot ADLO?

ADLO compiles as an ELF image so you have to set up LinuxBIOS to elf boot just as if you were using etherboot. Go read the etherboot IDE section of this faq and get to where you can boot etherboot.

ADLO is distributed with LinuxBIOS in the freebios/util/ADLO directory.

Int that directory are some README's. Make sure you have read them.

Compiling ADLO is quite simple. Mostly you just type 'make' You need a copy of your video BIOS if you want VGA to work. Again see the README.

Out-of-the box ADLO probally won't boot unless you are using the exact mainboard that the ADLO project uses. The reason is that various areas of shadowing must be enabled for ADLO to boot.

If you see elfboot indicate that its 'Jumping to boot code at 0x7c00' and then the board resets or hangs then its very likely that your shadow settings are incorrect.

Applying the serial debug patch to ADLO can help you further investigate this. /!\ Where is the defacto location for the serial patch?

The shadow settings are set in loader.s in the freebios/util/ADLO. Find section B) These are writes to PCI space that enable various areas of shadowing.

Technically all you need is the only 64kb at 0xF0000 and 64kb at 0xC0000. Your mileage may vary. I would start by enabling Read/Write for all shadow ranges supported by your chipset and then backing off to 0xF0000 and 0xC0000 after you get it working.

The ADLO makefile will copy your video bios from an existing setup. See the README and makefile for details.

If you have one of the BIOS kits provided by the video chipset mfg for your board then you may have a stock image an then a program that allows you to customize the stock image. If so then you need to set things up so that the video bios is set to be loaded at 0x0C0000 (sometimes called the C000 segment)

Also I found that ADLO expected the video bios to be 64k in size whereas my image file was only 32k. I solved this by just copying it twice in the same file and then letting ADLO use that. Some creative work with 'dd' would probally achieve the same result.

Lastly if you have applied the serial debug patch to BOCHS then _all_ the output is routed out to the serial port so your video screen will be blank. However VSYNC will still be generated if the video chip is initialized properly. You can watch for VSYNC with a Oscope or plug a newer type monitor up to the video output. Most modern monitors will tell you when they can/can't find the VSYNC signal. Note you may have to power cycle the monitor between attempts as sometimes they can get very confused.