iQUIK - the new old PowerMac bootloader for OldWorld machines

About three quarters of a year ago I found a PowerBook 3400c in the trash pile at work. Given my ongoing nostalgia for PowerPC and OpenFirmware, I couldn't pass up the opportunity to reminisce with this PowerBook.

It is by far the oldest mac I've had. The UMAX S900 I dumpster dove for back in 2002 was a dual 604e. This baby is a 603ev. That's three generations behind my old G4 iBook. It's OF is slightly less broken than 1.0.5 on the S900 - at least it doesn't default stdio to serial, and doesn't need nvramc patches to boot from disk. The 3400c booted into MacOS, but clearly it was asking for Linux.

Unfortunately, the best you could do is install via old miBoot floppies, and get a 2.2(!)-based Debian system, just like I had to on the S900 ten whole years ago. Of course you could painfully and slowly upgrade releases, only to realize you can't actually boot a 2.4 kernel with an initrd with the OldWorld bootloader, QUIK. Staring at a "VFS panic" message after investing a week into slowly getting to /that/ point would be bound to enrage most people just toss the aging laptop into trash...

I guess I have an odd fascination with obsolete hardware. I've decided to take ownership of the QUIK code, fixing many of its bugs and limitations. The effort is now called iQUIK and is available for everybody at https://github.com/andreiw/quik.

iQUIK is a Linux bootloader for "OldWorld" PowerMacs. "OldWorld" PowerMacs are all machines that have OpenFirmware, but that don't have built-in USB. Due to a lacking firmware implementation, the typical Yaboot bootloader cannot be used on "OldWorld" machines.

Some highlights:

• You can install and boot Debian Wheezy (the current stable release)
• You can install the boot loader on any medium, including floppy.
• Initrd image work fine, as do 2.2., 2.4 and 2.6 kernels.
• Can boot any kernel/initrd/argument combos without a quik.conf.
• Can list filesystems (only ext2 supported at the moment).
• Works around OF/hw bugs with an innovative shim layer. At least the many bugs on the 3400c.
• Single-stage installation for robustness, using partition-zero boot block and bootstrap partition.No more LILO-style block maps.

You can see the fairly exhaustive documentation at https://github.com/andreiw/quik/blob/master/README. It's only really been tested on a 3400c, although I'm getting a G3 PDQ (that's the last OldWorld PowerBook!) for testing soon.

...but that's not what I wanted to write this post about. I was curious if I could boot iQUIK successfully with the QEMU PowerPC system emulator and OpenBIOS. Turns out yes, but it's a bit painful. The problem is that OpenBIOS doesn't support the mac's "partition-zero" booting, e.g.

0 > boot ata0/ata-disk@0:0

How does "partition-zero" booting work? The mac partition table contains a structure that describes the disk offset of the bootloader, its size and where to load it. The bootloader has to be plain binary (i.e. not XCOFF). iQUIK leverages this by copying the boot code into it's own partition and setting up the boot descriptor in the partition table to point to it. http://www.opensource.apple.com/source/bless/bless-11/README.BOOTING is a pretty good document that describes this more in-depth.

So how to boot on QEMU, then? We could cheat and load the non-munged ELF file the boot code is created from, but I don't have my 3400c nearby to compile with. Instead we will convince OpenBIOS to load our code just like a PowerMac would.

This example assumes:

• You have qemu-system-ppc.
• You have floppy.img from the github quik/distrib.
• You created an install.img: FAT partitioned, ext2 on only FAT partition with the Debian files from http://ftp.nl.debian.org/debian/dists/wheezy/main/installer-powerpc/current/images/powerpc/hd-media/
• Note: take the 'initrd-size' out of yaboot.conf file you downloaded above.

Steps are pretty simple. We launch the simulator like so:

qemu-system-ppc  -hda floppy.img -hdb install.img -serial stdio

At the "0 >" prompt in the framebuffer window we type the following commands to switch the firmware to serial port for input/output. You might wonder why we couldn't use the "prom-env" option to set output-device and input-device? It doesn't work. Heh.

0 > " /pci/mac-io/escc/ch-a" output
0 > " /pci/mac-io/escc/ch-a" input

And now paste the rest of this script into terminal you ran QEMU from. Of course, you could put it on bootable media, but...

0 value ih
\
\ size and load-base need to match
\ SECOND_BASE and SECOND_SIZE in
\ quik/include/layout
\
10000 value size
setenv load-base 3e0000
\
\ boot-file specifies where iQUIK will look
\ for the configuration file. This corresponds to
\ the second ATA disk (-hdb), first FAT partition.
\
setenv boot-file /pci/mac-io/ata-1/disk@1:1/yaboot.conf
\
\ OpenBIOS doesn't know how to parse the MAC "partition-zero"
\ boot descriptor, so we'll manually load it. XXX:2 refers
\ to the Apple_Boostrap partition on -hda, which in the floppy.img
\ image is the first parition (wonky indexing... yes).
\
\ I don't really understand why OpenBIOS needs the seek to 0.
\ Seems like a bug...
\
" /pci/mac-io/ata-1/disk@0:2" open-dev to ih
0 " seek" ih $call-method .
load-base size " read" ih $call-method .
\
\ Based on OpenBIOS libopenbios/bootcode_load.c
\
load-base saved-program-state >sps.entry !
size saved-program-state >sps.file-size !
bootcode saved-program-state >sps.file-type !
-1 state-valid !
\
\ Now can boot. For completeness probably should set
\ /chosen/bootargs but iQUIK can handle the inconsistency.
\
ih close-dev
go

You should now see iQUIK in the framebuffer window (not the serial, because we haven't set the input-device and output-device env variables). You can press the tab key to show the boot labels available. Just press enter to boot the default 'install'.

There you have it.

Of course it would be ideal to just implement bootsector-zero support or even this hack as an nvramrc patch, but unfortunately QEMU PPC has no NVRAM support. Boo...