grub-ieee1275 on powerpc says "DEFAULT CATCH!" and then drops me into Open Firmware

[Daniel Kahn Gillmor]

Hey folks--

I'm trying to create a grub-based rescue USB stick for PowerPC
machines.

I've successfully gotten one machine to boot to this device, and grub
can see both the USB disk itself and the onboard (ide) HD.

However, when i try to load a linux kernel from either disk, i get an
error:

grub> linux (hd)/boot/vmlinux-2.6.25-2-powerpc
DEFAULT CATCH!, code=300 at %SRR0: 00013ae4 %SRR1: 00003030

(this is from my scribbled notes, not from a serial console,
unfortunately).

at this point, i get dropped to openfirmware, but it's in a
sufficiently weird state that even "mac-boot" doesn't work for me.  If
i reboot the machine, i can boot normally (via ofboot/yaboot
combination off of onboard disk).

This is with 1.96+20080724-5 and the kernel from debian lenny.

The machine in question is an old iBook (clamshell model) with 96M of
RAM, described by lshw as:

    product: iBook (first generation)
    vendor: Copyright 1983-1999 Apple Computer, Inc. All Rights Reserved

Any thoughts about what i might need to do to get grub to boot a linux
kernel properly?  Should i try to load something different from grub?

Regards,

        --dkg

0 clam:~# cat /proc/cpuinfo 
processor       : 0
cpu             : 740/750
temperature     : 54-56 C (uncalibrated)
clock           : 299.999997MHz
revision        : 131.0 (pvr 0008 8300)
bogomips        : 33.15
timebase        : 16644650
platform        : PowerMac
machine         : PowerBook2,1
motherboard     : PowerBook2,1 MacRISC Power Macintosh
detected as     : 64 (iBook (first generation))
pmac flags      : 0000000d
L2 cache        : 512K unified
pmac-generation : NewWorld
0 clam:~#

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