ppc32 debugging ppc64, 2011 revisit

[Stan Shebs <stanshebs at earthlink dot net>]

So Mentor Embedded Linux has a need for a run-anywhere native GDB for 
PowerPC, meaning in practice that we want a 32-bit GDB that can debug 
both 32- and 64-bit programs.  So I imagine I'm clever, and steal some 
bits from spu-linux-nat.c that use the *_3264 ptrace() commands that are 
the defined way to get at a 64-bit program from 32-bit land, and it 
works reasonably well, modulo various system hangs and crashes due to 
32-x-64 lameness in the oldish version of PPC Linux we have in-house.

But in the usual way, when preparing for submission, I discover that rth 
had posted similar code to solve the same problem - back in 2005! It's 
at http://www.cygwin.com/ml/gdb-patches/2005-09/msg00082.html , and 
there's even a bit of discussion thread; but it seems nothing was ever 
committed.

So I have a couple questions:

1. Does anybody remember a fatal flaw, or was the patch simply forgotten 
about?

2. The old patch works by making a clone of the generic xfer_partial, to 
accommodate the randomly-different API of the 32-x-64 ptrace commands, 
but I added #ifdef cases to inf-ptrace.c, which actually seemed cleaner, 
and avoided duplicating the semi-complicated algorithm.  (Yes yes, 
ifdefs are evil, but keep in mind that inf-ptrace.c is inherently 
native-only.)

3. Does anybody have an up-to-date Linux running on PPC64 hw that I 
could use?  There seem to be fewer compile farms around than formerly, 
and the in-house machine is very old and may not survive a kernel 
update, so we don't want to mess with it too much right now.

Stan
stan@codesourcery.com