Remote gdb works for i386 in both vms and physical machines; some of us at BBN have used it fairly recently. I am fuzzy on the details, but I think amd64 doesn't quite work and some register defs are backwards. Plus there may be some trick to using it under vmware rather than an actual hardware serial port. I have on my TODO list to grovel through our changes for those appropriate to send back, but that won't happen until December at least.
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