The longer jump was never documented, and so didn't exist. There was
definitely no way to rely on it.
The old command-line protocol had some really ugly interactions with the
absolutely insane hoisting code from the pre-2.02 days. I didn't have
enough guts back then to scream and just rip it out, mostly because it
took me a long time to figure out what the heck it really did (as
opposed to what it claimed it did.) That being said, we probably could
have gotten away with leaving the protocol as-is while ripping out the
guts (as I eventually did in the rewrite), even if the old protocol only
had a 16-bit pointer.
The problem is that that will only buy us 15 bytes, and eat up 3 (in
practice, 4) of them...
It might be worth doing anyway, as it'd only break the 32-bit entrypoint
users to reorganize struct boot_params.
-hpa
-