VAX emulator [was Re: Does the KA630 have a TB?]

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> Thanks to a very generously offered guest login (I have asked whether
> the person responsible cares about being named, but, since I haven't
> yet gotten a reply, I'm erring on the side of caution),

I have now got that reply, saying it's fine.

It's John Klos, to whom I say, thank you very much!

> First is the aforementioned abort() upon starting it not under gdb.
> I don't currently have any clue what's behind that; I need to dig
> more.

Turns out paxctl +m makes this symptom go away.

I have so far failed to find anything that documents what restrictions
this affects.  The closest I've found is security(7), which talks about
the restrictions, but doesn't say what they are, that is, exactly which
calls get rejected.

However, the resulting executable still calls mprotect cripplingly
often.

I'm tempted to link -static with an mprotect() that does nothing when
called for the stack, catch memory protection signals, and, if the pc
is on the stack, mprotect the whole stack executable and retry.  This
shouldn't need to happen more than a few times to get the stack, down
to the deepest level which gets used, executable.  But that really
feels like extreme lengths to work around an OS restriction when the
right answer is to lift the restriction.

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