Date: Wed, 10 Sep 1997 18:05:10 -0700 (PDT) From: Sean Eric Fagan <sef@Kithrup.COM> To: gallatin@CS.Duke.EDU, grog@lemis.com Cc: emulation@FreeBSD.ORG, jkh@time.cdrom.com, mike@smith.net.au, sos@sos.freebsd.dk Subject: Re: Net posting: SCO gets Linux emulation Message-ID: <199709110105.SAA09151@kithrup.com>
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>> Well, its somewhat interesting because it runs entirely in userland
>> and traps system calls via a SEGV handler.
>Ugh. Is this what we have come to expect of SCO?
That is both unfair and rude. (Bit of a warning here... I've known the
author ever since I interviewed at SCO, and I happen to like him.)
I looked at the program; it's interesting, but not terribly exciting.
However, I might have done the iBCS2 emulation the same way, if I could
have -- however, trapping the system call vector in a user-mode program is
hard. If 386BSD had used a different entry vector...
Mike also probably would have done the program using LDT manipulation,
except for the fact that the IDT is global.
>> And because of this, I imagine that its a good bit slower. Also,
>> their '$LINUX_ROOT' path remapping is interesting if only for its
>> flexibility, but their choice of what paths to remap is very
>> haphazard compared with the {Free,Net}BSD approach.
>Doesn't sound like a serious implementation effort to me.
To a large degree, it isn't. He did it as a quick&dirty way to be able to
run the Linux port of Acrobat Reader (there is/was no SCO version), and
apparantly convinced SCO to allow him to release it under a Berkeley-style
license.
All told, it probably took Mike about a day to write this.
Perhaps you should add support for kernel-mode vm86 drivers before you start
to insult Mike's efforts. (He had done this about six months before I left
SCO; he decided that they were too slow to be generally usable. However,
SCO doesn't have the problem that FreeBSD does, in getting documentation for
cards.)
Sean.
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