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Date:      Mon, 27 Nov 2000 12:27:36 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Jake Burkholder <jburkhol@home.com>
Cc:        smp@FreeBSD.ORG
Subject:   Re: BSD/OS interrupt code
Message-ID:  <20001127122736.G27697@echunga.lemis.com>
In-Reply-To: <20001127015006.5B7BDBA7A@io.yi.org>; from jburkhol@home.com on Sun, Nov 26, 2000 at 05:50:06PM -0800
References:  <grog@lemis.com> <20001127015006.5B7BDBA7A@io.yi.org>

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On Sunday, 26 November 2000 at 17:50:06 -0800, Jake Burkholder wrote:
>> On Sunday, 26 November 2000 at 14:07:49 -0800, Jake Burkholder wrote:
>>> Hi,
>>>
>>> If anyone with access to the BSD/OS code is interested, I've written
>>> a little program that runs their interrupt stub code generator in
>>> userland.  You can then abort(); and disassemble the stub from
>>> the core dump to look at the code all in one piece.  Makes it much
>>> easier to follow.
>>>
>>> In case you haven't looked, their interrupt handlers are generated
>>> by bcopy-ing various blocks of assembler code into an array at
>>> runtime, and then poking in arguments and relocating branches.
>>
>> Interesting.  I was wondering whether something similar would be a
>> good idea.  On the other hand, We don't waste much space by having
>> multiple alternate stubs.  What's your feeling?
>
> I suspect that it would be hard to do this for architectures
> other than x86, which has a relatively simple instruction format.
>
> I also think that BSD/OS went a little too far with this, and
> have produced code that is very difficult to understand, let
> alone maintain.  I think its cool what they did, I'm humbled
> and amazed that they made it work, but I don't know that its
> right for FreeBSD.

That's a reasonable objection.  Where's your program?

Greg
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