Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)

From: Peter Zijlstra
Date: Mon Jan 18 2010 - 02:23:48 EST

On Sat, 2010-01-16 at 18:48 -0500, Jim Keniston wrote:

> As you may have noted before, I think FP would be a special problem
> for your approach. I'm not sure how folks would react to the idea of
> executing FP instructions in kernel space. But emulating them is also
> tough. There's an IEEE FP emulation package somewhere in one of the
> Linux arch directories, but I'm not sure how precise it is, and
> dropping even 1 bit of precision is unacceptable for many
> applications, since such errors tend to grow in complex computations
> employing many FP instructions.

Well, we have kernel space using FP/MMX/SSE like things, its not hard if
you really need it, but in this case I think its easier than normal,
because we'll just allow it to change the userspace state because that
is exactly what we want it to do.

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