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Date:      Fri, 9 Mar 2007 18:10:25 -0500
From:      "Michael M. Press" <deathjestr@gmail.com>
To:        cokane@cokane.org, maslanbsd@gmail.com, freebsd-hackers@freebsd.org
Subject:   Re: Floating-point in kernel space
Message-ID:  <44b564930703091510r35e8c56eke0c8761fa5f234e9@mail.gmail.com>
In-Reply-To: <346a80220703091044p5759e6do521065203299c26b@mail.gmail.com>
References:  <319cceca0703090116p7e768630qd055be57bbe4953@mail.gmail.com> <200703091021.l29ALLVw067285@lurza.secnetix.de> <346a80220703091044p5759e6do521065203299c26b@mail.gmail.com>

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> I think i've seen somewhere but i don't remember that floating point
> arithmetic is not allowed in kernel space, if that's right, can anyone
> please tell why ???
> and why not not emulate the floating point in kernel space ???

That's nonsense! Floating point arithmetic is absolutely allowed in
kernel space, it's just that user space applications don't tend to
like their data being mangled very much.

I remember this topic coming up a short while ago on this list.
Perhaps if there is sufficient need someone could implement a pair
of floating-point save/restore functions to allow floating-point
(or MMX) calculations to be used in the kernel only when needed.
Something like the EngSaveFloatingPointState/
EngRestoreFloatingPointState functions that Windows has.

--Mike



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