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SubjectRe: Question: Using floating point in the kernel
Date
Hello,
You cannot use MMX registers in the kernel either, since the kernel doesen't
save and restore FX state (fxsave, fxrstor) either (just like
(fsave/frstor).

Best Wishes,
Lyle

** Reply to message from "Richard B. Johnson" <root@chaos.analogic.com> on
Tue,
19 Sep 2000 11:58:34 -0400 (EDT)


>Tell the driver maintainer that you found a BUG. There is no floating-
>point allowed in the kernel because the state of the FP Unit is
>undefined in the kernel. If you 'define' it, i.e., `finit` then you
>will mess up somebody who was using the FP Unit in user-mode.
>
>Also, the '386 FP emulation, which is still supported, can produce a
>double-fault if you try to use it (at some places) in kernel-mode
>code.
>
>Basically, there is nothing in the kernel that will ever require
>floating point. Use fixed point if you need 'decimals' and stuff for
>printing.

What about MMX? It uses floating point registers, but it's not technically
floating point.



--
Timur Tabi - ttabi@interactivesi.com
Interactive Silicon - http://www.interactivesi.com

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