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Re: [RESUME] fpu emulator

To: "Florian Lohoff" <flo@rfc822.org>, <linux-mips@oss.sgi.com>
Subject: Re: [RESUME] fpu emulator
From: "Kevin D. Kissell" <kevink@mips.com>
Date: Thu, 8 Feb 2001 12:43:30 +0100
References: <20010208122030.A5408@paradigm.rfc822.org>
Sender: owner-linux-mips@oss.sgi.com
> Hi,
> just to get it right - As i thought the FPU emulator is not really
> optional - It is even required for fpu-enabled devices which means
> we should clean the code in that way that if the user decides to 
> compile in the fpu emulator into the kernel we do an autodetection 
> upfront and change some of the entry/exit/lazy_fpu stuff.
> If the user decides not to compile in the FPU Emulator he is on his
> own and we ignore the whole FPU stuff and simply send SIGILL/SIGFPE
> to the processes causing all fpu binarys to fail on non-fpu enabled
> kernels.

Not quite.  Unless we create a variant of glibc that neither
initializes the FP control register on program startup, nor
saves/restores the FP registers in setjmp/longjmp, the
model of "simply sending SIGILL/SIGFPE" will result
in *all* processes being terminated with extreme prejudice,
starting with init!

            Regards,

            Kevin K.


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