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Re: [PATCH] Fix process crash in 2.4 on attempt to use FPU on MIPS32

To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Subject: Re: [PATCH] Fix process crash in 2.4 on attempt to use FPU on MIPS32
From: Ralf Baechle <ralf@linux-mips.org>
Date: Thu, 6 Jul 2006 23:57:18 +0100
Cc: Linux-MIPS <linux-mips@linux-mips.org>, a.voropay@equant.ru
In-reply-to: <44AD7FBA.8000203@ru.mvista.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <44AD7FBA.8000203@ru.mvista.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.4.2.1i
On Fri, Jul 07, 2006 at 01:25:14AM +0400, Sergei Shtylyov wrote:

> If there's built-in FPU in a MIPS32 CPU the first time the process tries
> to use it, the kernel should crash with "reserved instruction" -- CPU will 
> try
> to execute 'dmtc1' which is a MIPS64 only insn. _init_fpu() was apprently 
> blindly copied form arch/mips64/... :-)
> 
> Since this occured with GXemul recently resending this 1.5 year old patch.

I didn't like the patch back then because it drops the optimizations
for 64-bit processors.  So I just took the 2.6 variant of the code and
bolted it into 2.4.

  Ralf

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