From owner-freebsd-bugs  Mon Jul  8 16:40: 9 2002
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Date: Mon, 8 Jul 2002 16:40:03 -0700 (PDT)
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Cc: 
From: Bruce Evans <bde@zeta.org.au>
Subject: Re: i386/40354: crash, whith floating ops in kernel mode
Reply-To: Bruce Evans <bde@zeta.org.au>
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The following reply was made to PR i386/40354; it has been noted by GNATS.

From: Bruce Evans <bde@zeta.org.au>
To: unicorn@forest.od.ua
Cc: FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: i386/40354: crash, whith floating ops in kernel mode
Date: Tue, 9 Jul 2002 09:38:38 +1000 (EST)

 On Mon, 8 Jul 2002 unicorn@forest.od.ua wrote:
 
 > >Description:
 > 	npx dna handler tries to modify curpcb even if it does not exist (yet).
 > 	it couses page fault in kernel mode.
 
 curpcb is supposed to always exist if the npx dna handler is called.
 
 > >How-To-Repeat:
 > 	do some floating point operations before the first process created.
 
 Don't do that.  Normal floating point operations are only supported
 for user processes (*).  The kernel does some FP initializations, but
 it is supposed to be careful to call stop_emulating() before it does
 them so that an npx dna exception doesn't occur.
 
 (*) FP is close to working or working in kernel processes, but this
 is not supported.  FP is used in i586_bcopy() and i586_bzero(), but
 these are broken and not used in -current.
 
 Bruce
 

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