svn commit: r217587 - head/sys/i386/i386

[Kostik Belousov]

On Wed, Jan 19, 2011 at 05:09:07PM +0000, Jung-uk Kim wrote:
> Author: jkim
> Date: Wed Jan 19 17:09:07 2011
> New Revision: 217587
> URL: http://svn.freebsd.org/changeset/base/217587
> 
> Log:
>   Fix yet another fallout from r208833.  VM86 BIOS call may cause page fault
>   when FPU is in use.
>   
>   Reported by:	Marc UBM Bocklet (ubm dot freebsd at googlemail dot com)
>   Tested by:	b. f. (bf1783 at googlemail dot com)
>   MFC after:	3 days
> 
> Modified:
>   head/sys/i386/i386/vm86bios.s
> 
> Modified: head/sys/i386/i386/vm86bios.s
> ==============================================================================
> --- head/sys/i386/i386/vm86bios.s	Wed Jan 19 17:04:07 2011	(r217586)
> +++ head/sys/i386/i386/vm86bios.s	Wed Jan 19 17:09:07 2011	(r217587)
> @@ -73,10 +73,9 @@ ENTRY(vm86_bioscall)
>  	je 	1f			/* no curproc/npxproc */
>  	pushl	%edx
>  	movl	TD_PCB(%ecx),%ecx
> -	addl	$PCB_SAVEFPU,%ecx
> -	pushl	%ecx
> +	pushl	PCB_SAVEFPU(%ecx)
>  	call	npxsave
> -	popl	%ecx
> +	addl	$4,%esp
>  	popl	%edx			/* recover our pcb */
>  1:
>  	popfl
vm86_bioscall() in fact inlines the old version of npxexit().
Shouldn't the npxexit() be called from C code before call to
vm86_bioscall ?

Also, if bioscall can be used from the syscall context, I think
whatever npxsave()/npxexit() is used, and BIOS modifies FPU
state, we are corrupting usermode FPU context.

Probably, fpu_kern_enter()/fpu_kern_leave() braces around vm86_bioscall
is proper solution.
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