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Cc: Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?= <des@des.no>, hackers@freebsd.org
Subject: Re: PTE modified bit emulation trap
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On Wednesday 13 May 2009 7:47:38 pm Dag-Erling Sm=C3=B8rgrav wrote:
> Coverity complains about the lack of error checking in the following
> code in sys/kern/kern_sysctl.c, around line 1390:
>=20
> 	/*
> 	 * Touch all the wired pages to avoid PTE modified
> 	 * bit emulation traps on Alpha while holding locks
> 	 * in the sysctl handler.
> 	 */
> 	for (i =3D (wiredlen + PAGE_SIZE - 1) / PAGE_SIZE,
> 	    cp =3D req->oldptr; i > 0; i--, cp +=3D PAGE_SIZE) {
> 		copyin(cp, &dummy, 1);
> 		copyout(&dummy, cp, 1);
> 	}
>=20
> Since Alpha is dead, can we remove this, or is it still needed for other
> platforms?

I would check MIPS as it might have similar PTE bits as well (FOR, FOW) (ma=
ny=20
Alpha things are similar to MIPS).  I don't have my See MIPS Run handy or I=
=20
would check it myself.  It might be better to replace the loop with a=20
vm_fault(..., VM_FAULT_DIRTY) though if that would have the same effect.

=2D-=20
John Baldwin