From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x236.google.com (mail-pf0-x236.google.com [IPv6:2607:f8b0:400e:c00::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qfDrQ3Pb6zDq6R for ; Tue, 5 Apr 2016 13:30:14 +1000 (AEST) Received: by mail-pf0-x236.google.com with SMTP id 184so1356272pff.0 for ; Mon, 04 Apr 2016 20:30:14 -0700 (PDT) Subject: Re: [PATCH 03/65] powerpc/mm/subpage: Clear RWX bit to indicate no access To: "Aneesh Kumar K.V" , benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au References: <1459067053-10835-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1459067053-10835-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <56FC808B.7030704@gmail.com> <87pou5xvwj.fsf@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org From: Balbir Singh Message-ID: <5703313F.6010302@gmail.com> Date: Tue, 5 Apr 2016 13:30:07 +1000 MIME-Version: 1.0 In-Reply-To: <87pou5xvwj.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/04/16 00:59, Aneesh Kumar K.V wrote: > Balbir Singh writes: > >> [ text/plain ] >> >> >> On 27/03/16 19:23, Aneesh Kumar K.V wrote: >>> Subpage protection used to depend on _PAGE_USER bit to implement no >>> access mode. This patch switch that to use _PAGE_RWX. We clear READ, >>> Write and Execute access from pte instead of clearing _PAGE_USER now. >>> This was done so that we can switch to _PAGE_PRIVILEGED in later patch. >>> subpage_protection() returns pte bits that need to be cleared. >> Could you please clarify what bit needs to be cleared. I think the underlying >> assumption is that when this routine is called access cannot be _PAGE_RWX > > I didn't follow the question. subpage_protection() returns the pte bits > that need to be cleared for a specific access depending on the subpage > prot mask we set using subpage_prot syscall. What I meant is that if the subpage protection was no access, then _PAGE_RWX cannot be set in the access value. >>> Instead of updating the interface to handle no-access in a separate way, >>> it appears simple to clear RWX acecss to indicate no access. >>> > -aneesh >