From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e37.co.us.ibm.com (e37.co.us.ibm.com [32.97.110.158]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id DC8131A00BC for ; Tue, 8 Mar 2016 01:10:16 +1100 (AEDT) Received: from localhost by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 7 Mar 2016 06:39:57 -0700 Received: from b01cxnp23032.gho.pok.ibm.com (b01cxnp23032.gho.pok.ibm.com [9.57.198.27]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id E926F1FF0021 for ; Mon, 7 Mar 2016 06:28:03 -0700 (MST) Received: from d01av05.pok.ibm.com (d01av05.pok.ibm.com [9.56.224.195]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u27Ddsic31981570 for ; Mon, 7 Mar 2016 13:39:54 GMT Received: from d01av05.pok.ibm.com (localhost [127.0.0.1]) by d01av05.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u27DZTG3012761 for ; Mon, 7 Mar 2016 08:35:30 -0500 From: "Aneesh Kumar K.V" To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au Cc: linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" Subject: [PATCH 03/14] powerpc/mm/subpage: Clear RWX bit to indicate no access Date: Mon, 7 Mar 2016 19:09:23 +0530 Message-Id: <1457357974-20839-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com> In-Reply-To: <1457357974-20839-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> References: <1457357974-20839-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 and Write access from pte instead of clearing _PAGE_USER now. This was done to enable us to switch to _PAGE_PRIVILGED. subpage_protection() returns the pte bits that need to be cleared. Instead of updating the interface to handle no-access in a separate way, it appears simple to clear RWX acecss to indicate no access. We still don't insert hash pte for these ptes, hence we should not get PROT_FAULT with change. Signed-off-by: Aneesh Kumar K.V --- arch/powerpc/mm/hash_utils_64.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c index ea23403b3fc0..ec37f4b0a8ff 100644 --- a/arch/powerpc/mm/hash_utils_64.c +++ b/arch/powerpc/mm/hash_utils_64.c @@ -917,7 +917,7 @@ void demote_segment_4k(struct mm_struct *mm, unsigned long addr) * Userspace sets the subpage permissions using the subpage_prot system call. * * Result is 0: full permissions, _PAGE_RW: read-only, - * _PAGE_USER or _PAGE_USER|_PAGE_RW: no access. + * _PAGE_RWX: no access. */ static int subpage_protection(struct mm_struct *mm, unsigned long ea) { @@ -943,8 +943,13 @@ static int subpage_protection(struct mm_struct *mm, unsigned long ea) /* extract 2-bit bitfield for this 4k subpage */ spp >>= 30 - 2 * ((ea >> 12) & 0xf); - /* turn 0,1,2,3 into combination of _PAGE_USER and _PAGE_RW */ - spp = ((spp & 2) ? _PAGE_USER : 0) | ((spp & 1) ? _PAGE_RW : 0); + /* + * 0 -> full premission + * 1 -> Read only + * 2 -> no access. + * We return the flag that need to be cleared. + */ + spp = ((spp & 2) ? _PAGE_RWX : 0) | ((spp & 1) ? _PAGE_WRITE : 0); return spp; } -- 2.5.0