From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC1FEC433EF for ; Mon, 31 Jan 2022 03:25:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357503AbiAaDZW (ORCPT ); Sun, 30 Jan 2022 22:25:22 -0500 Received: from foss.arm.com ([217.140.110.172]:53890 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236781AbiAaDZT (ORCPT ); Sun, 30 Jan 2022 22:25:19 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 92B49ED1; Sun, 30 Jan 2022 19:25:18 -0800 (PST) Received: from [10.163.44.9] (unknown [10.163.44.9]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 303A33F774; Sun, 30 Jan 2022 19:25:15 -0800 (PST) Subject: Re: [RFC V1 02/31] mm/mmap: Clarify protection_map[] indices To: Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, hch@infradead.org, akpm@linux-foundation.org References: <1643029028-12710-1-git-send-email-anshuman.khandual@arm.com> <1643029028-12710-3-git-send-email-anshuman.khandual@arm.com> From: Anshuman Khandual Message-ID: <904f9623-0f02-9530-1d66-017baa082349@arm.com> Date: Mon, 31 Jan 2022 08:55:12 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/27/22 6:09 PM, Mike Rapoport wrote: > On Mon, Jan 24, 2022 at 06:26:39PM +0530, Anshuman Khandual wrote: >> protection_map[] maps vm_flags access combinations into page protection >> value as defined by the platform via __PXXX and __SXXX macros. The array >> indices in protection_map[], represents vm_flags access combinations but >> it's not very intuitive to derive. This makes it clear and explicit. > > The protection_map is going to be removed in one of the next patches, why > bother with this patch at all? This makes the transition from protection_map[] into __vm_get_page_prot() more intuitive, where protection_map[] gets dropped. This helps platforms (first ones subscribing ARCH_HAS_VM_GET_PAGE_PROT before this drop) create /formulate the required switch case elements in their vm_get_page_prot(). The existing protection_map[] is not clear in demonstrating how exactly the vm_flags combination is mapped into page protection map. This helps clarify the underlying switch before we move on defining it on platforms. > >> Cc: Andrew Morton >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >> mm/mmap.c | 18 ++++++++++++++++-- >> 1 file changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 1e8fdb0b51ed..254d716220df 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -102,8 +102,22 @@ static void unmap_region(struct mm_struct *mm, >> * x: (yes) yes >> */ >> pgprot_t protection_map[16] __ro_after_init = { >> - __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111, >> - __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111 >> + [VM_NONE] = __P000, >> + [VM_READ] = __P001, >> + [VM_WRITE] = __P010, >> + [VM_READ|VM_WRITE] = __P011, >> + [VM_EXEC] = __P100, >> + [VM_EXEC|VM_READ] = __P101, >> + [VM_EXEC|VM_WRITE] = __P110, >> + [VM_EXEC|VM_READ|VM_WRITE] = __P111, >> + [VM_SHARED] = __S000, >> + [VM_SHARED|VM_READ] = __S001, >> + [VM_SHARED|VM_WRITE] = __S010, >> + [VM_SHARED|VM_READ|VM_WRITE] = __S011, >> + [VM_SHARED|VM_EXEC] = __S100, >> + [VM_SHARED|VM_READ|VM_EXEC] = __S101, >> + [VM_SHARED|VM_WRITE|VM_EXEC] = __S110, >> + [VM_SHARED|VM_READ|VM_WRITE|VM_EXEC] = __S111 >> }; >> >> #ifndef CONFIG_ARCH_HAS_FILTER_PGPROT >> -- >> 2.25.1 >> >> >