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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5B36C04AB6 for ; Fri, 31 May 2019 09:05:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B432526660 for ; Fri, 31 May 2019 09:05:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727048AbfEaJFM (ORCPT ); Fri, 31 May 2019 05:05:12 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:48266 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726240AbfEaJFM (ORCPT ); Fri, 31 May 2019 05:05:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 93933341; Fri, 31 May 2019 02:05:11 -0700 (PDT) Received: from [10.162.42.223] (p8cg001049571a15.blr.arm.com [10.162.42.223]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 143BB3F59C; Fri, 31 May 2019 02:05:08 -0700 (PDT) Subject: Re: [PATCH 4/4] arm64/mm: Drop vm_fault_t argument from __do_page_fault() To: Mark Rutland Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , James Morse , Andrey Konovalov References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> <20190529151134.GH31777@lakrids.cambridge.arm.com> From: Anshuman Khandual Message-ID: <5e565fd3-0d2b-31a5-8644-c91ccc5fb05e@arm.com> Date: Fri, 31 May 2019 14:35:23 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190529151134.GH31777@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/29/2019 08:41 PM, Mark Rutland wrote: > On Wed, May 29, 2019 at 06:04:45PM +0530, Anshuman Khandual wrote: >> __do_page_fault() is over complicated with multiple goto statements. This >> cleans up code flow and while there drops the vm_fault_t argument. >> Signed-off-by: Anshuman Khandual >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: James Morse >> Cc: Andrey Konovalov >> --- >> arch/arm64/mm/fault.c | 38 ++++++++++++++++---------------------- >> 1 file changed, 16 insertions(+), 22 deletions(-) >> >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index 170c71f..a53a30e 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -397,37 +397,31 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re >> static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr, >> unsigned int mm_flags, unsigned long vm_flags) >> { >> - struct vm_area_struct *vma; >> - vm_fault_t fault; >> + struct vm_area_struct *vma = find_vma(mm, addr); >> >> - vma = find_vma(mm, addr); >> - fault = VM_FAULT_BADMAP; >> if (unlikely(!vma)) >> - goto out; >> - if (unlikely(vma->vm_start > addr)) >> - goto check_stack; >> + return VM_FAULT_BADMAP; >> >> /* >> - * Ok, we have a good vm_area for this memory access, so we can handle >> - * it. >> + * Check if the VMA has got the required permssion with respect >> + * to the access fault here. >> */ > > We already had a perfectly good comment for this check: > > /* > * Check that the permissions on the VMA allow for the fault which > * occurred. > */ > > ... so please keep that and minimize the diff. Sure, will keep all the existing comments here. > >> -good_area: >> + if (!(vma->vm_flags & vm_flags)) >> + return VM_FAULT_BADACCESS; >> + >> /* >> - * Check that the permissions on the VMA allow for the fault which >> - * occurred. >> + * There is a valid VMA for this access. But before proceeding >> + * make sure that it has required flags if there is an attempt >> + * to expand the stack downwards. >> */ > > I think we can drop this comment, given we didn't have it previously. Okay. > >> - if (!(vma->vm_flags & vm_flags)) { >> - fault = VM_FAULT_BADACCESS; >> - goto out; >> - } >> + if (unlikely(vma->vm_start > addr)) { >> + if (!(vma->vm_flags & VM_GROWSDOWN)) >> + return VM_FAULT_BADMAP; >> >> + if (expand_stack(vma, addr)) >> + return VM_FAULT_BADMAP; > > You can drop the line space between these two if statements. Will do. > >> + } >> return handle_mm_fault(vma, addr & PAGE_MASK, mm_flags); >> - >> -check_stack: >> - if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) >> - goto good_area; >> -out: >> - return fault; > > We used to check the stack before the checknig the rest of the vm_flags, > so this changes the precedence of the VM_FAULT_BADMAP and > VM_FAULT_BADACCESS return codes. > > Please check the stack before checking the other vm_flags. Though it makes some sense to move VMA permission check earlier in the function as it is the quicker one but I understand need to maintain the existing code flow in a clean up patch like this. Will retain the existing flow. 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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A118FC04AB6 for ; Fri, 31 May 2019 09:05:23 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6F3CE2666D for ; Fri, 31 May 2019 09:05:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="GQzRgjTI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F3CE2666D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bdVINPqK+bM1/VaI/qPGDgFJZPFDr7eSHREJui+2OR0=; b=GQzRgjTIxSNYfl gEPKUesDX6U8eAtdmt97d1HnZ53YrjqDV9Nvj0F32oBHk4UcIQa91y6+vYsmD3RHiV91gmV3vONV1 kvH9TbDdcWtt4LqsZORb6xzE6a7B9Q97dvqYR+rYLdARvShhc9rPdRp/cooQddbTGCLyfuhOdmz+s 0sCC1rM9gMGzuCPfuCucK6GHEy4splELqzwH+FH1n2UPHvXooI4e7FADMZWHMvvKzAzsVTg0RlgU2 i65UhTAAAunGQywZsy+7OiuhOAd+ABHOqggML1emUqHE5ZV8HvGnLyeryHnMoPyd+eIr7w68qiE4e +lL4M15f4G/62FMcRq/g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hWdTP-0006ky-8j; Fri, 31 May 2019 09:05:15 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hWdTM-0006kd-DH for linux-arm-kernel@lists.infradead.org; Fri, 31 May 2019 09:05:13 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 93933341; Fri, 31 May 2019 02:05:11 -0700 (PDT) Received: from [10.162.42.223] (p8cg001049571a15.blr.arm.com [10.162.42.223]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 143BB3F59C; Fri, 31 May 2019 02:05:08 -0700 (PDT) Subject: Re: [PATCH 4/4] arm64/mm: Drop vm_fault_t argument from __do_page_fault() To: Mark Rutland References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> <1559133285-27986-5-git-send-email-anshuman.khandual@arm.com> <20190529151134.GH31777@lakrids.cambridge.arm.com> From: Anshuman Khandual Message-ID: <5e565fd3-0d2b-31a5-8644-c91ccc5fb05e@arm.com> Date: Fri, 31 May 2019 14:35:23 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190529151134.GH31777@lakrids.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190531_020512_471801_43D30693 X-CRM114-Status: GOOD ( 26.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrey Konovalov , Will Deacon , linux-kernel@vger.kernel.org, James Morse , Catalin Marinas , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 05/29/2019 08:41 PM, Mark Rutland wrote: > On Wed, May 29, 2019 at 06:04:45PM +0530, Anshuman Khandual wrote: >> __do_page_fault() is over complicated with multiple goto statements. This >> cleans up code flow and while there drops the vm_fault_t argument. >> Signed-off-by: Anshuman Khandual >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: James Morse >> Cc: Andrey Konovalov >> --- >> arch/arm64/mm/fault.c | 38 ++++++++++++++++---------------------- >> 1 file changed, 16 insertions(+), 22 deletions(-) >> >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index 170c71f..a53a30e 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -397,37 +397,31 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re >> static vm_fault_t __do_page_fault(struct mm_struct *mm, unsigned long addr, >> unsigned int mm_flags, unsigned long vm_flags) >> { >> - struct vm_area_struct *vma; >> - vm_fault_t fault; >> + struct vm_area_struct *vma = find_vma(mm, addr); >> >> - vma = find_vma(mm, addr); >> - fault = VM_FAULT_BADMAP; >> if (unlikely(!vma)) >> - goto out; >> - if (unlikely(vma->vm_start > addr)) >> - goto check_stack; >> + return VM_FAULT_BADMAP; >> >> /* >> - * Ok, we have a good vm_area for this memory access, so we can handle >> - * it. >> + * Check if the VMA has got the required permssion with respect >> + * to the access fault here. >> */ > > We already had a perfectly good comment for this check: > > /* > * Check that the permissions on the VMA allow for the fault which > * occurred. > */ > > ... so please keep that and minimize the diff. Sure, will keep all the existing comments here. > >> -good_area: >> + if (!(vma->vm_flags & vm_flags)) >> + return VM_FAULT_BADACCESS; >> + >> /* >> - * Check that the permissions on the VMA allow for the fault which >> - * occurred. >> + * There is a valid VMA for this access. But before proceeding >> + * make sure that it has required flags if there is an attempt >> + * to expand the stack downwards. >> */ > > I think we can drop this comment, given we didn't have it previously. Okay. > >> - if (!(vma->vm_flags & vm_flags)) { >> - fault = VM_FAULT_BADACCESS; >> - goto out; >> - } >> + if (unlikely(vma->vm_start > addr)) { >> + if (!(vma->vm_flags & VM_GROWSDOWN)) >> + return VM_FAULT_BADMAP; >> >> + if (expand_stack(vma, addr)) >> + return VM_FAULT_BADMAP; > > You can drop the line space between these two if statements. Will do. > >> + } >> return handle_mm_fault(vma, addr & PAGE_MASK, mm_flags); >> - >> -check_stack: >> - if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) >> - goto good_area; >> -out: >> - return fault; > > We used to check the stack before the checknig the rest of the vm_flags, > so this changes the precedence of the VM_FAULT_BADMAP and > VM_FAULT_BADACCESS return codes. > > Please check the stack before checking the other vm_flags. Though it makes some sense to move VMA permission check earlier in the function as it is the quicker one but I understand need to maintain the existing code flow in a clean up patch like this. Will retain the existing flow. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel