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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 61CC8C10F11 for ; Wed, 10 Apr 2019 07:20:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2B2E22070D for ; Wed, 10 Apr 2019 07:20:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728952AbfDJHUg (ORCPT ); Wed, 10 Apr 2019 03:20:36 -0400 Received: from foss.arm.com ([217.140.101.70]:48846 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728787AbfDJHUf (ORCPT ); Wed, 10 Apr 2019 03:20:35 -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 15131A78; Wed, 10 Apr 2019 00:20:35 -0700 (PDT) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9A5AC3F68F; Wed, 10 Apr 2019 00:20:33 -0700 (PDT) Subject: Re: [PATCH 0/6] objtool: Add support for Arm64 To: Josh Poimboeuf , Ard Biesheuvel Cc: Raphael Gault , Linux Kernel Mailing List , linux-arm-kernel , Peter Zijlstra , Catalin Marinas , Will Deacon References: <20190409135243.12424-1-raphael.gault@arm.com> <20190410033732.ibtpnd36655afpfj@treble> From: Julien Thierry Message-ID: Date: Wed, 10 Apr 2019 08:20:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190410033732.ibtpnd36655afpfj@treble> 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 10/04/2019 04:37, Josh Poimboeuf wrote: > On Tue, Apr 09, 2019 at 10:43:18AM -0700, Ard Biesheuvel wrote: >> On Tue, 9 Apr 2019 at 06:53, Raphael Gault wrote: >>> >>> Hi, >>> >>> As of now, objtool only supports the x86_64 architecture but the >>> groundwork has already been done in order to add support for other >>> architecture without too much effort. >>> >>> This series of patches adds support for the arm64 architecture >>> based on the Armv8.5 Architecture Reference Manual. >>> >> >> I think it makes sense to clarify *why* we want this on arm64. Also, >> we should identify things that objtool does today that maybe we don't >> want on arm64, rather than buy into all of it by default. > > Agreed, the "why" should at least be in the cover letter. From my > perspective, the "why" includes: > > - Live patching - objtool stack validation is the foundation for a > reliable unwinder > Yes, as I understand Live patching is a work in progress for arm64. Having objtool to provide more guarantees would be nice. > - ORC unwinder - benefits include presumed improved overall performance > from disabling frame pointers, and the ability to unwind across > interrupts and exceptions > I'm unsure this will be part of the plan. I believe so far arm64 code heavily relies on the presence of frame pointers. It's also part of the Aarch64 Procedure Call Standard. But who knows. > - PeterZ's new uaccess validation? > Yes, we've reverted twice our implementation of user_access_begin/end() on arm64 because of the issue of potentially calling sleeping functions. Once we have the base of objtool work, this would be one of the next work items. Thanks, -- Julien Thierry 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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 74553C10F11 for ; Wed, 10 Apr 2019 07:20:45 +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 428502084B for ; Wed, 10 Apr 2019 07:20:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OgUjBehe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 428502084B 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=XOIguGcWR4IBNUY/PIxg189qz7qmrdB4MbWmpeyfLX0=; b=OgUjBeheWPaxUF OtVRdqN8VKtks4oXsmu5xgX0B/M4YLAKg8++S+Ypd1ldX1LnWqnDKbxH3cNjzx56XWmpUn949Q1hu yU5jDFf1etHAPMpG9JNfA+WHLSHxuP8dPPZ2uTK9liWVlPxExJfV8qloq5EhILVGcEmPoCMqdzUFB e5CHA+4CyyHqx6QGhHOgPnT+qz0xAk6mA8fOfb4u3NrTcUgDhGagmZrkH6Ox5H0g1u6y8hJ1xTbb4 AKPticluwefM91q65ewvuvtbsrk9Qy8d5prPK9PlRaDTEtEFLfif3lvkcTwtG/o7ZNmK0eb/tGc51 DFkop1j2VPfIoTabZLAA==; 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 1hE7XC-0005cK-Pq; Wed, 10 Apr 2019 07:20:38 +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 1hE7X9-0005bn-IN for linux-arm-kernel@lists.infradead.org; Wed, 10 Apr 2019 07:20:38 +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 15131A78; Wed, 10 Apr 2019 00:20:35 -0700 (PDT) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9A5AC3F68F; Wed, 10 Apr 2019 00:20:33 -0700 (PDT) Subject: Re: [PATCH 0/6] objtool: Add support for Arm64 To: Josh Poimboeuf , Ard Biesheuvel References: <20190409135243.12424-1-raphael.gault@arm.com> <20190410033732.ibtpnd36655afpfj@treble> From: Julien Thierry Message-ID: Date: Wed, 10 Apr 2019 08:20:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190410033732.ibtpnd36655afpfj@treble> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190410_002036_310584_431DCF57 X-CRM114-Status: GOOD ( 17.71 ) 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: Peter Zijlstra , Catalin Marinas , Will Deacon , Linux Kernel Mailing List , Raphael Gault , linux-arm-kernel 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 10/04/2019 04:37, Josh Poimboeuf wrote: > On Tue, Apr 09, 2019 at 10:43:18AM -0700, Ard Biesheuvel wrote: >> On Tue, 9 Apr 2019 at 06:53, Raphael Gault wrote: >>> >>> Hi, >>> >>> As of now, objtool only supports the x86_64 architecture but the >>> groundwork has already been done in order to add support for other >>> architecture without too much effort. >>> >>> This series of patches adds support for the arm64 architecture >>> based on the Armv8.5 Architecture Reference Manual. >>> >> >> I think it makes sense to clarify *why* we want this on arm64. Also, >> we should identify things that objtool does today that maybe we don't >> want on arm64, rather than buy into all of it by default. > > Agreed, the "why" should at least be in the cover letter. From my > perspective, the "why" includes: > > - Live patching - objtool stack validation is the foundation for a > reliable unwinder > Yes, as I understand Live patching is a work in progress for arm64. Having objtool to provide more guarantees would be nice. > - ORC unwinder - benefits include presumed improved overall performance > from disabling frame pointers, and the ability to unwind across > interrupts and exceptions > I'm unsure this will be part of the plan. I believe so far arm64 code heavily relies on the presence of frame pointers. It's also part of the Aarch64 Procedure Call Standard. But who knows. > - PeterZ's new uaccess validation? > Yes, we've reverted twice our implementation of user_access_begin/end() on arm64 because of the issue of potentially calling sleeping functions. Once we have the base of objtool work, this would be one of the next work items. Thanks, -- Julien Thierry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel