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 6D660C7618A for ; Fri, 17 Mar 2023 17:16:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230270AbjCQRQZ (ORCPT ); Fri, 17 Mar 2023 13:16:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229986AbjCQRQX (ORCPT ); Fri, 17 Mar 2023 13:16:23 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 738E02E0D9; Fri, 17 Mar 2023 10:16:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1679073381; x=1710609381; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=94pw9rxhjDC1X+hebb6ss2+DW8AEYbcU3bNVKEnzNSw=; b=Ouw2qDrE3dp6B+qN1zUjJ+OBvrVPOsUycbq7cCyfPN5cmvmk6NUH1Z+P pZw/0JEUzEF6GEyTk3afqgUP4xrwS8aHCfeq/Mx8JXQsEm4OfAR9q5t1E EpOO+s2VLw7PL1EdJCmZwQKGk0GaOevr1JJvSb/YkIErQigHEubMix4Nr X+qF5fT8rvQZQ7ZKVgEpXucbCdDSxYKH8jV6ybdHf2qbjhqLzI4Gkc2Sv w3q4mMjW7dv8n7GYbf/p+t0xAS0zSdMy5Do9MWZ4AZNfPzie9IYHlAqDf qnhjs/VWG2yz/yUlRO11x4BAslCcIRLvq74YPV0abdo8pVtRfI+ItuQlP Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="403185767" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="403185767" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2023 10:16:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10652"; a="682751665" X-IronPort-AV: E=Sophos;i="5.98,268,1673942400"; d="scan'208";a="682751665" Received: from dlacbain-mobl.amr.corp.intel.com (HELO [10.209.46.45]) ([10.209.46.45]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Mar 2023 10:16:18 -0700 Message-ID: <236ae66c-fafb-80e9-d58b-6b18a22071c1@intel.com> Date: Fri, 17 Mar 2023 10:16:18 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH v7 22/41] mm/mmap: Add shadow stack pages to memory accounting Content-Language: en-US To: Deepak Gupta , Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, Yu-cheng Yu References: <20230227222957.24501-1-rick.p.edgecombe@intel.com> <20230227222957.24501-23-rick.p.edgecombe@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 3/17/23 10:12, Deepak Gupta wrote: >> /* >> - * Stack area - automatically grows in one direction >> + * Stack area >> * >> - * VM_GROWSUP / VM_GROWSDOWN VMAs are always private anonymous: >> - * do_mmap() forbids all other combinations. >> + * VM_GROWSUP, VM_GROWSDOWN VMAs are always private >> + * anonymous. do_mmap() forbids all other combinations. >> */ >> static inline bool is_stack_mapping(vm_flags_t flags) >> { >> - return (flags & VM_STACK) == VM_STACK; >> + return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK); > Same comment here. `VM_SHADOW_STACK` is an x86 specific way of > encoding a shadow stack. > Instead let's have a proxy here which allows architectures to have > their own encodings to represent a shadow stack. This doesn't _preclude_ another architecture from coming along and doing that, right? I'd just prefer that shadow stack architecture #2 comes along and refactors this in precisely the way _they_ need it.