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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A36E7C3DA49 for ; Tue, 16 Jul 2024 11:41:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=lqjE0jWOrhYT2jZSFx8geZtOnUjGfNcPTMchXoKzX8I=; b=0attjDbgjWdHm9CDg/nqNEPUCC ZgW6PI4S4EqYM13P8t179YR3jR/0YzfhWqrYgk/h1SvWayoCChNviRyL+Uy5PuNW48Zx1IYZbfCYu BYOVK0jAbwEakLmxSiD+KVZ+u7vxC7KK3MTJMB1S84Jq98Tk4/Aq4llM9phJSpNyyXW0582bKgCVp cX1+h+b7GuWQ/ZshD14vzIJLj8ZGUAa04C2KuL9bA/uDiJqNBPNfNupga6gGT6avFx1Rq5wJ1LOsE ng75YcR9Fbf3whKp9ZvEvtSs7Mij+lJ5/Av2BnJy7Jw5qL3xeYN6obbihPxxch8IVIs85+PsrI+0z EcsIakLw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sTgYj-0000000AHQM-1vsF; Tue, 16 Jul 2024 11:41:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sTgYO-0000000AHMs-0Grb for linux-arm-kernel@lists.infradead.org; Tue, 16 Jul 2024 11:41:10 +0000 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 B19091063; Tue, 16 Jul 2024 04:41:30 -0700 (PDT) Received: from [10.163.52.225] (unknown [10.163.52.225]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BB35A3F766; Tue, 16 Jul 2024 04:40:54 -0700 (PDT) Message-ID: Date: Tue, 16 Jul 2024 17:10:50 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 17/29] arm64: implement PKEYS support To: Kevin Brodsky , Joey Gouly , linux-arm-kernel@lists.infradead.org Cc: akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, bp@alien8.de, broonie@kernel.org, catalin.marinas@arm.com, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, szabolcs.nagy@arm.com, tglx@linutronix.de, will@kernel.org, x86@kernel.org, kvmarm@lists.linux.dev References: <20240503130147.1154804-1-joey.gouly@arm.com> <20240503130147.1154804-18-joey.gouly@arm.com> <18aee949-7e07-45e1-85c8-c990f017f305@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <18aee949-7e07-45e1-85c8-c990f017f305@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240716_044108_189686_8E3A3D38 X-CRM114-Status: GOOD ( 13.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/9/24 18:37, Kevin Brodsky wrote: > On 03/05/2024 15:01, Joey Gouly wrote: >> @@ -267,6 +294,28 @@ static inline unsigned long mm_untag_mask(struct mm_struct *mm) >> return -1UL >> 8; >> } >> >> +/* >> + * We only want to enforce protection keys on the current process >> + * because we effectively have no access to POR_EL0 for other >> + * processes or any way to tell *which * POR_EL0 in a threaded >> + * process we could use. > > I see that this comment is essentially copied from x86, but to me it > misses the main point. Even with only one thread in the target process > and a way to obtain its POR_EL0, it still wouldn't make sense to check > that value. If we take the case of a debugger accessing an inferior via > ptrace(), for instance, the kernel is asked to access some memory in > another mm. However, the debugger's POR_EL0 is tied to its own address > space, and the target's POR_EL0 is relevant to its own execution flow > only. In such situations, there is essentially no user context for the > access, so It fundamentally does not make sense to make checks based on > pkey/POE or similar restrictions to memory accesses (e.g. MTE). Indeed this makes more sense. There is no memory context even if there is access to another POR_EL0. The comment above could be improved describing this limitation.