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 63D6AF36C24 for ; Mon, 20 Apr 2026 06:47:20 +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=Fc4cd5bq7sZ2w7++0hS3ePoxG3H95CYNSIueuKwgKCY=; b=Je5L8Q15U8Qr64DzNwKgtf15I0 qUIoCMkcMkMT+h7eRdl8GZYPxqHsnd1eV7qvgGCOpeZuuEPMhrfZQfgnb4+U2IXd5MYYfdC1y2okS kPxrSNILuKimvAlNfd6guMyP2y1nMVOyebMORDJxF34jS87csFWhJ8RBH/MI+MVAQMOvsrrVsgjxJ IbmkksuxzvhwdAFXwbkmiV53LYsK6DckrzKEgDMwnGrL6Tv6SGiQnMQBteyTyFXWenKh/x+VE4W21 5et0lMUknehiZFvWDBFz9lDXAiMUSLvl8Hc8Bha8VfQ4L2FxwU6+85VpXHsQ+Ho7tvNRMvf8qqM6o gU4cL9gw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wEiPa-00000006VbA-2neK; Mon, 20 Apr 2026 06:47:14 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wEiPY-00000006VaA-0z0S for linux-arm-kernel@lists.infradead.org; Mon, 20 Apr 2026 06:47:13 +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 0650E1516; Sun, 19 Apr 2026 23:47:03 -0700 (PDT) Received: from [10.57.63.177] (unknown [10.57.63.177]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 84A3F3F641; Sun, 19 Apr 2026 23:47:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1776667628; bh=FOT+rxetMCCm/Vt/n/onmxMCYGq9cNElSNypd+yNhnw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=j4epmrx6ayUafCVEQ7h5jQnxg6ml5eCR2lSQ+K/AG8/lUgNRBeMqJIC9TwDXgnhFL m4RmLBmEqyihwgMV+Er/qJM7r3qMVW+zoaiWAHClxUtZ0fNTb8Y2Qj6fEA/l8Wldud UmkwT8YdneFQ678p88xVouNXYqX+mgCG6ljkWgoQ= Message-ID: Date: Mon, 20 Apr 2026 08:46:58 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 01/30] mm: Introduce kpkeys To: "David Hildenbrand (Arm)" , linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Lorenzo Stoakes , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Thomas Gleixner , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org References: <20260227175518.3728055-1-kevin.brodsky@arm.com> <20260227175518.3728055-2-kevin.brodsky@arm.com> <00b24db8-0063-48d6-8bc4-e8b670d8f0d5@kernel.org> <913002a5-e002-4001-ad19-037102d1f97d@arm.com> From: Kevin Brodsky Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260419_234712_524359_5413EE92 X-CRM114-Status: GOOD ( 23.94 ) 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 17/04/2026 19:38, David Hildenbrand (Arm) wrote: > On 4/17/26 17:59, Kevin Brodsky wrote: >> On 17/04/2026 16:37, David Hildenbrand (Arm) wrote: >>> On 2/27/26 18:54, Kevin Brodsky wrote: >>>> kpkeys is a simple framework to enable the use of protection keys >>>> (pkeys) to harden the kernel itself. This patch introduces the basic >>>> API in : a couple of functions to set and restore >>>> the pkey register and macros to define guard objects. >>>> >>>> kpkeys introduces a new concept on top of pkeys: the kpkeys level. >>>> Each level is associated to a set of permissions for the pkeys >>>> managed by the kpkeys framework. kpkeys_set_level(lvl) sets those >>>> permissions according to lvl, and returns the original pkey >>>> register, to be later restored by kpkeys_restore_pkey_reg(). To >>>> start with, only KPKEYS_LVL_DEFAULT is available, which is meant >>>> to grant RW access to KPKEYS_PKEY_DEFAULT (i.e. all memory since >>>> this is the only available pkey for now). >>>> >>>> Because each architecture implementing pkeys uses a different >>>> representation for the pkey register, and may reserve certain pkeys >>>> for specific uses, support for kpkeys must be explicitly indicated >>>> by selecting ARCH_HAS_KPKEYS and defining the following functions in >>>> , in addition to the macros provided in >>>> : >>>> >>>> - arch_kpkeys_set_level() >>>> - arch_kpkeys_restore_pkey_reg() >>>> - arch_kpkeys_enabled() >>> Another thing: why not simply drop the "arch_" stuff from these helpers? >> The first two are not meant to be directly called, they're the >> arch-specific implementation of kpkeys_set_level() and >> kpkeys_restore_pkey_reg(), and those generic functions handle some >> generic logic. >> >> arch_kpkeys_enabled() is directly used in generic code, so I suppose it >> could be renamed to kpkeys_enabled()? It's actually implemented in an >> arch header so I wasn't too sure about it. > I was skimming over patch #13 and spotted: > > +void·__init·kpkeys_hardened_pgtables_init(void) > +{ > +› if·(!arch_kpkeys_enabled()) > +› › return; > + > +› static_branch_enable(&kpkeys_hardened_pgtables_key); > +} > > The arch_* there can just go IMHO. > > I'd also do it for the two ones used by the GUARD macros. If we don't > expect common code wrappers (arch_kpkeys_enabled() vs. kpkeys_enabled), > then the arch_ is unnecessary information -- IMHO Makes sense. I could just rename arch_kpkeys_enabled() to kpkeys_enabled(), but I'm thinking having an arch abstraction could be clearer, after looking into protecting sparse-vmemmap page tables. The new version would look like this: * :     - arch_supports_kpkeys()     - arch_supports_kpkeys_early() [can be called before features have been detected] * defines:     - kpkeys_enabled() -> arch_supports_kpkeys()     - kpkeys_hardened_pgtables_enabled() -> static key     - kpkeys_hardened_pgtables_early_enabled() -> arch_supports_kpkeys_early() [called when setting up sparse-vmemmap, linear map, etc.] There is extra #ifdef'ing going on in , but doesn't need to worry about it. I think this might be easier to follow, I don't like too much having an interface function like kpkeys_enabled() defined in an arch header (not great for kernel-doc comments either). Any thoughts? - Kevin