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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 228B1F43693 for ; Fri, 17 Apr 2026 12:01:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 799376B0089; Fri, 17 Apr 2026 08:01:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 770B66B009F; Fri, 17 Apr 2026 08:01:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6868F6B00A1; Fri, 17 Apr 2026 08:01:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 584516B0089 for ; Fri, 17 Apr 2026 08:01:06 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D7DC0160151 for ; Fri, 17 Apr 2026 12:01:05 +0000 (UTC) X-FDA: 84667906890.23.5907FCA Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id 185664001B for ; Fri, 17 Apr 2026 12:01:03 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gixXRhDe; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776427264; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=o5i6ZwwLoLQhesYYrf2MVqwthd8ZBbpIOC2DaMlIh4k=; b=Kmm5Ks4DZ2WMsJfShN9MQcm5FY2io2ymg4HhYvoiIM0yU6MASBrSoba28e4hSzTAIvZQDE dQaMP2AvmbQzFXi22q0mur8yf6uz+91iDw3frc49k0gaLZEqnyuohV2MZbrJC0G57PbZ3N oKzVRDr1L8rCBCG4uugLG3VDHZTjYhg= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gixXRhDe; spf=pass (imf07.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776427264; a=rsa-sha256; cv=none; b=L+/4h9n6fYqEYTVngEJP/stjWkNXAOotFUC7Hp5cKMyH66SeHpCni6YNJUQBv9loplJemF ZktkgtMDD1QP5OVAM42970NF1IJh3Ke8Cp/iPhzn78XZFyfyZygg9orq60aKFU8LrR+Y3p uSTKXq9pF5Q7Vro29YS8ZnLptCUF4/E= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 6076C60128; Fri, 17 Apr 2026 12:01:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2638AC19425; Fri, 17 Apr 2026 12:00:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776427263; bh=mU3rZj67IqrTTnj++/n+dIVHR+LNXGChH2TwgHtrl7c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gixXRhDebXpKk32RlamutnzhZ1GLLADsv69hPJWEWYEjKtp3w8dF8lF6PgtCGdwZM tHyhMMIUE1WhuCUXAIevFo9WCqiNv6W5zqdELOSVxL8JkzeDVQP/bUGzP00tcpX5Me 8noj3V3GvefKdJTw10NZe+Dl1Qh7flMuer7J7K+UfzlR//frRT9NBnPz7gyBws+jj5 xD5K/9xYPH3+BjB4PtpVCdRXZvdqpJXiJtSCkbniaMGj83hycL+c6WB0+res+2nkir 1EB5YpMtEuQeKnM0Z7JXWRYUpCp3tkdfiWJmZrf6xu1CNqzLIqcS3OMLbBNOnef/jQ OoJolHOLfmzOg== Message-ID: Date: Fri, 17 Apr 2026 14:00:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 01/30] mm: Introduce kpkeys To: Kevin Brodsky , 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> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 185664001B X-Stat-Signature: juu8fmywbay7rsetbb3g8gixbgfoa8zp X-Rspam-User: X-HE-Tag: 1776427263-753911 X-HE-Meta: U2FsdGVkX18J1IMMrelVzuUb7BDX8nw/L+98ka1bqKefCmLuVmiJc2IYHTkGCEwVDWhdMBN4Yb2o/Z7snCjDyVRzd4wD7DRZApB7A/6xU0COebsf4suj1KrfaIVb1nwZp8PGgzlf8KCKh5VQYk/sYH4u0s/tBxieYDPmVjIyjkOYqVeaMAsx6d/sEAb203QwtmY9N8Y8avb8L+jGxMtsnphcb776te57cvqwTmVKqYIQy8ux4cJarTywpgiX6XtL5+Lcg39f5zYf/nMnctc4aDV9nxc3tg6C2oF8JRc7a2CAhchgMzoDyJ+4yMHWMrLAqLAcqDn3U2faEhWGazncQMYkdXixms60CQdq8FEW2wjdYPDE/Pw1bM7URGy86iqWCipYBcrTJ5uSlU2kswXbE/16vE+fAagLJKKJudm8BtWUmwf/IZcX/TWslHci0nBnu+W8a0kbQ0z2mJOmTWScJlyEJAQhllRclUaXR9W/iT9/2xR9bubEjEF8eWm8q5PwwRr42Ft+AGa6n3ZvMQ6SvmcSuoC0KVPRivYH5ZV2Kv5nk+TT0tlbsUR/d3nwg33JFnTpcweEgbTQgm6DuRTOB4hNpewOQHVXASOKAMAXdEZBhbAWu/Mw2i8z8lHx03nRxt+AmZ3Sazx0c+LKnacTLXYUjMgHo0MOXalHhhB8m0KQiuDz1Zl8SPLeWk1iCogv5iZlwkUVNCvCHYYv9aVpkkhVF1l0bpwfZTVb1OpfR+LXjGlMXVwBJsgfofqBgJQ7eZOp48sOI3iNr9eRRVQUJVPLq6u9W7PisyyemNeE0Y/uiTgFmy/+hBoxOHUzcHMdni1T41Ey8HE6bo6U/pVLtNHKfDCz/DX+egLiBSi5b0jr953bUbxwuJ06S+pcRxhpiF2TmKVcJIdPZG6cknatxRTupHn3lNV6KqHAzMwYDf7CWASjPGwj0Hji9qKXFcnzuU8iXiWVprVJCz5pvVr 4nWhWKeC c2pHJ3D5ddiffRPgmcvz1/m3kxNhzIjQclrRVGmUwWHPnIw6BPGYGi4N0w+pMk3CZXvkX/embGhcBj889jNq6PHHsCpUgJatquCIze6E5tX46Q20hu9dhKLw03J+lvBkmWkltfF8hf65dXV3FSfQzbNgkwRob9I8pSORCo7yUFlFO+onX5crpvACjCJFIz2PYvETTzPOOQy5/BTiWmK2C+kEovI72v1OPt3DBmnJ9iJQqQ3Ny7AKjHVFPmgUIaQukhKo1 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 17:50, Kevin Brodsky wrote: > On 15/04/2026 15:00, 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 >>> : >> I don't quite understand the reason for using levels. Levels sounds like >> it would all be in some ordered fashion, where higher levels have access >> to lower levels. > > That was originally the idea indeed, but in practice I don't expect > levels to have a strict ordering, as it's not practical for composing > features. > >> Think of that as a key that can unlock all "lower" locks, not just a >> single lock. >> >> Then, the question is about the ordering once we introduce new >> keys/locks. With two, it obviously doesn't matter :) >> >> So naturally I wonder whether levels is really the right abstraction >> here, and why we are not simply using "distinct" keys, like >> >> KPKEY_DEFAULT >> KPKEY_PGTABLE >> KPKEY_SUPER_SECRET1 >> KPKEY_SUPER_SECRET2 >> >> Is it because you want KPKEY_PGTABLE also be able to write to KPKEY_DEFAULT? > > Right, and in general a given level may be able to write to any number > of pkeys. That's why I don't want to conflate pkeys and levels. Agreed > that "level" might not be the clearest term though, since there's no > strict ordering. As discussed offline, maybe the right terminology to use here would be something like a "context". You'd be activating/setting a context. KPKEY_CTX_DEFAULT KPKEY_CTX_PGTABLE KPKEY_CTX_SUPER_SECRET1 What is accessible (and how) is defined for each context. For example, I would assume that all context allow for read/write access to everything that KPKEY_CTX_DEFAULT has access to. -- Cheers, David