From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E3663822A6; Wed, 15 Apr 2026 13:00:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776258060; cv=none; b=WSXrxfrzDozIN5ulWuxskIVLBAvMhsiJ6TzMie4CmmCuPpDin+xv51Fn+zv5f5A+9M1Mm08MfZwl0ZGflQUpu8CX+cfuRb8v+zGo10VgJUcXHiY5KLAhEPs0hNe4PXaVSP2esMAa9hvbG7TYZKqllN2u1uwtSQUScOJBez7A0RQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776258060; c=relaxed/simple; bh=R9She/fty570ixfUUkm+hiI2Yw0EuREkb6cYfJweZ5Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CTAwGqn8L3t7HfxW+PNaFfc0UzMdz8973plY4KdcAgTdb6UfbqYWlHc0v7eiS45YBadIT4c0plR5ldgOzdN4fBBNWJO/Jj7971RtpYcdo5RvheRC4a/rPBlmze2no9LSZhITunHj76QMDPr6gFkyYGQhCpKanyNI707zxP8lsYw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Jb+0DT4W; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Jb+0DT4W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7ECE5C19424; Wed, 15 Apr 2026 13:00:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776258059; bh=R9She/fty570ixfUUkm+hiI2Yw0EuREkb6cYfJweZ5Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Jb+0DT4W1wA4KEIVY4FoTtbFdUSZtISD7worO4gRLlYY13CxQryM6AF6d0YWZbYzF LyX3FSawfZ0kMCSA4gRZSBZHETiCihTbBLv/EP9F1CduZHloB/MmIg5Ui7E/EouNKn TeHzhu0uercSUy9wjPxl5S4QDwqFdGmdvmn6wfms/pbWEDnjVLyCz2CpziNgPzIJ6U 9lyu2kDRnQ8Q38D98pATzyqu4XMt0IBR4d44V2436QrK3tQsQUdmouWn62qrqXx3kE btgIr4R3pdICtncO7p14CMOiRN4I88Pu2GDKcg/lLWRmMr8FkvK1VZqsV94h3ZAIFU /EQQgy7FE+paQ== Message-ID: Date: Wed, 15 Apr 2026 15:00:46 +0200 Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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. 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? But how would you handle KPKEY_SUPER_SECRET1 and KPKEY_SUPER_SECRET2 then? -- Cheers, David