From patchwork Fri Apr 11 09:16:14 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 14047925 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 3831CC369A2 for ; Fri, 11 Apr 2025 09:23:45 +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: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=0TInbeeHsJ1w6rsCRtJk/Jeb1cP06TeabMr1jT8HfEs=; b=J2oMe4svO8Xq00nSoO5h8Hha/3 L6GsN8JX0DG+1NEoRwsq63FjKf6i0dfikHGWn+xSw7WpxDAec07mF4bjYA6kb9GHlanhw4SJlXoMD uFcjHqEEDmLCbS3I4vK1Vm4l5zxtg9lhLTi/9tX49HxMMYzj+exQXO6N8rPqRQ8li8et6npXzsOZY osO3m8gfFUHEb1x0X7Zkd59/PJ4QlJoqgRiGZ0m48Q3CYHruSrzE8HKB37xt8dhA1aak9kIXHV8cG xSsRUuWE4bfUoBdam9p5k7Yj5EK6ym/t2FlEFmnAqXCF9IgGiFvTDuI69RIrGv18qBloOcwreikIS Km1c00gg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1u3Abk-0000000DC7b-159O; Fri, 11 Apr 2025 09:23:32 +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 1u3AVR-0000000DALL-34xg for linux-arm-kernel@lists.infradead.org; Fri, 11 Apr 2025 09:17:02 +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 081411596; Fri, 11 Apr 2025 02:17:01 -0700 (PDT) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 763A83F6A8; Fri, 11 Apr 2025 02:16:57 -0700 (PDT) From: Kevin Brodsky To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Andrew Morton , Mark Brown , Catalin Marinas , Dave Hansen , David Hildenbrand , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Andy Lutomirski , Marc Zyngier , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , "Mike Rapoport (IBM)" , Ryan Roberts , Thomas Gleixner , Will Deacon , Matthew Wilcox , Qi Zheng , linux-arm-kernel@lists.infradead.org, x86@kernel.org Subject: [RFC PATCH v4 01/18] mm: Introduce kpkeys Date: Fri, 11 Apr 2025 10:16:14 +0100 Message-ID: <20250411091631.954228-2-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250411091631.954228-1-kevin.brodsky@arm.com> References: <20250411091631.954228-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250411_021701_858464_61C2CBF6 X-CRM114-Status: GOOD ( 25.21 ) 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 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() Signed-off-by: Kevin Brodsky --- include/asm-generic/kpkeys.h | 17 ++++++ include/linux/kpkeys.h | 113 +++++++++++++++++++++++++++++++++++ mm/Kconfig | 2 + 3 files changed, 132 insertions(+) create mode 100644 include/asm-generic/kpkeys.h create mode 100644 include/linux/kpkeys.h diff --git a/include/asm-generic/kpkeys.h b/include/asm-generic/kpkeys.h new file mode 100644 index 000000000000..ab819f157d6a --- /dev/null +++ b/include/asm-generic/kpkeys.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef __ASM_GENERIC_KPKEYS_H +#define __ASM_GENERIC_KPKEYS_H + +#ifndef KPKEYS_PKEY_DEFAULT +#define KPKEYS_PKEY_DEFAULT 0 +#endif + +/* + * Represents a pkey register value that cannot be used, typically disabling + * access to all keys. + */ +#ifndef KPKEYS_PKEY_REG_INVAL +#define KPKEYS_PKEY_REG_INVAL 0 +#endif + +#endif /* __ASM_GENERIC_KPKEYS_H */ diff --git a/include/linux/kpkeys.h b/include/linux/kpkeys.h new file mode 100644 index 000000000000..faa6e2615798 --- /dev/null +++ b/include/linux/kpkeys.h @@ -0,0 +1,113 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef _LINUX_KPKEYS_H +#define _LINUX_KPKEYS_H + +#include +#include + +#define KPKEYS_LVL_DEFAULT 0 + +#define KPKEYS_LVL_MIN KPKEYS_LVL_DEFAULT +#define KPKEYS_LVL_MAX KPKEYS_LVL_DEFAULT + +#define __KPKEYS_GUARD(name, set_level, restore_pkey_reg, set_arg, ...) \ + __DEFINE_CLASS_IS_CONDITIONAL(name, false); \ + DEFINE_CLASS(name, u64, \ + restore_pkey_reg, set_level, set_arg); \ + static inline void *class_##name##_lock_ptr(u64 *_T) \ + { return _T; } + +/** + * KPKEYS_GUARD_NOOP() - define a guard type that does nothing + * @name: the name of the guard type + * @cond_arg: an argument specification (optional) + * + * Define a guard type that does nothing, useful to match a real guard type + * that is defined under an #ifdef. @cond_arg may optionally be passed to match + * a guard defined using KPKEYS_GUARD_COND(). + */ +#define KPKEYS_GUARD_NOOP(name, ...) \ + __KPKEYS_GUARD(name, 0, (void)_T, ##__VA_ARGS__, void) + +#ifdef CONFIG_ARCH_HAS_KPKEYS + +#include + +/** + * KPKEYS_GUARD_COND() - define a guard type that conditionally switches to + * a given kpkeys level + * @name: the name of the guard type + * @level: the kpkeys level to switch to + * @cond: an expression that is evaluated as condition + * @cond_arg: an argument specification for the condition (optional) + * + * Define a guard type that switches to @level if @cond evaluates to true, and + * does nothing otherwise. @cond_arg may be specified to give access to a + * caller-defined argument to @cond. + */ +#define KPKEYS_GUARD_COND(name, level, cond, ...) \ + __KPKEYS_GUARD(name, \ + cond ? kpkeys_set_level(level) \ + : KPKEYS_PKEY_REG_INVAL, \ + kpkeys_restore_pkey_reg(_T), \ + ##__VA_ARGS__, void) + +/** + * KPKEYS_GUARD() - define a guard type that switches to a given kpkeys level + * if kpkeys are enabled + * @name: the name of the guard type + * @level: the kpkeys level to switch to + * + * Define a guard type that switches to @level if the system supports kpkeys. + */ +#define KPKEYS_GUARD(name, level) \ + KPKEYS_GUARD_COND(name, level, arch_kpkeys_enabled()) + +/** + * kpkeys_set_level() - switch kpkeys level + * @level: the level to switch to + * + * Switches the kpkeys level to the specified value. @level must be a + * compile-time constant. The arch-specific pkey register will be updated + * accordingly, and the original value returned. + * + * Return: the original pkey register value if the register was written to, or + * KPKEYS_PKEY_REG_INVAL otherwise (no write to the register was + * required). + */ +static __always_inline u64 kpkeys_set_level(int level) +{ + BUILD_BUG_ON_MSG(!__builtin_constant_p(level), + "kpkeys_set_level() only takes constant levels"); + BUILD_BUG_ON_MSG(level < KPKEYS_LVL_MIN || level > KPKEYS_LVL_MAX, + "Invalid level passed to kpkeys_set_level()"); + + return arch_kpkeys_set_level(level); +} + +/** + * kpkeys_restore_pkey_reg() - restores a pkey register value + * @pkey_reg: the pkey register value to restore + * + * This function is meant to be passed the value returned by kpkeys_set_level(), + * in order to restore the pkey register to its original value (thus restoring + * the original kpkeys level). + */ +static __always_inline void kpkeys_restore_pkey_reg(u64 pkey_reg) +{ + if (pkey_reg != KPKEYS_PKEY_REG_INVAL) + arch_kpkeys_restore_pkey_reg(pkey_reg); +} + +#else /* CONFIG_ARCH_HAS_KPKEYS */ + +#include + +static inline bool arch_kpkeys_enabled(void) +{ + return false; +} + +#endif /* CONFIG_ARCH_HAS_KPKEYS */ + +#endif /* _LINUX_KPKEYS_H */ diff --git a/mm/Kconfig b/mm/Kconfig index e113f713b493..819ef5b70695 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1131,6 +1131,8 @@ config ARCH_USES_HIGH_VMA_FLAGS bool config ARCH_HAS_PKEYS bool +config ARCH_HAS_KPKEYS + bool config ARCH_USES_PG_ARCH_2 bool