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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-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DA33F80008 X-Stat-Signature: 9xk44r4fu1cwikwiwcza9dxohhuzswnb X-HE-Tag: 1744363021-796632 X-HE-Meta: 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 khPZ6jaw us48hYEufwSrD6rviJIOUKqu+BJ7W0S+bcpavqd7mf1eN8Pbpk+V4Nf1LCygcKsMDGLb9gEPRGvUwYletoEU+qV/AE+uRzePz55Bc1bVyH3rp7PgEXOmCryKtRCRDcwqsHkjRqFAjvXT6Z1U+i4Lmds6Wxnq5vkpMYxkjbNni7ujN+2lKlrq53PzWwCurwZTF1T/N X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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