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a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1787062287; bh=9dqIiwyGVVVxGSjHeF+MAxucmgOd3jqjzZqWJtM2VB8=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=mbyRdbQKlO/26/1Fa4w7m6hPuhvlnytHQISAVLXNFMFm2TRNGzVS887HJloU+7YFI EhwgLWAo7jUlXEB9y9MveCPjEeP/SCYRV0egYsHA/wHS7GchteF9wmfkFRh5vtG0tw hYHMyLbtBL+KBswx02wzpRLfu1K/xbvltgcfOikQ= From: Kevin Brodsky Date: Tue, 18 Aug 2026 15:08:43 +0100 Subject: [PATCH RFC v9 01/25] mm: Introduce kpkeys MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260818-kpkeys-v9-1-743ad31b2c8f@arm.com> References: <20260818-kpkeys-v9-0-743ad31b2c8f@arm.com> In-Reply-To: <20260818-kpkeys-v9-0-743ad31b2c8f@arm.com> To: linux-hardening@vger.kernel.org Cc: Kevin Brodsky , Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linu Cherian , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , =?utf-8?q?Pierre-Cl=C3=A9ment_Tosi?= , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Ira Weiny , Lorenzo Stoakes , Thomas Gleixner X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787062276; l=5979; i=kevin.brodsky@arm.com; s=20260427; h=from:subject:message-id; bh=9dqIiwyGVVVxGSjHeF+MAxucmgOd3jqjzZqWJtM2VB8=; b=mahw5b1Ggs/ZgmHXvp1+lRl2JXwUwDEs2wO6R50H/rbCAhz9vVQsA9V4MOhyhrRgRZSG93KtJ u3AmxqgV//JDyT3mBF536urNrR4z5MugwWxb7CJPyJbzpxbN6IDf9DU X-Developer-Key: i=kevin.brodsky@arm.com; a=ed25519; pk=N2QG+eJKrvkNovwhhwJhnJ4+ScVfsGCHldmqLfcMTFs= X-Rspamd-Queue-Id: B53101A0006 X-Rspam-User: X-Stat-Signature: osia9nwupfwq6g867zpra9fej5ecucuc X-Rspamd-Server: rspam06 X-HE-Tag: 1787062287-193326 X-HE-Meta: U2FsdGVkX18egVVBr+OHqMHOTRGBFwOu249O7+Dx1VebhRbJz8/VCKRYO1HyIAhuYPCy9/JQf32VCNCTpEhNOQbtH79yViZ1aL8aQ9paTwbYHH0a/zclIOrb4xW5QDkwtgny7PY3CiR3Z5lunpJtN3aqn9e36pecSLyFW5uFsJZUW9VIJwBV6wgfplryoRSelG0BDzhRXaHo2AIizlFfSm7R2LfrpaKGagOLip/rAJhm0o8HjU2v+pvLgFKQiuyi41d/cGYJOaIW95bA7p3tWAe1PwiD6dSthUZbM67nkk9FNyBIu+dTtOUfAH1lB2sgNkIQG4qH0MrFRqUOOBKiYxA0SooSXvo9aGChbwvrPqY7NQkUMXDKWJ2GQvw3rHRbcda9RsPcCMnMTqXXqg1Lw5/fGfOyMw3Pvaj69zs47KJN5MAQf0+boDeC/22jfH8ofvAPWURLuM1rtLaToAEmF+5tREiAJJMKpDOj2MUu+646dnytmE/LFP//N5hArurFj+zJ08MxbWqUzS9l3KVvDGTclDX7PcMGAVB+WCVK5kPOG4N/1B+TrSNrHkYtAMqe5NMzR/msczZDiyuwSOTXPFcEXHc1YO1jPmp8s7dSkhwOEFyRNpCc3m+hBU7f0R/vaFkKt6Zq9JB9VoFq+WHWXMjSDhp5vF+1qdGf3Ekg30uqJh95lzGVUZJMcONdNxIELPJL/Ljojj5YtZGLfnzeanoIHdSdBtCxnRLBuYYcoG+R7M7ixYkOdvGmottchtHuUg1bgYViyT8+/lbeHse+bTfRyq1iRZ18bn2M6WY37ZiwuEeWeSh9jK/NUTeB6Uuqw6gIgQzEDxT/n13DpP7KGEZabddD0qmvd3G1mUGOeXIzsckrEbCs6FxhhlkuySQ4cOrA/J8imRH45PV2nhpO+t8JvMI6oB02JXBOvprEQRrVfMdmuM3w2gD4uz+JqErRuKh+ujbThSqvMrzgX0y E+ASsdiK 8CsPkLkCQpHWio+f3upaJphBPGyQ6BuTOGNLViMGj1lFkeVqOWcCk5XtjpEiIrEmM8RzWKKVdMrrTVxtBz8AiB69ZdnzDnNkOv1TLLqPZQ201iB6u+m82mi1qy/+knhztDjBuntW9pwTtpueNFi2HR0bTmO/+0lpehB7cMQ/FQQw9CgJC83lcJJM9AcMAVPe0FNpvBj276//lLLOoOQ1j4nsjHsTvR5hdLooGlEmOtIND3B1mv11OFkBR2MNTaIHhVOlcG88/W85rngFYObdgrYxY2WshRyXj2r/t9Dzi6LaYf38= 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 enter/leave a kpkeys context and macros to define guard objects. kpkeys introduces a new concept on top of pkeys: the kpkeys context. Each context is associated with a set of permissions for the pkeys managed by the kpkeys framework. kpkeys_enter_context(ctx) sets those permissions according to ctx, and returns the original kpkeys state (typically the arch-specific pkeys register) that is later restored by calling kpkeys_leave_context(). To start with, only KPKEYS_CTX_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). The underlying representation of each kpkeys context is entirely architecture-specific. Support for kpkeys must be explicitly indicated by selecting ARCH_HAS_KPKEYS and defining the following functions in : * arch_kpkeys_enter_context() * arch_kpkeys_leave_context() * arch_supports_kpkeys() Additionally, must define struct arch_kpkeys_state, which typically provides storage for the pkeys register. Signed-off-by: Kevin Brodsky --- include/linux/kpkeys.h | 104 +++++++++++++++++++++++++++++++++++++++++++ include/linux/kpkeys_types.h | 25 +++++++++++ mm/Kconfig | 2 + 3 files changed, 131 insertions(+) diff --git a/include/linux/kpkeys.h b/include/linux/kpkeys.h new file mode 100644 index 000000000000..eac522f55214 --- /dev/null +++ b/include/linux/kpkeys.h @@ -0,0 +1,104 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef _LINUX_KPKEYS_H +#define _LINUX_KPKEYS_H + +#include +#include +#include + +/** + * KPKEYS_GUARD_NOOP() - define a guard type that does nothing + * @name: the name of the guard type + * + * Define a guard type that does nothing, useful to match a real guard type + * that is defined under an #ifdef. + */ +#define KPKEYS_GUARD_NOOP(name) \ + __DEFINE_CLASS_IS_CONDITIONAL(name, false); \ + DEFINE_CLASS(name, bool, (void)_T, false, void); \ + static inline void *class_##name##_lock_ptr(bool *_T) \ + { return _T; } + +#ifdef CONFIG_ARCH_HAS_KPKEYS + +#include + +/** + * KPKEYS_GUARD_COND() - define a guard type that conditionally switches to + * a given kpkeys context + * @name: the name of the guard type + * @ctx: the kpkeys context to switch to + * @cond: an expression that is evaluated as condition + * + * Define a guard type that switches to @ctx if @cond evaluates to true, + * and does nothing otherwise. + */ +#define KPKEYS_GUARD_COND(name, ctx, cond) \ + __DEFINE_CLASS_IS_CONDITIONAL(name, false); \ + DEFINE_CLASS(name, struct kpkeys_state, \ + kpkeys_leave_context(&_T), \ + (cond) ? kpkeys_enter_context(ctx) : \ + (struct kpkeys_state) {}, void); \ + static inline \ + void *class_##name##_lock_ptr(struct kpkeys_state *_T) \ + { return _T; } + +/** + * KPKEYS_GUARD() - define a guard type that switches to a given kpkeys context + * if kpkeys are supported + * @name: the name of the guard type + * @ctx: the kpkeys context to switch to + * + * Define a guard type that switches to @ctx if the system supports kpkeys. + */ +#define KPKEYS_GUARD(name, ctx) \ + KPKEYS_GUARD_COND(name, ctx, kpkeys_supported()) + +/** + * kpkeys_enter_context() - enter a kpkeys context + * @ctx: the context to switch to + * + * Enters the specified kpkeys context. @ctx must be a compile-time constant. + * + * Return: state to be passed to kpkeys_leave_context(). + */ +static __always_inline +struct kpkeys_state kpkeys_enter_context(enum kpkeys_ctx ctx) +{ + BUILD_BUG_ON_MSG(!__builtin_constant_p(ctx), + "kpkeys_enter_context() only takes constant values"); + BUILD_BUG_ON_MSG(ctx < 0 || ctx >= KPKEYS_CTX_COUNT, + "Invalid value passed to kpkeys_enter_context()"); + + return arch_kpkeys_enter_context(ctx); +} + +/** + * kpkeys_leave_context() - leave a kpkeys context + * @state: state returned by kpkeys_enter_context() + * + * Restores the state saved when entering a kpkeys context. If no context was + * entered, this function does nothing. + */ +static __always_inline +void kpkeys_leave_context(const struct kpkeys_state *state) +{ + if (state->entered_context) + arch_kpkeys_leave_context(state); +} + +static inline bool kpkeys_supported(void) +{ + return arch_supports_kpkeys(); +} + +#else /* CONFIG_ARCH_HAS_KPKEYS */ + +static inline bool kpkeys_supported(void) +{ + return false; +} + +#endif /* CONFIG_ARCH_HAS_KPKEYS */ + +#endif /* _LINUX_KPKEYS_H */ diff --git a/include/linux/kpkeys_types.h b/include/linux/kpkeys_types.h new file mode 100644 index 000000000000..9de59092e9c3 --- /dev/null +++ b/include/linux/kpkeys_types.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef _LINUX_KPKEYS_TYPES_H +#define _LINUX_KPKEYS_TYPES_H + +#include + +#ifdef CONFIG_ARCH_HAS_KPKEYS +#include +#endif + +#if defined(CONFIG_ARCH_HAS_KPKEYS) && !defined(__ASSEMBLY__) + +enum kpkeys_ctx { + KPKEYS_CTX_DEFAULT = 0, + KPKEYS_CTX_COUNT, +}; + +struct kpkeys_state { + bool entered_context; + struct arch_kpkeys_state arch_state; +}; + +#endif /* CONFIG_ARCH_HAS_KPKEYS && !__ASSEMBLY__ */ + +#endif /* _LINUX_KPKEYS_TYPES_H */ diff --git a/mm/Kconfig b/mm/Kconfig index 9e0ca4824905..55e6763d5792 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1281,6 +1281,8 @@ config ARCH_USES_HIGH_VMA_FLAGS bool config ARCH_HAS_PKEYS bool +config ARCH_HAS_KPKEYS + bool config ARCH_USES_PG_ARCH_2 bool -- 2.51.2