linux-kernel - [RFC PATCH v5 16/18] arm64: Enable kpkeys_hardened

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Message-ID: <20250815085512.2182322-17-kevin.brodsky@arm.com>
Date: Fri, 15 Aug 2025 09:55:10 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-hardening@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Hildenbrand <david@...hat.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Jann Horn <jannh@...gle.com>,
	Jeff Xu <jeffxu@...omium.org>,
	Joey Gouly <joey.gouly@....com>,
	Kees Cook <kees@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Maxwell Bland <mbland@...orola.com>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Pierre Langlois <pierre.langlois@....com>,
	Quentin Perret <qperret@...gle.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mm@...ck.org,
	x86@...nel.org
Subject: [RFC PATCH v5 16/18] arm64: Enable kpkeys_hardened_pgtables support

kpkeys_hardened_pgtables should be enabled as early as possible (if
selected). It does however require kpkeys being available, which
means on arm64 POE being detected and enabled. POE is a boot
feature, so calling kpkeys_hardened_pgtables_enable() just after
setup_boot_cpu_features() in smp_prepare_boot_cpu() is the best we
can do.

With that done, all the bits are in place and we can advertise
support for kpkeys_hardened_pgtables by selecting
ARCH_HAS_KPKEYS_HARDENED_PGTABLES if ARM64_POE is enabled.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/arm64/Kconfig      | 1 +
 arch/arm64/kernel/smp.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 88b544244829..6c77f446ab09 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2188,6 +2188,7 @@ config ARM64_POE
 	select ARCH_USES_HIGH_VMA_FLAGS
 	select ARCH_HAS_PKEYS
 	select ARCH_HAS_KPKEYS
+	select ARCH_HAS_KPKEYS_HARDENED_PGTABLES
 	help
 	  The Permission Overlay Extension is used to implement Memory
 	  Protection Keys. Memory Protection Keys provides a mechanism for
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 68cea3a4a35c..04ce6b2fd884 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -35,6 +35,7 @@
 #include <linux/kgdb.h>
 #include <linux/kvm_host.h>
 #include <linux/nmi.h>
+#include <linux/kpkeys.h>
 
 #include <asm/alternative.h>
 #include <asm/atomic.h>
@@ -460,6 +461,7 @@ void __init smp_prepare_boot_cpu(void)
 	if (system_uses_irq_prio_masking())
 		init_gic_priority_masking();
 
+	kpkeys_hardened_pgtables_enable();
 	kasan_init_hw_tags();
 	/* Init percpu seeds for random tags after cpus are set up. */
 	kasan_init_sw_tags();
-- 
2.47.0