linux-kernel - [RFC PATCH 07/16] arm64: Enable kpkeys

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Message-ID: <20241206101110.1646108-8-kevin.brodsky@arm.com>
Date: Fri,  6 Dec 2024 10:11:01 +0000
From: Kevin Brodsky <kevin.brodsky@....com>
To: linux-hardening@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Kevin Brodsky <kevin.brodsky@....com>,
	aruna.ramakrishna@...cle.com,
	broonie@...nel.org,
	catalin.marinas@....com,
	dave.hansen@...ux.intel.com,
	jannh@...gle.com,
	jeffxu@...omium.org,
	joey.gouly@....com,
	kees@...nel.org,
	maz@...nel.org,
	pierre.langlois@....com,
	qperret@...gle.com,
	ryan.roberts@....com,
	will@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org
Subject: [RFC PATCH 07/16] arm64: Enable kpkeys

This is the final step to enable kpkeys on arm64. We enable
POE at EL1 by setting TCR2_EL1.POE, and initialise POR_EL1 so that
it enables access to the default pkey/POIndex (default kpkeys
level). An ISB is added so that POE restrictions are enforced
immediately.

Having done this, we can now select ARCH_HAS_KPKEYS if ARM64_POE is
enabled.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/arm64/Kconfig             | 1 +
 arch/arm64/kernel/cpufeature.c | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 100570a048c5..f35964641c1a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2183,6 +2183,7 @@ config ARM64_POE
 	def_bool y
 	select ARCH_USES_HIGH_VMA_FLAGS
 	select ARCH_HAS_PKEYS
+	select ARCH_HAS_KPKEYS
 	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/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6ce71f444ed8..3925bf04fb2f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -75,6 +75,7 @@
 #include <linux/cpu.h>
 #include <linux/kasan.h>
 #include <linux/percpu.h>
+#include <linux/kpkeys.h>
 
 #include <asm/cpu.h>
 #include <asm/cpufeature.h>
@@ -2376,8 +2377,10 @@ static void cpu_enable_mops(const struct arm64_cpu_capabilities *__unused)
 #ifdef CONFIG_ARM64_POE
 static void cpu_enable_poe(const struct arm64_cpu_capabilities *__unused)
 {
-	sysreg_clear_set(REG_TCR2_EL1, 0, TCR2_EL1x_E0POE);
+	write_sysreg_s(por_set_kpkeys_level(0, KPKEYS_LVL_DEFAULT), SYS_POR_EL1);
+	sysreg_clear_set(REG_TCR2_EL1, 0, TCR2_EL1x_E0POE | TCR2_EL1x_POE);
 	sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_E0POE);
+	isb();
 }
 #endif
 
-- 
2.47.0