linux-kernel - [RFC PATCH 05/16] arm64: Implement asm/kpkeys.h using POE

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Message-ID: <20241206101110.1646108-6-kevin.brodsky@arm.com>
Date: Fri,  6 Dec 2024 10:10:59 +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 05/16] arm64: Implement asm/kpkeys.h using POE

Implement the kpkeys interface if CONFIG_ARM64_POE is enabled.
The permissions for KPKEYS_PKEY_DEFAULT (pkey 0) are set to RWX as
this pkey is also used for code mappings.

Signed-off-by: Kevin Brodsky <kevin.brodsky@....com>
---
 arch/arm64/include/asm/kpkeys.h | 43 +++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 arch/arm64/include/asm/kpkeys.h

diff --git a/arch/arm64/include/asm/kpkeys.h b/arch/arm64/include/asm/kpkeys.h
new file mode 100644
index 000000000000..e17f6df41873
--- /dev/null
+++ b/arch/arm64/include/asm/kpkeys.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_KPKEYS_H
+#define __ASM_KPKEYS_H
+
+#include <asm/barrier.h>
+#include <asm/cpufeature.h>
+#include <asm/por.h>
+
+#include <asm-generic/kpkeys.h>
+
+static inline bool arch_kpkeys_enabled(void)
+{
+	return system_supports_poe();
+}
+
+#ifdef CONFIG_ARM64_POE
+
+static inline u64 por_set_kpkeys_level(u64 por, int level)
+{
+	por = por_set_pkey_perms(por, KPKEYS_PKEY_DEFAULT, POE_RXW);
+
+	return por;
+}
+
+static inline int arch_kpkeys_set_level(int level)
+{
+	u64 prev_por = read_sysreg_s(SYS_POR_EL1);
+
+	write_sysreg_s(por_set_kpkeys_level(prev_por, level), SYS_POR_EL1);
+	isb();
+
+	return prev_por;
+}
+
+static inline void arch_kpkeys_restore_pkey_reg(u64 pkey_reg)
+{
+	write_sysreg_s(pkey_reg, SYS_POR_EL1);
+	isb();
+}
+
+#endif /* CONFIG_ARM64_POE */
+
+#endif	/* __ASM_KPKEYS_H */
-- 
2.47.0