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Date: Fri, 12 Aug 2016 16:27:46 +0100
From: Catalin Marinas <>
	Will Deacon <>,
	James Morse <>,
	Kees Cook <>
Subject: [PATCH 7/7] arm64: Enable CONFIG_ARM64_TTBR0_PAN

This patch adds the Kconfig option to enable support for TTBR0 PAN. The
option is default off because of a slight performance hit when enabled,
caused by the additional TTBR0_EL1 switching during user access
operations or exception entry/exit code.

Cc: Will Deacon <>
Cc: James Morse <>
Cc: Kees Cook <>
Signed-off-by: Catalin Marinas <>
 arch/arm64/Kconfig | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 69c8787bec7d..e7d5d0a7f6b4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -784,6 +784,14 @@ config SETEND_EMULATION
 	  If unsure, say Y
+config ARM64_TTBR0_PAN
+	bool "Priviledged Access Never using TTBR0_EL1 switching"
+	help
+	  Enabling this option prevents the kernel from accessing
+	  user-space memory directly by pointing TTBR0_EL1 to a reserved
+	  zeroed area and reserved ASID. The user access routines
+	  restore the valid TTBR0_EL1 temporarily.
 menu "ARMv8.1 architectural features"
 config ARM64_HW_AFDBM

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