Commit ba42822a authored Jul 01, 2016 by Catalin Marinas

arm64: Enable CONFIG_ARM64_SW_TTBR0_PAN

This patch adds the Kconfig option to enable support for TTBR0 PAN
emulation. 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 <will.deacon@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 9cf09d68

arch/arm64/Kconfig

+8 −0

Original line number	Diff line number	Diff line
		@@ -794,6 +794,14 @@ config SETEND_EMULATION
		If unsure, say Y
		endif

		config ARM64_SW_TTBR0_PAN
		bool "Emulate Privileged 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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