From ba42822af1c287f038aa550f3578c61c212a892e Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 1 Jul 2016 18:25:31 +0100 Subject: [PATCH] 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 Cc: James Morse Cc: Kees Cook Cc: Mark Rutland 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 0b8227f23eed..e8dd55e7db38 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -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 -- 2.20.1