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UPSTREAM: arm64: Enable CONFIG_ARM64_SW_TTBR0_PAN

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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>

Bug: 31432001
Change-Id: I2f0b5f332e3c56ea0453ff69826525dec49f034b
(cherry picked from commit ba42822af1)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Catalin Marinas
2016-07-01 18:25:31 +01:00
committed by Sami Tolvanen
parent 9fcab0c5b4
commit 7f89f7225c
1 changed files with 8 additions and 0 deletions
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8
arch/arm64/Kconfig
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@@ -706,6 +706,14 @@ 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