[PATCH v10 13/13] arm64: BTI: Add Kconfig entry for userspace BTI

Mark Brown
2020-03-16T16:54:49Z

From: Dave Martin <Dave.Martin@arm.com>

Now that the code for userspace BTI support is in the kernel add the
Kconfig entry so that it can be built and used.

[Split out of "arm64: Basic Branch Target Identification support"
-- broonie]

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/Kconfig | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 8a15bc68dadd..d65d226a77ec 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1522,6 +1522,28 @@ endmenu

menu "ARMv8.5 architectural features"

+config ARM64_BTI
+ bool "Branch Target Identification support"
+ default y
+ help
+ Branch Target Identification (part of the ARMv8.5 Extensions)
+ provides a mechanism to limit the set of locations to which computed
+ branch instructions such as BR or BLR can jump.
+
+ To make use of BTI on CPUs that support it, say Y.
+
+ BTI is intended to provide complementary protection to other control
+ flow integrity protection mechanisms, such as the Pointer
+ authentication mechanism provided as part of the ARMv8.3 Extensions.
+ For this reason, it does not make sense to enable this option without
+ also enabling support for pointer authentication. Thus, when
+ enabling this option you should also select ARM64_PTR_AUTH=y.
+
+ Userspace binaries must also be specifically compiled to make use of
+ this mechanism. If you say N here or the hardware does not support
+ BTI, such binaries can still run, but you get no additional
+ enforcement of branch destinations.
+
config ARM64_E0PD
bool "Enable support for E0PD"
default y
--
2.20.1