On Thu, Feb 27, 2020 at 05:44:09PM +0000, Mark Brown wrote: > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 0b30e884e088..e37f4f07b990 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1519,6 +1519,28 @@ 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. To keep the series bisectable, I'd move the Kconfig into a separate patch towards the end. It looks like the feature is only partially supported after patch 3, so let's not advertise it here. -- Catalin
