Re: [PATCH v9 13/13] arm64: BTI: Add Kconfig entry for userspace BTI
From: Kees Cook <hidden>
Date: 2020-03-13 00:01:52
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linux-arm-kernel, linux-fsdevel, lkml
On Wed, Mar 11, 2020 at 07:26:08PM +0000, Mark Brown wrote:
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 <redacted> -Kees
quoted hunk ↗ jump to hunk
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
-- Kees Cook