[RFC PATCH v9 1/7] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking

Yu-cheng Yu
2020-02-05T18:23:02Z

Introduce Kconfig option X86_INTEL_BRANCH_TRACKING_USER.

Indirect Branch Tracking (IBT) provides protection against CALL-/JMP-
oriented programming attacks. It is active when the kernel has this
feature enabled, and the processor and the application support it.
When this feature is enabled, legacy non-IBT applications continue to
work, but without IBT protection.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/Kconfig | 15 +++++++++++++++
arch/x86/Makefile | 7 +++++++
2 files changed, 22 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d1447380e02e..563f3c81f323 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1998,6 +1998,21 @@ config X86_INTEL_SHADOW_STACK_USER

If unsure, say y.

+config X86_INTEL_BRANCH_TRACKING_USER
+ prompt "Intel Indirect Branch Tracking for user-mode"
+ def_bool n
+ depends on CPU_SUP_INTEL && X86_64
+ select X86_INTEL_CET
+ ---help---
+ Indirect Branch Tracking (IBT) provides protection against
+ CALL-/JMP-oriented programming attacks. It is active when
+ the kernel has this feature enabled, and the processor and
+ the application support it. When this feature is enabled,
+ legacy non-IBT applications continue to work, but without
+ IBT protection.
+
+ If unsure, say y
+
config EFI
bool "EFI runtime service support"
depends on ACPI
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index c34f5befa4c8..f97b2c1c4d04 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -156,6 +156,13 @@ ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
endif
endif

+# Check compiler ibt support
+ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+ ifeq ($(call cc-option-yn, -fcf-protection=branch), n)
+ $(error CONFIG_X86_INTEL_BRANCH_TRACKING_USER not supported by compiler)
+ endif
+endif
+
#
# If the function graph tracer is used with mcount instead of fentry,
# '-maccumulate-outgoing-args' is needed to prevent a GCC bug
--
2.21.0