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Subject[RFC PATCH v2 21/27] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking
Date
The user-mode indirect branch tracking support is done mostly by
GCC to insert ENDBR64/ENDBR32 instructions at branch targets.
The kernel provides CPUID enumeration, feature MSR setup and
the allocation of legacy bitmap.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/Kconfig | 12 ++++++++++++
arch/x86/Makefile | 7 +++++++
2 files changed, 19 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 768343768643..01de9743efe6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1945,6 +1945,18 @@ 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
+ select ARCH_HAS_PROGRAM_PROPERTIES
+ ---help---
+ Indirect Branch Tracking provides hardware protection against return-/jmp-
+ oriented programing attacks.
+
+ 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 ad1314e5ef65..a7913de34866 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -164,6 +164,13 @@ 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
--
2.17.1
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