[RFC PATCH 3/3] ArmVirtPkg/ArmVirtQemu: Implement BTI for runtime regions

["Ard Biesheuvel" <ardb@kernel.org>]

Add a build option RUNTIM_BTI_ENABLE, and wire it up to the newly added
PCD that controls the value of the BTI flag in the memory attributes
table, as well as the command line options passed to the compiler to get
it to emit BTI landing pads in BASE and DXE_RUNTIME_DRIVER modules.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 ArmVirtPkg/ArmVirtQemu.dsc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 0f1c6395488a..0a67fe250d86 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -32,6 +32,7 @@ [Defines]
   DEFINE TPM2_ENABLE             = FALSE
   DEFINE TPM2_CONFIG_ENABLE      = FALSE
   DEFINE CAVIUM_ERRATUM_27456    = FALSE
+  DEFINE RUNTIME_BTI_ENABLE      = TRUE
 
   #
   # Network definition
@@ -124,6 +125,11 @@ [BuildOptions]
   GCC:*_*_AARCH64_CC_XIPFLAGS ==
 !endif
 
+!if $(RUNTIME_BTI_ENABLE) == TRUE
+[BuildOptions.common.BASE,BuildOptions.common.DXE_RUNTIME_DRIVER]
+  GCC:*_*_AARCH64_CC_FLAGS = -mbranch-protection=bti
+!endif
+
 !include NetworkPkg/NetworkBuildOptions.dsc.inc
 
 ################################################################################
@@ -148,6 +154,8 @@ [PcdsFeatureFlag.common]
 [PcdsFixedAtBuild.common]
 !if $(ARCH) == AARCH64
   gArmTokenSpaceGuid.PcdVFPEnabled|1
+
+  gEfiMdeModulePkgTokenSpaceGuid.PcdMemoryAttributesTableForwardCfi|$(RUNTIME_BTI_ENABLE)
 !endif
 
   gArmPlatformTokenSpaceGuid.PcdCPUCoresStackBase|0x4007c000
-- 
2.39.1