[RFC PATCH v2 7/7] ArmVirtPkg: Implement BTI for runtime regions

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

Add a build option RUNTIME_BTI_ENABLE, and wire it up to the command
line options passed to the compiler to get it to emit BTI landing pads
into all modules. Note that runtime DXE modules may incorporate
libraries of type BASE, UEFI_DRIVER or DXE_DRIVER, so the only safe
option here is to apply the command line option to all types.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 ArmVirtPkg/ArmVirt.dsc.inc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ArmVirtPkg/ArmVirt.dsc.inc b/ArmVirtPkg/ArmVirt.dsc.inc
index 74d98e6314c4..9cb37f3d46a3 100644
--- a/ArmVirtPkg/ArmVirt.dsc.inc
+++ b/ArmVirtPkg/ArmVirt.dsc.inc
@@ -10,6 +10,7 @@
 
 [Defines]
   DEFINE DEBUG_PRINT_ERROR_LEVEL = 0x8000004F
+  DEFINE RUNTIME_BTI_ENABLE      = FALSE
 
 !if $(TARGET) != NOOPT
   DEFINE FD_SIZE_IN_MB    = 2
@@ -33,6 +34,11 @@ [BuildOptions.common.EDKII.DXE_RUNTIME_DRIVER]
   GCC:*_*_ARM_DLINK_FLAGS = -z common-page-size=0x1000
   GCC:*_*_AARCH64_DLINK_FLAGS = -z common-page-size=0x10000
 
+[BuildOptions]
+!if $(RUNTIME_BTI_ENABLE) == TRUE
+  GCC:*_*_AARCH64_CC_FLAGS = -mbranch-protection=bti
+!endif
+
 [LibraryClasses.common]
 !if $(TARGET) == RELEASE
   DebugLib|MdePkg/Library/BaseDebugLibNull/BaseDebugLibNull.inf
-- 
2.39.1