[PATCH v2 01/17] MdePkg/ProcessorBind AARCH64: Add asm macro to emit GNU BTI note

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

Implement a CPP macro that can be called from .S files to emit the .note
section carrying the annotation that informs the linker that the object
file is compatible with BTI control flow integrity checks.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 MdePkg/Include/AArch64/ProcessorBind.h | 31 ++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/MdePkg/Include/AArch64/ProcessorBind.h b/MdePkg/Include/AArch64/ProcessorBind.h
index abe2571245c665f3..11814f1ffaef698a 100644
--- a/MdePkg/Include/AArch64/ProcessorBind.h
+++ b/MdePkg/Include/AArch64/ProcessorBind.h
@@ -186,6 +186,37 @@ typedef INT64 INTN;
 #define GCC_ASM_IMPORT(func__)  \
          .extern  _CONCATENATE (__USER_LABEL_PREFIX__, func__)
 
+#if defined(__ARM_FEATURE_BTI_DEFAULT) && __ARM_FEATURE_BTI_DEFAULT == 1
+#define AARCH64_BTI(__type)                                        \
+    .ifnc         __type,                                         ;\
+    bti           __type                                          ;\
+    .endif                                                        ;\
+    .ifndef       .Lgnu_bti_notesize                              ;\
+    .pushsection  .note.gnu.property, "a"                         ;\
+    .set          NT_GNU_PROPERTY_TYPE_0, 0x5                     ;\
+    .set          GNU_PROPERTY_AARCH64_FEATURE_1_AND, 0xc0000000  ;\
+    .set          GNU_PROPERTY_AARCH64_FEATURE_1_BTI, 0x1         ;\
+    .align        3                                               ;\
+    .long         .Lnamesize                                      ;\
+    .long         .Lgnu_bti_notesize                              ;\
+    .long         NT_GNU_PROPERTY_TYPE_0                          ;\
+0:  .asciz        "GNU"                                           ;\
+    .set          .Lnamesize, . - 0b                              ;\
+    .align        3                                               ;\
+1:  .long         GNU_PROPERTY_AARCH64_FEATURE_1_AND              ;\
+    .long         .Lvalsize                                       ;\
+2:  .long         GNU_PROPERTY_AARCH64_FEATURE_1_BTI              ;\
+    .set          .Lvalsize, . - 2b                               ;\
+    .align        3                                               ;\
+    .set          .Lgnu_bti_notesize, . - 1b                      ;\
+    .popsection                                                   ;\
+    .endif
+#endif
+
+#endif
+
+#ifndef AARCH64_BTI
+#define AARCH64_BTI(__type)
 #endif
 
 /**
-- 
2.39.2