[compiler-rt] Fix interceptors with AArch64 BTI (#84061)

On AArch64 with BTI, we have to start functions with the appropriate
BTI hint to indicate that the function is a valid call target.

To support interceptors with AArch64 BTI, add "BTI c".

Author: melver

compiler-rt/lib/interception/interception.h

@@ -204,11 +204,11 @@ const interpose_substitution substitution_##func_name[]             \
        ".type  " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", "                    \
          ASM_TYPE_FUNCTION_STR "\n"                                            \
        SANITIZER_STRINGIFY(TRAMPOLINE(func)) ":\n"                             \
-       SANITIZER_STRINGIFY(CFI_STARTPROC) "\n"                                 \
+       C_ASM_STARTPROC "\n"                                                    \
        C_ASM_TAIL_CALL(SANITIZER_STRINGIFY(TRAMPOLINE(func)),                  \
                        "__interceptor_"                                        \
                          SANITIZER_STRINGIFY(ASM_PREEMPTIBLE_SYM(func))) "\n"  \
-       SANITIZER_STRINGIFY(CFI_ENDPROC) "\n"                                   \
+       C_ASM_ENDPROC "\n"                                                      \
        ".size  " SANITIZER_STRINGIFY(TRAMPOLINE(func)) ", "                    \
             ".-" SANITIZER_STRINGIFY(TRAMPOLINE(func)) "\n"                    \
      );

compiler-rt/lib/sanitizer_common/sanitizer_asm.h

@@ -42,6 +42,16 @@
 # define CFI_RESTORE(reg)
 #endif
 
+#if defined(__aarch64__) && defined(__ARM_FEATURE_BTI_DEFAULT)
+# define ASM_STARTPROC CFI_STARTPROC; hint #34
+# define C_ASM_STARTPROC SANITIZER_STRINGIFY(CFI_STARTPROC) "\nhint #34"
+#else
+# define ASM_STARTPROC CFI_STARTPROC
+# define C_ASM_STARTPROC SANITIZER_STRINGIFY(CFI_STARTPROC)
+#endif
+#define ASM_ENDPROC CFI_ENDPROC
+#define C_ASM_ENDPROC SANITIZER_STRINGIFY(CFI_ENDPROC)
+
 #if defined(__x86_64__) || defined(__i386__) || defined(__sparc__)
 # define ASM_TAIL_CALL jmp
 #elif defined(__arm__) || defined(__aarch64__) || defined(__mips__) || \
@@ -114,9 +124,9 @@
          .globl __interceptor_trampoline_##name;                               \
          ASM_TYPE_FUNCTION(__interceptor_trampoline_##name);                   \
          __interceptor_trampoline_##name:                                      \
-                 CFI_STARTPROC;                                                \
+                 ASM_STARTPROC;                                                \
                  ASM_TAIL_CALL ASM_PREEMPTIBLE_SYM(__interceptor_##name);      \
-                 CFI_ENDPROC;                                                  \
+                 ASM_ENDPROC;                                                  \
          ASM_SIZE(__interceptor_trampoline_##name)
 #  define ASM_INTERCEPTOR_TRAMPOLINE_SUPPORT 1
 # endif  // Architecture supports interceptor trampoline