ART: Fix Mac-specific things in x86-64 assembly

We incorrectly used double-underscore on x86-64 as VAR (used by
trampoline macros) introduced an additional underscore. Add CALLVAR
just as on x86.

Bug: 30212852
Change-Id: I2a95dd736453160769ea1a8b24c66f1738049ccb
Test: m test-art-host (Linux)
Test: builds on Mac
diff --git a/runtime/arch/x86/fault_handler_x86.cc b/runtime/arch/x86/fault_handler_x86.cc
index 533905e..3efeb40 100644
--- a/runtime/arch/x86/fault_handler_x86.cc
+++ b/runtime/arch/x86/fault_handler_x86.cc
@@ -71,18 +71,9 @@
 
 namespace art {
 
-#if defined(__APPLE__) && defined(__x86_64__)
-// mac symbols have a prefix of _ on x86_64
-extern "C" void _art_quick_throw_null_pointer_exception_from_signal();
-extern "C" void _art_quick_throw_stack_overflow();
-extern "C" void _art_quick_test_suspend();
-#define EXT_SYM(sym) _ ## sym
-#else
 extern "C" void art_quick_throw_null_pointer_exception_from_signal();
 extern "C" void art_quick_throw_stack_overflow();
 extern "C" void art_quick_test_suspend();
-#define EXT_SYM(sym) sym
-#endif
 
 // Note this is different from the others (no underscore on 64 bit mac) due to
 // the way the symbol is defined in the .S file.
@@ -320,7 +311,7 @@
   uc->CTX_ESP = reinterpret_cast<uintptr_t>(next_sp);
 
   uc->CTX_EIP = reinterpret_cast<uintptr_t>(
-      EXT_SYM(art_quick_throw_null_pointer_exception_from_signal));
+      art_quick_throw_null_pointer_exception_from_signal);
   // Pass the faulting address as the first argument of
   // art_quick_throw_null_pointer_exception_from_signal.
 #if defined(__x86_64__)
@@ -397,7 +388,7 @@
     *next_sp = retaddr;
     uc->CTX_ESP = reinterpret_cast<uintptr_t>(next_sp);
 
-    uc->CTX_EIP = reinterpret_cast<uintptr_t>(EXT_SYM(art_quick_test_suspend));
+    uc->CTX_EIP = reinterpret_cast<uintptr_t>(art_quick_test_suspend);
 
     // Now remove the suspend trigger that caused this fault.
     Thread::Current()->RemoveSuspendTrigger();
@@ -443,7 +434,7 @@
   // the previous frame.
 
   // Now arrange for the signal handler to return to art_quick_throw_stack_overflow.
-  uc->CTX_EIP = reinterpret_cast<uintptr_t>(EXT_SYM(art_quick_throw_stack_overflow));
+  uc->CTX_EIP = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
 
   return true;
 }