[runtime]Revert the fast tls check as we always need it on mach. Add …

…another iOS 7 offset.

mono/utils/mach-support-arm.c

@@ -21,9 +21,14 @@
 
 /* Known offsets used for TLS storage*/
 
-/*Found on iOS 6 */
-#define TLS_VECTOR_OFFSET_0 0x48
-#define TLS_VECTOR_OFFSET_1 0xA8
+
+static const int known_tls_offsets[] = {
+	0x48, /*Found on iOS 6 */
+	0xA4,
+	0xA8,
+};
+
+#define TLS_PROBE_COUNT (sizeof (known_tls_offsets) / sizeof (int))
 
 static int tls_vector_offset;
 
@@ -95,7 +100,6 @@ mono_mach_arch_set_thread_state (thread_port_t thread, thread_state_t state, mac
 void *
 mono_mach_get_tls_address_from_thread (pthread_t thread, pthread_key_t key)
 {
-#ifdef MONO_HAVE_FAST_TLS
 	/* Mach stores TLS values in a hidden array inside the pthread_t structure
 	 * They are keyed off a giant array from a known offset into the pointer. This value
 	 * is baked into their pthread_getspecific implementation
@@ -104,9 +108,6 @@ mono_mach_get_tls_address_from_thread (pthread_t thread, pthread_key_t key)
 	intptr_t **tsd = (intptr_t **) ((char*)p + tls_vector_offset);
 
 	return (void *) &tsd [key];
-#else
-	g_error ("fast tls not supported on this target");
-#endif
 }
 
 void *
@@ -118,7 +119,7 @@ mono_mach_arch_get_tls_value_from_thread (pthread_t thread, guint32 key)
 void
 mono_mach_init (pthread_key_t key)
 {
-#ifdef MONO_HAVE_FAST_TLS
+	int i;
 	void *old_value = pthread_getspecific (key);
 	void *canary = (void*)0xDEADBEEFu;
 
@@ -128,18 +129,15 @@ mono_mach_init (pthread_key_t key)
 	pthread_setspecific (key, canary);
 
 	/*First we probe for cats*/
-	tls_vector_offset = TLS_VECTOR_OFFSET_0;
-	if (mono_mach_arch_get_tls_value_from_thread (pthread_self (), key) == canary)
-		goto ok;
-
-	tls_vector_offset = TLS_VECTOR_OFFSET_1;
-	if (mono_mach_arch_get_tls_value_from_thread (pthread_self (), key) == canary)
-		goto ok;
+	for (i = 0; i < TLS_PROBE_COUNT; ++i) {
+		tls_vector_offset = known_tls_offsets [i];
+		if (mono_mach_arch_get_tls_value_from_thread (pthread_self (), key) == canary)
+			goto ok;
+	}
 
 	g_error ("could not discover the mach TLS offset");
 ok:
 	pthread_setspecific (key, old_value);
-#endif
 }
 
 #endif