Fix __errno for LP64 and clean up __get_tls.

If __get_tls has the right type, a lot of confusing casting can disappear.

It was probably a mistake that __get_tls was exposed as a function for mips
and x86 (but not arm), so let's (a) ensure that the __get_tls function
always matches the macro, (b) that we have the function for arm too, and
(c) that we don't have the function for any 64-bit architecture.

Change-Id: Ie9cb989b66e2006524ad7733eb6e1a65055463be
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index 2e20364..a14bd3c 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -25,10 +25,12 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#ifndef _SYS_TLS_H
-#define _SYS_TLS_H
+
+#ifndef __BIONIC_PRIVATE_BIONIC_TLS_H_
+#define __BIONIC_PRIVATE_BIONIC_TLS_H_
 
 #include <sys/cdefs.h>
+#include "__get_tls.h"
 
 __BEGIN_DECLS
 
@@ -83,39 +85,6 @@
 #define BIONIC_ALIGN(x, a) (((x) + (a - 1)) & ~(a - 1))
 #define BIONIC_TLS_SLOTS BIONIC_ALIGN(128 + TLS_SLOT_FIRST_USER_SLOT + GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT, 4)
 
-/* syscall only, do not call directly */
-extern int __set_tls(void* ptr);
-
-/* get the TLS */
-#if defined(__arm__)
-# define __get_tls() \
-    ({ unsigned int __val; \
-       asm ("mrc p15, 0, %0, c13, c0, 3" : "=r"(__val)); \
-       (volatile void*) __val; })
-#elif defined(__mips__)
-# define __get_tls() \
-    /* On mips32r1, this goes via a kernel illegal instruction trap that's optimized for v1. */ \
-    ({ register unsigned int __val asm("v1"); \
-       asm ("   .set    push\n" \
-            "   .set    mips32r2\n" \
-            "   rdhwr   %0,$29\n" \
-            "   .set    pop\n" : "=r"(__val)); \
-       (volatile void*) __val; })
-#elif defined(__i386__)
-# define __get_tls() \
-    ({ void* __val; \
-       asm ("movl %%gs:0, %0" : "=r"(__val)); \
-       (volatile void*) __val; })
-
-#elif defined(__x86_64__)
-# define __get_tls() \
-    ({ void* __val; \
-       asm ("mov %%fs:0, %0" : "=r"(__val)); \
-       (volatile void*) __val; })
-#else
-#error unsupported architecture
-#endif
-
 __END_DECLS
 
 #if defined(__cplusplus)
@@ -123,4 +92,4 @@
 extern __LIBC_HIDDEN__ void __libc_init_tls(KernelArgumentBlock& args);
 #endif
 
-#endif /* _SYS_TLS_H */
+#endif /* __BIONIC_PRIVATE_BIONIC_TLS_H_ */