AArch64: Add initial support for AArch64

This is the first patch out of a series of patches that add support for
AArch64, the new 64bit execution state of the ARMv8 Architecture. The
patches add support for LP64 programming model.

The patch adds:
* "arch-aarch64" to the architecture directories.
* "arch-aarch64/include" - headers used by libc
* "arch-aarch64/bionic":
    - crtbegin, crtend support;
    - aarch64 specific syscall stubs;
    - setjmp, clone, vfork assembly files.

Change-Id: If72b859f81928d03ad05d4ccfcb54c2f5dbf99a5
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
diff --git a/libc/arch-aarch64/bionic/crtbegin.c b/libc/arch-aarch64/bionic/crtbegin.c
new file mode 100644
index 0000000..73d2010
--- /dev/null
+++ b/libc/arch-aarch64/bionic/crtbegin.c
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "../../bionic/libc_init_common.h"
+#include <stddef.h>
+#include <stdint.h>
+
+__attribute__ ((section (".preinit_array")))
+void (*__PREINIT_ARRAY__)(void) = (void (*)(void)) -1;
+
+__attribute__ ((section (".init_array")))
+void (*__INIT_ARRAY__)(void) = (void (*)(void)) -1;
+
+__attribute__ ((section (".fini_array")))
+void (*__FINI_ARRAY__)(void) = (void (*)(void)) -1;
+
+
+__LIBC_HIDDEN__ void do_aarch64_start(void* raw_args) {
+  structors_array_t array;
+  array.preinit_array = &__PREINIT_ARRAY__;
+  array.init_array = &__INIT_ARRAY__;
+  array.fini_array = &__FINI_ARRAY__;
+  __libc_init(raw_args, NULL, &main, &array);
+}
+
+/*
+ * Put the value of sp in x0 and call do_aarch64_init(). The latter will then
+ * then be able to access the stack as prepared by the kernel's execve system
+ * call (via the first argument).
+ */
+__asm__ (
+"        .text                      \n"
+"        .align  2                  \n"
+"        .global _start             \n"
+"        .hidden _start             \n"
+"        .type   _start, %function  \n"
+"_start:                            \n"
+"        add     x0, sp, xzr        \n"
+"        b       do_aarch64_start   \n"
+"        .size   _start, .-_start   \n"
+);
+
+#include "../../arch-common/bionic/__dso_handle.h"
+#include "../../arch-common/bionic/atexit.h"