Add a test to check the initial register state for a new thread

tests/common/register_set.h

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef NATIVE_CLIENT_TESTS_COMMON_REGISTER_SET_H_
 #define NATIVE_CLIENT_TESTS_COMMON_REGISTER_SET_H_
 
 #include "native_client/src/include/nacl_macros.h"
@@ skipping 236 matching lines @@
  * "push {sp}" is undefined ("unpredictable") on ARM, so we move sp to
  * a temporary register to push its original value.  (Indeed, whether
  * sp is modified before or after being written differs between QEMU
  * and the Panda boards.)
  */
 # define REGS_SAVER_FUNC(def_func, callee_func) \
     void def_func(); \
     void callee_func(struct NaClSignalContext *regs); \
     __asm__( \
         ".pushsection .text, \"ax\", %progbits\n" \
+        ".p2align 4\n" \
         #def_func ":\n" \
         "push {r0}\n"  /* Leave space for cpsr */ \
         "push {r0}\n"  /* Leave space for prog_ctr */ \
         "push {r14}\n" \
         /* Save r0-r12 and sp; adjust sp for the pushes above */ \
         "add r14, sp, #0xc\n" \
         "push {r10-r12, r14}\n" \
         /* Push a dummy value for r9, which the tests need not compare */ \
         "mov r10, #0\n" \
         "push {r10}\n" \
@@ skipping 23 matching lines @@
 void RegsApplySandboxConstraints(struct NaClSignalContext *regs);
 
 /* This compares for equality all registers saved by REGS_SAVER_FUNC. */
 void RegsAssertEqual(const struct NaClSignalContext *actual,
                      const struct NaClSignalContext *expected);
 
 /* Zero out registers that are clobbered by function calls. */
 void RegsUnsetNonCalleeSavedRegisters(struct NaClSignalContext *regs);
 
 #endif