[MIPS] Add remaining parts for building tests for MIPS

tests/barebones/top_of_sandbox.c

 /*
  * 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.
  */
 
 #include "native_client/tests/barebones/barebones.h"
 
 /*
  * This is a test for the issue described in:
  * http://code.google.com/p/nativeclient/issues/detail?id=2909
  */
 
 void _start(unsigned int info[]) {
 #if defined(__arm__)
   char *sp, *scratch;
   __asm__("mov %0, sp" : "=r" (sp));
   __asm__ volatile(
       ".p2align 4\n"
       "bic %0, %0, #0xc0000000\n"
       "ldr %0, [%0, #-4095]\n"
       : "=r" (scratch) : "0" (sp + 4095));
 #elif defined(__x86_64__)
   unsigned long long scratch;
   __asm__ volatile(
       ".p2align 5\n"
       "leal 4095(%%rsp), %k0\n"
       "movl -4095(%%r15,%0), %k0"
       : "=r" (scratch));
+#elif defined(__mips__)
+  char *sp, *scratch;
+  __asm__("move %0, $sp" : "=r" (sp));
+  __asm__ volatile(
+      ".p2align 4\n"
+      "and %0, %0, $t7\n"
+      "lw  %0, -32767(%0)\n"

[Mark Seaborn, 2013/03/11 15:54:38]

Can you write -0x7fff instead for readability?  Same below.

[petarj, 2013/03/14 01:13:03]

Done.

+      : "=r" (scratch) : "0" (sp + 32767));
 #endif
   NACL_SYSCALL(exit)(0);
 }