Fix two register leaks in the trusted->untrusted context switch

tests/common/register_set.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/common/register_set.h"
 
 #include "native_client/src/include/nacl_assert.h"
 
@@ skipping 75 matching lines @@
   CHECK_REG(r11);
   CHECK_REG(r12);
   CHECK_REG(stack_ptr);
   CHECK_REG(lr);
 #else
 # error Unsupported architecture
 #endif
 
 #undef CHECK_REG
 }
+
+void RegsUnsetNonCalleeSavedRegisters(struct NaClSignalContext *regs) {
+#if defined(__i386__)
+  regs->eax = 0;
+  regs->ecx = 0;
+  regs->edx = 0;
+#elif defined(__x86_64__)
+  regs->rax = 0;
+  regs->rcx = 0;
+  regs->rdx = 0;
+  regs->rsi = 0;
+  regs->rdi = 0;
+  regs->r8 = 0;
+  regs->r9 = 0;
+  regs->r10 = 0;
+  regs->r11 = 0;
+#elif defined(__arm__)
+  regs->r0 = 0;
+  regs->r1 = 0;
+  regs->r2 = 0;
+  regs->r3 = 0;
+  regs->r12 = 0;
+  regs->lr = 0;
+#else
+# error Unsupported architecture
+#endif
+}