Make validator require read sandboxing on ARM.

src/trusted/service_runtime/arch/arm/nacl_switch_to_app_arm.c

 /*
  * Copyright (c) 2011 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.
  */
 
 /*
  * NaCl Service Runtime, C-level context switch code.
  */
 
@@ skipping 26 matching lines @@
 #if defined(NACL_TARGET_ARM_THUMB2_MODE)
   /*
    * An odd control flow transfer target address is how ARM processors switch
    * to thumb mode.  If either of the entry points (dynamic loader or user
    * code) is to thumb mode targets, then we are in thumb mode.  If we are in
    * thumb mode, the springboard target address must also be a thumb-mode
    * address.
    */
   CHECK((nap->user_entry_pt & 0x1) | (nap->initial_entry_pt & 0x1));
   /* The real springboard target addresses are aligned 0xe mod 16. */
-  /* Skipping a 2-byte halt brings us to 0 mod 16. */

[robertm, 2011/10/18 21:19:55]

this change was not mentioned in the description

[sehr (please use chromium), 2011/10/18 22:44:11]

Thanks.  This was not intended for this CL.

-  CHECK((nap->springboard_addr & 0xf) == 0x0);
+  CHECK((nap->springboard_addr & 0xf) == 0xe);
   return nap->springboard_addr | 0x1;
 #else
   return nap->springboard_addr;
 #endif
 }
 
 NORETURN void NaClStartThreadInApp(struct NaClAppThread *natp,
                                    uint32_t             new_prog_ctr) {
   struct NaClApp  *nap;
   struct NaClThreadContext  *context;
@@ skipping 35 matching lines @@
 
   nap = natp->nap;
   context = &natp->user;
   context->spring_addr = NaClSysToUser(nap,
                                        nap->mem_start + SpringboardAddr(nap));
   context->new_eip = new_prog_ctr;
   context->sysret = natp->sysret;
 
   NaClSwitch(context);
 }