Intial Thumb2 Sandbox (naclrev 6680)

src/trusted/service_runtime/arch/arm/springboard_thumb2.S

 /*
  * 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.
  */
 
 #include "native_client/src/trusted/service_runtime/nacl_config.h"
 #include "native_client/src/trusted/service_runtime/include/bits/nacl_syscalls.h"
 
 .text
 .thumb
 .syntax unified
 
+ /*
+  * NOTE: it is not clear whether we need a spring board for ARM at all
+  * TODO(robertm): maybe delete the code
+  *
+  * Assembly code template.
+  * This is linked into the service runtime but is unused as code -- it is used
+  * as data to be patched into a NaCl app's address space as a "hidden" part of
+  * its trampoline region.
+  *
+  * This code takes the last slot in trampoline region, and it is
+  * loaded by NaClLoadSpringboard() (sel_ldr.c).
+  *
+  * NaCl_springboard is used for syscall return and any time we want
+  * to do an upcall into NaCl application.
+  *
+  * r0 -- syscall return value
+  * r1 -- new pc (already sandboxed)
+  * == user stack ==
+  * top
+  * =====
+  * arg 1
+  * arg 2
+  * .....
+  * arg N
+  */
+
 /*
- * NOTE: it is not clear whether we need a spring board for ARM at all
- * TODO(robertm): maybe delete the code
- *
- * Assembly code template.
- * This is linked into the service runtime but is unused as code -- it is used
- * as data to be patched into a NaCl app's address space as a "hidden" part of
- * its trampoline region.
- *
- * This code takes the last slot in trampoline region, and it is
- * loaded by NaClLoadSpringboard() (sel_ldr.c).
- *
- * NaCl_springboard is used for syscall return and any time we want
- * to do an upcall into NaCl application.
- *
- * r0 -- syscall return value
- * r1 -- new pc (already sandboxed)
- * == user stack ==
- * top
- * =====
- * arg 1
- * arg 2
- * .....
- * arg N
+ * We will load the springboard to be aligned 14mod16, as a thumb2 branch
+ * target must be.  To ensure that the instructions in the springboard are
+ * properly aligned, we misalign by 2 here.
  */
-
- /*
-  * We will load the springboard to be aligned 14mod16, as a thumb2 branch
-  * target must be.  To ensure that the instructions in the springboard are
-  * properly aligned, we misalign by 2 here.
-  */
 .p2align 4
 .skip 2
 DEFINE_GLOBAL_HIDDEN_IDENTIFIER(NaCl_springboard):
   /*
    * This instruction prevents indirect jumps from untrusted code into the
    * springboard.  The service runtime jumps past it.
    */
   bkpt
 
   add sp, #16 /* popping four arguments placed by trampoline code */
   bx r1
 
 DEFINE_GLOBAL_HIDDEN_IDENTIFIER(NaCl_springboard_end):