NaCl SDK doc: Recover sandbox internal doc for x86-64

native_client_sdk/src/doc/reference/sandbox_internals/index.rst

 .. _sandbox-internals-index:
 
 #################
 Sandbox Internals
 #################
 
 The sandbox internals documentation describes implementation details for
 Native Client sandboxing, which is also used by Portable Native
 Client. These details can be useful to reimplement a sandbox, or to
 write assembly code that follows sandboxing rules for Native Client
 (Portable Native Client does not allow platform-specific assembly code).
 
 As an implementation detail, the Native Client sandboxes described here
 are currently used by Portable Native Client to execute code on the
 corresponding machines in a safe manner. The portable bitcode contained
 in a **pexe** is translated to a machine-specific **nexe** before
 execution. This may change at a point in time: Portable Native Client
 doesn't necessarily need these sandboxes to execute code on these
 machines. Note that the Portable Native Client compiler itself is also
 untrusted: it too runs in a Native Client sandbox described below.
 
 Native Client has sandboxes for:
 
 * :ref:`ARM 32-bit <arm-32-bit-sandbox>`.
 * x86-32: the original design is described in `Native Client: A Sandbox
   for Portable, Untrusted x86 Native Code
   <http://research.google.com/pubs/archive/34913.pdf>`_, the current
   design has changed slightly since then.
-* x86-64: the original design is described in `Adapting Software Fault
-  Isolation to Contemporary CPU Architectures
+* :ref:`x86-64 <x86-64-sandbox>`: the original design is described in
+  `Adapting Software Fault Isolation to Contemporary CPU Architectures
   <http://research.google.com/pubs/archive/35649.pdf>`_, the current
   design has changed slightly since then.

[JF, 2014/06/12 20:00:46]

The link to the research paper is already in the document you ported, so this
section should only have the <x86-64-sandbox> link that you added.

[hamaji, 2014/06/13 04:08:18]

Done.

 * MIPS32, described in the `overview of Native Client for MIPS
   <https://code.google.com/p/nativeclient/issues/attachmentText?id=2275&aid=22750018000&name=native-client-mips-0.4.txt>`_,
   and `bug 2275
   <https://code.google.com/p/nativeclient/issues/detail?id=2275>`_.