[AAELF64] Reserve relocation codes for PAuthABIELF64

The Alpha PAuthABIELF64 defines a small number of static and dynamic
relocations in the private vendor experiment space. When an upstream
implementation lands we will want to use non-experimental codes.
Step 1 is to reserve a range of static and dynamic relocations in
AAELF64 so we can guarantee no clash with any relocations defined in
the PAuthABI. When PAuthABIELF64 gets to Release state then
relocations can be added to the AAELF64 and the reservation can be
removed.

aaelf64/aaelf64.rst

@@ -11,6 +11,7 @@
 
 .. _AAPCS64: https://github.com/ARM-software/abi-aa/releases
 .. _Addenda32: https://github.com/ARM-software/abi-aa/releases
+.. _PAuthABIELF64: https://github.com/ARM-software/abi-aa/releases
 .. _SCO-ELF: http://www.sco.com/developers/gabi/
 .. _LINUX_ABI: https://github.com/hjl-tools/linux-abi/wiki
 .. _LSB: http://www.linuxbase.org/
@@ -247,6 +248,9 @@ changes to the content of the document for that release.
   |               |                    |   section `Thread-local storage         |
   |               |                    |   descriptors`_                         |
   +---------------+--------------------+-----------------------------------------+
+  | 2021Q2        |                    | - Reserved relocation codes for         |
+  |               |                    |   `PAuthABIELF64`_                      |
+  +---------------+--------------------+-----------------------------------------+
 
 References
 ----------
@@ -264,6 +268,8 @@ This document refers to, or is referred to by, the following documents.
   +------------------------------+-------------------------------------------------------------+-------------------------------------------------------------+
   | Addenda32_                   | IHI 0045                                                    | Addenda to, and Errata in, the ABI for the Arm Architecture |
   +------------------------------+-------------------------------------------------------------+-------------------------------------------------------------+
+  | PAuthABIELF64_               | pauthabielf64                                               | PAuth Extension to ELF for the Arm 64-bit Architecture      |
+  +------------------------------+-------------------------------------------------------------+-------------------------------------------------------------+
   | LSB_                         | http://www.linuxbase.org/                                   | Linux Standards Base                                        |
   +------------------------------+-------------------------------------------------------------+-------------------------------------------------------------+
   | SCO-ELF_                     | http://www.sco.com/developers/gabi/                         | System V Application Binary Interface – DRAFT               |
@@ -1596,6 +1602,10 @@ Unallocated relocations
 
 All unallocated relocation types are reserved for use by future revisions of this specification.
 
+PAuthABI relocations
+^^^^^^^^^^^^^^^^^^^^
+
+The `PAuthABIELF64`_ ELF extension, currently in Alpha state, defines several relocations in the vendor experiment space. Arm reserves codes 580 to 600 for static `PAuthABIELF64`_ relocations and 1040 - 1060 for dynamic `PAuthABIELF64`_ relocations. When the extension moves to Release state the relocations defined in `PAuthABIELF64`_ will be added to this document and all unused codes in the reserved ranges will be released.
 
 Idempotency
 ^^^^^^^^^^^