[clang] [clang][ObjC][PAC] Add ptrauth protections to objective-c (PR #147899)

[John McCall via cfe-commits]

================
@@ -1003,15 +1003,29 @@ Arm and AArch64 Support
   `as specified here <https://github.com/ARM-software/acle/blob/main/main/acle.md#modal-8-bit-floating-point-extensions>`_
   is now available.
 - Support has been added for the following processors (command-line identifiers in parentheses):
+
   - Arm Cortex-A320 (``cortex-a320``)
+
 - For ARM targets, cc1as now considers the FPU's features for the selected CPU or Architecture.
 - The ``+nosimd`` attribute is now fully supported for ARM. Previously, this had no effect when being used with
   ARM targets, however this will now disable NEON instructions being generated. The ``simd`` option is
   also now printed when the ``--print-supported-extensions`` option is used.
 - When a feature that depends on NEON (``simd``) is used, NEON is now automatically enabled.
 - When NEON is disabled (``+nosimd``), all features that depend on NEON will now be disabled.
 
--  Support for __ptrauth type qualifier has been added.
+- Pointer authentication
+
+  - Support for __ptrauth type qualifier has been added.
+  - Objective-C adoption of pointer authentication
+
+    - ``isa`` and ``super`` pointers are protected with address diversity and separate
+      usage specific discriminators.
+    - methodlist pointers and content are protected with address diversity and methodlist
+      pointers have a usage specific discriminator.
+    - ``class_ro_t`` pointers are protected with address diversity and usage specific
+      discriminators.
+    - ``SEL`` typed ivars are protected with address diversity and usage specific
+      discriminators.
----------------
rjmccall wrote:

Does the `SEL` thing need more of a release note? The rest of this is all implementation-level, but `SEL` being implicitly `__ptrauth`ed makes it user-affecting, and we probably need to talk through it for the corner-case user using arm64e ObjC.

https://github.com/llvm/llvm-project/pull/147899