[llvm-branch-commits] [llvm] Add deactivation symbol operand to ConstantPtrAuth. (PR #133537)

[Peter Collingbourne via llvm-branch-commits]

pcc wrote:

> I have checked in with @ahmedbougacha and his feeling is that this is fine as it requires a bunch of work to opt in, and for places where the security is important enough that we don't want people using this it's easy enough to block.

Thanks for checking.

> I'm concerned about the interaction of these changes with ptrauth intrinsic optimizations

I took a look and found some cases where we needed to inhibit optimizations. There was no practical effect due to how PFP uses these intrinisics, but I implemented the inhibitions in #133536 and this PR.

> the ability for attackers to gain control of the enablement flags.

This isn't possible, the symbols are resolved at static link time. See the RFC for more information: https://discourse.llvm.org/t/rfc-deactivation-symbols/85556

https://github.com/llvm/llvm-project/pull/133537