[compiler-rt] [libcxx] [libcxxabi] [libunwind] [runtimes][PAC] Harden unwinding when possible (PR #143230)

[Daniil Kovalev via llvm-commits]

kovdan01 wrote:

@ojhunt Thanks for an update! With the latest fixes, we only have one trivial issue which prevents Linux tests from passing (and I believe that it was introduced accidentally and it looks like that we need literally zero effort to fix that). With that being fixed, tests are passing on Linux in the following configurations:

1. Pauthtest for both runtime libraries and executables
2. Pac-ret for both runtime libraries and executables
3. Pac-ret for executables but not runtime libraries
4. No pauth at all (on aarch64)

Besides that, there are several other small issues here and there. See the list below.

Please let me know if any help with fixing these issues is needed - I would be glad to provide any support.

1. Use a check against `_LIBUNWIND_TARGET_AARCH64_AUTHENTICATED_UNWINDING` against a check against arm64e: https://github.com/llvm/llvm-project/pull/143230#discussion_r2407141767
   This is the only thing which prevents linux tests from passing.

2. Avoid UB in `get_handler_function`: https://github.com/llvm/llvm-project/pull/143230#discussion_r2406229405
   Similar issue should also be addressed in https://github.com/llvm/llvm-project/pull/161027#discussion_r2388230955

3. It looks like that while `_LIBUNWIND_TARGET_AARCH64_AUTHENTICATED_UNWINDING` macro was added (and it's used in some places), in most cases we still have plain checks against `__has_feature(ptrauth_calls)` and `__has_feature(ptrauth_returns)`. As discussed earlier, it's better to use this macro for such checks. See thread https://github.com/llvm/llvm-project/pull/143230#discussion_r2369029642 and proposed fix [644405b](https://github.com/llvm/llvm-project/commit/644405b56cfa59dd3787119182df087dff6e756c)

4. Add a comment explaining conditionals regarding `__ptrauth_restricted_intptr` qualifier to make it clearer for thouse not familiar with Apple's clang specific. I've provided an example comments, see https://github.com/llvm/llvm-project/pull/143230#discussion_r2407114846

5. `__ptrauth_unwind_pacret_personality_disc` should probably be renamed to `__ptrauth_unwind_pauthtest_personality_disc`. It's clearly not related to pac-ret which is about LR signing only. See https://github.com/llvm/llvm-project/pull/143230#discussion_r2406175800

Looking forward for further updates and hope that this could be finally merged relatively soon :)



https://github.com/llvm/llvm-project/pull/143230