[PAC] Make __is_function_overridden pauth-aware on ELF platforms

[asl]

Apparently, there are two almost identical implementations: one for MachO and another one for ELF. The ELF bits somehow slipped while #84573 was reviewed.

The particular implementation is identical to MachO case.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Anton Korobeynikov (asl)

Changes

Apparently, there are two almost identical implementations: one for MachO and another one for ELF. The ELF bits somehow slipped while #84573 was reviewed.

The particular implementation is identical to MachO case.

---

Full diff: https://github.com/llvm/llvm-project/pull/107498.diff

1 Files Affected:

• (modified) libcxx/src/include/overridable_function.h (+8)

diff --git a/libcxx/src/include/overridable_function.h b/libcxx/src/include/overridable_function.h
index e83ca7be7befaf..c56a00defbc56b 100644
--- a/libcxx/src/include/overridable_function.h
+++ b/libcxx/src/include/overridable_function.h
@@ -116,6 +116,14 @@ _LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__fptr)(_Args...)) no
   uintptr_t __end   = reinterpret_cast<uintptr_t>(&__stop___lcxx_override);
   uintptr_t __ptr   = reinterpret_cast<uintptr_t>(__fptr);
 
+#  if __has_feature(ptrauth_calls)
+  // We must pass a void* to ptrauth_strip since it only accepts a pointer type. Also, in particular,
+  // we must NOT pass a function pointer, otherwise we will strip the function pointer, and then attempt
+  // to authenticate and re-sign it when casting it to a uintptr_t again, which will fail because we just
+  // stripped the function pointer.
+  __ptr = reinterpret_cast<uintptr_t>(ptrauth_strip(reinterpret_cast<void*>(__ptr), ptrauth_key_function_pointer));
+#  endif
+
   return __ptr < __start || __ptr > __end;
 }
 _LIBCPP_END_NAMESPACE_STD

[ldionne]

LGTM with a comment.