From 98244c4e2acafb7568e8337088c6caaaffcb7831 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2@gmail.com>
Date: Wed, 3 Apr 2024 08:04:43 -0400
Subject: [libc++] Upstream ptrauth support in libc++ and libc++abi (#84573)

This is an exact upstreaming of the downstream diff. Minor
simplifications can be made in the future but upstreaming as-is will
make it easier for us to deal with downstream merge conflicts.

Partially fixes #83805
---
 libcxxabi/src/private_typeinfo.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'libcxxabi')

diff --git a/libcxxabi/src/private_typeinfo.cpp b/libcxxabi/src/private_typeinfo.cpp
index 5c68f3e..9e58501 100644
--- a/libcxxabi/src/private_typeinfo.cpp
+++ b/libcxxabi/src/private_typeinfo.cpp
@@ -51,6 +51,21 @@
 #include <atomic>
 #endif
 
+#if __has_feature(ptrauth_calls)
+#include <ptrauth.h>
+#endif
+
+
+template<typename T>
+static inline
+T *
+get_vtable(T *vtable) {
+#if __has_feature(ptrauth_calls)
+    vtable = ptrauth_strip(vtable, ptrauth_key_cxx_vtable_pointer);
+#endif
+    return vtable;
+}
+
 static inline
 bool
 is_equal(const std::type_info* x, const std::type_info* y, bool use_strcmp)
@@ -103,6 +118,7 @@ void dyn_cast_get_derived_info(derived_object_info* info, const void* static_ptr
     info->dynamic_type = *(reinterpret_cast<const __class_type_info* const*>(ptr_to_ti_proxy));
 #else
     void **vtable = *static_cast<void ** const *>(static_ptr);
+    vtable = get_vtable(vtable);
     info->offset_to_derived = reinterpret_cast<ptrdiff_t>(vtable[-2]);
     info->dynamic_ptr = static_cast<const char*>(static_ptr) + info->offset_to_derived;
     info->dynamic_type = static_cast<const __class_type_info*>(vtable[-1]);
@@ -561,6 +577,7 @@ __base_class_type_info::has_unambiguous_public_base(__dynamic_cast_info* info,
     offset_to_base = __offset_flags >> __offset_shift;
     if (is_virtual) {
       const char* vtable = *static_cast<const char* const*>(adjustedPtr);
+      vtable = get_vtable(vtable);
       offset_to_base = update_offset_to_base(vtable, offset_to_base);
     }
   } else if (!is_virtual) {
@@ -1501,6 +1518,7 @@ __base_class_type_info::search_above_dst(__dynamic_cast_info* info,
     if (__offset_flags & __virtual_mask)
     {
         const char* vtable = *static_cast<const char*const*>(current_ptr);
+        vtable = get_vtable(vtable);
         offset_to_base = update_offset_to_base(vtable, offset_to_base);
     }
     __base_type->search_above_dst(info, dst_ptr,
@@ -1521,6 +1539,7 @@ __base_class_type_info::search_below_dst(__dynamic_cast_info* info,
     if (__offset_flags & __virtual_mask)
     {
         const char* vtable = *static_cast<const char*const*>(current_ptr);
+        vtable = get_vtable(vtable);
         offset_to_base = update_offset_to_base(vtable, offset_to_base);
     }
     __base_type->search_below_dst(info,
-- 
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