Index: head/contrib/llvm/projects/libunwind/src/UnwindLevel1-gcc-ext.c
===================================================================
--- head/contrib/llvm/projects/libunwind/src/UnwindLevel1-gcc-ext.c
+++ head/contrib/llvm/projects/libunwind/src/UnwindLevel1-gcc-ext.c
@@ -224,6 +224,47 @@
 
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
 
+#ifdef __FreeBSD__
+
+// Based on LLVM's lib/ExecutionEngine/RuntimeDyld/RTDyldMemoryManager.cpp
+// and XXX should be fixed to be alignment-safe.
+static void processFDE(const char *addr, bool isDeregister) {
+  uint64_t length;
+  while ((length = *((const uint32_t *)addr)) != 0) {
+    const char *p = addr + 4;
+    if (length == 0xffffffff) {
+      length = *((const uint64_t *)p);
+      p += 8;
+    }
+    uint32_t offset = *((const uint32_t *)p);
+    if (offset != 0) {
+      if (isDeregister)
+        _unw_remove_dynamic_fde((unw_word_t)(uintptr_t)addr);
+      else
+        _unw_add_dynamic_fde((unw_word_t)(uintptr_t)addr);
+    }
+    addr = p + length;
+  }
+}
+
+/// Called by programs with dynamic code generators that want to register
+/// dynamically generated FDEs, with a libgcc-compatible API.
+
+_LIBUNWIND_EXPORT void __register_frame(const void *addr) {
+  _LIBUNWIND_TRACE_API("__register_frame(%p)", addr);
+  processFDE(addr, false);
+}
+
+/// Called by programs with dynamic code generators that want to unregister
+/// dynamically generated FDEs, with a libgcc-compatible API.
+_LIBUNWIND_EXPORT void __deregister_frame(const void *addr) {
+  _LIBUNWIND_TRACE_API("__deregister_frame(%p)", addr);
+  processFDE(addr, true);
+}
+
+
+#else
+
 /// Called by programs with dynamic code generators that want
 /// to register a dynamically generated FDE.
 /// This function has existed on Mac OS X since 10.4, but
@@ -243,6 +284,7 @@
   _unw_remove_dynamic_fde((unw_word_t)(uintptr_t) fde);
 }
 
+#endif
 
 // The following register/deregister functions are gcc extensions.
 // They have existed on Mac OS X, but have never worked because Mac OS X