VM: Teach GetAndValidateIsolateStackBounds(...) to fallback to OS thread stack bounds.

runtime/vm/os_thread_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"  // NOLINT
 #if defined(TARGET_OS_WINDOWS)
 
 #include "vm/growable_array.h"
 #include "vm/lockers.h"
 #include "vm/os_thread.h"
@@ skipping 155 matching lines @@
 ThreadId OSThread::ThreadIdFromIntPtr(intptr_t id) {
   return static_cast<ThreadId>(id);
 }
 
 
 bool OSThread::Compare(ThreadId a, ThreadId b) {
   return a == b;
 }
 
 
+bool OSThread::GetCurrentStackBounds(uword* lower, uword* upper) {
+// On Windows stack limits for the current thread are available in
+// the thread information block (TIB). Its fields can be accessed through
+// FS segment register on x86 and GS segment register on x86_64.
+#ifdef _WIN64
+  *upper = static_cast<uword>(__readgsqword(offsetof(NT_TIB64, StackBase)));
+  *lower = static_cast<uword>(__readgsqword(offsetof(NT_TIB64, StackLimit)));
+#else
+  *upper = static_cast<uword>(__readfsdword(offsetof(NT_TIB, StackBase)));
+  *lower = static_cast<uword>(__readfsdword(offsetof(NT_TIB, StackLimit)));
+#endif
+  return true;
+}
+
+
 void OSThread::SetThreadLocal(ThreadLocalKey key, uword value) {
   ASSERT(key != kUnsetThreadLocalKey);
   BOOL result = TlsSetValue(key, reinterpret_cast<void*>(value));
   if (!result) {
     FATAL1("TlsSetValue failed %d", GetLastError());
   }
 }
 
 
 Mutex::Mutex() {
@@ skipping 493 matching lines @@
 #pragma data_seg(".CRT$XLB")
 PIMAGE_TLS_CALLBACK p_thread_callback_dart = OnDartThreadExit;
 
 // Reset the default section.
 #pragma data_seg()
 
 #endif  // _WIN64
 }  // extern "C"
 
 #endif  // defined(TARGET_OS_WINDOWS)