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

runtime/vm/profiler.cc

 // Copyright (c) 2013, 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/address_sanitizer.h"
 #include "platform/memory_sanitizer.h"
 #include "platform/utils.h"
 
 #include "vm/allocation.h"
 #include "vm/atomic.h"
@@ skipping 779 matching lines @@
                        sizeof(fault_address), new_protect, &old_protect);
     USE(success);
     ASSERT(success);
     ASSERT(old_protect == PAGE_READWRITE);
   }
 #endif
 }
 
 
 // Get |isolate|'s stack boundary and verify that |sp| and |fp| are within
-// it. Return |false| if anything looks suspicious.
-static bool GetAndValidateIsolateStackBounds(Thread* thread,
-                                             uintptr_t fp,
-                                             uintptr_t sp,
-                                             uword* stack_lower,
-                                             uword* stack_upper) {
+// it. If |get_os_thread_bounds| is true then if |isolate| stackbounds are
+// not available we fallback to using underlying OS thread bounds. This only
+// works for the current thread.
+// Return |false| if anything looks suspicious.
+static bool GetAndValidateIsolateStackBounds(

[Cutch, 2017/02/09 16:45:24]

While you're here, this could be renamed to GetAndValidateThreadStackBounds

[Vyacheslav Egorov (Google), 2017/02/09 17:19:20]

Done.

+    Thread* thread,
+    uintptr_t fp,
+    uintptr_t sp,
+    uword* stack_lower,
+    uword* stack_upper,
+    bool get_os_thread_bounds = false) {
   ASSERT(thread != NULL);
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != NULL);
   ASSERT(stack_lower != NULL);
   ASSERT(stack_upper != NULL);
+  ASSERT(!get_os_thread_bounds || (Thread::Current() == thread));
+
 #if defined(USING_SIMULATOR)
-  const bool in_dart_code = thread->IsExecutingDartCode();
-  if (in_dart_code) {
+  const bool use_simulator_stack_bounds = thread->IsExecutingDartCode();
+  if (use_simulator_stack_bounds) {
     Isolate* isolate = thread->isolate();
     ASSERT(isolate != NULL);
     Simulator* simulator = isolate->simulator();
     *stack_lower = simulator->StackBase();
     *stack_upper = simulator->StackTop();
-  } else if (!os_thread->GetProfilerStackBounds(stack_lower, stack_upper)) {
+  }
+#else
+  const bool use_simulator_stack_bounds = false;
+#endif
+
+  if (!use_simulator_stack_bounds &&
+      !os_thread->GetProfilerStackBounds(stack_lower, stack_upper) &&
+      !(get_os_thread_bounds &&
+        OSThread::GetCurrentStackBounds(stack_lower, stack_upper))) {
     // Could not get stack boundary.
     return false;
   }
+
   if ((*stack_lower == 0) || (*stack_upper == 0)) {
     return false;
   }
-#else
-  if (!os_thread->GetProfilerStackBounds(stack_lower, stack_upper) ||
-      (*stack_lower == 0) || (*stack_upper == 0)) {
-    // Could not get stack boundary.
-    return false;
-  }
-#endif
 
-#if defined(TARGET_ARCH_DBC)
-  if (!in_dart_code && (sp > *stack_lower)) {
+  if (!use_simulator_stack_bounds && (sp > *stack_lower)) {
     // The stack pointer gives us a tighter lower bound.
     *stack_lower = sp;
   }
-#else
-  if (sp > *stack_lower) {
-    // The stack pointer gives us a tighter lower bound.
-    *stack_lower = sp;
-  }
-#endif
 
   if (*stack_lower >= *stack_upper) {
     // Stack boundary is invalid.
     return false;
   }
 
   if ((sp < *stack_lower) || (sp >= *stack_upper)) {
     // Stack pointer is outside thread's stack boundary.
     return false;
   }
@@ skipping 121 matching lines @@
 
   uword stack_lower = 0;
   uword stack_upper = 0;
 
   if (!InitialRegisterCheck(pc, fp, sp)) {
     OS::PrintErr("Stack dump aborted because InitialRegisterCheck.\n");
     return;
   }
 
   if (!GetAndValidateIsolateStackBounds(thread, fp, sp, &stack_lower,
-                                        &stack_upper)) {
+                                        &stack_upper,
+                                        /*get_os_thread_bounds=*/true)) {

[Cutch, 2017/02/09 16:45:24]

I wonder why this isn't the default now?

[Vyacheslav Egorov (Google), 2017/02/09 17:19:20]

Because it only works if thread == Thread::Current(), however this function is
called from places where this does not necessarily hold (e.g. on Windows thread
sampling is done from another thread).

     OS::PrintErr(
         "Stack dump aborted because GetAndValidateIsolateStackBounds.\n");
     return;
   }
 
   ProfilerNativeStackWalker native_stack_walker(
       isolate, NULL, NULL, stack_lower, stack_upper, pc, fp, sp);
   native_stack_walker.walk();
   OS::PrintErr("-- End of DumpStackTrace\n");
 }
@@ skipping 516 matching lines @@
 
 
 ProcessedSampleBuffer::ProcessedSampleBuffer()
     : code_lookup_table_(new CodeLookupTable(Thread::Current())) {
   ASSERT(code_lookup_table_ != NULL);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart