Collect a single frame sample in the profiler if we can't validate stack boundaries

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 927 matching lines @@
   } else {
     // Fall back.
     uintptr_t pc = GetProgramCounter();
     Sample* sample = SetupSample(thread, sample_buffer, os_thread->trace_id());
     sample->SetAllocationCid(cid);
     sample->SetAt(0, pc);
   }
 }
 
 
+void Profiler::SampleThreadSingleFrame(Thread* thread, uintptr_t pc) {
+  ASSERT(thread != NULL);
+  OSThread* os_thread = thread->os_thread();
+  ASSERT(os_thread != NULL);
+  Isolate* isolate = thread->isolate();
+
+  SampleBuffer* sample_buffer = Profiler::sample_buffer();
+  if (sample_buffer == NULL) {
+    // Profiler not initialized.
+    return;
+  }
+
+  // Setup sample.
+  Sample* sample = SetupSample(thread, sample_buffer, os_thread->trace_id());
+  // Increment counter for vm tag.
+  VMTagCounters* counters = isolate->vm_tag_counters();
+  ASSERT(counters != NULL);
+  if (thread->IsMutatorThread()) {
+    counters->Increment(sample->vm_tag());
+  }
+
+  // Write the single pc value.
+  sample->SetAt(0, pc);
+}
+
+
 void Profiler::SampleThread(Thread* thread,
                             const InterruptedThreadState& state) {
   ASSERT(thread != NULL);
   OSThread* os_thread = thread->os_thread();
   ASSERT(os_thread != NULL);
   Isolate* isolate = thread->isolate();
 
   // Thread is not doing VM work.
   if (thread->task_kind() == Thread::kUnknownTask) {
     return;
@@ skipping 24 matching lines @@
     fp = simulator->get_register(FPREG);
     pc = simulator->get_pc();
 #else
     sp = state.dsp;
 #endif
   } else {
     // If we're in runtime code, use the C stack pointer.
     sp = state.csp;
   }
 
-  if (!InitialRegisterCheck(pc, fp, sp)) {
-    return;
-  }
-
   if (!CheckIsolate(isolate)) {
     return;
   }
 
   if (thread->IsMutatorThread() && isolate->IsDeoptimizing()) {
     return;

[sra1, 2016/03/29 17:22:18]

Should this be sampled as a single frame too?

[Cutch, 2016/03/29 17:43:18]

Might as well.

   }
 
+  if (!InitialRegisterCheck(pc, fp, sp)) {
+    SampleThreadSingleFrame(thread, pc);
+    return;
+  }
+
   uword stack_lower = 0;
   uword stack_upper = 0;
   if (!GetAndValidateIsolateStackBounds(thread,
                                         fp,
                                         sp,
                                         &stack_lower,
                                         &stack_upper)) {
+    SampleThreadSingleFrame(thread, pc);
     // Could not get stack boundary.
     return;
   }
 
   // At this point we have a valid stack boundary for this isolate and
   // know that our initial stack and frame pointers are within the boundary.
   SampleBuffer* sample_buffer = Profiler::sample_buffer();
   if (sample_buffer == NULL) {
     // Profiler not initialized.
     return;
@@ skipping 375 matching lines @@
 
 
 ProcessedSampleBuffer::ProcessedSampleBuffer()
     : code_lookup_table_(new CodeLookupTable(Thread::Current())) {
   ASSERT(code_lookup_table_ != NULL);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart