StackSamplingProfiler clean up

base/profiler/stack_sampling_profiler_win.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/profiler/stack_sampling_profiler.h"
 
-#include <dbghelp.h>
+#include <windows.h>
+
 #include <map>
 #include <utility>
-#include <windows.h>
 
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "base/win/pe_image.h"
 #include "base/win/scoped_handle.h"
 
 namespace base {
 
 namespace {
 
-class NativeStackSamplerWin : public StackSamplingProfiler::NativeStackSampler {
- public:
-  explicit NativeStackSamplerWin(win::ScopedHandle thread_handle);
-  ~NativeStackSamplerWin() override;
-
-  // StackSamplingProfiler::NativeStackSampler:
-  void ProfileRecordingStarting(
-      StackSamplingProfiler::Profile* profile) override;
-  void RecordStackSample(StackSamplingProfiler::Sample* sample) override;
-  void ProfileRecordingStopped() override;
-
- private:
-  static bool GetModuleInfo(HMODULE module,
-                            StackSamplingProfiler::Module* module_info);
-
-  void CopyToSample(const void* const instruction_pointers[],
-                    const HMODULE modules[],
-                    int stack_depth,
-                    StackSamplingProfiler::Sample* sample,
-                    std::vector<StackSamplingProfiler::Module>* module_infos);
-
-  win::ScopedHandle thread_handle_;
-  // Weak. Points to the profile being recorded between
-  // ProfileRecordingStarting() and ProfileRecordingStopped().
-  StackSamplingProfiler::Profile* current_profile_;
-  // Maps a module to the module's index within current_profile_->modules.
-  std::map<HMODULE, int> profile_module_index_;
-
-  DISALLOW_COPY_AND_ASSIGN(NativeStackSamplerWin);
-};
-
-// Walk the stack represented by |context| from the current frame downwards,
+// Walks the stack represented by |context| from the current frame downwards,
 // recording the instruction pointers for each frame in |instruction_pointers|.
 int RecordStack(CONTEXT* context,
                 int max_stack_size,
                 const void* instruction_pointers[],
                 bool* last_frame_is_unknown_function) {
 #ifdef _WIN64
   *last_frame_is_unknown_function = false;
 
-  IMAGEHLP_SYMBOL64 sym;
-  sym.SizeOfStruct = sizeof(sym);
-  sym.MaxNameLength = 0;
-
-  for (int i = 0; i < max_stack_size; ++i) {
+  int i = 0;
+  for (; (i < max_stack_size) && context->Rip; ++i) {
     // Try to look up unwind metadata for the current function.
     ULONG64 image_base;
     PRUNTIME_FUNCTION runtime_function =
         RtlLookupFunctionEntry(context->Rip, &image_base, nullptr);
 
     instruction_pointers[i] = reinterpret_cast<void*>(context->Rip);
 
     if (runtime_function) {
       KNONVOLATILE_CONTEXT_POINTERS nvcontext = {0};
       void* handler_data;
       ULONG64 establisher_frame;
       RtlVirtualUnwind(0, image_base, context->Rip, runtime_function, context,
-          &handler_data, &establisher_frame, &nvcontext);
+                       &handler_data, &establisher_frame, &nvcontext);
     } else {
-      // If we don't have a RUNTIME_FUNCTION, then we've encountered
-      // a leaf function.  Adjust the stack appropriately.
+      // If we don't have a RUNTIME_FUNCTION, then we've encountered a leaf
+      // function.  Adjust the stack appropriately prior to the next function
+      // lookup.
       context->Rip = *reinterpret_cast<PDWORD64>(context->Rsp);
       context->Rsp += 8;
       *last_frame_is_unknown_function = true;
     }
-
-    if (!context->Rip)
-      return i;
   }
-  return max_stack_size;
+  return i;
 #else
   return 0;
 #endif
 }
 
 // Fills in |modules| corresponding to the pointers to code in |addresses|. The
-// modules are returned with reference counts incremented should be freed with
-// FreeModules.
+// modules are returned with reference counts incremented and should be freed
+// with FreeModules.
 void FindModulesForAddresses(const void* const addresses[], HMODULE modules[],
                              int stack_depth,
                              bool last_frame_is_unknown_function) {
-  const int module_frames = last_frame_is_unknown_function ? stack_depth - 1 :
-      stack_depth;
+  const int module_frames =
+      last_frame_is_unknown_function ? stack_depth - 1 : stack_depth;
   for (int i = 0; i < module_frames; ++i) {
     HMODULE module = NULL;
     if (GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
                           reinterpret_cast<LPCTSTR>(addresses[i]),
                           &module)) {
-      // HMODULE is the base address of the module.
-      DCHECK_LT(reinterpret_cast<const void*>(module), addresses[i]);
+      // HMODULE actually represents the base address of the module, so we can
+      // use it directly as an address.
+      DCHECK_LE(reinterpret_cast<const void*>(module), addresses[i]);
       modules[i] = module;
     }
   }
 }
 
-// Free the modules returned by FindModulesForAddresses.
+// Frees the modules returned by FindModulesForAddresses.
 void FreeModules(int stack_depth, HMODULE modules[]) {
   for (int i = 0; i < stack_depth; ++i) {
     if (modules[i])
       ::FreeLibrary(modules[i]);
   }
 }
 
 // Disables priority boost on a thread for the lifetime of the object.
 class ScopedDisablePriorityBoost {
  public:
   ScopedDisablePriorityBoost(HANDLE thread_handle);
   ~ScopedDisablePriorityBoost();
 
  private:
   HANDLE thread_handle_;
   BOOL got_previous_boost_state_;
   BOOL boost_state_was_disabled_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedDisablePriorityBoost);
 };
 
 ScopedDisablePriorityBoost::ScopedDisablePriorityBoost(HANDLE thread_handle)
     : thread_handle_(thread_handle),
       got_previous_boost_state_(false),
       boost_state_was_disabled_(false) {
   got_previous_boost_state_ =
       ::GetThreadPriorityBoost(thread_handle_, &boost_state_was_disabled_);
-  if (got_previous_boost_state_ && !boost_state_was_disabled_) {
-    // Confusingly, TRUE disables priority boost ...
+  if (got_previous_boost_state_) {
+    // Confusingly, TRUE disables priority boost.
     ::SetThreadPriorityBoost(thread_handle_, TRUE);
   }
 }
 
 ScopedDisablePriorityBoost::~ScopedDisablePriorityBoost() {
-  if (got_previous_boost_state_ && !boost_state_was_disabled_) {
-    // ... and FALSE enables priority boost.
-    ::SetThreadPriorityBoost(thread_handle_, FALSE);
-  }
+  if (got_previous_boost_state_)
+    ::SetThreadPriorityBoost(thread_handle_, boost_state_was_disabled_);
 }
 
 // Suspends the thread with |thread_handle|, records the stack into
 // |instruction_pointers|, then resumes the thread. Returns the size of the
 // stack.
+//
+// IMPORTANT NOTE: No heap allocations may occur between SuspendThread and
+// ResumeThread. Otherwise this code can deadlock on heap locks acquired by the
+// target thread before it was suspended. This is why we pass instruction
+// pointers as a bare array rather than a vector.
 int SuspendThreadAndRecordStack(HANDLE thread_handle, int max_stack_size,
                                 const void* instruction_pointers[],
                                 bool* last_frame_is_unknown_function) {
-#if defined(_WIN64)
-  if (RtlVirtualUnwind == nullptr || RtlLookupFunctionEntry == nullptr)
-    return 0;
-#endif
-
   if (::SuspendThread(thread_handle) == -1) {
-    LOG(ERROR) << "SuspendThread failed: " << GetLastError();
+    NOTREACHED() << "SuspendThread failed: " << GetLastError();

[Peter Kasting, 2015/03/27 23:44:47]

A side effect of changing LOG -> NOTREACHED, coupled with how NOTREACHED is
really a DCHECK and Chrome's style guide says not to handle DCHECK failure, is
that the return here (and the "else" a few lines below) are actually against the
Chromium style guide.  Compliant code would either omit the NOTREACHED or omit
the return.

As before, if you think this could fail, but you want to understand when, you
could change to a CHECK in these places with a TODO to remove later.

[Mike Wittman, 2015/03/30 21:01:13]

Here also, it's not worth crashing people and committing to trying to understand
possible failure modes at this point. The one exception is failure of
ResumeThread which certainly would leave the application in a bad state.

     return 0;
   }
 
+  int stack_depth = 0;
   CONTEXT thread_context = {0};
   thread_context.ContextFlags = CONTEXT_FULL;
-  if (!::GetThreadContext(thread_handle, &thread_context)) {
-    LOG(ERROR) << "GetThreadContext failed: " << GetLastError();
+  if (::GetThreadContext(thread_handle, &thread_context)) {
+    stack_depth = RecordStack(&thread_context, max_stack_size,
+                              instruction_pointers,
+                              last_frame_is_unknown_function);
+  } else {
+    NOTREACHED() << "GetThreadContext failed: " << GetLastError();
   }
 
-  int stack_depth = RecordStack(&thread_context, max_stack_size,
-                                instruction_pointers,
-                                last_frame_is_unknown_function);
-
-  {
-    ScopedDisablePriorityBoost disable_priority_boost(thread_handle);
-    if (::ResumeThread(thread_handle) == -1)
-      LOG(ERROR) << "ResumeThread failed: " << GetLastError();
-  }
+  // Disable the priority boost that the thread would otherwise receive on
+  // resume. We do this to avoid artificially altering the dynamics of the
+  // executing application any more than we already are by suspending and
+  // resuming the thread.
+  ScopedDisablePriorityBoost disable_priority_boost(thread_handle);
+  if (::ResumeThread(thread_handle) == -1)
+    NOTREACHED() << "ResumeThread failed: " << GetLastError();
 
   return stack_depth;
 }
 
-}  // namespace
+class NativeStackSamplerWin : public StackSamplingProfiler::NativeStackSampler {
+ public:
+  explicit NativeStackSamplerWin(win::ScopedHandle thread_handle);
+  ~NativeStackSamplerWin() override;
 
-scoped_ptr<StackSamplingProfiler::NativeStackSampler>
-StackSamplingProfiler::NativeStackSampler::Create(PlatformThreadId thread_id) {
-#if _WIN64
-  // Get the thread's handle.
-  HANDLE thread_handle = ::OpenThread(
-      THREAD_GET_CONTEXT | THREAD_SUSPEND_RESUME | THREAD_QUERY_INFORMATION,
-      FALSE,
-      thread_id);
-  DCHECK(thread_handle) << "OpenThread failed";
+  // StackSamplingProfiler::NativeStackSampler:
+  void ProfileRecordingStarting(
+      StackSamplingProfiler::Profile* profile) override;
+  void RecordStackSample(StackSamplingProfiler::Sample* sample) override;
+  void ProfileRecordingStopped() override;
 
-  return scoped_ptr<NativeStackSampler>(new NativeStackSamplerWin(
-      win::ScopedHandle(thread_handle)));
-#else
-  return scoped_ptr<NativeStackSampler>();
-#endif
-}
+ private:
+  // Attempts to query the module filename, base address, and id and store them
+  // in |module_info|. Returns true if it succeeded.
+  static bool GetModuleInfo(HMODULE module,
+                            StackSamplingProfiler::Module* module_info);
+
+  // Gets the module index for |module| in |modules|, adding it if it's not
+  // already present. Returns StackSamplingProfiler::Frame::kUnknownModuleIndex
+  // if no Module can be determined for |module|
+  size_t GetModuleIndex(HMODULE module,
+                        std::vector<StackSamplingProfiler::Module>* modules);
+
+  // Copies the stack information represented by |instruction_pointers| into
+  // |sample| and |module_infos|.
+  void CopyToSample(const void* const instruction_pointers[],
+                    const HMODULE modules[],
+                    int stack_depth,
+                    StackSamplingProfiler::Sample* sample,
+                    std::vector<StackSamplingProfiler::Module>* module_infos);
+
+  win::ScopedHandle thread_handle_;
+  // Weak. Points to the profile being recorded between
+  // ProfileRecordingStarting() and ProfileRecordingStopped().
+  StackSamplingProfiler::Profile* current_profile_;
+  // Maps a module to the module's index within current_profile_->modules.
+  std::map<HMODULE, size_t> profile_module_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(NativeStackSamplerWin);
+};
 
 NativeStackSamplerWin::NativeStackSamplerWin(win::ScopedHandle thread_handle)
     : thread_handle_(thread_handle.Take()) {
-#ifdef _WIN64
-  if (RtlVirtualUnwind == nullptr && RtlLookupFunctionEntry == nullptr) {
-    const HMODULE nt_dll_handle = ::GetModuleHandle(L"ntdll.dll");
-    // This should always be non-null, but handle just in case.
-    if (nt_dll_handle) {
-      reinterpret_cast<void*&>(RtlVirtualUnwind) =
-          ::GetProcAddress(nt_dll_handle, "RtlVirtualUnwind");
-      reinterpret_cast<void*&>(RtlLookupFunctionEntry) =
-          ::GetProcAddress(nt_dll_handle, "RtlLookupFunctionEntry");
-    }
-  }
-#endif
 }
 
 NativeStackSamplerWin::~NativeStackSamplerWin() {
 }
 
 void NativeStackSamplerWin::ProfileRecordingStarting(
     StackSamplingProfiler::Profile* profile) {
   current_profile_ = profile;
   profile_module_index_.clear();
 }
@@ skipping 31 matching lines @@
   if (result_length == 0)
     return false;
 
   module_info->filename = base::FilePath(module_name);
 
   module_info->base_address = reinterpret_cast<const void*>(module);
 
   GUID guid;
   DWORD age;
   win::PEImage(module).GetDebugId(&guid, &age);
-  module_info->id.insert(module_info->id.end(),
-                         reinterpret_cast<char*>(&guid),
-                         reinterpret_cast<char*>(&guid + 1));
-  module_info->id.insert(module_info->id.end(),
-                         reinterpret_cast<char*>(&age),
-                         reinterpret_cast<char*>(&age + 1));
+  module_info->id.assign(reinterpret_cast<char*>(&guid), sizeof(guid));
+  module_info->id.append(reinterpret_cast<char*>(&age), sizeof(age));
 
   return true;
 }
 
+size_t NativeStackSamplerWin::GetModuleIndex(
+    HMODULE module,
+    std::vector<StackSamplingProfiler::Module>* modules) {
+  if (!module)
+    return StackSamplingProfiler::Frame::kUnknownModuleIndex;
+
+  auto loc = profile_module_index_.find(module);
+  if (loc == profile_module_index_.end()) {
+    StackSamplingProfiler::Module module_info;
+    if (!GetModuleInfo(module, &module_info))
+      return StackSamplingProfiler::Frame::kUnknownModuleIndex;
+    modules->push_back(module_info);
+    loc = profile_module_index_.insert(std::make_pair(
+        module, modules->size() - 1)).first;
+  }
+
+  return loc->second;
+}
+
 void NativeStackSamplerWin::CopyToSample(
     const void* const instruction_pointers[],
     const HMODULE modules[],
     int stack_depth,
     StackSamplingProfiler::Sample* sample,
     std::vector<StackSamplingProfiler::Module>* module_infos) {
   sample->clear();
   sample->reserve(stack_depth);
 
   for (int i = 0; i < stack_depth; ++i) {
-    sample->push_back(StackSamplingProfiler::Frame());
-    StackSamplingProfiler::Frame& frame = sample->back();
-
-    frame.instruction_pointer = instruction_pointers[i];
-
-    // Record an invalid module index if we don't have a valid module.
-    if (!modules[i]) {
-      frame.module_index = -1;
-      continue;
-    }
-
-    auto loc = profile_module_index_.find(modules[i]);
-    if (loc == profile_module_index_.end()) {
-      StackSamplingProfiler::Module module_info;
-      // Record an invalid module index if we have a module but can't find
-      // information on it.
-      if (!GetModuleInfo(modules[i], &module_info)) {
-        frame.module_index = -1;
-        continue;
-      }
-      module_infos->push_back(module_info);
-      loc = profile_module_index_.insert(std::make_pair(
-          modules[i], static_cast<int>(module_infos->size() - 1))).first;
-    }
-
-    frame.module_index = loc->second;
+    sample->push_back(StackSamplingProfiler::Frame(
+        instruction_pointers[i], GetModuleIndex(modules[i], module_infos)));
   }
 }
 
+}  // namespace
+
+scoped_ptr<StackSamplingProfiler::NativeStackSampler>
+StackSamplingProfiler::NativeStackSampler::Create(PlatformThreadId thread_id) {
+#if _WIN64
+  // Get the thread's handle.
+  HANDLE thread_handle = ::OpenThread(
+      THREAD_GET_CONTEXT | THREAD_SUSPEND_RESUME | THREAD_QUERY_INFORMATION,
+      FALSE,
+      thread_id);
+
+  if (thread_handle) {
+    return scoped_ptr<NativeStackSampler>(new NativeStackSamplerWin(
+        win::ScopedHandle(thread_handle)));
+  }
+#endif
+  return scoped_ptr<NativeStackSampler>();
+}
+
 }  // namespace base
+