Support the Syzygy instrumenting profiler.

base/debug/profiler.cc

Index: base/debug/profiler.cc
diff --git a/base/debug/profiler.cc b/base/debug/profiler.cc
index be442cf1fd66fc981ebd352bc6601c7b1a7a4fa0..41950575f93d71bc947e164989a66f1b0f52e661 100644
--- a/base/debug/profiler.cc
+++ b/base/debug/profiler.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -10,6 +10,10 @@
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 
+#if defined(OS_WIN)
+#include "base/win/pe_image.h"
+#endif  // defined(OS_WIN)
+
 #if defined(ENABLE_PROFILING) && !defined(NO_TCMALLOC)
 #include "third_party/tcmalloc/chromium/src/google/profiler.h"
 #endif
@@ -68,5 +72,89 @@ void RestartProfilingAfterFork() {
 
 #endif
 
+#if !defined(OS_WIN)
+
+bool IsBinaryInstrumented() {
+  return false;
+}
+
+ReturnAddressLocationResolver GetProfilerReturnAddrResolutionFunc() {
+  return NULL;
+}
+
+#else  // defined(OS_WIN)
+
+// http://blogs.msdn.com/oldnewthing/archive/2004/10/25/247180.aspx
+extern "C" IMAGE_DOS_HEADER __ImageBase;
+
+bool IsBinaryInstrumented() {
+  HMODULE this_module = reinterpret_cast<HMODULE>(&__ImageBase);
+  base::win::PEImage image(this_module);
+
+  // This should be self-evident, soon as we're executing.
+  DCHECK(image.VerifyMagic());
+
+  // Syzygy-instrumented binaries contain a PE image section named ".thunks",
+  // and all Syzygy-modified binaries contain the ".syzygy" image section.
+  // This is a very fast check, as it only looks at the image header.
+  return (image.GetImageSectionHeaderByName(".thunks") != NULL) &&
+      (image.GetImageSectionHeaderByName(".syzygy") != NULL);
+}
+
+// Callback function to PEImage::EnumImportChunks.
+static bool FindResolutionFunctionInImports(
+    const base::win::PEImage &image, const char* module_name,
+    PIMAGE_THUNK_DATA unused_name_table, PIMAGE_THUNK_DATA import_address_table,
+    PVOID cookie) {
+  // Our import address table contains pointers to the functions we import
+  // at this point. Let's retrieve the first such function and use it to
+  // find the module this import was resolved to by the loader.
+  const wchar_t* function_in_module =
+      reinterpret_cast<const wchar_t*>(import_address_table->u1.Function);
+
+  // Retrieve the module by a function in the module.
+  const DWORD kFlags = GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                       GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT;
+  HMODULE module = NULL;
+  if (!::GetModuleHandleEx(kFlags, function_in_module, &module)) {
+    // This can happen if someone IAT patches us to a thunk.
+    return true;
+  }
+
+  // See whether this module exports the function we're looking for.
+  ReturnAddressLocationResolver exported_func =
+      reinterpret_cast<ReturnAddressLocationResolver>(
+          ::GetProcAddress(module, "ResolveReturnAddressLocation"));
+
+  if (exported_func != NULL) {
+    ReturnAddressLocationResolver* resolver_func =
+        reinterpret_cast<ReturnAddressLocationResolver*>(cookie);
+    DCHECK(resolver_func != NULL);
+    DCHECK(*resolver_func == NULL);
+
+    // We found it, return the function and terminate the enumeration.
+    *resolver_func = exported_func;
+    return false;
+  }
+
+  // Keep going.
+  return true;
+}
+
+ReturnAddressLocationResolver GetProfilerReturnAddrResolutionFunc() {
+  if (!IsBinaryInstrumented())
+    return NULL;
+
+  HMODULE this_module = reinterpret_cast<HMODULE>(&__ImageBase);
+  base::win::PEImage image(this_module);
+
+  ReturnAddressLocationResolver resolver_func = NULL;
+  image.EnumImportChunks(FindResolutionFunctionInImports, &resolver_func);
+
+  return resolver_func;
+}
+
+#endif  // defined(OS_WIN)
+
 }  // namespace debug
 }  // namespace base