Support the Syzygy instrumenting profiler.

base/debug/profiler.cc

 // Copyright (c) 2011 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/debug/profiler.h"
 
 #include <string>
 
 #include "base/process_util.h"
 #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
 
 namespace base {
 namespace debug {
 
 #if defined(ENABLE_PROFILING) && !defined(NO_TCMALLOC)
 
 static int profile_count = 0;
@@ skipping 38 matching lines @@
 
 bool BeingProfiled() {
   return false;
 }
 
 void RestartProfilingAfterFork() {
 }
 
 #endif
 
+#if 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);
+}
+
+static bool FindResolutionFunctionInImports(const base::win::PEImage &image,
+                                            const char* module_name,
+                                            PIMAGE_THUNK_DATA name_table,

[jar (doing other things), 2012/02/27 22:44:10]

Why was name_table passed in.... as it is never used.

[Sigurður Ásgeirsson, 2012/02/28 16:31:40]

This is a callback function to the PEImage class, the signature is mandated by
the interface.

+                                            PIMAGE_THUNK_DATA iat,

[jar (doing other things), 2012/02/27 22:44:10]

Avoiding the abreviation iat might help with readability.

[Sigurður Ásgeirsson, 2012/02/28 16:31:40]

Done.

+                                            PVOID cookie) {
+  ReturnAddressLocationResolver* resolver_func =
+      reinterpret_cast<ReturnAddressLocationResolver*>(cookie);
+  DCHECK(resolver_func != NULL);
+  DCHECK(*resolver_func == NULL);

[jar (doing other things), 2012/02/27 22:44:10]

Could lines 99-102 be moved closer to the first (only) use of resolver_func on
line 126?   ... or are you super psyched to do the DCHECKs up front??

[Sigurður Ásgeirsson, 2012/02/28 16:31:40]

Done.

+
+  // 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 we were linked with.
+  const wchar_t* function_in_module =
+      reinterpret_cast<const wchar_t*>(iat[0].u1.Function);
+
+  // Retrieve the module by a function in it.
+  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) {
+    // 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;
+}
+
+#else  // defined(OS_WIN)
+
+bool IsBinaryInstrumented() {

[jar (doing other things), 2012/02/27 22:44:10]

silly personal nit: I always like the shortest branch of an if to come first, so
I don't have to search for it way down in code.  Consider putting this up at the
top of the ifdef..

[Sigurður Ásgeirsson, 2012/02/28 16:31:40]

Done.

+  return false;
+}
+
+ReturnAddressLocationResolver GetProfilerReturnAddrResolutionFunc() {
+  return NULL;
+}
+
+#endif  // defined(OS_WIN)
+
 }  // namespace debug
 }  // namespace base