Support the Syzygy instrumenting profiler.

base/debug/profiler.h

-// 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.
 
 #ifndef BASE_DEBUG_PROFILER_H
 #define BASE_DEBUG_PROFILER_H
 #pragma once
 
 #include <string>
 
 #include "base/base_export.h"
+#include "base/basictypes.h"
 
 // The Profiler functions allow usage of the underlying sampling based
 // profiler. If the application has not been built with the necessary
 // flags (-DENABLE_PROFILING and not -DNO_TCMALLOC) then these functions
 // are noops.
 namespace base {
 namespace debug {
 
 // Start profiling with the supplied name.
 // {pid} will be replaced by the process' pid and {count} will be replaced
 // by the count of the profile run (starts at 1 with each process).
 BASE_EXPORT void StartProfiling(const std::string& name);
 
 // Stop profiling and write out data.
 BASE_EXPORT void StopProfiling();
 
 // Force data to be written to file.
 BASE_EXPORT void FlushProfiling();
 
 // Returns true if process is being profiled.
 BASE_EXPORT bool BeingProfiled();
 
 // Reset profiling after a fork, which disables timers.
 BASE_EXPORT void RestartProfilingAfterFork();
 
+// Returns true iff this executable is instrumented with the Syzygy profiler.
+BASE_EXPORT bool IsBinaryInstrumented();
+
+// There's a class of profilers that use "return address swizzling" to get a
+// hook on function exits. This class of profilers uses some form of entry hook,
+// like e.g. binary instrumentation, or a compiler flag, that calls a hook each
+// time a function is invoked. The hook then switches the return address on the
+// stack for the address of an exit hook function, and pushes the original
+// return address to a shadow stack of some type. When in due course the CPU
+// executes a return to the exit hook, the exit hook will do whatever work it
+// does on function exit, then arrange to return to the original return address.
+// This class of profiler does not play well with programs that look at the
+// return address, as does e.g. V8. V8 uses the return address to certain
+// runtime functions to find the JIT code that called it, and from there finds
+// the V8 data structures associated to the JS function involved.
+// A return address resolution function is used to fix this. It allows such
+// programs to resolve a location on stack where a return address originally
+// resided, to the shadow stack location where the profiler stashed it.
+typedef uintptr_t (*ReturnAddressLocationResolver)(
+    uintptr_t return_addr_location);
+
+// If this binary is instrumented and the instrumentation supplies a return
+// address resolution function, finds and returns the address resolution
+// function. Otherwise returns NULL.
+BASE_EXPORT ReturnAddressLocationResolver
+    GetProfilerReturnAddrResolutionFunc();
+
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_DEBUGGER_H