base/debug/profiler.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_DEBUG_PROFILER_H_
   6 #define BASE_DEBUG_PROFILER_H_
   7
   8 #include <string>
   9
  10 #include "base/base_export.h"
  11 #include "base/basictypes.h"
  12
  13 // The Profiler functions allow usage of the underlying sampling based
  14 // profiler. If the application has not been built with the necessary
  15 // flags (-DENABLE_PROFILING and not -DNO_TCMALLOC) then these functions
  16 // are noops.
  17 namespace base {
  18 namespace debug {
  19
  20 // Start profiling with the supplied name.
  21 // {pid} will be replaced by the process' pid and {count} will be replaced
  22 // by the count of the profile run (starts at 1 with each process).
  23 BASE_EXPORT void StartProfiling(const std::string& name);
  24
  25 // Stop profiling and write out data.
  26 BASE_EXPORT void StopProfiling();
  27
  28 // Force data to be written to file.
  29 BASE_EXPORT void FlushProfiling();
  30
  31 // Returns true if process is being profiled.
  32 BASE_EXPORT bool BeingProfiled();
  33
  34 // Reset profiling after a fork, which disables timers.
  35 BASE_EXPORT void RestartProfilingAfterFork();
  36
  37 // Returns true iff this executable is instrumented with the Syzygy profiler.
  38 BASE_EXPORT bool IsBinaryInstrumented();
  39
  40 // There's a class of profilers that use "return address swizzling" to get a
  41 // hook on function exits. This class of profilers uses some form of entry hook,
  42 // like e.g. binary instrumentation, or a compiler flag, that calls a hook each
  43 // time a function is invoked. The hook then switches the return address on the
  44 // stack for the address of an exit hook function, and pushes the original
  45 // return address to a shadow stack of some type. When in due course the CPU
  46 // executes a return to the exit hook, the exit hook will do whatever work it
  47 // does on function exit, then arrange to return to the original return address.
  48 // This class of profiler does not play well with programs that look at the
  49 // return address, as does e.g. V8. V8 uses the return address to certain
  50 // runtime functions to find the JIT code that called it, and from there finds
  51 // the V8 data structures associated to the JS function involved.
  52 // A return address resolution function is used to fix this. It allows such
  53 // programs to resolve a location on stack where a return address originally
  54 // resided, to the shadow stack location where the profiler stashed it.
  55 typedef uintptr_t (*ReturnAddressLocationResolver)(
  56     uintptr_t return_addr_location);
  57
  58 // This type declaration must match V8's FunctionEntryHook.
  59 typedef void (*DynamicFunctionEntryHook)(uintptr_t function,
  60                                          uintptr_t return_addr_location);
  61
  62 // The functions below here are to support profiling V8-generated code.
  63 // V8 has provisions for generating a call to an entry hook for newly generated
  64 // JIT code, and it can push symbol information on code generation and advise
  65 // when the garbage collector moves code. The functions declarations below here
  66 // make glue between V8's facilities and a profiler.
  67
  68 // This type declaration must match V8's FunctionEntryHook.
  69 typedef void (*DynamicFunctionEntryHook)(uintptr_t function,
  70                                          uintptr_t return_addr_location);
  71
  72 typedef void (*AddDynamicSymbol)(const void* address,
  73                                  size_t length,
  74                                  const char* name,
  75                                  size_t name_len);
  76 typedef void (*MoveDynamicSymbol)(const void* address, const void* new_address);
  77
  78
  79 // If this binary is instrumented and the instrumentation supplies a function
  80 // for each of those purposes, find and return the function in question.
  81 // Otherwise returns NULL.
  82 BASE_EXPORT ReturnAddressLocationResolver GetProfilerReturnAddrResolutionFunc();
  83 BASE_EXPORT DynamicFunctionEntryHook GetProfilerDynamicFunctionEntryHookFunc();
  84 BASE_EXPORT AddDynamicSymbol GetProfilerAddDynamicSymbolFunc();
  85 BASE_EXPORT MoveDynamicSymbol GetProfilerMoveDynamicSymbolFunc();
  86
  87 }  // namespace debug
  88 }  // namespace base
  89
  90 #endif  // BASE_DEBUG_PROFILER_H_