1    :  // Copyright 2013 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #ifndef SYZYGY_TRACE_COMMON_CLOCK_H_
  16    :  #define SYZYGY_TRACE_COMMON_CLOCK_H_
  17    :  
  18    :  #include <intrin.h>
  19    :  #include <stdint.h>
  20    :  #include <windows.h>
  21    :  
  22    :  #include "syzygy/common/assertions.h"
  23    :  
  24    :  namespace trace {
  25    :  namespace common {
  26    :  
  27    :  // A structure representing information about a timer. This can be used
  28    :  // (along with reference times) to translate between timers and clocks.
  29    :  // Both values will be set to zero for a timer that is not valid on a given
  30    :  // system.
  31    :  // NOTE: This is meant to be POD so that it can be written directly as is to and
  32    :  //     from disk.
  33    :  struct TimerInfo {
  34    :    // The frequency of this timer, in counts per second.
  35    :    uint64_t frequency;
  36    :    // The resolution of this timer, in counts.
  37    :    uint64_t resolution;
  38    :  };
  39    :  COMPILE_ASSERT_IS_POD(TimerInfo);
  40    :  
  41    :  // Gets timer information about the various timers. A timer whose information
  42    :  // can not be found will have the frequency set to 0.
  43    :  // @param timer_info Will be populated with the information about the timer.
  44    :  void GetTickTimerInfo(TimerInfo* timer_info);
  45    :  void GetTscTimerInfo(TimerInfo* timer_info);
  46    :  
  47    :  // @returns the current value of the ticks timer.
  48    :  uint64_t GetTicks();
  49    :  
  50    :  // @returns the current value of the TSC register using RDTSC.
  51  E :  inline uint64_t GetTsc() {
  52  E :    return ::__rdtsc();
  53  E :  }
  54    :  
  55    :  // Given a file time, a reference time and TimerInfo, convert the given
  56    :  // timer value to the corresponding file time. This can fail if the timer
  57    :  // info is invalid (frequency is 0, ie: unknown).
  58    :  // @param file_time_ref A reference file time.
  59    :  // @param timer_info Information regarding the timer frequency.
  60    :  // @param timer_ref The corresponding reference timer value.
  61    :  // @param timer_value The timer value to be converted.
  62    :  // @param file_time The file time to be populated.
  63    :  // @returns true on success, false otherwise.
  64    :  bool TimerToFileTime(const FILETIME& file_time_ref,
  65    :                       const TimerInfo& timer_info,
  66    :                       const uint64_t& timer_ref,
  67    :                       const uint64_t& timer_value,
  68    :                       FILETIME* file_time);
  69    :  
  70    :  // Information about the system clock and various timers.
  71    :  // NOTE: This is meant to be POD so that it can be written directly as is to and
  72    :  //     from disk.
  73    :  struct ClockInfo {
  74    :    // Reference times. Used for converting between time formats.
  75    :    FILETIME file_time;
  76    :    uint64_t ticks_reference;
  77    :    uint64_t tsc_reference;
  78    :  
  79    :    // Information about the timers at our disposal.
  80    :    TimerInfo ticks_info;
  81    :    TimerInfo tsc_info;
  82    :  };
  83    :  COMPILE_ASSERT_IS_POD(ClockInfo);
  84    :  
  85    :  // Populates a ClockInfo struct with information about the system clock and
  86    :  // timers.
  87    :  // NOTE: This requires read access to the registry to get full information, and
  88    :  //     is intended to be run from a process that has no restrictions. For
  89    :  //     example, if this is run from a sandboxed process the TSC timer
  90    :  //     information will be incomplete. A warning will be logged if this is the
  91    :  //     case.
  92    :  // @param clock_info The struct to be populated.
  93    :  void GetClockInfo(ClockInfo* clock_info);
  94    :  
  95    :  // Converts a timer value to a file time given the clock info. This can fail if
  96    :  // the given timer has an invalid corresponding TimerInfo in @p clock_info.
  97    :  // @param clock_info The system clock information.
  98    :  // @param ticks The value of the tick counter.
  99    :  // @param tsc The value of the TSC counter.
 100    :  // @param file_time The file time to be populated.
 101    :  // @returns true on success, false otherwise.
 102    :  bool TicksToFileTime(const ClockInfo& clock_info,
 103    :                       uint64_t ticks,
 104    :                       FILETIME* file_time);
 105    :  bool TscToFileTime(const ClockInfo& clock_info,
 106    :                     uint64_t tsc,
 107    :                     FILETIME* file_time);
 108    :  
 109    :  }  // namespace common
 110    :  }  // namespace trace
 111    :  
 112    :  #endif  // SYZYGY_TRACE_COMMON_CLOCK_H_