path: root/MdeModulePkg/Library/DxeCorePerformanceLib/DxeCorePerformanceLib.c

/** @file
  Performance library instance mainly used by DxeCore.

  This library provides the performance measurement interfaces and initializes performance
  logging for DXE phase. It first initializes its private global data structure for
  performance logging and saves the performance GUIDed HOB passed from PEI phase. 
  It initializes DXE phase performance logging by publishing the Performance and PerformanceEx Protocol,
  which are consumed by DxePerformanceLib to logging performance data in DXE phase.

  This library is mainly used by DxeCore to start performance logging to ensure that
  Performance Protocol is installed at the very beginning of DXE phase.

Copyright (c) 2006 - 2012, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/


#include "DxeCorePerformanceLibInternal.h"


//
// The data structure to hold global performance data.
//
GAUGE_DATA_HEADER    *mGaugeData;

//
// The current maximum number of logging entries. If current number of 
// entries exceeds this value, it will re-allocate a larger array and
// migration the old data to the larger array.
//
UINT32               mMaxGaugeRecords;

//
// The handle to install Performance Protocol instance.
//
EFI_HANDLE           mHandle = NULL;

//
// Interfaces for Performance Protocol.
//
PERFORMANCE_PROTOCOL mPerformanceInterface = {
  StartGauge,
  EndGauge,
  GetGauge
  };

//
// Interfaces for PerformanceEx Protocol.
//
PERFORMANCE_EX_PROTOCOL mPerformanceExInterface = {
  StartGaugeEx,
  EndGaugeEx,
  GetGaugeEx
  };

/**
  Searches in the gauge array with keyword Handle, Token, Module and Identifier.

  This internal function searches for the gauge entry in the gauge array.
  If there is an entry that exactly matches the given keywords
  and its end time stamp is zero, then the index of that gauge entry is returned;
  otherwise, the the number of gauge entries in the array is returned.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  Identifier              32-bit identifier.

  @retval The index of gauge entry in the array.

**/
UINT32
InternalSearchForGaugeEntry (
  IN CONST VOID                 *Handle,  OPTIONAL
  IN CONST CHAR8                *Token,   OPTIONAL
  IN CONST CHAR8                *Module,   OPTIONAL
  IN UINT32                     Identifier
  )
{
  UINT32                    Index;
  UINT32                    Index2;
  UINT32                    NumberOfEntries;
  GAUGE_DATA_ENTRY_EX       *GaugeEntryExArray;

  if (Token == NULL) {
    Token = "";
  }
  if (Module == NULL) {
    Module = "";
  }

  NumberOfEntries = mGaugeData->NumberOfEntries;
  GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1);

  Index2 = 0;

  for (Index = 0; Index < NumberOfEntries; Index++) {
    Index2 = NumberOfEntries - 1 - Index;
    if (GaugeEntryExArray[Index2].EndTimeStamp == 0 &&
        (GaugeEntryExArray[Index2].Handle == (EFI_PHYSICAL_ADDRESS) (UINTN) Handle) &&
        AsciiStrnCmp (GaugeEntryExArray[Index2].Token, Token, DXE_PERFORMANCE_STRING_LENGTH) == 0 &&
        AsciiStrnCmp (GaugeEntryExArray[Index2].Module, Module, DXE_PERFORMANCE_STRING_LENGTH) == 0 &&
        (GaugeEntryExArray[Index2].Identifier == Identifier)) {
      Index = Index2;
      break;
    }
  }

  return Index;
}

/**
  Adds a record at the end of the performance measurement log
  that records the start time of a performance measurement.

  Adds a record to the end of the performance measurement log
  that contains the Handle, Token, Module and Identifier.
  The end time of the new record must be set to zero.
  If TimeStamp is not zero, then TimeStamp is used to fill in the start time in the record.
  If TimeStamp is zero, the start time in the record is filled in with the value
  read from the current time stamp.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.
  @param  Identifier              32-bit identifier. If the value is 0, the created record
                                  is same as the one created by StartGauge of PERFORMANCE_PROTOCOL.

  @retval EFI_SUCCESS             The data was read correctly from the device.
  @retval EFI_OUT_OF_RESOURCES    There are not enough resources to record the measurement.

**/
EFI_STATUS
EFIAPI
StartGaugeEx (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp,
  IN UINT32       Identifier
  )
{
  GAUGE_DATA_ENTRY_EX       *GaugeEntryExArray;
  UINTN                     GaugeDataSize;
  GAUGE_DATA_HEADER         *NewGaugeData;
  UINTN                     OldGaugeDataSize;
  GAUGE_DATA_HEADER         *OldGaugeData;
  UINT32                    Index;

  Index = mGaugeData->NumberOfEntries;
  if (Index >= mMaxGaugeRecords) {
    //
    // Try to enlarge the scale of gauge array.
    //
    OldGaugeData      = mGaugeData;
    OldGaugeDataSize  = sizeof (GAUGE_DATA_HEADER) + sizeof (GAUGE_DATA_ENTRY_EX) * mMaxGaugeRecords;

    GaugeDataSize     = sizeof (GAUGE_DATA_HEADER) + sizeof (GAUGE_DATA_ENTRY_EX) * mMaxGaugeRecords * 2;

    NewGaugeData = AllocateZeroPool (GaugeDataSize);
    if (NewGaugeData == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }

    mGaugeData = NewGaugeData;
    mMaxGaugeRecords *= 2;

    //
    // Initialize new data array and migrate old data one.
    //
    mGaugeData = CopyMem (mGaugeData, OldGaugeData, OldGaugeDataSize);

    FreePool (OldGaugeData);
  }

  GaugeEntryExArray               = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1);
  GaugeEntryExArray[Index].Handle = (EFI_PHYSICAL_ADDRESS) (UINTN) Handle;

  if (Token != NULL) {
    AsciiStrnCpy (GaugeEntryExArray[Index].Token, Token, DXE_PERFORMANCE_STRING_LENGTH);
  }
  if (Module != NULL) {
    AsciiStrnCpy (GaugeEntryExArray[Index].Module, Module, DXE_PERFORMANCE_STRING_LENGTH);
  }

  GaugeEntryExArray[Index].EndTimeStamp = 0;
  GaugeEntryExArray[Index].Identifier = Identifier;

  if (TimeStamp == 0) {
    TimeStamp = GetPerformanceCounter ();
  }
  GaugeEntryExArray[Index].StartTimeStamp = TimeStamp;

  mGaugeData->NumberOfEntries++;

  return EFI_SUCCESS;
}

/**
  Searches the performance measurement log from the beginning of the log
  for the first matching record that contains a zero end time and fills in a valid end time.

  Searches the performance measurement log from the beginning of the log
  for the first record that matches Handle, Token, Module and Identifier and has an end time value of zero.
  If the record can not be found then return EFI_NOT_FOUND.
  If the record is found and TimeStamp is not zero,
  then the end time in the record is filled in with the value specified by TimeStamp.
  If the record is found and TimeStamp is zero, then the end time in the matching record
  is filled in with the current time stamp value.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.
  @param  Identifier              32-bit identifier. If the value is 0, the found record
                                  is same as the one found by EndGauge of PERFORMANCE_PROTOCOL.

  @retval EFI_SUCCESS             The end of  the measurement was recorded.
  @retval EFI_NOT_FOUND           The specified measurement record could not be found.

**/
EFI_STATUS
EFIAPI
EndGaugeEx (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp,
  IN UINT32       Identifier
  )
{
  GAUGE_DATA_ENTRY_EX *GaugeEntryExArray;
  UINT32              Index;

  if (TimeStamp == 0) {
    TimeStamp = GetPerformanceCounter ();
  }

  Index = InternalSearchForGaugeEntry (Handle, Token, Module, Identifier);
  if (Index >= mGaugeData->NumberOfEntries) {
    return EFI_NOT_FOUND;
  }
  GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1);
  GaugeEntryExArray[Index].EndTimeStamp = TimeStamp;

  return EFI_SUCCESS;
}

/**
  Retrieves a previously logged performance measurement.
  It can also retrieve the log created by StartGauge and EndGauge of PERFORMANCE_PROTOCOL,
  and then assign the Identifier with 0.

  Retrieves the performance log entry from the performance log specified by LogEntryKey.
  If it stands for a valid entry, then EFI_SUCCESS is returned and
  GaugeDataEntryEx stores the pointer to that entry.

  @param  LogEntryKey             The key for the previous performance measurement log entry.
                                  If 0, then the first performance measurement log entry is retrieved.
  @param  GaugeDataEntryEx        The indirect pointer to the extended gauge data entry specified by LogEntryKey
                                  if the retrieval is successful.

  @retval EFI_SUCCESS             The GuageDataEntryEx is successfully found based on LogEntryKey.
  @retval EFI_NOT_FOUND           The LogEntryKey is the last entry (equals to the total entry number).
  @retval EFI_INVALIDE_PARAMETER  The LogEntryKey is not a valid entry (greater than the total entry number).
  @retval EFI_INVALIDE_PARAMETER  GaugeDataEntryEx is NULL.

**/
EFI_STATUS
EFIAPI
GetGaugeEx (
  IN  UINTN                 LogEntryKey,
  OUT GAUGE_DATA_ENTRY_EX   **GaugeDataEntryEx
  )
{
  UINTN               NumberOfEntries;
  GAUGE_DATA_ENTRY_EX *GaugeEntryExArray;

  NumberOfEntries = (UINTN) (mGaugeData->NumberOfEntries);
  if (LogEntryKey > NumberOfEntries) {
    return EFI_INVALID_PARAMETER;
  }
  if (LogEntryKey == NumberOfEntries) {
    return EFI_NOT_FOUND;
  }

  GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1);

  if (GaugeDataEntryEx == NULL) {
    return EFI_INVALID_PARAMETER;
  }
  *GaugeDataEntryEx = &GaugeEntryExArray[LogEntryKey];

  return EFI_SUCCESS;
}

/**
  Adds a record at the end of the performance measurement log
  that records the start time of a performance measurement.

  Adds a record to the end of the performance measurement log
  that contains the Handle, Token, and Module.
  The end time of the new record must be set to zero.
  If TimeStamp is not zero, then TimeStamp is used to fill in the start time in the record.
  If TimeStamp is zero, the start time in the record is filled in with the value
  read from the current time stamp.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.

  @retval EFI_SUCCESS             The data was read correctly from the device.
  @retval EFI_OUT_OF_RESOURCES    There are not enough resources to record the measurement.

**/
EFI_STATUS
EFIAPI
StartGauge (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp
  )
{
  return StartGaugeEx (Handle, Token, Module, TimeStamp, 0);
}

/**
  Searches the performance measurement log from the beginning of the log
  for the first matching record that contains a zero end time and fills in a valid end time.

  Searches the performance measurement log from the beginning of the log
  for the first record that matches Handle, Token, and Module and has an end time value of zero.
  If the record can not be found then return EFI_NOT_FOUND.
  If the record is found and TimeStamp is not zero,
  then the end time in the record is filled in with the value specified by TimeStamp.
  If the record is found and TimeStamp is zero, then the end time in the matching record
  is filled in with the current time stamp value.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.

  @retval EFI_SUCCESS             The end of  the measurement was recorded.
  @retval EFI_NOT_FOUND           The specified measurement record could not be found.

**/
EFI_STATUS
EFIAPI
EndGauge (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp
  )
{
  return EndGaugeEx (Handle, Token, Module, TimeStamp, 0);
}

/**
  Retrieves a previously logged performance measurement.
  It can also retrieve the log created by StartGaugeEx and EndGaugeEx of PERFORMANCE_EX_PROTOCOL,
  and then eliminate the Identifier.

  Retrieves the performance log entry from the performance log specified by LogEntryKey.
  If it stands for a valid entry, then EFI_SUCCESS is returned and
  GaugeDataEntry stores the pointer to that entry.

  @param  LogEntryKey             The key for the previous performance measurement log entry.
                                  If 0, then the first performance measurement log entry is retrieved.
  @param  GaugeDataEntry          The indirect pointer to the gauge data entry specified by LogEntryKey
                                  if the retrieval is successful.

  @retval EFI_SUCCESS             The GuageDataEntry is successfully found based on LogEntryKey.
  @retval EFI_NOT_FOUND           The LogEntryKey is the last entry (equals to the total entry number).
  @retval EFI_INVALIDE_PARAMETER  The LogEntryKey is not a valid entry (greater than the total entry number).
  @retval EFI_INVALIDE_PARAMETER  GaugeDataEntry is NULL.

**/
EFI_STATUS
EFIAPI
GetGauge (
  IN  UINTN               LogEntryKey,
  OUT GAUGE_DATA_ENTRY    **GaugeDataEntry
  )
{
  EFI_STATUS          Status;
  GAUGE_DATA_ENTRY_EX *GaugeEntryEx;

  GaugeEntryEx = NULL;

  Status = GetGaugeEx (LogEntryKey, &GaugeEntryEx);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  if (GaugeDataEntry == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  *GaugeDataEntry = (GAUGE_DATA_ENTRY *) GaugeEntryEx;

  return EFI_SUCCESS;
}

/**
  Dumps all the PEI performance log to DXE performance gauge array.

  This internal function dumps all the PEI performance log to the DXE performance gauge array.
  It retrieves the optional GUID HOB for PEI performance and then saves the performance data
  to DXE performance data structures.

**/
VOID
InternalGetPeiPerformance (
  VOID
  )
{
  EFI_HOB_GUID_TYPE                 *GuidHob;
  PEI_PERFORMANCE_LOG_HEADER        *LogHob;
  PEI_PERFORMANCE_LOG_ENTRY         *LogEntryArray;
  UINT32                            *LogIdArray;
  GAUGE_DATA_ENTRY_EX               *GaugeEntryExArray;
  UINT32                            Index;
  UINT32                            NumberOfEntries;

  NumberOfEntries = 0;
  GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1);

  //
  // Dump PEI Log Entries to DXE Guage Data structure.
  //
  GuidHob = GetFirstGuidHob (&gPerformanceProtocolGuid);
  if (GuidHob != NULL) {
    LogHob          = GET_GUID_HOB_DATA (GuidHob);
    LogEntryArray   = (PEI_PERFORMANCE_LOG_ENTRY *) (LogHob + 1);

    NumberOfEntries = LogHob->NumberOfEntries;
    for (Index = 0; Index < NumberOfEntries; Index++) {
      GaugeEntryExArray[Index].Handle         = LogEntryArray[Index].Handle;
      AsciiStrnCpy (GaugeEntryExArray[Index].Token,  LogEntryArray[Index].Token,  DXE_PERFORMANCE_STRING_LENGTH);
      AsciiStrnCpy (GaugeEntryExArray[Index].Module, LogEntryArray[Index].Module, DXE_PERFORMANCE_STRING_LENGTH);
      GaugeEntryExArray[Index].StartTimeStamp = LogEntryArray[Index].StartTimeStamp;
      GaugeEntryExArray[Index].EndTimeStamp   = LogEntryArray[Index].EndTimeStamp;
      GaugeEntryExArray[Index].Identifier     = 0;
    }

    GuidHob = GetFirstGuidHob (&gPerformanceExProtocolGuid);
    if (GuidHob != NULL) {
      LogIdArray    = GET_GUID_HOB_DATA (GuidHob);
      for (Index = 0; Index < NumberOfEntries; Index++) {
        GaugeEntryExArray[Index].Identifier   = LogIdArray[Index];
      }
    }
  }
  mGaugeData->NumberOfEntries = NumberOfEntries;
}

/**
  The constructor function initializes Performance infrastructure for DXE phase.

  The constructor function publishes Performance and PerformanceEx protocol, allocates memory to log DXE performance
  and merges PEI performance data to DXE performance log.
  It will ASSERT() if one of these operations fails and it will always return EFI_SUCCESS.

  @param  ImageHandle   The firmware allocated handle for the EFI image.
  @param  SystemTable   A pointer to the EFI System Table.

  @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.

**/
EFI_STATUS
EFIAPI
DxeCorePerformanceLibConstructor (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS                Status;

  if (!PerformanceMeasurementEnabled ()) {
    //
    // Do not initialize performance infrastructure if not required.
    //
    return EFI_SUCCESS;
  }
  //
  // Install the protocol interfaces.
  //
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &mHandle,
                  &gPerformanceProtocolGuid,
                  &mPerformanceInterface,
                  &gPerformanceExProtocolGuid,
                  &mPerformanceExInterface,
                  NULL
                  );
  ASSERT_EFI_ERROR (Status);

  mMaxGaugeRecords = INIT_DXE_GAUGE_DATA_ENTRIES + PcdGet8 (PcdMaxPeiPerformanceLogEntries);

  mGaugeData = AllocateZeroPool (sizeof (GAUGE_DATA_HEADER) + (sizeof (GAUGE_DATA_ENTRY_EX) * mMaxGaugeRecords));
  ASSERT (mGaugeData != NULL);

  InternalGetPeiPerformance ();

  return Status;
}

/**
  Adds a record at the end of the performance measurement log
  that records the start time of a performance measurement.

  Adds a record to the end of the performance measurement log
  that contains the Handle, Token, Module and Identifier.
  The end time of the new record must be set to zero.
  If TimeStamp is not zero, then TimeStamp is used to fill in the start time in the record.
  If TimeStamp is zero, the start time in the record is filled in with the value
  read from the current time stamp.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.
  @param  Identifier              32-bit identifier. If the value is 0, the created record
                                  is same as the one created by StartPerformanceMeasurement.

  @retval RETURN_SUCCESS          The start of the measurement was recorded.
  @retval RETURN_OUT_OF_RESOURCES There are not enough resources to record the measurement.

**/
RETURN_STATUS
EFIAPI
StartPerformanceMeasurementEx (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp,
  IN UINT32       Identifier
  )
{
  return (RETURN_STATUS) StartGaugeEx (Handle, Token, Module, TimeStamp, Identifier);
}

/**
  Searches the performance measurement log from the beginning of the log
  for the first matching record that contains a zero end time and fills in a valid end time.

  Searches the performance measurement log from the beginning of the log
  for the first record that matches Handle, Token, Module and Identifier and has an end time value of zero.
  If the record can not be found then return RETURN_NOT_FOUND.
  If the record is found and TimeStamp is not zero,
  then the end time in the record is filled in with the value specified by TimeStamp.
  If the record is found and TimeStamp is zero, then the end time in the matching record
  is filled in with the current time stamp value.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.
  @param  Identifier              32-bit identifier. If the value is 0, the found record
                                  is same as the one found by EndPerformanceMeasurement.

  @retval RETURN_SUCCESS          The end of  the measurement was recorded.
  @retval RETURN_NOT_FOUND        The specified measurement record could not be found.

**/
RETURN_STATUS
EFIAPI
EndPerformanceMeasurementEx (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp,
  IN UINT32       Identifier
  )
{
  return (RETURN_STATUS) EndGaugeEx (Handle, Token, Module, TimeStamp, Identifier);
}

/**
  Attempts to retrieve a performance measurement log entry from the performance measurement log.
  It can also retrieve the log created by StartPerformanceMeasurement and EndPerformanceMeasurement,
  and then assign the Identifier with 0.

  Attempts to retrieve the performance log entry specified by LogEntryKey.  If LogEntryKey is
  zero on entry, then an attempt is made to retrieve the first entry from the performance log,
  and the key for the second entry in the log is returned.  If the performance log is empty,
  then no entry is retrieved and zero is returned.  If LogEntryKey is not zero, then the performance
  log entry associated with LogEntryKey is retrieved, and the key for the next entry in the log is
  returned.  If LogEntryKey is the key for the last entry in the log, then the last log entry is
  retrieved and an implementation specific non-zero key value that specifies the end of the performance
  log is returned.  If LogEntryKey is equal this implementation specific non-zero key value, then no entry
  is retrieved and zero is returned.  In the cases where a performance log entry can be returned,
  the log entry is returned in Handle, Token, Module, StartTimeStamp, EndTimeStamp and Identifier.
  If LogEntryKey is not a valid log entry key for the performance measurement log, then ASSERT().
  If Handle is NULL, then ASSERT().
  If Token is NULL, then ASSERT().
  If Module is NULL, then ASSERT().
  If StartTimeStamp is NULL, then ASSERT().
  If EndTimeStamp is NULL, then ASSERT().
  If Identifier is NULL, then ASSERT().

  @param  LogEntryKey             On entry, the key of the performance measurement log entry to retrieve.
                                  0, then the first performance measurement log entry is retrieved.
                                  On exit, the key of the next performance log entry.
  @param  Handle                  Pointer to environment specific context used to identify the component
                                  being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string that identifies the component
                                  being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string that identifies the module
                                  being measured.
  @param  StartTimeStamp          Pointer to the 64-bit time stamp that was recorded when the measurement
                                  was started.
  @param  EndTimeStamp            Pointer to the 64-bit time stamp that was recorded when the measurement
                                  was ended.
  @param  Identifier              Pointer to the 32-bit identifier that was recorded.

  @return The key for the next performance log entry (in general case).

**/
UINTN
EFIAPI
GetPerformanceMeasurementEx (
  IN  UINTN       LogEntryKey, 
  OUT CONST VOID  **Handle,
  OUT CONST CHAR8 **Token,
  OUT CONST CHAR8 **Module,
  OUT UINT64      *StartTimeStamp,
  OUT UINT64      *EndTimeStamp,
  OUT UINT32      *Identifier
  )
{
  EFI_STATUS           Status;
  GAUGE_DATA_ENTRY_EX  *GaugeData;

  GaugeData = NULL;
  
  ASSERT (Handle != NULL);
  ASSERT (Token != NULL);
  ASSERT (Module != NULL);
  ASSERT (StartTimeStamp != NULL);
  ASSERT (EndTimeStamp != NULL);
  ASSERT (Identifier != NULL);

  Status = GetGaugeEx (LogEntryKey++, &GaugeData);

  //
  // Make sure that LogEntryKey is a valid log entry key,
  //
  ASSERT (Status != EFI_INVALID_PARAMETER);

  if (EFI_ERROR (Status)) {
    //
    // The LogEntryKey is the last entry (equals to the total entry number).
    //
    return 0;
  }

  ASSERT (GaugeData != NULL);

  *Handle         = (VOID *) (UINTN) GaugeData->Handle;
  *Token          = GaugeData->Token;
  *Module         = GaugeData->Module;
  *StartTimeStamp = GaugeData->StartTimeStamp;
  *EndTimeStamp   = GaugeData->EndTimeStamp;
  *Identifier     = GaugeData->Identifier;

  return LogEntryKey;
}

/**
  Adds a record at the end of the performance measurement log
  that records the start time of a performance measurement.

  Adds a record to the end of the performance measurement log
  that contains the Handle, Token, and Module.
  The end time of the new record must be set to zero.
  If TimeStamp is not zero, then TimeStamp is used to fill in the start time in the record.
  If TimeStamp is zero, the start time in the record is filled in with the value
  read from the current time stamp.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.

  @retval RETURN_SUCCESS          The start of the measurement was recorded.
  @retval RETURN_OUT_OF_RESOURCES There are not enough resources to record the measurement.

**/
RETURN_STATUS
EFIAPI
StartPerformanceMeasurement (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp
  )
{
  return StartPerformanceMeasurementEx (Handle, Token, Module, TimeStamp, 0);
}

/**
  Searches the performance measurement log from the beginning of the log
  for the first matching record that contains a zero end time and fills in a valid end time.

  Searches the performance measurement log from the beginning of the log
  for the first record that matches Handle, Token, and Module and has an end time value of zero.
  If the record can not be found then return RETURN_NOT_FOUND.
  If the record is found and TimeStamp is not zero,
  then the end time in the record is filled in with the value specified by TimeStamp.
  If the record is found and TimeStamp is zero, then the end time in the matching record
  is filled in with the current time stamp value.

  @param  Handle                  Pointer to environment specific context used
                                  to identify the component being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string
                                  that identifies the component being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string
                                  that identifies the module being measured.
  @param  TimeStamp               64-bit time stamp.

  @retval RETURN_SUCCESS          The end of  the measurement was recorded.
  @retval RETURN_NOT_FOUND        The specified measurement record could not be found.

**/
RETURN_STATUS
EFIAPI
EndPerformanceMeasurement (
  IN CONST VOID   *Handle,  OPTIONAL
  IN CONST CHAR8  *Token,   OPTIONAL
  IN CONST CHAR8  *Module,  OPTIONAL
  IN UINT64       TimeStamp
  )
{
  return EndPerformanceMeasurementEx (Handle, Token, Module, TimeStamp, 0);
}

/**
  Attempts to retrieve a performance measurement log entry from the performance measurement log.
  It can also retrieve the log created by StartPerformanceMeasurementEx and EndPerformanceMeasurementEx,
  and then eliminate the Identifier.

  Attempts to retrieve the performance log entry specified by LogEntryKey.  If LogEntryKey is
  zero on entry, then an attempt is made to retrieve the first entry from the performance log,
  and the key for the second entry in the log is returned.  If the performance log is empty,
  then no entry is retrieved and zero is returned.  If LogEntryKey is not zero, then the performance
  log entry associated with LogEntryKey is retrieved, and the key for the next entry in the log is
  returned.  If LogEntryKey is the key for the last entry in the log, then the last log entry is
  retrieved and an implementation specific non-zero key value that specifies the end of the performance
  log is returned.  If LogEntryKey is equal this implementation specific non-zero key value, then no entry
  is retrieved and zero is returned.  In the cases where a performance log entry can be returned,
  the log entry is returned in Handle, Token, Module, StartTimeStamp, and EndTimeStamp.
  If LogEntryKey is not a valid log entry key for the performance measurement log, then ASSERT().
  If Handle is NULL, then ASSERT().
  If Token is NULL, then ASSERT().
  If Module is NULL, then ASSERT().
  If StartTimeStamp is NULL, then ASSERT().
  If EndTimeStamp is NULL, then ASSERT().

  @param  LogEntryKey             On entry, the key of the performance measurement log entry to retrieve.
                                  0, then the first performance measurement log entry is retrieved.
                                  On exit, the key of the next performance log entry.
  @param  Handle                  Pointer to environment specific context used to identify the component
                                  being measured.
  @param  Token                   Pointer to a Null-terminated ASCII string that identifies the component
                                  being measured.
  @param  Module                  Pointer to a Null-terminated ASCII string that identifies the module
                                  being measured.
  @param  StartTimeStamp          Pointer to the 64-bit time stamp that was recorded when the measurement
                                  was started.
  @param  EndTimeStamp            Pointer to the 64-bit time stamp that was recorded when the measurement
                                  was ended.

  @return The key for the next performance log entry (in general case).

**/
UINTN
EFIAPI
GetPerformanceMeasurement (
  IN  UINTN       LogEntryKey,
  OUT CONST VOID  **Handle,
  OUT CONST CHAR8 **Token,
  OUT CONST CHAR8 **Module,
  OUT UINT64      *StartTimeStamp,
  OUT UINT64      *EndTimeStamp
  )
{
  UINT32 Identifier;
  return GetPerformanceMeasurementEx (LogEntryKey, Handle, Token, Module, StartTimeStamp, EndTimeStamp, &Identifier);
}

/**
  Returns TRUE if the performance measurement macros are enabled.

  This function returns TRUE if the PERFORMANCE_LIBRARY_PROPERTY_MEASUREMENT_ENABLED bit of
  PcdPerformanceLibraryPropertyMask is set.  Otherwise FALSE is returned.

  @retval TRUE                    The PERFORMANCE_LIBRARY_PROPERTY_MEASUREMENT_ENABLED bit of
                                  PcdPerformanceLibraryPropertyMask is set.
  @retval FALSE                   The PERFORMANCE_LIBRARY_PROPERTY_MEASUREMENT_ENABLED bit of
                                  PcdPerformanceLibraryPropertyMask is clear.

**/
BOOLEAN
EFIAPI
PerformanceMeasurementEnabled (
  VOID
  )
{
  return (BOOLEAN) ((PcdGet8(PcdPerformanceLibraryPropertyMask) & PERFORMANCE_LIBRARY_PROPERTY_MEASUREMENT_ENABLED) != 0);
}