libtpms/src/tpm2/Clock.c

/********************************************************************************/
/*										*/
/*		 Used by the simulator to mimic a hardware clock  		*/
/*			     Written by Ken Goldman				*/
/*		       IBM Thomas J. Watson Research Center			*/
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/********************************************************************************/

//** Description
//
// This file contains the routines that are used by the simulator to mimic
// a hardware clock on a TPM.
//
// In this implementation, all the time values are measured in millisecond.
// However, the precision of the clock functions may be implementation dependent.

//** Includes and Data Definitions
#include <assert.h>
#include "Platform.h"

// CLOCK_NOMINAL is the number of hardware ticks per ms. A value of 30000 means
// that the nominal clock rate used to drive the hardware clock is 30 MHz. The
// adjustment rates are used to determine the conversion of the hardware ticks to
// internal hardware clock value. In practice, we would expect that there would be
// a hardware register will accumulated mS. It would be incremented by the output
// of a pre-scaler. The pre-scaler would divide the ticks from the clock by some
// value that would compensate for the difference between clock time and real time.
// The code in Clock does the emulation of this function.
#define CLOCK_NOMINAL 30000
// A 1% change in rate is 300 counts
#define CLOCK_ADJUST_COARSE 300
// A 0.1% change in rate is 30 counts
#define CLOCK_ADJUST_MEDIUM 30
// A minimum change in rate is 1 count
#define CLOCK_ADJUST_FINE 1
// The clock tolerance is +/-15% (4500 counts)
// Allow some guard band (16.7%)
#define CLOCK_ADJUST_LIMIT 5000

/* libtpms added begin */
/* ClockGetTime -- get time given a specified clock type */
uint64_t
ClockGetTime(
               clockid_t clk_id
               )
{
    uint64_t           time;
#ifdef TPM_WINDOWS
#error Not supported for TPM_WINDOWS
#else
    struct timespec     systime;

    clock_gettime(clk_id, &systime);
    time = (uint64_t)systime.tv_sec * 1000 + (systime.tv_nsec / 1000000);
#endif

    return time;
}

/* ClockAdjustPostResume -- adjust time parameters post resume */
#include "Tpm.h"
void
ClockAdjustPostResume(UINT64 backthen, BOOL timesAreRealtime)
{
    UINT64 now = ClockGetTime(CLOCK_REALTIME);
    INT64 timediff = now - backthen;

    if (timesAreRealtime) {
        /* g_time, s_realTimePrevious, s_tpmTime are all in real time */
        s_suspendedElapsedTime = now;
        s_hostMonotonicAdjustTime = -ClockGetTime(CLOCK_MONOTONIC);

        /* s_lastSystemTime & s_lastReportTime need to be set as well */
        s_lastSystemTime = now;
        s_lastReportedTime = now;
    } else if (timediff >= 0) {
        s_suspendedElapsedTime += timediff;
    }
}
/* libtpms added end */

//** Simulator Functions
//*** Introduction
// This set of functions is intended to be called by the simulator environment in
// order to simulate hardware events.

//***_plat__TimerReset()
// This function sets current system clock time as t0 for counting TPM time.
// This function is called at a power on event to reset the clock. When the clock
// is reset, the indication that the clock was stopped is also set.
LIB_EXPORT void _plat__TimerReset(void)
{
    s_lastSystemTime = 0;
    s_tpmTime        = 0;
    s_adjustRate     = CLOCK_NOMINAL;
    s_timerReset     = TRUE;
    s_timerStopped   = TRUE;
    s_hostMonotonicAdjustTime = 0; /* libtpms added */
    s_suspendedElapsedTime = 0; /* libtpms added */
    return;
}

//*** _plat__TimerRestart()
// This function should be called in order to simulate the restart of the timer
// should it be stopped while power is still applied.
LIB_EXPORT void _plat__TimerRestart(void)
{
    s_timerStopped = TRUE;
    return;
}

//** Functions Used by TPM
//*** Introduction
// These functions are called by the TPM code. They should be replaced by
// appropriated hardware functions.

#include <time.h>
clock_t debugTime;

//*** _plat__RealTime()
// This is another, probably futile, attempt to define a portable function
// that will return a 64-bit clock value that has mSec resolution.
LIB_EXPORT uint64_t _plat__RealTime(void)
{
    clock64_t time;
    //#ifdef _MSC_VER	kgold
#ifdef TPM_WINDOWS
    #include <sys/timeb.h>
    struct _timeb sysTime;
    //
    _ftime(&sysTime);	/* kgold, mingw doesn't have _ftime_s */
    time = (clock64_t)(sysTime.time) * 1000 + sysTime.millitm;
    // set the time back by one hour if daylight savings
    if(sysTime.dstflag)
	time -= 1000 * 60 * 60;  // mSec/sec * sec/min * min/hour = ms/hour
#else
    // hopefully, this will work with most UNIX systems
    struct timespec systime;
    //
    clock_gettime(CLOCK_MONOTONIC, &systime);
    time = (clock64_t)systime.tv_sec * 1000 + (systime.tv_nsec / 1000000);
#endif
    /* libtpms added begin */
    /* We have to make sure that this function returns monotonically increasing time
       also when a vTPM has been suspended and the host has been rebooted.
       Example:
         - The vTPM is suspended at systime '5'
         - The vTPM is resumed   at systime '1' after a host reboot
         -> we now need to add '4' to the time
         Besides this we want to account for the time a vTPM was suspended.
         If it was suspended for 10 time units, we need to add '10' here.
     */
    time += s_hostMonotonicAdjustTime + s_suspendedElapsedTime;
    /* libtpms added end */
    return time;
}

//***_plat__TimerRead()
// This function provides access to the tick timer of the platform. The TPM code
// uses this value to drive the TPM Clock.
//
// The tick timer is supposed to run when power is applied to the device. This timer
// should not be reset by time events including _TPM_Init. It should only be reset
// when TPM power is re-applied.
//
// If the TPM is run in a protected environment, that environment may provide the
// tick time to the TPM as long as the time provided by the environment is not
// allowed to go backwards. If the time provided by the system can go backwards
// during a power discontinuity, then the _plat__Signal_PowerOn should call
// _plat__TimerReset().
LIB_EXPORT uint64_t _plat__TimerRead(void)
{
#ifdef HARDWARE_CLOCK
#  error "need a defintion for reading the hardware clock"
    return HARDWARE_CLOCK
#else
	clock64_t timeDiff;
    clock64_t adjustedTimeDiff;
    clock64_t timeNow;
    clock64_t readjustedTimeDiff;

    // This produces a timeNow that is basically locked to the system clock.
    timeNow = _plat__RealTime();

    // if this hasn't been initialized, initialize it
    if(s_lastSystemTime == 0)
	{
	    s_lastSystemTime   = timeNow;
	    debugTime          = clock();
	    s_lastReportedTime = 0;
	    s_realTimePrevious = 0;
	}
    // The system time can bounce around and that's OK as long as we don't allow
    // time to go backwards. When the time does appear to go backwards, set
    // lastSystemTime to be the new value and then update the reported time.
    if(timeNow < s_lastReportedTime)
	s_lastSystemTime = timeNow;
    s_lastReportedTime = s_lastReportedTime + timeNow - s_lastSystemTime;
    s_lastSystemTime   = timeNow;
    timeNow            = s_lastReportedTime;

    // The code above produces a timeNow that is similar to the value returned
    // by Clock(). The difference is that timeNow does not max out, and it is
    // at a ms. rate rather than at a CLOCKS_PER_SEC rate. The code below
    // uses that value and does the rate adjustment on the time value.
    // If there is no difference in time, then skip all the computations
    if(s_realTimePrevious >= timeNow)
	return s_tpmTime;
    // Compute the amount of time since the last update of the system clock
    timeDiff = timeNow - s_realTimePrevious;

    // Do the time rate adjustment and conversion from CLOCKS_PER_SEC to mSec
    adjustedTimeDiff = (timeDiff * CLOCK_NOMINAL) / ((uint64_t)s_adjustRate);

    // update the TPM time with the adjusted timeDiff
    s_tpmTime += (clock64_t)adjustedTimeDiff;

    // Might have some rounding error that would loose CLOCKS. See what is not
    // being used. As mentioned above, this could result in putting back more than
    // is taken out. Here, we are trying to recreate timeDiff.
    readjustedTimeDiff = (adjustedTimeDiff * (uint64_t)s_adjustRate) / CLOCK_NOMINAL;

    // adjusted is now converted back to being the amount we should advance the
    // previous sampled time. It should always be less than or equal to timeDiff.
    // That is, we could not have use more time than we started with.
    s_realTimePrevious = s_realTimePrevious + readjustedTimeDiff;

#  ifdef DEBUGGING_TIME
    // Put this in so that TPM time will pass much faster than real time when
    // doing debug.
    // A value of 1000 for DEBUG_TIME_MULTIPLER will make each ms into a second
    // A good value might be 100
    return (s_tpmTime * DEBUG_TIME_MULTIPLIER);
#  endif
    return s_tpmTime;
#endif
}

//*** _plat__TimerWasReset()
// This function is used to interrogate the flag indicating if the tick timer has
// been reset.
//
// If the resetFlag parameter is SET, then the flag will be CLEAR before the
// function returns.
LIB_EXPORT int _plat__TimerWasReset(void)
{
    int retVal   = s_timerReset;
    s_timerReset = FALSE;
    return retVal;
}

//*** _plat__TimerWasStopped()
// This function is used to interrogate the flag indicating if the tick timer has
// been stopped. If so, this is typically a reason to roll the nonce.
//
// This function will CLEAR the s_timerStopped flag before returning. This provides
// functionality that is similar to status register that is cleared when read. This
// is the model used here because it is the one that has the most impact on the TPM
// code as the flag can only be accessed by one entity in the TPM. Any other
// implementation of the hardware can be made to look like a read-once register.
LIB_EXPORT int _plat__TimerWasStopped(void)
{
    int retVal     = s_timerStopped;
    s_timerStopped = FALSE;
    return retVal;
}

//***_plat__ClockAdjustRate()
// Adjust the clock rate
LIB_EXPORT void _plat__ClockRateAdjust(_plat__ClockAdjustStep adjust)
{
    // We expect the caller should only use a fixed set of constant values to
    // adjust the rate
    switch(adjust)
	{
	    // slower increases the divisor
	  case PLAT_TPM_CLOCK_ADJUST_COARSE_SLOWER:
	    s_adjustRate += CLOCK_ADJUST_COARSE;
	    break;
	  case PLAT_TPM_CLOCK_ADJUST_MEDIUM_SLOWER:
	    s_adjustRate += CLOCK_ADJUST_MEDIUM;
	    break;
	  case PLAT_TPM_CLOCK_ADJUST_FINE_SLOWER:
	    s_adjustRate += CLOCK_ADJUST_FINE;
	    break;
	    // faster decreases the divisor
	  case PLAT_TPM_CLOCK_ADJUST_FINE_FASTER:
	    s_adjustRate -= CLOCK_ADJUST_FINE;
	    break;
	  case PLAT_TPM_CLOCK_ADJUST_MEDIUM_FASTER:
	    s_adjustRate -= CLOCK_ADJUST_MEDIUM;
	    break;
	  case PLAT_TPM_CLOCK_ADJUST_COARSE_FASTER:
	    s_adjustRate -= CLOCK_ADJUST_COARSE;
	    break;
	}

    if(s_adjustRate > (CLOCK_NOMINAL + CLOCK_ADJUST_LIMIT))
	s_adjustRate = CLOCK_NOMINAL + CLOCK_ADJUST_LIMIT;
    if(s_adjustRate < (CLOCK_NOMINAL - CLOCK_ADJUST_LIMIT))
	s_adjustRate = CLOCK_NOMINAL - CLOCK_ADJUST_LIMIT;

    return;
}

#if 0

/* added for portability because Linux clock is 32 bits */

#include <stdint.h>
#include <stdio.h>
#include <time.h>

#include "TpmFail_fp.h"

LIB_EXPORT uint64_t
_plat__RealTime(
		void
		)
{
    clock64_t           time;
    //#ifdef _MSC_VER	kgold
#ifdef TPM_WINDOWS
    #include <sys/timeb.h>
    struct _timeb       sysTime;
    //
    _ftime(&sysTime);	/* kgold, mingw doesn't have _ftime_s */
    time = (clock64_t)(sysTime.time) * 1000 + sysTime.millitm;
    // set the time back by one hour if daylight savings
    if(sysTime.dstflag)
	time -= 1000 * 60 * 60;  // mSec/sec * sec/min * min/hour = ms/hour
#else
    // hopefully, this will work with most UNIX systems
    struct timespec     systime;
    //
    clock_gettime(CLOCK_MONOTONIC, &systime);
    time = (clock64_t)systime.tv_sec * 1000 + (systime.tv_nsec / 1000000);
#endif
    return time;
}

#endif