/* Microsoft Reference Implementation for TPM 2.0
 *
 *  The copyright in this software is being made available under the BSD License,
 *  included below. This software may be subject to other third party and
 *  contributor rights, including patent rights, and no such rights are granted
 *  under this license.
 *
 *  Copyright (c) Microsoft Corporation
 *
 *  All rights reserved.
 *
 *  BSD License
 *
 *  Redistribution and use in source and binary forms, with or without modification,
 *  are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice, this list
 *  of conditions and the following disclaimer.
 *
 *  Redistributions in binary form must reproduce the above copyright notice, this
 *  list of conditions and the following disclaimer in the documentation and/or
 *  other materials provided with the distribution.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ""AS IS""
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 *  ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 *  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 *  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "Tpm.h"

// This function is called to process a _TPM_Hash_Start indication.
LIB_EXPORT void _TPM_Hash_Start(void)
{
    TPM_RC         result;
    TPMI_DH_OBJECT handle;

    // If a DRTM sequence object exists, free it up
    if(g_DRTMHandle != TPM_RH_UNASSIGNED)
    {
        FlushObject(g_DRTMHandle);
        g_DRTMHandle = TPM_RH_UNASSIGNED;
    }

    // Create an event sequence object and store the handle in global
    // g_DRTMHandle. A TPM_RC_OBJECT_MEMORY error may be returned at this point
    // The NULL value for the first parameter will cause the sequence structure to
    // be allocated without being set as present. This keeps the sequence from
    // being left behind if the sequence is terminated early.
    result = ObjectCreateEventSequence(NULL, &g_DRTMHandle);

    // If a free slot was not available, then free up a slot.
    if(result != TPM_RC_SUCCESS)
    {
        // An implementation does not need to have a fixed relationship between
        // slot numbers and handle numbers. To handle the general case, scan for
        // a handle that is assigned and free it for the DRTM sequence.
        // In the reference implementation, the relationship between handles and
        // slots is fixed. So, if the call to ObjectCreateEvenSequence()
        // failed indicating that all slots are occupied, then the first handle we
        // are going to check (TRANSIENT_FIRST) will be occupied. It will be freed
        // so that it can be assigned for use as the DRTM sequence object.
        for(handle = TRANSIENT_FIRST; handle < TRANSIENT_LAST; handle++)
        {
            // try to flush the first object
            if(IsObjectPresent(handle))
                break;
        }
        // If the first call to find a slot fails but none of the slots is occupied
        // then there's a big problem
        pAssert(handle < TRANSIENT_LAST);

        // Free the slot
        FlushObject(handle);

        // Try to create an event sequence object again.  This time, we must
        // succeed.
        result = ObjectCreateEventSequence(NULL, &g_DRTMHandle);
        if(result != TPM_RC_SUCCESS)
            FAIL(FATAL_ERROR_INTERNAL);
    }

    return;
}