hook_dtr.c

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/*
 * Copyright (c) 2020 Bitdefender
 * SPDX-License-Identifier: Apache-2.0
 */
#include "hook_dtr.h"
#include "callbacks.h"
#include "guests.h"


INTSTATUS
IntHookDtrSetHook(
    _In_ DWORD Flags,
    _In_ PFUNC_DtrReadWriteHookCallback Callback,
    _Out_opt_ void **Hook
    )
{
    if (Callback == NULL)
    {
        return INT_STATUS_INVALID_PARAMETER_3;
    }

    HOOK_DTR *pHook = HpAllocWithTag(sizeof(*pHook), IC_TAG_DTRH);
    if (NULL == pHook)
    {
        return INT_STATUS_INSUFFICIENT_RESOURCES;
    }

    pHook->Flags = Flags;
    pHook->Callback = Callback;

    if (0 == gGuest.DtrHooks->HooksCount++)
    {
        INTSTATUS status = IntEnableDtrNotifications();
        if (!INT_SUCCESS(status))
        {
            HpFreeAndNullWithTag(&pHook, IC_TAG_DTRH);
            return status;
        }
    }

    InsertTailList(&gGuest.DtrHooks->DtrHooksList, &pHook->Link);

    if (NULL != Hook)
    {
        *Hook = pHook;
    }

    return INT_STATUS_SUCCESS;
}


static INTSTATUS
IntHookDtrDeleteHook(
    _In_ HOOK_DTR *Hook
    )
{
    if (!Hook->Disabled)
    {
        return INT_STATUS_INVALID_PARAMETER_1;
    }

    HpFreeAndNullWithTag(&Hook, IC_TAG_DTRH);

    if (0 >= --gGuest.DtrHooks->HooksCount)
    {
        return IntDisableDtrNotifications();
    }

    return INT_STATUS_SUCCESS;
}


INTSTATUS
IntHookDtrRemoveHook(
    _In_ HOOK_DTR *Hook
    )
{
    if (NULL == Hook)
    {
        return INT_STATUS_INVALID_PARAMETER_1;
    }

    Hook->Disabled = TRUE;

    // If we're not handling an DTR violation right now than we can safely delete the DTR hook.
    if (CPU_STATE_DTR_LOAD != gVcpu->State)
    {
        RemoveEntryList(&Hook->Link);

        INTSTATUS status = IntHookDtrDeleteHook(Hook);
        if (!INT_SUCCESS(status))
        {
            ERROR("[ERROR] IntHookDtrDeleteHook failed: 0x%08x\n", status);
        }
    }

    return INT_STATUS_SUCCESS;
}


static void
IntHookDtrRemoveAllHooks(
    void
    )
{
    list_for_each(gGuest.DtrHooks->DtrHooksList, HOOK_DTR, pHook)
    {
        INTSTATUS status = IntHookDtrRemoveHook(pHook);
        if (!INT_SUCCESS(status))
        {
            ERROR("[ERROR] IntHookDtrRemoveHook failed: 0x%08x\n", status);
        }
    }
}


INTSTATUS
IntHookDtrCommit(
    void
    )
{
    INTSTATUS status = INT_STATUS_SUCCESS;

    if (NULL == gGuest.DtrHooks)
    {
        return INT_STATUS_NOT_INITIALIZED;
    }

    list_for_each(gGuest.DtrHooks->DtrHooksList, HOOK_DTR, pHook)
    {
        if (pHook->Disabled)
        {
            RemoveEntryList(&pHook->Link);

            status = IntHookDtrDeleteHook(pHook);
            if (!INT_SUCCESS(status))
            {
                ERROR("[ERROR] IntHookDtrDeleteHook failed: 0x%08x\n", status);
            }
        }
    }

    return status;
}


INTSTATUS
IntHookDtrInit(
    void
    )
{
    gGuest.DtrHooks = HpAllocWithTag(sizeof(*gGuest.DtrHooks), IC_TAG_DTRS);
    if (NULL == gGuest.DtrHooks)
    {
        return INT_STATUS_INSUFFICIENT_RESOURCES;
    }

    InitializeListHead(&gGuest.DtrHooks->DtrHooksList);

    return INT_STATUS_SUCCESS;
}


INTSTATUS
IntHookDtrUninit(
    void
    )
{
    if (NULL == gGuest.DtrHooks)
    {
        return INT_STATUS_NOT_INITIALIZED_HINT;
    }

    IntHookDtrRemoveAllHooks();

    HpFreeAndNullWithTag(&gGuest.DtrHooks, IC_TAG_DTRS);

    return INT_STATUS_SUCCESS;
}