/*
 * PROJECT:         ReactOS Kernel
 * LICENSE:         GPL - See COPYING in the top level directory
 * PURPOSE:         x64 trap handlers
 * PROGRAMMERS:     Timo Kreuzer (timo.kreuzer@reactos.org)
 */

/* INCLUDES ******************************************************************/

#include <ntoskrnl.h>

#define NDEBUG
#include <debug.h>

VOID
KiRetireDpcListInDpcStack(
    PKPRCB Prcb,
    PVOID DpcStack);

NTSTATUS
KiConvertToGuiThread(
    VOID);

_Requires_lock_not_held_(Prcb->PrcbLock)
VOID
NTAPI
KiDpcInterruptHandler(VOID)
{
    PKPRCB Prcb = KeGetCurrentPrcb();
    PKTHREAD NewThread, OldThread;
    KIRQL OldIrql;

    /* Raise to DISPATCH_LEVEL */
    OldIrql = KfRaiseIrql(DISPATCH_LEVEL);

    /* Send an EOI */
    KiSendEOI();

    /* Check for pending timers, pending DPCs, or pending ready threads */
    if ((Prcb->DpcData[0].DpcQueueDepth) ||
        (Prcb->TimerRequest) ||
        (Prcb->DeferredReadyListHead.Next))
    {
        /* Retire DPCs while under the DPC stack */
        KiRetireDpcListInDpcStack(Prcb, Prcb->DpcStack);
    }

    /* Enable interrupts */
    _enable();

    /* Check for quantum end */
    if (Prcb->QuantumEnd)
    {
        /* Handle quantum end */
        Prcb->QuantumEnd = FALSE;
        KiQuantumEnd();
    }
    else if (Prcb->NextThread)
    {
        /* Acquire the PRCB lock */
        KiAcquirePrcbLock(Prcb);

        /* Capture current thread data */
        OldThread = Prcb->CurrentThread;
        NewThread = Prcb->NextThread;

        /* Set new thread data */
        Prcb->NextThread = NULL;
        Prcb->CurrentThread = NewThread;

        /* The thread is now running */
        NewThread->State = Running;
        OldThread->WaitReason = WrDispatchInt;

        /* Make the old thread ready */
        KxQueueReadyThread(OldThread, Prcb);

        /* Swap to the new thread */
        KiSwapContext(APC_LEVEL, OldThread);
    }

    /* Disable interrupts and go back to old irql */
    _disable();
    KeLowerIrql(OldIrql);
}

#define MAX_SYSCALL_PARAMS 16

NTSTATUS
NtSyscallFailure(void)
{
    /* This is the failure function */
    return (NTSTATUS)KeGetCurrentThread()->TrapFrame->Rax;
}

PVOID
KiSystemCallHandler(
    VOID)
{
    PKTRAP_FRAME TrapFrame;
    PKSERVICE_TABLE_DESCRIPTOR DescriptorTable;
    PKTHREAD Thread;
    PULONG64 KernelParams, UserParams;
    ULONG ServiceNumber, Offset, Count;
    ULONG64 UserRsp;

    /* Get a pointer to the trap frame */
    TrapFrame = (PKTRAP_FRAME)((PULONG64)_AddressOfReturnAddress() + 1 + MAX_SYSCALL_PARAMS);

    /* Increase system call count */
    __addgsdword(FIELD_OFFSET(KIPCR, Prcb.KeSystemCalls), 1);

    /* Get the current thread */
    Thread = KeGetCurrentThread();

    /* Set previous mode */
    Thread->PreviousMode = TrapFrame->PreviousMode = UserMode;

    /* Save the old trap frame and set the new */
    TrapFrame->TrapFrame = (ULONG64)Thread->TrapFrame;
    Thread->TrapFrame = TrapFrame;

    /* We don't have an exception frame yet */
    TrapFrame->ExceptionFrame = 0;

    /* Before enabling interrupts get the user rsp from the KPCR */
    UserRsp = __readgsqword(FIELD_OFFSET(KIPCR, UserRsp));
    TrapFrame->Rsp = UserRsp;

    /* Enable interrupts */
    _enable();

    /* If the usermode rsp was not a usermode address, prepare an exception */
    if (UserRsp > MmUserProbeAddress) UserRsp = MmUserProbeAddress;

    /* Get the address of the usermode and kernelmode parameters */
    UserParams = (PULONG64)UserRsp + 1;
    KernelParams = (PULONG64)TrapFrame - MAX_SYSCALL_PARAMS;

    /* Get the system call number from the trap frame and decode it */
    ServiceNumber = (ULONG)TrapFrame->Rax;
    Offset = (ServiceNumber >> SERVICE_TABLE_SHIFT) & SERVICE_TABLE_MASK;
    ServiceNumber &= SERVICE_NUMBER_MASK;

    /* Check for win32k system calls */
    if (Offset & SERVICE_TABLE_TEST)
    {
        ULONG GdiBatchCount;

        /* Read the GDI batch count from the TEB */
        _SEH2_TRY
        {
            GdiBatchCount = NtCurrentTeb()->GdiBatchCount;
        }
        _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
        {
            GdiBatchCount = 0;
        }
        _SEH2_END;

        /* Flush batch, if there are entries */
        if (GdiBatchCount != 0)
        {
            KeGdiFlushUserBatch();
        }
    }

    /* Get descriptor table */
    DescriptorTable = (PVOID)((ULONG_PTR)Thread->ServiceTable + Offset);

    /* Validate the system call number */
    if (ServiceNumber >= DescriptorTable->Limit)
    {
        /* Check if this is a GUI call */
        if (!(Offset & SERVICE_TABLE_TEST))
        {
            /* Fail the call */
            TrapFrame->Rax = STATUS_INVALID_SYSTEM_SERVICE;
            return (PVOID)NtSyscallFailure;
        }

        /* Convert us to a GUI thread
           To be entirely correct. we return KiConvertToGuiThread,
           which allocates a new stack, switches to it, calls
           PsConvertToGuiThread and resumes in the middle of
           KiSystemCallEntry64 to restart the system call handling. */
        return (PVOID)KiConvertToGuiThread;
    }

    /* Get stack bytes and calculate argument count */
    Count = DescriptorTable->Number[ServiceNumber] / 8;

    _SEH2_TRY
    {
        switch (Count)
        {
            case 16: KernelParams[15] = UserParams[15];
            case 15: KernelParams[14] = UserParams[14];
            case 14: KernelParams[13] = UserParams[13];
            case 13: KernelParams[12] = UserParams[12];
            case 12: KernelParams[11] = UserParams[11];
            case 11: KernelParams[10] = UserParams[10];
            case 10: KernelParams[9] = UserParams[9];
            case 9: KernelParams[8] = UserParams[8];
            case 8: KernelParams[7] = UserParams[7];
            case 7: KernelParams[6] = UserParams[6];
            case 6: KernelParams[5] = UserParams[5];
            case 5: KernelParams[4] = UserParams[4];
            case 4:
            case 3:
            case 2:
            case 1:
            case 0:
                break;

            default:
                ASSERT(FALSE);
                break;
        }
    }
    _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
    {
        TrapFrame->Rax = _SEH2_GetExceptionCode();
        return (PVOID)NtSyscallFailure;
    }
    _SEH2_END;

    return (PVOID)DescriptorTable->Base[ServiceNumber];
}


// FIXME: we need to
VOID
KiSystemService(IN PKTHREAD Thread,
                IN PKTRAP_FRAME TrapFrame,
                IN ULONG Instruction)
{
    UNIMPLEMENTED;
    __debugbreak();
}