/*++
Copyright (c) 1990  Microsoft Corporation

Module Name:
    apcuser.c

Abstract:
    This module implements the machine dependent code necessary to initialize a user mode APC.

Author:
    David N. Cutler (davec) 23-Apr-1990

Environment:
    Kernel mode only, IRQL APC_LEVEL.

Revision History:
    Thomas Van Baak (tvb) 13-May-1992
        Adapted for Alpha AXP.
--*/

#include "ki.h"


VOID KiInitializeUserApc (
    IN PKEXCEPTION_FRAME ExceptionFrame,
    IN PKTRAP_FRAME TrapFrame,
    IN PKNORMAL_ROUTINE NormalRoutine,
    IN PVOID NormalContext,
    IN PVOID SystemArgument1,
    IN PVOID SystemArgument2
    )
/*++
Routine Description:
    This function is called to initialize the context for a user mode APC.
Arguments:
    ExceptionFrame - Supplies a pointer to an exception frame.
    TrapFrame - Supplies a pointer to a trap frame.
    NormalRoutine - Supplies a pointer to the user mode APC routine.
    NormalContext - Supplies a pointer to the user context for the APC routine.
    SystemArgument1 - Supplies the first system supplied value.
    SystemArgument2 - Supplies the second system supplied value.
--*/
{
    CONTEXT ContextRecord;
    EXCEPTION_RECORD ExceptionRecord;
    LONG_PTR Length;
    ULONG_PTR UserStack;

    // Move the user mode state from the trap and exception frames to the context frame.
    ContextRecord.ContextFlags = CONTEXT_FULL;
    KeContextFromKframes(TrapFrame, ExceptionFrame, &ContextRecord);

    // Transfer the context information to the user stack, initialize the APC routine parameters, and modify the trap frame so execution will continue in user mode at the user mode APC dispatch routine.
    try {
        // Compute length of context record and new aligned user stack pointer.
        Length = (sizeof(CONTEXT) + 15) & (~15);
        UserStack = ((ULONG_PTR)ContextRecord.IntSp & (~15)) - Length;

        // Probe user stack area for writeability and then transfer the context record to the user stack.
        ProbeForWrite((PVOID)UserStack, (ULONG)Length, sizeof(QUAD));
        RtlMoveMemory((PVOID)UserStack, &ContextRecord, sizeof(CONTEXT));

        // Set the address of the user APC routine, the APC parameters, the new frame pointer, and the new stack pointer in the current trap frame.
        // Set the continuation address so control will be transferred to the user APC dispatcher.

        // N.B. It is not possible to pass 64 bit arguments to the routine.
        // N.B. ULONG becomes canonical longword with (ULONGLONG)(LONG) cast.
        TrapFrame->IntSp = (ULONGLONG)(LONG_PTR)UserStack;
        TrapFrame->IntFp = (ULONGLONG)(LONG_PTR)UserStack;
        TrapFrame->IntA0 = (ULONGLONG)(LONG_PTR)NormalContext;
        TrapFrame->IntA1 = (ULONGLONG)(LONG_PTR)SystemArgument1;
        TrapFrame->IntA2 = (ULONGLONG)(LONG_PTR)SystemArgument2;
        TrapFrame->IntA3 = (ULONGLONG)(LONG_PTR)NormalRoutine;
        TrapFrame->Fir = (ULONGLONG)(LONG_PTR)KeUserApcDispatcher;

    // If an exception occurs, then copy the exception information to an exception record and handle the exception.
    } except (KiCopyInformation(&ExceptionRecord, (GetExceptionInformation())->ExceptionRecord)) {
        // Set the address of the exception to the current program address and raise the exception by calling the exception dispatcher.
        ExceptionRecord.ExceptionAddress = (PVOID)(TrapFrame->Fir);
        KiDispatchException(&ExceptionRecord, ExceptionFrame, TrapFrame, UserMode, TRUE);
    }
}