exp.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

    {
        /* Get the FX Save Area */
        FxSaveArea = (PFX_SAVE_AREA)(TrapFrame + 1);

        /* Make sure we have an NPX */
        if (KeI386NpxPresent)
         {
            /* Check if we have Fxsr support */
            if (KeI386FxsrPresent)
            {
                /* Align the floating area to 16-bytes */
                FloatSaveArea = (FLOATING_SAVE_AREA*)
                                ((ULONG_PTR)&FloatSaveBuffer.UnalignedArea &~ 0xF);

                /* Get the State */
                KiFlushNPXState(FloatSaveArea);
            }
            else
            {
                /* We don't, use the FN area and flush the NPX State */
                FloatSaveArea = (FLOATING_SAVE_AREA*)&FxSaveArea->U.FnArea;
                KiFlushNPXState(NULL);
            }

            /* Copy structure */
            Context->FloatSave.ControlWord = FloatSaveArea->ControlWord;
            Context->FloatSave.StatusWord = FloatSaveArea->StatusWord;
            Context->FloatSave.TagWord = FloatSaveArea->TagWord;
            Context->FloatSave.ErrorOffset = FloatSaveArea->ErrorOffset;
            Context->FloatSave.ErrorSelector = FloatSaveArea->ErrorSelector;
            Context->FloatSave.DataOffset = FloatSaveArea->DataOffset;
            Context->FloatSave.DataSelector = FloatSaveArea->DataSelector;
            Context->FloatSave.Cr0NpxState = FxSaveArea->Cr0NpxState;

            /* Loop registers */
            for (i = 0; i < SIZE_OF_80387_REGISTERS; i++)
            {
                /* Copy them */
                Context->FloatSave.RegisterArea[i] =
                    FloatSaveArea->RegisterArea[i];
            }
         }
         else
         {
            /* FIXME: Handle Emulation */
            ASSERT(FALSE);
         }
    }

    /* Handle debug registers */
    if ((Context->ContextFlags & CONTEXT_DEBUG_REGISTERS) ==
        CONTEXT_DEBUG_REGISTERS)
    {
        /* Make sure DR7 is valid */
        if (TrapFrame->Dr7 & ~DR7_RESERVED_MASK)
        {
            /* Copy the debug registers */
            Context->Dr0 = TrapFrame->Dr0;
            Context->Dr1 = TrapFrame->Dr1;
            Context->Dr2 = TrapFrame->Dr2;
            Context->Dr3 = TrapFrame->Dr3;
            Context->Dr6 = TrapFrame->Dr6;

            /* Update DR7 */
            //Context->Dr7 = KiUpdateDr7(TrapFrame->Dr7);
        }
        else
        {
            /* Otherwise clear DR registers */
            Context->Dr0 =
            Context->Dr1 =
            Context->Dr3 =
            Context->Dr6 =
            Context->Dr7 = 0;
        }
    }

    /* Restore IRQL */
    if (OldIrql < APC_LEVEL) KeLowerIrql(OldIrql);
}

VOID
NTAPI
KiDispatchException(IN PEXCEPTION_RECORD ExceptionRecord,
                    IN PKEXCEPTION_FRAME ExceptionFrame,
                    IN PKTRAP_FRAME TrapFrame,
                    IN KPROCESSOR_MODE PreviousMode,
                    IN BOOLEAN FirstChance)
{
    CONTEXT Context;
    ULONG_PTR Stack, NewStack;
    ULONG Size;
    EXCEPTION_RECORD LocalExceptRecord;
    _SEH_DECLARE_LOCALS(KiCopyInfo);

    /* Increase number of Exception Dispatches */
    KeGetCurrentPrcb()->KeExceptionDispatchCount++;

    /* Set the context flags */
    Context.ContextFlags = CONTEXT_FULL | CONTEXT_DEBUG_REGISTERS;

    /* Check if User Mode or if the debugger is enabled */
    if ((PreviousMode == UserMode) || (KdDebuggerEnabled))
    {
        /* Add the FPU Flag */
        Context.ContextFlags |= CONTEXT_FLOATING_POINT;

        /* Check for NPX Support */
        if (KeI386FxsrPresent)
        {
            /* Save those too */
            Context.ContextFlags |= CONTEXT_EXTENDED_REGISTERS;
        }
    }

    /* Get a Context */
    KeTrapFrameToContext(TrapFrame, ExceptionFrame, &Context);

    /* Look at our exception code */
    switch (ExceptionRecord->ExceptionCode)
    {
        /* Breakpoint */
        case STATUS_BREAKPOINT:

            /* Decrement EIP by one */
            Context.Eip--;
            break;

        /* Internal exception */
        case KI_EXCEPTION_ACCESS_VIOLATION:

            /* Set correct code */
            ExceptionRecord->ExceptionCode = STATUS_ACCESS_VIOLATION;
            if (PreviousMode == UserMode)
            {
                /* FIXME: Handle no execute */
            }
            break;
    }

    /* Sanity check */
    ASSERT(!((PreviousMode == KernelMode) &&
             (Context.EFlags & EFLAGS_V86_MASK)));

    /* Handle kernel-mode first, it's simpler */
    if (PreviousMode == KernelMode)
    {
        /* Check if this is a first-chance exception */
        if (FirstChance == TRUE)
        {
            /* Break into the debugger for the first time */
            if (KiDebugRoutine(TrapFrame,
                               ExceptionFrame,
                               ExceptionRecord,
                               &Context,
                               PreviousMode,
                               FALSE))
            {
                /* Exception was handled */
                goto Handled;
            }

            /* If the Debugger couldn't handle it, dispatch the exception */
            if (RtlDispatchException(ExceptionRecord, &Context)) goto Handled;
        }

        /* This is a second-chance exception, only for the debugger */
        if (KiDebugRoutine(TrapFrame,
                           ExceptionFrame,
                           ExceptionRecord,
                           &Context,
                           PreviousMode,
                           TRUE))
        {
            /* Exception was handled */
            goto Handled;
        }

        /* Third strike; you're out */
        KeBugCheckEx(KMODE_EXCEPTION_NOT_HANDLED,
                     ExceptionRecord->ExceptionCode,
                     (ULONG_PTR)ExceptionRecord->ExceptionAddress,
                     (ULONG_PTR)TrapFrame,
                     0);
    }
    else
    {
        /* User mode exception, was it first-chance? */
        if (FirstChance)
        {
            /* Enter Debugger if available */
            if (PsGetCurrentProcess()->DebugPort)
            {
                /* FIXME : TODO */
                //KEBUGCHECK(0);
            }
            else if (KiDebugRoutine(TrapFrame,
                                    ExceptionFrame,
                                    ExceptionRecord,
                                    &Context,
                                    PreviousMode,
                                    FALSE))
            {
                /* Exception was handled */
                goto Handled;
            }

            /* Forward exception to user mode debugger */
            if (DbgkForwardException(ExceptionRecord, TRUE, FALSE)) goto Exit;

            /* Set up the user-stack */
DispatchToUser:
            _SEH_TRY
            {
                /* Make sure we have a valid SS and that this isn't V86 mode */
                if ((TrapFrame->HardwareSegSs != (KGDT_R3_DATA | RPL_MASK)) ||
                    (TrapFrame->EFlags & EFLAGS_V86_MASK))
                {
                    /* Raise an exception instead */
                    LocalExceptRecord.ExceptionCode = STATUS_ACCESS_VIOLATION;
                    LocalExceptRecord.ExceptionFlags = 0;
                    LocalExceptRecord.NumberParameters = 0;
                    RtlRaiseException(&LocalExceptRecord);
                }

                /* Align context size and get stack pointer */
                Size = (sizeof(CONTEXT) + 3) & ~3;
                Stack = (Context.Esp & ~3) - Size;

                /* Probe stack and copy Context */
                ProbeForWrite((PVOID)Stack, Size, sizeof(ULONG));
                RtlCopyMemory((PVOID)Stack, &Context, sizeof(CONTEXT));

                /* Align exception record size and get stack pointer */
                Size = (sizeof(EXCEPTION_RECORD) -
                       (EXCEPTION_MAXIMUM_PARAMETERS -
                        ExceptionRecord->NumberParameters) *
                       sizeof(ULONG) + 3) & ~3;
                NewStack = Stack - Size;

                /* Probe stack and copy exception record */
                ProbeForWrite((PVOID)(NewStack - 2 * sizeof(ULONG_PTR)),
                              Size +  2 * sizeof(ULONG_PTR),
                              sizeof(ULONG));
                RtlCopyMemory((PVOID)NewStack, ExceptionRecord, Size);

                /* Now write the two params for the user-mode dispatcher */
                *(PULONG_PTR)(NewStack - 1 * sizeof(ULONG_PTR)) = Stack;
                *(PULONG_PTR)(NewStack - 2 * sizeof(ULONG_PTR)) = NewStack;

                /* Set new Stack Pointer */
                KiSsToTrapFrame(TrapFrame, KGDT_R3_DATA);
                KiEspToTrapFrame(TrapFrame, NewStack - 2 * sizeof(ULONG_PTR));

                /* Force correct segments */
                TrapFrame->SegCs = Ke386SanitizeSeg(KGDT_R3_CODE, PreviousMode);
                TrapFrame->SegDs = Ke386SanitizeSeg(KGDT_R3_DATA, PreviousMode);
                TrapFrame->SegEs = Ke386SanitizeSeg(KGDT_R3_DATA, PreviousMode);
                TrapFrame->SegFs = Ke386SanitizeSeg(KGDT_R3_TEB,  PreviousMode);
                TrapFrame->SegGs = 0;

                /* Set EIP to the User-mode Dispatcher */
                TrapFrame->Eip = (ULONG)KeUserExceptionDispatcher;

                /* Dispatch exception to user-mode */
                _SEH_YIELD(return);
            }
            _SEH_EXCEPT(KiCopyInformation)
            {
                /* Check if we got a stack overflow and raise that instead */
                if (_SEH_VAR(SehExceptRecord).ExceptionCode ==
                    STATUS_STACK_OVERFLOW)
                {
                    /* Copy the exception address and record */
                    _SEH_VAR(SehExceptRecord).ExceptionAddress =
                        ExceptionRecord->ExceptionAddress;
                    RtlCopyMemory(ExceptionRecord,
                                  (PVOID)&_SEH_VAR(SehExceptRecord),
                                  sizeof(EXCEPTION_RECORD));

                    /* Do the exception again */
                    _SEH_YIELD(goto DispatchToUser);
                }
            }
            _SEH_END;
        }

        /* Try second chance */
        if (DbgkForwardException(ExceptionRecord, TRUE, FALSE))
        {
            /* Handled, get out */
            goto Exit;
        }
        else if (DbgkForwardException(ExceptionRecord, FALSE, TRUE))
        {
            /* Handled, get out */
            goto Exit;
        }

        /* 3rd strike, kill the process */
        DPRINT1("Kill %.16s, ExceptionCode: %lx, ExceptionAddress: %lx\n",
                PsGetCurrentProcess()->ImageFileName,
                ExceptionRecord->ExceptionCode,
                ExceptionRecord->ExceptionAddress);

        ZwTerminateProcess(NtCurrentProcess(), ExceptionRecord->ExceptionCode);
        KeBugCheckEx(KMODE_EXCEPTION_NOT_HANDLED,
                     ExceptionRecord->ExceptionCode,
                     (ULONG_PTR)ExceptionRecord->ExceptionAddress,
                     (ULONG_PTR)TrapFrame,
                     0);
    }

Handled:
    /* Convert the context back into Trap/Exception Frames */
    KeContextToTrapFrame(&Context,
                         ExceptionFrame,
                         TrapFrame,
                         Context.ContextFlags,
                         PreviousMode);
Exit:
    return;
}

/*
 * @implemented
 */
NTSTATUS
NTAPI
KeRaiseUserException(IN NTSTATUS ExceptionCode)
{
    NTSTATUS Status = STATUS_SUCCESS;
    ULONG OldEip;
    PTEB Teb = KeGetCurrentThread()->Teb;
    PKTRAP_FRAME TrapFrame = KeGetCurrentThread()->TrapFrame;

    /* Make sure we can access the TEB */
    _SEH_TRY
    {
        /* Set the exception code */
        Teb->ExceptionCode = ExceptionCode;
    }
    _SEH_HANDLE
    {
        /* Save exception code */
        Status = ExceptionCode;
    }
    _SEH_END;
    if (!NT_SUCCESS(Status)) return Status;

    /* Get the old EIP */
    OldEip = TrapFrame->Eip;

    /* Change it to the user-mode dispatcher */
    TrapFrame->Eip = (ULONG_PTR)KeRaiseUserExceptionDispatcher;

    /* Return the old EIP */
    return (NTSTATUS)OldEip;
}