驱动程序和应用程序之间通信（For Win2000 or later ）

正文
Q:
请问有什么方法实现驱动程序主动和应用程序进行实时通讯，而不用应用程序采用定时查询的方法？
比如驱动有一事件发生需要立即通知应用程序，或驱动程序需要向应用程序读取一些内容.

A:
有一个很容易的方式，在驱动程序和应用程序之间用一个事件。
在应用程序CreateFile的时候，驱动程序IoCreateSynchronizationEvent一个有名的事件，然后应用程序CreateEvent/OpenEvent此有名事件即可。
注意点：
1，不要在驱动初始化的时候创建事件，此时大多不能成功创建；
2，让驱动先创建，那么此后应用程序打开时，只能读（Waitxxxx）,不能写(SetEvent/ResetEvent)。反之，如果应用程序先创建，则应用程序和驱动程序都有读写权限；
3，用名字比较理想，注意驱动中名字在/BaseNamedObjects/下，例如应用程序用“xxxEvent”,那么驱动中就是“/BaseNamedObjects/xxxEvent”；
4，用HANDLE的方式也可以，但是在WIN98下是否可行，未知。
5，此后，驱动对读请求应立即返回，否则就返回失败。不然将失去用事件通知的意义（不再等待读完成，而是有需要（通知事件）时才会读）；
6，应用程序发现有事件，应该在一个循环中读取，直到读取失败，表明没有数据可读；否则会漏掉后续数据，而没有及时读取；

Sample Code:


// Describe the share memory.
typedef struct _PKT_BUFFER
{
PMDL BufferMdl;
PVOID UserBaseAddress;
PVOID KernelBaseAddress;
}PKT_BUFFER, *PPKT_BUFFER;

typedef struct _SHARE_EVENT_CONTEXT
{
WCHAR EventName[128]; // Event name, the only connection btw ring0/ring3
HANDLE Win32EventHandle; // Ring3 copy of the event handle
HANDLE DriverEventHandle; // Ring0 copy of the event handle
PVOID DriverEventObject; // The event object
}SHARE_EVENT_CONTEXT, *PSHARE_EVENT_CONTEXT;


BOOLEAN CreateShareMemory(PPKT_BUFFER PktBuffer, ULONG Size)
{
PktBuffer->KernelBaseAddress = ExAllocatePoolWithTag(NonPagedPool,
Size,
'MpaM');

if(!PktBuffer->KernelBaseAddress)
return FALSE;

//
// Allocate and initalize an MDL that describes the buffer
//
PktBuffer->BufferMdl = IoAllocateMdl(PktBuffer->KernelBaseAddress,
Size,
FALSE,
FALSE,
NULL);

if(!PktBuffer->BufferMdl)
{
ExFreePool(PktBuffer->KernelBaseAddress);
PktBuffer->KernelBaseAddress =NULL;
return FALSE;
}

MmBuildMdlForNonPagedPool(PktBuffer->BufferMdl);

DEBUGP(DL_INFO, ("CreateShareMemory: KernelBaseAddress = 0x%p/n", PktBuffer->KernelBaseAddress));

return TRUE;
}

VOID DestroyShareMemory(PPKT_BUFFER PktBuffer)
{
if(PktBuffer->BufferMdl)
{
IoFreeMdl(PktBuffer->BufferMdl);
PktBuffer->BufferMdl = NULL;
}

if(PktBuffer->KernelBaseAddress)
{
ExFreePool(PktBuffer->KernelBaseAddress);
PktBuffer->KernelBaseAddress = NULL;
}
}

//This function works in user dispatch code.
BOOLEAN MapSharedMemory(PPKT_BUFFER PktBuffer)
{
if(!PktBuffer->BufferMdl)
return FALSE;

//
// The preferred V5 way to map the buffer into user space
//
PktBuffer->UserBaseAddress =
MmMapLockedPagesSpecifyCache(PktBuffer->BufferMdl, // MDL
UserMode, // Mode
MmCached, // Caching
NULL, // Address
FALSE, // Bugcheck?
NormalPagePriority); // Priority

if(!PktBuffer->UserBaseAddress)
return FALSE;

DEBUGP(DL_INFO, ("MapSharedMemory SUCCESS, UserBaseAddress %p/n", PktBuffer->UserBaseAddress));
return TRUE;
}

VOID UnmapSharedMemory(PPKT_BUFFER PktBuffer)
{
if(PktBuffer->UserBaseAddress)
{
MmUnmapLockedPages(PktBuffer->UserBaseAddress, PktBuffer->BufferMdl);
PktBuffer->UserBaseAddress = NULL;
}
}

BOOLEAN CreateShareEvent(PSHARE_EVENT_CONTEXT ShareEvent)
{
UNICODE_STRING UnicodeName;
WCHAR UnicodeBuffer[128] = L"/BaseNamedObjects/";

RtlInitUnicodeString(&UnicodeName, UnicodeBuffer);
UnicodeName.MaximumLength = 128;
RtlAppendUnicodeToString(&UnicodeName, ShareEvent->EventName);

ShareEvent->DriverEventObject = IoCreateSynchronizationEvent(&UnicodeName,
&ShareEvent->DriverEventHandle);

if(ShareEvent->DriverEventObject == NULL)
{
ShareEvent->DriverEventHandle = NULL;
DEBUGP(DL_INFO, ("CreateSynchronizationEvent FAILED Name=%ws/n", UnicodeBuffer));
return FALSE;
}
else
{
KeClearEvent(ShareEvent->DriverEventObject);

DEBUGP(DL_INFO, ("CreateSynchronizationEvent SUCCESS Name=%ws DriverEventObject=%p, DriverEventHandle=%u/n",
UnicodeBuffer,
ShareEvent->DriverEventObject,
ShareEvent->DriverEventHandle));

return TRUE;
}
}

VOID DestroyShareEvents(PSHARE_EVENT_CONTEXT ShareEvent)
{
if(ShareEvent->DriverEventHandle)
{
ZwClose(ShareEvent->DriverEventHandle);
ShareEvent->DriverEventObject = NULL;
ShareEvent->DriverEventHandle = NULL;
}
}