static NTSTATUS
UcaGetContext(_In_ PFLT_INSTANCE Instance,
_In_ PVOID Target,
_In_ FLT_CONTEXT_TYPE ContextType,
_Outptr_ PFLT_CONTEXT *Context)
{
NTSTATUS Status;
PAGED_CODE();
switch (ContextType)
{
case FLT_STREAM_CONTEXT:
Status = FltGetStreamContext(Instance,
(PFILE_OBJECT)Target,
Context);
break;
case FLT_FILE_CONTEXT:
Status = FltGetFileContext(Instance,
(PFILE_OBJECT)Target,
Context);
break;
case FLT_TRANSACTION_CONTEXT:
Status = FltGetTransactionContext(Instance,
(PKTRANSACTION)Target,
Context);
break;
case FLT_INSTANCE_CONTEXT:
Status = FltGetInstanceContext(Instance,
Context);
break;
default:
Status = STATUS_INVALID_PARAMETER;
break;
}
return Status;
}
/*++
Routine Description:
这个函数查找目标流的流上下文。
This routine finds the stream context for the target stream.
Optionally, if the context does not exist this routing creates
a new one and attaches the context to the stream.
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
CreateIfNotFound - Supplies if the stream must be created if missing
StreamContext - Returns the stream context
ContextCreated - Returns if a new context was created
Return Value:
Status
--*/
NTSTATUS
CtxFindOrCreateStreamContext (
__in PFLT_CALLBACK_DATA Cbd,
__in BOOLEAN CreateIfNotFound,
__deref_out PCTX_STREAM_CONTEXT *StreamContext,
__out_opt PBOOLEAN ContextCreated
)
{
NTSTATUS status;
PCTX_STREAM_CONTEXT streamContext;
PCTX_STREAM_CONTEXT oldStreamContext;
PAGED_CODE();
*StreamContext = NULL;
if (ContextCreated != NULL) *ContextCreated = FALSE;
//
// First try to get the stream context.
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Trying to get stream context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = FltGetStreamContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
&streamContext );
//
// If the call failed because the context does not exist
// and the user wants to creat a new one, the create a
// new context
//
if (!NT_SUCCESS( status ) && (status == STATUS_NOT_FOUND) && CreateIfNotFound)
{
//
// Create a stream context
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Creating stream context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = CtxCreateStreamContext( &streamContext );
if (!NT_SUCCESS( status ))
{
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Failed to create stream context with status 0x%x. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
return status;
}
//
// Set the new context we just allocated on the file object
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Setting stream context %p (FileObject = %p, Instance = %p)\n",
streamContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = FltSetStreamContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamContext,
&oldStreamContext );
if (!NT_SUCCESS( status ))
{
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set stream context with status 0x%x. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// We release the context here because FltSetStreamContext failed
//
// If FltSetStreamContext succeeded then the context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Releasing stream context %p (FileObject = %p, Instance = %p)\n",
streamContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( streamContext );
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED)
{
//
// FltSetStreamContext failed for a reason other than the context already
// existing on the stream. So the object now does not have any context set
// on it. So we return failure to the caller.
//
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set stream context with status 0x%x != STATUS_FLT_CONTEXT_ALREADY_DEFINED. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
return status;
}
//
// Race condition. Someone has set a context after we queried it.
// Use the already set context instead
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Stream context already defined. Retaining old stream context %p (FileObject = %p, Instance = %p)\n",
oldStreamContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
streamContext = oldStreamContext;
status = STATUS_SUCCESS;
}
else
{
if (ContextCreated != NULL)
*ContextCreated = TRUE;
}
}
*StreamContext = streamContext;
return status;
}
NTSTATUS
CtxFindOrCreateStreamContext (
__in PFLT_CALLBACK_DATA Cbd,
__in BOOLEAN CreateIfNotFound,
__deref_out PSTREAM_CONTEXT *StreamContext,
__out_opt PBOOLEAN ContextCreated
)
/*++
Routine Description:
This routine finds the stream context for the target stream.
Optionally, if the context does not exist this routing creates
a new one and attaches the context to the stream.
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
CreateIfNotFound - Supplies if the stream must be created if missing
StreamContext - Returns the stream context
ContextCreated - Returns if a new context was created
Return Value:
Status
--*/
{
NTSTATUS status;
PSTREAM_CONTEXT streamContext;
PSTREAM_CONTEXT oldStreamContext;
PAGED_CODE();
*StreamContext = NULL;
if (ContextCreated != NULL) *ContextCreated = FALSE;
//
// First try to get the stream context.
//
status = FltGetStreamContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
&streamContext );
//
// If the call failed because the context does not exist
// and the user wants to creat a new one, the create a
// new context
//
if (!NT_SUCCESS( status ) &&
(status == STATUS_NOT_FOUND) &&
CreateIfNotFound) {
//
// Create a stream context
//
status = CtxCreateStreamContext( &streamContext );
if (!NT_SUCCESS( status )) {
return status;
}
//
// Set the new context we just allocated on the file object
//
status = FltSetStreamContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamContext,
&oldStreamContext );
if (!NT_SUCCESS( status )) {
//
// We release the context here because FltSetStreamContext failed
//
// If FltSetStreamContext succeeded then the context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
FltReleaseContext( streamContext );
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED) {
//
// FltSetStreamContext failed for a reason other than the context already
// existing on the stream. So the object now does not have any context set
// on it. So we return failure to the caller.
//
return status;
}
//
// Race condition. Someone has set a context after we queried it.
// Use the already set context instead
//
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
streamContext = oldStreamContext;
status = STATUS_SUCCESS;
} else {
if (ContextCreated != NULL) *ContextCreated = TRUE;
}
}
*StreamContext = streamContext;
return status;
}
NTSTATUS
Ctx_FindOrCreateStreamContext (
__in PFLT_CALLBACK_DATA Data,
__in PFLT_RELATED_OBJECTS FltObjects,
__in BOOLEAN CreateIfNotFound,
__deref_out PSTREAM_CONTEXT *StreamContext,
__out_opt PBOOLEAN ContextCreated
)
/*++
Routine Description:
This routine finds the stream context for the target stream.
Optionally, if the context does not exist this routing creates
a new one and attaches the context to the stream.
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
CreateIfNotFound - Supplies if the stream must be created if missing
StreamContext - Returns the stream context
ContextCreated - Returns if a new context was created
Return Value:
Status
--*/
{
NTSTATUS status;
PSTREAM_CONTEXT streamContext;
PSTREAM_CONTEXT oldStreamContext;
PAGED_CODE();
*StreamContext = NULL;
if (ContextCreated != NULL) *ContextCreated = FALSE;
// First try to get the stream context.
status = FltGetStreamContext( Data->Iopb->TargetInstance,
Data->Iopb->TargetFileObject,&streamContext );
if (!NT_SUCCESS( status ) &&
(status == STATUS_NOT_FOUND) &&
CreateIfNotFound)
{
status = iCtx_CreateStreamContext(FltObjects, &streamContext );
if (!NT_SUCCESS( status ))
return status;
status = FltSetStreamContext( Data->Iopb->TargetInstance,
Data->Iopb->TargetFileObject,
FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamContext,
&oldStreamContext );
if (!NT_SUCCESS( status ))
{
FltReleaseContext(streamContext);
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED)
{
// FltSetStreamContext failed for a reason other than the context already
// existing on the stream. So the object now does not have any context set
// on it. So we return failure to the caller.
return status;
}
streamContext = oldStreamContext;
status = STATUS_SUCCESS;
}
else
{
if (ContextCreated != NULL) *ContextCreated = TRUE;
}
}
*StreamContext = streamContext;
return status;
}
