Sample Code
Windows Driver Samples/ Ctx File System Minifilter Driver/ C++/ context.c/
/*++
Copyright (c) 1999 - 2002 Microsoft Corporation
Module Name:
context.c
Abstract:
This is the stream nd stream handle context module of the kernel mode
context sample filter driver
Environment:
Kernel mode
--*/
#include "pch.h"
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, CtxFindOrCreateFileContext)
#pragma alloc_text(PAGE, CtxCreateFileContext)
#pragma alloc_text(PAGE, CtxFindOrCreateStreamContext)
#pragma alloc_text(PAGE, CtxCreateStreamContext)
#pragma alloc_text(PAGE, CtxUpdateNameInStreamContext)
#pragma alloc_text(PAGE, CtxCreateOrReplaceStreamHandleContext)
#pragma alloc_text(PAGE, CtxCreateStreamHandleContext)
#pragma alloc_text(PAGE, CtxUpdateNameInStreamHandleContext)
#endif
NTSTATUS
CtxFindOrCreateFileContext (
_In_ PFLT_CALLBACK_DATA Cbd,
_In_ BOOLEAN CreateIfNotFound,
_When_( CreateIfNotFound != FALSE, _In_ ) _When_( CreateIfNotFound == FALSE, _In_opt_ ) PUNICODE_STRING FileName,
_Outptr_ PCTX_FILE_CONTEXT *FileContext,
_Out_opt_ PBOOLEAN ContextCreated
)
/*++
Routine Description:
This routine finds the file context for the target file.
Optionally, if the context does not exist this routing creates
a new one and attaches the context to the file.
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
CreateIfNotFound - Supplies if the file context must be created if missing
FileName - Supplies the file name
FileContext - Returns the file context
ContextCreated - Returns if a new context was created
Return Value:
Status
--*/
{
NTSTATUS status;
PCTX_FILE_CONTEXT fileContext;
PCTX_FILE_CONTEXT oldFileContext;
PAGED_CODE();
*FileContext = NULL;
if (ContextCreated != NULL) *ContextCreated = FALSE;
//
// First try to get the file context.
//
DebugTrace( DEBUG_TRACE_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Trying to get file context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = FltGetFileContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
&fileContext );
//
// 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 file context
//
DebugTrace( DEBUG_TRACE_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Creating file context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = CtxCreateFileContext( FileName, &fileContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to create file 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_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Setting file context %p (FileObject = %p, Instance = %p)\n",
fileContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = FltSetFileContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
FLT_SET_CONTEXT_KEEP_IF_EXISTS,
fileContext,
&oldFileContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set file context with status 0x%x. (FileObject = %p, Instance = %p)\n",
status,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// We release the context here because FltSetFileContext failed
//
// If FltSetFileContext 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_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Releasing file context %p (FileObject = %p, Instance = %p)\n",
fileContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( fileContext );
if (status != STATUS_FLT_CONTEXT_ALREADY_DEFINED) {
//
// FltSetFileContext failed for a reason other than the context already
// existing on the file. 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_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set file 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_FILE_CONTEXT_OPERATIONS,
("[Ctx]: File context already defined. Retaining old file context %p (FileObject = %p, Instance = %p)\n",
oldFileContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
fileContext = oldFileContext;
status = STATUS_SUCCESS;
} else {
if (ContextCreated != NULL) *ContextCreated = TRUE;
}
}
*FileContext = fileContext;
return status;
}
NTSTATUS
CtxCreateFileContext (
_In_ PUNICODE_STRING FileName,
_Outptr_ PCTX_FILE_CONTEXT *FileContext
)
/*++
Routine Description:
This routine creates a new file context
Arguments:
FileName - Supplies the file name
FileContext - Returns the file context
Return Value:
Status
--*/
{
NTSTATUS status;
PCTX_FILE_CONTEXT fileContext;
PAGED_CODE();
//
// Allocate a file context
//
DebugTrace( DEBUG_TRACE_FILE_CONTEXT_OPERATIONS,
("[Ctx]: Allocating file context \n") );
status = FltAllocateContext( Globals.Filter,
FLT_FILE_CONTEXT,
CTX_FILE_CONTEXT_SIZE,
PagedPool,
&fileContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_FILE_CONTEXT_OPERATIONS | DEBUG_TRACE_ERROR,
("[Ctx]: Failed to allocate file context with status 0x%x \n",
status) );
return status;
}
//
// Initialize the newly created context
//
//
// Allocate and copy off the file name
//
fileContext->FileName.MaximumLength = FileName->Length;
status = CtxAllocateUnicodeString( &fileContext->FileName );
if (NT_SUCCESS( status )) {
RtlCopyUnicodeString( &fileContext->FileName, FileName );
}
*FileContext = fileContext;
return STATUS_SUCCESS;
}
NTSTATUS
CtxFindOrCreateStreamContext (
_In_ PFLT_CALLBACK_DATA Cbd,
_In_ BOOLEAN CreateIfNotFound,
_Outptr_ PCTX_STREAM_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;
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
CtxCreateStreamContext (
_Outptr_ PCTX_STREAM_CONTEXT *StreamContext
)
/*++
Routine Description:
This routine creates a new stream context
Arguments:
StreamContext - Returns the stream context
Return Value:
Status
--*/
{
NTSTATUS status;
PCTX_STREAM_CONTEXT streamContext;
PAGED_CODE();
//
// Allocate a stream context
//
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS,
("[Ctx]: Allocating stream context \n") );
status = FltAllocateContext( Globals.Filter,
FLT_STREAM_CONTEXT,
CTX_STREAM_CONTEXT_SIZE,
PagedPool,
&streamContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_STREAM_CONTEXT_OPERATIONS | DEBUG_TRACE_ERROR,
("[Ctx]: Failed to allocate stream context with status 0x%x \n",
status) );
return status;
}
//
// Initialize the newly created context
//
RtlZeroMemory( streamContext, CTX_STREAM_CONTEXT_SIZE );
streamContext->Resource = CtxAllocateResource();
if(streamContext->Resource == NULL) {
FltReleaseContext( streamContext );
return STATUS_INSUFFICIENT_RESOURCES;
}
ExInitializeResourceLite( streamContext->Resource );
*StreamContext = streamContext;
return STATUS_SUCCESS;
}
NTSTATUS
CtxUpdateNameInStreamContext (
_In_ PUNICODE_STRING DirectoryName,
_Inout_ PCTX_STREAM_CONTEXT StreamContext
)
/*++
Routine Description:
This routine updates the name of the target in the supplied stream context
Arguments:
DirectoryName - Supplies the directory name
StreamContext - Returns the updated name in the stream context
Return Value:
Status
Note:
The caller must synchronize access to the context. This routine does no
synchronization
--*/
{
NTSTATUS status;
PAGED_CODE();
//
// Free any existing name
//
if (StreamContext->FileName.Buffer != NULL) {
CtxFreeUnicodeString(&StreamContext->FileName);
}
//
// Allocate and copy off the directory name
//
StreamContext->FileName.MaximumLength = DirectoryName->Length;
status = CtxAllocateUnicodeString(&StreamContext->FileName);
if (NT_SUCCESS(status)) {
RtlCopyUnicodeString(&StreamContext->FileName, DirectoryName);
}
return status;
}
NTSTATUS
CtxCreateOrReplaceStreamHandleContext (
_In_ PFLT_CALLBACK_DATA Cbd,
_In_ BOOLEAN ReplaceIfExists,
_Outptr_ PCTX_STREAMHANDLE_CONTEXT *StreamHandleContext,
_Out_opt_ PBOOLEAN ContextReplaced
)
/*++
Routine Description:
This routine creates a stream handle context for the target stream
handle. Optionally, if the context already exists, this routine
replaces it with the new context and releases the old context
Arguments:
Cbd - Supplies a pointer to the callbackData which
declares the requested operation.
ReplaceIfExists - Supplies if the stream handle context must be
replaced if already present
StreamContext - Returns the stream context
ContextReplaced - Returns if an existing context was replaced
Return Value:
Status
--*/
{
NTSTATUS status;
PCTX_STREAMHANDLE_CONTEXT streamHandleContext;
PCTX_STREAMHANDLE_CONTEXT oldStreamHandleContext;
PAGED_CODE();
*StreamHandleContext = NULL;
if (ContextReplaced != NULL) *ContextReplaced = FALSE;
//
// Create a stream context
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Creating stream handle context (FileObject = %p, Instance = %p)\n",
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
status = CtxCreateStreamHandleContext( &streamHandleContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_ERROR | DEBUG_TRACE_STREAMHANDLE_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_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Setting stream context %p (FileObject = %p, Instance = %p, ReplaceIfExists = %x)\n",
streamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance,
ReplaceIfExists) );
status = FltSetStreamHandleContext( Cbd->Iopb->TargetInstance,
Cbd->Iopb->TargetFileObject,
ReplaceIfExists ? FLT_SET_CONTEXT_REPLACE_IF_EXISTS : FLT_SET_CONTEXT_KEEP_IF_EXISTS,
streamHandleContext,
&oldStreamHandleContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Failed to set stream handle 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_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Releasing stream handle context %p (FileObject = %p, Instance = %p)\n",
streamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( streamHandleContext );
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_STREAMHANDLE_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;
}
//
// We will reach here only if we have failed with STATUS_FLT_CONTEXT_ALREADY_DEFINED
// and we can fail with that code only if the context already exists and we have used
// the FLT_SET_CONTEXT_KEEP_IF_EXISTS flag
FLT_ASSERT( ReplaceIfExists == FALSE );
//
// Race condition. Someone has set a context after we queried it.
// Use the already set context instead
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Stream context already defined. Retaining old stream context %p (FileObject = %p, Instance = %p)\n",
oldStreamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
//
// Return the existing context. Note that the new context that we allocated has already been
// realeased above.
//
streamHandleContext = oldStreamHandleContext;
status = STATUS_SUCCESS;
} else {
//
// FltSetStreamContext has suceeded. The new context will be returned
// to the caller. The caller will use the context and then release it
// when he is done with the context.
//
// However, if we have replaced an existing context then we need to
// release the old context so as to decrement the ref count on it.
//
// Note that the memory allocated to the objects within the context
// will be freed in the context cleanup and must not be done here.
//
if ( ReplaceIfExists &&
oldStreamHandleContext != NULL) {
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Releasing old stream handle context %p (FileObject = %p, Instance = %p)\n",
oldStreamHandleContext,
Cbd->Iopb->TargetFileObject,
Cbd->Iopb->TargetInstance) );
FltReleaseContext( oldStreamHandleContext );
if (ContextReplaced != NULL) *ContextReplaced = TRUE;
}
}
*StreamHandleContext = streamHandleContext;
return status;
}
NTSTATUS
CtxCreateStreamHandleContext (
_Outptr_ PCTX_STREAMHANDLE_CONTEXT *StreamHandleContext
)
/*++
Routine Description:
This routine creates a new stream context
Arguments:
StreamContext - Returns the stream context
Return Value:
Status
--*/
{
NTSTATUS status;
PCTX_STREAMHANDLE_CONTEXT streamHandleContext;
PAGED_CODE();
//
// Allocate a stream context
//
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS,
("[Ctx]: Allocating stream handle context \n") );
status = FltAllocateContext( Globals.Filter,
FLT_STREAMHANDLE_CONTEXT,
CTX_STREAMHANDLE_CONTEXT_SIZE,
PagedPool,
&streamHandleContext );
if (!NT_SUCCESS( status )) {
DebugTrace( DEBUG_TRACE_STREAMHANDLE_CONTEXT_OPERATIONS | DEBUG_TRACE_ERROR,
("[Ctx]: Failed to allocate stream handle context with status 0x%x \n",
status) );
return status;
}
//
// Initialize the newly created context
//
RtlZeroMemory( streamHandleContext, CTX_STREAMHANDLE_CONTEXT_SIZE );
streamHandleContext->Resource = CtxAllocateResource();
if(streamHandleContext->Resource == NULL) {
FltReleaseContext( streamHandleContext );
return STATUS_INSUFFICIENT_RESOURCES;
}
ExInitializeResourceLite( streamHandleContext->Resource );
*StreamHandleContext = streamHandleContext;
return STATUS_SUCCESS;
}
NTSTATUS
CtxUpdateNameInStreamHandleContext (
_In_ PUNICODE_STRING DirectoryName,
_Inout_ PCTX_STREAMHANDLE_CONTEXT StreamHandleContext
)
/*++
Routine Description:
This routine updates the name of the target in the supplied stream handle context
Arguments:
DirectoryName - Supplies the directory name
StreamHandleContext - Returns the updated name in the stream context
Return Value:
Status
Note:
The caller must synchronize access to the context. This routine does no
synchronization
--*/
{
NTSTATUS status;
PAGED_CODE();
//
// Free any existing name
//
if (StreamHandleContext->FileName.Buffer != NULL) {
CtxFreeUnicodeString(&StreamHandleContext->FileName);
}
//
// Allocate and copy off the directory name
//
StreamHandleContext->FileName.MaximumLength = DirectoryName->Length;
status = CtxAllocateUnicodeString(&StreamHandleContext->FileName);
if (NT_SUCCESS(status)) {
RtlCopyUnicodeString(&StreamHandleContext->FileName, DirectoryName);
}
return status;
}
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