obdevmap.c File Reference

#include "obp.h"

Go to the source code of this file.

Functions
NTSTATUS	ObSetDeviceMap (IN PEPROCESS TargetProcess OPTIONAL, IN HANDLE DirectoryHandle)
NTSTATUS	ObQueryDeviceMapInformation (IN PEPROCESS TargetProcess OPTIONAL, OUT PPROCESS_DEVICEMAP_INFORMATION DeviceMapInformation)
VOID	ObInheritDeviceMap (IN PEPROCESS NewProcess, IN PEPROCESS ParentProcess OPTIONAL)
VOID	ObDereferenceDeviceMap (IN PEPROCESS Process)

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Function Documentation

VOID ObDereferenceDeviceMap (  IN PEPROCESS  Process  )

Definition at line 416 of file obdevmap.c. References _OBJECT_DIRECTORY::DeviceMap, _DEVICE_MAP::DosDevicesDirectory, ExFreePool(), NULL, ObDereferenceObject, ObpDeviceMapLock, and _DEVICE_MAP::ReferenceCount. Referenced by ObSetDeviceMap(), and PspProcessDelete(). : This function is called at process tear down time to decrement the reference count on a device map. When the reference count goes to zero, it means no more processes are using this, so it can be freed and the reference on the associated object directory can be released. Arguments: Process - Process being destroyed. Return Value: None. --*/ { PDEVICE_MAP DeviceMap; KIRQL OldIrql; // // Grab the device map and then we only have work to do // it there is one // DeviceMap = Process->DeviceMap; if (DeviceMap != NULL) { // // To dereference the device map we need to null out the // processes device map pointer, and decrement its ref count // If the ref count goes to zero we can free up the memory // and dereference the dos device directory object // ExAcquireSpinLock( &ObpDeviceMapLock, &OldIrql ); Process->DeviceMap = NULL; DeviceMap->ReferenceCount--; if (DeviceMap->ReferenceCount == 0) { DeviceMap->DosDevicesDirectory->DeviceMap = NULL; ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); ObDereferenceObject( DeviceMap->DosDevicesDirectory ); ExFreePool( DeviceMap ); } else { ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); } } // // And return to our caller // return; }

VOID ObInheritDeviceMap (  IN PEPROCESS  NewProcess, IN PEPROCESS ParentProcess  OPTIONAL )

Definition at line 343 of file obdevmap.c. References NULL, ObpDeviceMapLock, ObSystemDeviceMap, and _DEVICE_MAP::ReferenceCount. Referenced by PspCreateProcess(). : This function is called at process initialization time to inherit the device map for a process. If no parent process, then inherits from the system device map. Arguments: NewProcess - Supplies the process being initialized that needs a new dos device map ParentProcess - - Optionally specifies the parent process whose device map we inherit. This process if specified must have a device map Return Value: None. --*/ { PDEVICE_MAP DeviceMap; KIRQL OldIrql; // // If we are called with a parent process then grab its device map // otherwise grab the system wide device map and check that is does // exist // if (ParentProcess) { DeviceMap = ParentProcess->DeviceMap; } else { // // Note: WindowStation guys may want a callout here to get the // device map to use for this case. // DeviceMap = ObSystemDeviceMap; if (DeviceMap == NULL) { return; } } // // With the device map bumps its reference count and add it to the // new process // ExAcquireSpinLock( &ObpDeviceMapLock, &OldIrql ); DeviceMap->ReferenceCount++; NewProcess->DeviceMap = DeviceMap; ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); return; }

NTSTATUS ObQueryDeviceMapInformation (  IN PEPROCESS TargetProcess  OPTIONAL, OUT PPROCESS_DEVICEMAP_INFORMATION  DeviceMapInformation )

Definition at line 236 of file obdevmap.c. References _DEVICE_MAP::DriveMap, EXCEPTION_EXECUTE_HANDLER, NTSTATUS(), NULL, ObpDeviceMapLock, ObSystemDeviceMap, and Status. Referenced by NtQueryInformationProcess(). : This function queries information from the device map associated with the specified process. The returned information contains a bit map indicating which drive letters are defined in the associated object directory, along with an array of drive types that give the type of each drive letter. Arguments: TargetProcess - Specifies the target process to retreive the device map from. If not specified then we return the global default device map DeviceMapInformation - Specifies the location where to store the results. Return Value: Returns one of the following status codes: STATUS_SUCCESS - normal, successful completion. STATUS_END_OF_FILE - The specified process was not associated with a device map. STATUS_ACCESS_VIOLATION - The DeviceMapInformation buffer pointer value specified an invalid address. --*/ { NTSTATUS Status; PDEVICE_MAP DeviceMap; KIRQL OldIrql; PROCESS_DEVICEMAP_INFORMATION LocalMapInformation; // // Check if the caller gave us a target process and if not then use // the globally defined one // if (ARGUMENT_PRESENT( TargetProcess )) { DeviceMap = TargetProcess->DeviceMap; } else { DeviceMap = ObSystemDeviceMap; } // // If we do not have a device map then we'll return an error otherwise // we simply copy over the device map structure (bitmap and drive type // array) into the output buffer // if (DeviceMap == NULL) { Status = STATUS_END_OF_FILE; } else { Status = STATUS_SUCCESS; // // First, while using a spinlock to protect the device map from // going away we will make local copy of the information. // ExAcquireSpinLock( &ObpDeviceMapLock, &OldIrql ); RtlMoveMemory( &LocalMapInformation.Query, &DeviceMap->DriveMap, sizeof( DeviceMapInformation->Query )); ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); // // Now we can copy the information to the caller buffer using // a try-except to guard against the output buffer changing. // Note that the caller must have already probed the buffer // for write. // try { RtlMoveMemory( &DeviceMapInformation->Query, &LocalMapInformation.Query, sizeof( DeviceMapInformation->Query )); } except( EXCEPTION_EXECUTE_HANDLER ) { Status = GetExceptionCode(); } } return Status; }

NTSTATUS ObSetDeviceMap (  IN PEPROCESS TargetProcess  OPTIONAL, IN HANDLE  DirectoryHandle )

Definition at line 30 of file obdevmap.c. References _EPROCESS::DeviceMap, _OBJECT_DIRECTORY::DeviceMap, DirectoryHandle, ExAllocatePoolWithTag, Handle, NonPagedPool, NT_SUCCESS, NTSTATUS(), NULL, ObDereferenceDeviceMap(), ObDereferenceObject, ObpDeviceMapLock, ObpDirectoryObjectType, ObReferenceObjectByHandle(), ObSystemDeviceMap, PAGED_CODE, PsGetCurrentProcess, _DEVICE_MAP::ReferenceCount, and Status. Referenced by NtSetInformationProcess(), and ObpCreateDosDevicesDirectory(). : This function sets the device map for the specified process, using the specified object directory. A device map is a structure associated with an object directory and a process. When the object manager sees a references to a name beginning with \??\ or just \??, then it follows the device map object in the calling process's EPROCESS structure to get to the object directory to use for that reference. This allows multiple virtual \?? object directories on a per process basis. The WindowStation logic will use this functionality to allocate devices unique to each WindowStation. Arguments: TargetProcess - Specifies the target process to associate the device map with. If null then the current process is used and the directory becomes the system default dos device map. DirectoryHandle - Specifies the object directory to associate with the device map. Return Value: Returns one of the following status codes: STATUS_SUCCESS - normal, successful completion. STATUS_SHARING_VIOLATION - The specified object directory is already associated with a device map. STATUS_INSUFFICIENT_RESOURCES - Unable to allocate pool for the device map data structure; STATUS_ACCESS_DENIED - Caller did not have DIRECTORY_TRAVERSE access to the specified object directory. --*/ { NTSTATUS Status; POBJECT_DIRECTORY DosDevicesDirectory; PDEVICE_MAP DeviceMap; PVOID Object; HANDLE Handle; KIRQL OldIrql; PAGED_CODE(); // // Reference the object directory handle and see if it is already // associated with a device map structure. If so, fail this call. // Status = ObReferenceObjectByHandle( DirectoryHandle, DIRECTORY_TRAVERSE, ObpDirectoryObjectType, KeGetPreviousMode(), &DosDevicesDirectory, NULL ); if (!NT_SUCCESS( Status )) { return( Status ); } // // Capture the device map // ExAcquireSpinLock( &ObpDeviceMapLock, &OldIrql ); DeviceMap = DosDevicesDirectory->DeviceMap; // // Check if the directory already has a dos device map // if (DeviceMap != NULL) { // // Test if the DeviceMap is about to delete and has the // ReferenceCount 0 // if (DeviceMap->ReferenceCount != 0) { // // We have a dos device map, so setup the target process to be either // what the caller specified or the current process // PEPROCESS Target = TargetProcess; if (Target == NULL) { Target = PsGetCurrentProcess(); } // // If the current process already has the exact same dos device map // then everything is already done and nothing left for us to do. // if (Target->DeviceMap == DeviceMap) { ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); ObDereferenceObject( DosDevicesDirectory ); return Status; } // // Add a new reference before releasing the spinlock // to make sure nobody will release the devicemap while // we try to attach to the process. // DeviceMap->ReferenceCount++; ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); // // We can dereference the target processes device map because it // no longer will have it's old dos device map. // ObDereferenceDeviceMap ( Target ); // // Now setup the new device map that we were feed in. We lock it // bump its ref count, make the targe process point to it, unlock it, // and return to our caller // ExAcquireSpinLock( &ObpDeviceMapLock, &OldIrql ); Target->DeviceMap = DeviceMap; ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); ObDereferenceObject( DosDevicesDirectory ); return Status; } } ExReleaseSpinLock( &ObpDeviceMapLock, OldIrql ); // // The input directory does not have a dos device map. so we'll // allocate and initialize a new device map structure. // DeviceMap = ExAllocatePoolWithTag( NonPagedPool, sizeof( *DeviceMap ), 'mDbO' ); if (DeviceMap == NULL) { ObDereferenceObject( DosDevicesDirectory ); Status = STATUS_INSUFFICIENT_RESOURCES; } else { RtlZeroMemory( DeviceMap, sizeof( *DeviceMap ) ); DeviceMap->ReferenceCount = 1; DeviceMap->DosDevicesDirectory = DosDevicesDirectory; DosDevicesDirectory->DeviceMap = DeviceMap; // // If the caller specified a target process then remove the // processes device map if in use and replace it with the new // one, otherwise set this new device map to the system wide one // and put it into the current process // if (TargetProcess != NULL) { ObDereferenceDeviceMap ( TargetProcess ); TargetProcess->DeviceMap = DeviceMap; } else { ObSystemDeviceMap = DeviceMap; ObDereferenceDeviceMap ( PsGetCurrentProcess() ); PsGetCurrentProcess()->DeviceMap = DeviceMap; } } return( Status ); }

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