CODEWITHSUNDEEP
c++windowsdriver
xina1i
xina1i

Reputation: 788

How can I get symbol link name in windows NT driver?

I'm writing a windows nt driver. I define a DEVICE_EXTENSION 

typedef struct _DEVICE_EXTENSION {
PDEVICE_OBJECT pDevice;
UNICODE_STRING ustrDeviceName;
UNICODE_STRING ustrSymLinkName;
} DEVICE_EXTENSION, *PDEVICE_EXTENSION;

And I create a device,

status = IoCreateDevice(pDriverObject,
    sizeof(DEVICE_EXTENSION),
    &devName,
    FILE_DEVICE_UNKNOWN,
    0, TRUE,
    &pDevObj);
if (!NT_SUCCESS(status))
{ 
    DbgPrint("CreateDevice Error...\n");
    return status;
}
pDevObj->Flags |= DO_BUFFERED_IO;
pDevExt = (PDEVICE_EXTENSION)pDevObj->DeviceExtension;
pDevExt->pDevice = pDevObj;
pDevExt->ustrDeviceName = devName;

UNICODE_STRING symLinkName;
RtlInitUnicodeString(&symLinkName, DOS_DEVICE_NAME);
pDevExt->ustrSymLinkName = symLinkName;
status = IoCreateSymbolicLink(&symLinkName, &devName);

you can see, I store symLinkName in DEVICE_EXTENSION pDevExt. When it unloads from device, I read this symLinkName

NTSTATUS status;
PDEVICE_OBJECT  pNextObj;
DbgPrint(("Enter DriverUnload\n"));
pNextObj = pDriverObject->DeviceObject;
UNICODE_STRING pLinkName;

while (pNextObj != NULL)
{
    PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pNextObj->DeviceExtension;
    RtlCopyUnicodeString(&pLinkName, &(pDevExt->ustrSymLinkName));
    DbgPrint("Start delete symlinkname %wZ ...\n", &pLinkName);n // meet a error
    status = IoDeleteSymbolicLink(&pLinkName);
    if (!NT_SUCCESS(status))
    {
        DbgPrint("Delete SymbolLink Error\n");
        goto finish;
    }
    pNextObj = pNextObj->NextDevice;
    IoDeleteDevice(pDevExt->pDevice);
}

Before executing IoDeleteSymbolicLink, I want to print this pLinkName, but I meet a error.

enter image description here To solve this problem ,I try many methods.

while (pNextObj != NULL)
{
    PDEVICE_EXTENSION pDevExt = (PDEVICE_EXTENSION)pNextObj->DeviceExtension;
    // RtlCopyUnicodeString(&pLinkName, &(pDevExt->ustrSymLinkName));
    RtlInitUnicodeString(&pLinkName, DOS_DEVICE_NAME);     
    DbgPrint("Start delete symlinkname %wZ ...\n", &pLinkName);
    status = IoDeleteSymbolicLink(&pLinkName);
    if (!NT_SUCCESS(status))
    {
        DbgPrint("Delete SymbolLink Error\n");
        goto finish;
    }
    pNextObj = pNextObj->NextDevice;
    IoDeleteDevice(pDevExt->pDevice);
}

this will execute successfully, but I don't know why this happen.

Upvotes: 0

Views: 231

Answers (1)

pat
pat

Reputation: 497

I guess you are using this #pragma alloc_text(INIT, DriverEntry) in your code. If so, this is the explanation:

/* 
 * These compiler directives tell the Operating System how to load the
 * driver into memory. The "INIT" section is discardable as you only
 * need the driver entry upon initialization, then it can be discarded.
 *
 */

After loading, INIT sesison will be discarded and your pDevExt->ustrSymLinkName data has been released if it is in that session. You can remove all #pragma alloc_text to avoid this problem.

Upvotes: 1

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