Re: [ros-dev] [ros-diffs] 01/01: [NULL] Additions for the Null driver.

[Thomas Faber]

On 2018-04-22 22:23, Hermès Bélusca-Maïto wrote:
>   diff --git a/drivers/base/null/null.c
> b/drivers/base/null/null.c
>  index 610e886ddd..0d4ed541de 100644
>  --- a/drivers/base/null/null.c
>  +++ b/drivers/base/null/null.c
>  @@ -181,26 +199,16 @@ DriverEntry(IN PDRIVER_OBJECT DriverObject,
>        DriverObject->MajorFunction[IRP_MJ_READ] = NullDispatch;
>        DriverObject->MajorFunction[IRP_MJ_LOCK_CONTROL] = NullDispatch;
>        DriverObject->MajorFunction[IRP_MJ_QUERY_INFORMATION] = NullDispatch;
>  +    DriverObject->DriverUnload = NullUnload;
>    
>  -    /* Allocate the fast I/O dispatch table */
>  -    FastIoDispatch = ExAllocatePoolWithTag(NonPagedPool,
>  -                                           sizeof(FAST_IO_DISPATCH),
>  -                                           'llun');
>  -    if (!FastIoDispatch)
>  -    {
>  -        /* Failed, cleanup */
>  -        IoDeleteDevice(DeviceObject);
>  -        return STATUS_INSUFFICIENT_RESOURCES;
>  -    }
>  -
>  -    /* Initialize it */
>  -    RtlZeroMemory(FastIoDispatch, sizeof(FAST_IO_DISPATCH));
>  -    FastIoDispatch->SizeOfFastIoDispatch = sizeof(FAST_IO_DISPATCH);
>  +    /* Initialize the fast I/O dispatch table */
>  +    RtlZeroMemory(&FastIoDispatch, sizeof(FastIoDispatch));
>  +    FastIoDispatch.SizeOfFastIoDispatch = sizeof(FastIoDispatch);
>    
>        /* Setup our pointers */
>  -    FastIoDispatch->FastIoRead = NullRead;
>  -    FastIoDispatch->FastIoWrite = NullWrite;
>  -    DriverObject->FastIoDispatch = FastIoDispatch;
>  +    FastIoDispatch.FastIoRead = NullRead;
>  +    FastIoDispatch.FastIoWrite = NullWrite;
>  +    DriverObject->FastIoDispatch = &FastIoDispatch; 

Are you sure FAST_IO_DISPATCH is allowed to be pageable? It seems to
only be used at low IRQLs, so it seems logical. However I see it
allocated nonpaged everywhere else and can't seem to find definitive
documentation on the subject.
(And yes, most filesystem drivers use a static structure, but those
  drivers don't use MmPageEntireDriver)

Thanks,
Thomas

[Ged Murphy]

They're pagable in NT6, I don't know whether that's the case in NT5.

Change looks good to me, I'm not really sure why Alex used NNP? 
Perhaps our kernel does/did things slightly differently back when he wrote the Null
driver?

Ged.

-----Original Message-----
From: Ros-dev <ros-dev-bounces(a)reactos.org> On Behalf Of Thomas Faber
Sent: Monday, 23 April 2018 07:49
To: Hermès Bélusca-Maïto <hermes.belusca-maito(a)reactos.org>
Cc: ros-dev(a)reactos.org
Subject: Re: [ros-dev] [ros-diffs] 01/01: [NULL] Additions for the Null driver.

On 2018-04-22 22:23, Hermès Bélusca-Maïto wrote:
>   diff --git a/drivers/base/null/null.c
> b/drivers/base/null/null.c index 
>  610e886ddd..0d4ed541de 100644
>  --- a/drivers/base/null/null.c
>  +++ b/drivers/base/null/null.c
>  @@ -181,26 +199,16 @@ DriverEntry(IN PDRIVER_OBJECT DriverObject,
>        DriverObject->MajorFunction[IRP_MJ_READ] = NullDispatch;
>        DriverObject->MajorFunction[IRP_MJ_LOCK_CONTROL] = NullDispatch;
>        DriverObject->MajorFunction[IRP_MJ_QUERY_INFORMATION] = 
>  NullDispatch;
>  +    DriverObject->DriverUnload = NullUnload;
>    
>  -    /* Allocate the fast I/O dispatch table */
>  -    FastIoDispatch = ExAllocatePoolWithTag(NonPagedPool,
>  -                                           sizeof(FAST_IO_DISPATCH),
>  -                                           'llun');
>  -    if (!FastIoDispatch)
>  -    {
>  -        /* Failed, cleanup */
>  -        IoDeleteDevice(DeviceObject);
>  -        return STATUS_INSUFFICIENT_RESOURCES;
>  -    }
>  -
>  -    /* Initialize it */
>  -    RtlZeroMemory(FastIoDispatch, sizeof(FAST_IO_DISPATCH));
>  -    FastIoDispatch->SizeOfFastIoDispatch = sizeof(FAST_IO_DISPATCH);
>  +    /* Initialize the fast I/O dispatch table */
>  +    RtlZeroMemory(&FastIoDispatch, sizeof(FastIoDispatch));
>  +    FastIoDispatch.SizeOfFastIoDispatch = sizeof(FastIoDispatch);
>    
>        /* Setup our pointers */
>  -    FastIoDispatch->FastIoRead = NullRead;
>  -    FastIoDispatch->FastIoWrite = NullWrite;
>  -    DriverObject->FastIoDispatch = FastIoDispatch;
>  +    FastIoDispatch.FastIoRead = NullRead;
>  +    FastIoDispatch.FastIoWrite = NullWrite;
>  +    DriverObject->FastIoDispatch = &FastIoDispatch; 

Are you sure FAST_IO_DISPATCH is allowed to be pageable? It seems to only be used at low
IRQLs, so it seems logical. However I see it allocated nonpaged everywhere else and
can't seem to find definitive documentation on the subject.
(And yes, most filesystem drivers use a static structure, but those
  drivers don't use MmPageEntireDriver)

Thanks,
Thomas

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