Opening a file as a memory mapped file

NTFSD
1

How do I go about opening a file as a memory mapped file?

I figure I would use ZwCreateFile(…) then call something else based upon
it’s params.

can someone help me out or point me to some sample code?

thanks! - jb

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2

You need to use the file handle to create a section object, then use the
section object to map a view of the file. See ZwCreateFile,
ZwCreateSection, ObReferenceObjectByHandle, and MmMapViewInSystemSpace.

-----Original Message-----
From: xxxxx@earthlink.net [mailto:xxxxx@earthlink.net]
Sent: Wednesday, January 17, 2001 8:00 PM
To: File Systems Developers
Subject: [ntfsd] Opening a file as a memory mapped file

How do I go about opening a file as a memory mapped file?

I figure I would use ZwCreateFile(…) then call something
else based upon
it’s params.

can someone help me out or point me to some sample code?

thanks! - jb

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3

> I figure I would use ZwCreateFile(…) then call something else based upon

it’s params.

Then ZwCreateSection, then ZwMapViewOfSection. Note that the file will be
mapped to the user space of the current process - there is no API to map
the file to the kernel space.

Max

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4

> You need to use the file handle to create a section object, then use the

section object to map a view of the file. See ZwCreateFile,
ZwCreateSection, ObReferenceObjectByHandle, and MmMapViewInSystemSpace.

Thanks for mentioning the latter API. Is it documented somewhere?

Max

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5

Where can I find the prototype and information on how to call
MmMapViewInSystemSpace?

thanks again.

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Rob Fuller
Sent: Thursday, January 18, 2001 12:58 PM
To: File Systems Developers
Subject: [ntfsd] RE: Opening a file as a memory mapped file

You need to use the file handle to create a section object, then use the
section object to map a view of the file. See ZwCreateFile,
ZwCreateSection, ObReferenceObjectByHandle, and MmMapViewInSystemSpace.

-----Original Message-----
From: xxxxx@earthlink.net [mailto:xxxxx@earthlink.net]
Sent: Wednesday, January 17, 2001 8:00 PM
To: File Systems Developers
Subject: [ntfsd] Opening a file as a memory mapped file

How do I go about opening a file as a memory mapped file?

I figure I would use ZwCreateFile(…) then call something
else based upon
it’s params.

can someone help me out or point me to some sample code?

thanks! - jb

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6

You apparently could use the functions:

NTKERNELAPI
NTSTATUS
MmMapViewInSystemSpace (
IN PVOID Section,
OUT PVOID *MappedBase,
IN PULONG ViewSize
);

NTKERNELAPI
NTSTATUS
MmUnmapViewInSystemSpace (
IN PVOID MappedBase
);

These are in the ntddk.h. Does anyone know if this is incorrect?

  • jb

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Maxim S. Shatskih
Sent: Thursday, January 18, 2001 1:51 PM
To: File Systems Developers
Subject: [ntfsd] Re: Opening a file as a memory mapped file

I figure I would use ZwCreateFile(…) then call something else based upon
it’s params.

Then ZwCreateSection, then ZwMapViewOfSection. Note that the file will be
mapped to the user space of the current process - there is no API to map
the file to the kernel space.

Max

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7

I remember some nasties about this call. I think it is used for mapping into
the cacheaddress space. Can someone enlighten us?

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Maxim S. Shatskih
Sent: Thursday, January 18, 2001 11:58 AM
To: File Systems Developers
Subject: [ntfsd] RE: Opening a file as a memory mapped file

> You need to use the file handle to create a section object, then use the
> section object to map a view of the file. See ZwCreateFile,
> ZwCreateSection, ObReferenceObjectByHandle, and MmMapViewInSystemSpace.

Thanks for mentioning the latter API. Is it documented somewhere?

Max

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