Windows System Software -- Consulting, Training, Development -- Unique Expertise, Guaranteed Results

Home NTFSD

More Info on Driver Writing and Debugging


The free OSR Learning Library has more than 50 articles on a wide variety of topics about writing and debugging device drivers and Minifilters. From introductory level to advanced. All the articles have been recently reviewed and updated, and are written using the clear and definitive style you've come to expect from OSR over the years.


Check out The OSR Learning Library at: https://www.osr.com/osr-learning-library/


Before Posting...

Please check out the Community Guidelines in the Announcements and Administration Category.

Re: How to access named kernel object created by use-r mode applicati on in kernel driver?

OSR_Community_UserOSR_Community_User Member Posts: 110,217
Thanks, allow me to ask one more question in regard to this, how do you
figure out the parameters of each of these functions ?

Jack

> -----Original Message-----
> From: Prasad Dabak [SMTP:[email protected]]
> Sent: Wednesday, March 01, 2000 12:53 AM
> To: File Systems Developers Interest List
> Subject: [ntfsd] Re: How to access named kernel object created by
> user mode applicati on in kernel driver?
>
> Hello,
>
> For event, you can use ZwOpenEvent call.
>
> For Semaphore & Mutant, ZwOpenSemaphore and
> ZwOpenMutant can be
> used. However the problem is, these Zwxx calls are not
> exported
> by NTOSKRNL.EXE.
>
> Hence you need to write these Zwxx wrappers yourself.
>
> All the Zwxx calls are nothing but the wrapper
> functions which
> fills in the EAX register with the unique service id,
> fills in
> the EDX register with pointer to stack frame and
> issues interrupt
> 2eh. In the end, appropriate number of parameter bytes
> are popped
> off the stack.
>
> Hence you can write your own Zwxx wrappers as follows.
>
> _declspec(naked) NTSTATUS NTAPI ZwOpenSemaphore(param
> list)
> {
> _asm {
> mov eax, 57h
> lea edx, [esp+4]
> int 2eh
> ret 0Ch
> }
> }
>
> _declspec(naked) NTSTATUS NTAPI ZwOpenMutant(param
> list)
> {
> _asm {
> mov eax, 52h
> lea edx, [esp+4]
> int 2eh
> ret 0Ch
> }
> }
>
> The above code is written assuming the machine is NT
> 4.0
> SP5 and hence is coupled to OS version. The service
> ids
> for Zwxx calls (57h & 52h) can change between OS
> versions
> and some times between service packs.
>
> To make the above code version independent, one needs
> to
> find out the service ids dynamically.
>
> This can be done as follows.
>
> The user mode NTDLL.DLL exports all the Ntxx wrapper
> functions (identical to Zwxx wrappers) for all the
> system
> services. One can find the service id of the
> particular
> system service by walking the code of these wrapper
> functions.
>
> e.g To find service id of ZwOpenMutant one can do the
> following
>
> unsigned char *ptr;
>
> ptr=(unsigned char *)
> GetProcAddress(GetModuleHandle("NTDLL.DLL"),
> "NtOpenMutant");
> //ptr + 1 will skip the 'MOV EAX' instruction opcode
> and ULONG
> //at that location will be the service id
> ServiceId=*((ULONG *)(ptr+1))
>
> This service id can be then be passed to kernel mode
> using some
> communication method (DeviceIoControl)
>
> Hope this helps.
>
> -Prasad
>
>
>
>
> --- "CHENG, WEI CHI (LNG)"
> wrote:
> > Hi all,
> >
> > I have a user mode application that uses the
> > SWMRG(single writer multiple
> > readers guard) as implemented in chap 10 of Advanced
> > windows to protect a
> > named memory mapped file.
> >
> > In the kernel mode file filter driver, I need to
> > access the memory mapped
> > file. In ZwOpenSection, we can pass an
> > ObjectAttributes that encapsulates
> > the name. However, I did not know how to do that for
> > Mutex, Event &
> > Semaphore kernel objects.
> >
> > Any idea ?
> >
> > Thanks,
> >
> >
> > Jack(Wei-Chi) Cheng
> > Lexis-Nexis DCE Support Team
> > email: [email protected]
> > phone: 937-8656800 x 4028
> >
> >
> > ---
> > You are currently subscribed to ntfsd as:
> > [email protected]
> > To unsubscribe send a blank email to
> > $subst('Email.Unsub')
> >
> >
>
> =====
> Prasad S. Dabak
> Director of Engineering, Windows NT/2000 Division
> Cybermedia Software Private Limited
> http://www.cybermedia.co.in
> Co-author of the book "Undocumented Windows NT"
> ISBN 0764545698
> __________________________________________________
> Do You Yahoo!?
> Talk to your friends online with Yahoo! Messenger.
> http://im.yahoo.com
>
> ---
> You are currently subscribed to ntfsd as: [email protected]
> To unsubscribe send a blank email to $subst('Email.Unsub')
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. Sign in or register to get started.

Upcoming OSR Seminars
OSR has suspended in-person seminars due to the Covid-19 outbreak. But, don't miss your training! Attend via the internet instead!
Writing WDF Drivers 24 January 2022 Live, Online
Internals & Software Drivers 7 February 2022 Live, Online
Kernel Debugging 21 March 2022 Live, Online
Developing Minifilters 23 May 2022 Live, Online