File properties & access mask wierdness...

NTFSD
1

Ok, So I start looking at the access masks (in Windbg) associated with FileOpen
calls (in the kernel) and all of a sudden I am seeing masks with a “c” or
and “8” in the high order byte…but the DDk does not mention what these
are for. It would appear that a file open for write has a “c” hex mask set
for the highest byte but I can’t confirm this…there is plenty in the ddk
.h files about the lower order bytes in the access mask but nothing about
these higher ones…I thought a file open for write would have a 0x02 in
the lower byte but that doesnt appear to be the case…I know the confusion
lies within me but I need a dope slap…

Can someone toss me a bone? All I want to know is when I file is open in
write mode so I can work some semaphores… :^(

thanks
Ken “need the info” Steinberg

2

The upper bits of the access mask are used for the “Generic Rights”.
You don’t care, because by the time they have gone through the I/O
Manager they have been translated into the necessary standard and
specific rights that YOU do care about. Here they are (straight from
the header file):

#define GENERIC_READ (0x80000000L)
#define GENERIC_WRITE (0x40000000L)
#define GENERIC_EXECUTE (0x20000000L)
#define GENERIC_ALL (0x10000000L)

So 0xc is GENERIC_READ|GENERIC_WRITE and 0x8 is GENERIC_READ.

I hope this clarifies things for you.

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

-----Original Message-----
From: bounce-212

xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of
Ken Steinberg
Sent: Thursday, June 16, 2005 9:38 PM
To: ntfsd redirect
Subject: [ntfsd] File properties & access mask wierdness…

Ok, So I start looking at the access masks (in Windbg) associated with
FileOpen
calls (in the kernel) and all of a sudden I am seeing masks with a “c”
or
and “8” in the high order byte…but the DDk does not mention what these

are for. It would appear that a file open for write has a “c” hex mask
set
for the highest byte but I can’t confirm this…there is plenty in the
ddk
.h files about the lower order bytes in the access mask but nothing
about
these higher ones…I thought a file open for write would have a 0x02
in
the lower byte but that doesnt appear to be the case…I know the
confusion
lies within me but I need a dope slap…

Can someone toss me a bone? All I want to know is when I file is open
in
write mode so I can work some semaphores… :^(

thanks
Ken “need the info” Steinberg

Questions? First check the IFS FAQ at
https://www.osronline.com/article.cfm?id=17

You are currently subscribed to ntfsd as: xxxxx@osr.com
To unsubscribe send a blank email to xxxxx@lists.osr.com

3

Hello Tony,

Thanks a lot…that atleast cleared up an confusion…I dont like not knowing
mask values…they have a tendency to bite!

Ken

The upper bits of the access mask are used for the “Generic Rights”.
You don’t care, because by the time they have gone through the I/O
Manager they have been translated into the necessary standard and
specific rights that YOU do care about. Here they are (straight from
the header file):

#define GENERIC READ (0x80000000L) #define GENERIC
WRITE (0x40000000L) #define GENERIC EXECUTE
(0x20000000L) #define GENERIC ALL (0x10000000L)

So 0xc is GENERIC READ|GENERIC WRITE and 0x8 is GENERIC READ.

I hope this clarifies things for you.

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com
-----Original Message-----
> From: bounce-212
>
> xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf
> Of
> Ken Steinberg
> Sent: Thursday, June 16, 2005 9:38 PM
> To: ntfsd redirect
> Subject: [ntfsd] File properties & access mask wierdness…
> Ok, So I start looking at the access masks (in Windbg) associated
> with
> FileOpen
> calls (in the kernel) and all of a sudden I am seeing masks with a
> “c”
> or
> and “8” in the high order byte…but the DDk does not mention what
> these
> are for. It would appear that a file open for write has a “c” hex
> mask
> set
> for the highest byte but I can’t confirm this…there is plenty in
> the
> ddk
> .h files about the lower order bytes in the access mask but nothing
> about
> these higher ones…I thought a file open for write would have a
> 0x02
> in
> the lower byte but that doesnt appear to be the case…I know the
> confusion
> lies within me but I need a dope slap…
> Can someone toss me a bone? All I want to know is when I file is
> open
> in
> write mode so I can work some semaphores… :^(
> thanks
> Ken “need the info” Steinberg
> —
> Questions? First check the IFS FAQ at
> https://www.osronline.com/article.cfm?id=17
> You are currently subscribed to ntfsd as: xxxxx@osr.com To
> unsubscribe send a blank email to xxxxx@lists.osr.com
>