Intercept first MBR reads for external disk

NTFSD
1

hi, i have a legacy system that generates FAT16 PCMCIA ATA cards with MBR.

I used the hitachi cfadisk driver example to force the pcmcia card to be detected not as removable thus making the OS interpret the MBR.

The problem is that MBR is dirty and Windows does not like it so i was thinking of extending the driver to intercept also IRP_MJ_READ and modify the read MBR to report a clean one that Windows like.

I tryed a simple passthrough IRP_MJ_READ function but i’ve discovered that no IRP_MJ_READ are issued as i insert the PCMCIA disk into the pc.

using DeviceTree when the disk is inserted the tree looks like

\driver\cfadisk
DEV (unnamed)
ATT \driver\disk\Harddisk1\DR1
ATT (unnamed) \driver\partmgr

if this is the tree shouldnt i be able to intercept IRP_MJ_READ of the MBR???

Or the first MBR read is done somewhere else or some other way?

Thanks for your time

2

>driver to intercept also IRP_MJ_READ and modify the read MBR to report

At least in XP you cannot filter MJ_READ for the MBR itself, this is some very intimate relation between Disk and PartMgr.

–
Maxim S. Shatskih
Windows DDK MVP
xxxxx@storagecraft.com
http://www.storagecraft.com

3

Thanks Maxim,
I kept looking around and i found an old useful post from you that was stating the from Vista and Vista+ the IoReadPartitionTable is done by partmgr while in Vista- this is done by disk.
If this is correct (the driver will go to Vista and/or Win 7) i could use the diskperf example (obviously modify it for my purposes) and install it in between disk and partmgr instead like as of now that it goes on top of disk and partmgr.
Am i right?

4

I think you’re right.

–
Maxim S. Shatskih
Windows DDK MVP
xxxxx@storagecraft.com
http://www.storagecraft.com

wrote in message news:xxxxx@ntfsd…
> Thanks Maxim,
> I kept looking around and i found an old useful post from you that was stating the from Vista and Vista+ the IoReadPartitionTable is done by partmgr while in Vista- this is done by disk.
> If this is correct (the driver will go to Vista and/or Win 7) i could use the diskperf example (obviously modify it for my purposes) and install it in between disk and partmgr instead like as of now that it goes on top of disk and partmgr.
> Am i right?
>
>

5

Success.
Really thanks for your information. I was able to modify MBR and now windows is happy when i insert the drive.
Only thing is that automount is not working. i have to manually go to computer management and select the disk and assign a letter.
also it is unclear to me how to install the class filter before partmgr.
The diskperf installation file shows an addreg with an append flag, but i cannot see any prepend flag. Should i delete the key and recreate with partmgr as second filter?

6

Ok, about the automount, my bad.
I had the NoAutoMount set to 1 in the registry.