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

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

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:

Determining Boot Volume from DriverEntry() in Boot Start minifilter

rstruempfrstruempf Member Posts: 103
edited April 2019 in NTFSD

Is there a means to reliably determine the system root and/or boot volume in DriverEntry() in a boot start driver?

Our driver currently determines the boot volume using FltGetVolumeFromName("\SystemRoot"), and then using FltGetVolumeName() on the volume that is returned. That method doesn't work for a boot start driver. I figure if I can get the driver's image name, that I will have what I need, but I haven't found a way to get that.

I tried the registry entry for the service, but it has a string value, ImagePath, that gives only "system32\DRIVERS\mydriver.sys", less the actual system root.

I tried ObQueryNameString() on the DriverObject, but it returns "\FileSystem\mydriver"


  • Scott_Noone_(OSR)Scott_Noone_(OSR) Administrator Posts: 3,260

    The system and boot volumes aren't created yet when you're called at DriverEntry for boot start.

    You need to wait for InstanceSetup and check the Flags field in the FltGetDiskDeviceObject device object:

    • DO_SYSTEM_BOOT_PARTITION - \Windows directory


  • rstruempfrstruempf Member Posts: 103

    Thanks Scott! I figured they were not known yet, but then it knew where to find my driver, so I wasn't sure.


Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

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!
Kernel Debugging 30 Mar 2020 OSR Seminar Space
Developing Minifilters 15 Jun 2020 LIVE ONLINE
Writing WDF Drivers 22 June 2020 LIVE ONLINE
Internals & Software Drivers 28 Sept 2020 Dulles, VA