Re: Exporting USB device ids from the kernel

[Andrey Konovalov <andreyknvl@google.com>]

On Fri, Nov 15, 2019 at 4:44 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, 15 Nov 2019, Andrey Konovalov wrote:
>
> > Hi Greg and Alan,
> >
> > For USB fuzzing it would be nice to be able to export usb_device_id
> > structs from the kernel to facilitate the fuzzer with generating USB
> > descriptors that match to actual drivers. The same is required for
> > hid_device_id structs, since those are matched separately by the
> > usbhid driver (are there other cases like this?).
> >
> > Currently I have a hacky patch [1] that walks all drivers for USB and
> > HID buses and then prints all device ids for those drivers into the
> > kernel log. Those are manually parsed and built into the fuzzer [2]
> > and then used to generate USB descriptors [3].
>
> There are so many different flags for those id structures, parsing and
> understanding them must be quite difficult.
>
> > I'm thinking of making a proper patch that will add a debugfs entry
> > like usb/drivers (and usb/hid_drivers?), that can be read to get
> > USB/HID device ids for all loaded drivers. Would that be acceptable?
> > Or should I use some other interface to do that?
>
> I can't think of a better way to get the information from a running
> kernel.
>
> There is another possibility, though.  If the drivers are built as
> modules, the information is already available to userspace tools via
> depmod.  You could get it from the modules.dep.bin file.  This has the
> advantage that it will work even for drivers that aren't currently
> loaded.

This is the same thing Greg mentions above, right? Would this work for
drivers that are built into the kernel (as =y)?