From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Date: Thu, Apr 25, 2019 at 4:25 PM To: Andrey Konovalov Cc: Alan Stern, Gustavo A. R. Silva, USB list, Dmitry Vyukov, Kostya Serebryany, Alexander Potapenko > On Thu, Apr 25, 2019 at 02:44:11PM +0200, Andrey Konovalov wrote: > > On Wed, Apr 24, 2019 at 6:05 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > > > > On Fri, Apr 19, 2019 at 10:35 AM Greg Kroah-Hartman > > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > 2. Is there an easy way to figure out which config options enable > > > > > drivers reachable over USB? > > > > > > > > Looking for all options that depend on USB is a good start. > > > > > > > > > Right now our kernel config is based on one of the Debian kernel > > > > > configs, that supposedly enables enough relevant USB drivers. At the > > > > > same time it enables a lot of other unnecessary stuff, which makes the > > > > > kernel big and long to compile. Ideally, we would to have a way to > > > > > auto-generate a kernel config that enables all the relevant (enabled > > > > > by at least one of the distros) USB drivers. I've looked at whether > > > > > it's possible to figure out which particular options in some kernel > > > > > config are related to USB, but it seems that neither the option names, > > > > > nor the way they are grouped in the config file, are representative > > > > > enough. > > > > > > > > Yeah, it's hard to just carve out this type of configuration, but here's > > > > what I have done in the past to try to be sure I enabled all USB drivers > > > > in my kernel configuration. > > > > > > > > First, start with a "minimally working configuration" by running: > > > > make localmodconfig > > > > on a working system, with the needed modules for booting and operating > > > > properly already loaded. > > > > > > > > That gives you a .config file that should take only minutes to build, > > > > compared to much longer for the normal distro configuration (also be > > > > sure to disable some debugging options so you don't spend extra time > > > > building and stripping symbols). > > > > > > > > Boot and make sure that configuration works. > > > > > > > > Then, take that .config and do: > > > > - disable USB from the configuration by deleting the: > > > > CONFIG_USB_SUPPORT=y > > > > option from your .config > > > > - run 'make oldconfig' to disable all USB drivers > > > > - turn USB back on by setting CONFIG_USB_SUPPORT=y back on in > > > > your .config > > > > - run 'make oldconfig' and answer 'y' or 'm' to all of the > > > > driver options you are presented with. > > > > > > > > That usually catches almost all of them. Sometimes you need to make > > > > sure you have some other subsystem enabled (like SCSI), but odds are, if > > > > you start with a "normally stripped down" configuration that works, you > > > > should be fine. > > > > > > I suspect that make localmodconfig (+ switching CONFIG_USB_SUPPORT off > > > and on) would likely include a lot of stuff that we don't need (there > > > are many options that are =y, but not related to USB at all), but it > > > definitely sounds better than what I have right now (converting almost > > > all =m into =y). I'll give it a shot, thanks! > > > > I've tried this and unfortunately it doesn't work as desired. The > > reason is that localmodconfig will only enable options for the modules > > that are currently loaded, and if a module that some USB driver > > depends on is not loaded, then this driver won't be enabled after yes > > | make oldconfig. For example my machine didn't have the cfg80211 > > module loaded, and thus e.g. CONFIG_AT76C50X_USB didn't get enabled > > after oldconfig. However when I plug in a wireless USB adapter, > > cfg80211 gets loaded together with the USB driver for that adapter. I > > guess the same applies to other kinds of dependency modules (e.g. > > bluetooth). So this would only work if all the dependency modules are > > already loaded. > > Yes, sorry, I thought I said that with: > > > > > First, start with a "minimally working configuration" by running: > > > > make localmodconfig > > > > on a working system, with the needed modules for booting and operating > > > > properly already loaded. > > I guess "working system" implied everything that you _knew_ you wanted > to have loaded :) > > Sorry about the dependancy mess, hopefully you have sorted this out > better now. I've written a script [1], [2] on top of Kconfiglib [3] that merges in all USB configs and their dependencies from a provided (distro) config. The dependency extraction a somewhat best effort, but seems to be working. Maybe you'll find some use for it as well. Thanks! [1] https://github.com/google/syzkaller/blob/master/dashboard/config/kconfiglib-merge-usb-configs.py [2] https://github.com/google/syzkaller/blob/master/dashboard/config/generate-config-usb.sh [3] https://github.com/ulfalizer/Kconfiglib
