On Tue, Nov 24, 2020 at 09:24:26PM +0100, Greg Kroah-Hartman wrote: > On Tue, Nov 24, 2020 at 10:31:39AM -0800, William Mcvicker wrote: > > On Tue, Nov 24, 2020 at 07:12:40PM +0100, Greg Kroah-Hartman wrote: > > > On Tue, Nov 24, 2020 at 10:05:16AM -0800, William Mcvicker wrote: > > > > On Tue, Nov 24, 2020 at 10:31:18AM +0100, Jessica Yu wrote: > > > > > +++ William Mcvicker [23/11/20 14:13 -0800]: > > > > > > On Mon, Nov 23, 2020 at 09:02:57AM +0000, Christoph Hellwig wrote: > > > > > > > On Sat, Nov 21, 2020 at 01:16:49AM +0000, Will McVicker wrote: > > > > > > > > These two patches add module support to capture an external > > > > > > > > module's SCM > > > > > > > > version as a MODULE_INFO() attribute. This allows users to > > > > > > > > identity the SCM > > > > > > > > version of a given kernel module by using the modinfo tool or > > > > > > > > on the device > > > > > > > > via sysfs: > > > > > > > > > > > > > > As this obviously is of no use for in-tree modules it falls under > > > > > > > the we > > > > > > > don't add code to support things that are not in tree rule and > > > > > > > has no > > > > > > > business in the kernel. > > > > > > > > > > > > Hi Christoph, > > > > > > > > > > > > Ah sorry, I didn't intend this to come across as only for external > > > > > > modules. > > > > > > That just seemed like the easiest way to explain how the scmversion > > > > > > attribute > > > > > > can be different from the vermagic. We mainly need this for in-tree > > > > > > kernel > > > > > > modules since that's where most our drivers are. Let me re-phrase > > > > > > this with > > > > > > that in mind. Basically, I like to look at this as an improved > > > > > > version of the > > > > > > existing srcversion module attribute since it allows you to easily > > > > > > identify the > > > > > > module version with a quick SCM version string check instead of > > > > > > doing a full > > > > > > checksum on the module source. > > > > > > > > > > > > For example, we have a setup to test kernel changes on the hikey > > > > > > and db845c > > > > > > devices without updating the kernel modules. Without this > > > > > > scmversion module > > > > > > attribute, you can't identify the original module version using > > > > > > `uname > > > > > > -r`. And for kernel modules in the initramfs, you can't even use > > > > > > modinfo to get > > > > > > the module vermagic. With this patch, you are able to get the SCM > > > > > > version for > > > > > > *all* kernel modules (on disk and in the initramfs) via the sysfs > > > > > > node: > > > > > > /sys/module/<mod>/scmversion. This also works the other way around > > > > > > when > > > > > > developers update their kernel modules to fix some bug (like a > > > > > > security > > > > > > vulnerability) but don't need to update the full kernel. > > > > > > > > > > Hi Will, > > > > > > > > > > If this were also intended for in-tree kernel modules, then why do > > > > > intree modules only get the UTS_RELEASE string in their scmversion > > > > > field, which basically already exists in the vermagic? Or do you plan > > > > > to change that? > > > > > > > > > > Jessica > > > > > > > > Hi Jessica, > > > > > > > > Thanks for asking! The reason in-tree kernel modules get the > > > > UTS_RELEASE string > > > > is for a few reasons: > > > > > > > > (1) It contains the SCM version (since UTS_RELEASE has that). > > > > (2) It allows you to get the SCM version via the sysfs node (useful for > > > > modules > > > > in the initramfs). > > > > (3) It helps identify that that particular kernel module was in-tree > > > > when > > > > originally compiled. > > > > (4) Using UTS_RELEASE also allows us to respect the privacy of kernels > > > > with > > > > "# CONFIG_LOCALVERSION_AUTO is not set" by not including the SCM > > > > version in the > > > > module scmversion attribute. > > > > > > > > Now, if we don't care about knowing if a module was in-tree or not > > > > (since > > > > we only care about in-tree modules here anyway), I can update the patch > > > > to have > > > > a consistent format regardless of in-tree or external. Personally, I > > > > like the > > > > UTS_RELEASE version better because it gives me more information from > > > > the sysfs > > > > node which is useful when debugging issues related to modules loaded in > > > > initramfs. > > > > > > We already know if a module was built in-or-out of tree, the "O" taint > > > flag is set, so that information is already in the module today, right? > > > Can't that be used somehow here? > > > > > > thanks, > > > > > > greg k-h > > Hi Greg, > > > > Let me prefix this with this, I do see the benefits of having a consistent > > scmversion format for intree and out-of-tree modules. So I'm happy to fix > > that > > in the next patchset. > > > > Now, I could be wrong, but I believe the taint flag is only printed when the > > module is loaded: > > > > XXX: loading out-of-tree module taints kernel. > > > > or when there's a kernel WARNING or kernel crash. But that assumes you have > > the > > full logs when the kernel booted or you have a full crash stack in the > > kernel. > > > > Modinfo does have an attribute that indicates if the module is intree or > > not: > > > > $ modinfo -F intree out_dir/./net/netfilter/nf_log_common.ko > > Y > > > > But that is not queriable via sysfs. > > Look at the file in /sys/modules/MODULENAME/taint > > That should show you this value. > > > Ideally, we'd like to be able to get all > > this information via sysfs so that it can be captured in our bug reports. > > I think you already have it :) > > This is independent of your "source code id value" idea though... > > thanks, > > greg k-h
Thanks for pointing out the taint sysfs node. With that, the only reason I can see using UTS_RELEASE over always using the SCM version is to immediately get the extra version information like the 5.10.0-rc4 part without having to extract that from the SCM version. For scripting reasons and consistency I think it would be best to just stick to using the SCM version alone and not UTS_RELEASE. Unless someone objects, I'll update v2 to use the SCM version (not UTS_RELEASE) always. Thanks, Will
