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
