Re: [PATCH v1 0/2] Add support to capture external module's SCM version

[Jessica Yu]

+++ 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