Re: [RFC PATCH v2 1/1] kern/dl: Add module version check

[Zhang Boyang]

Hi,

On 2022/12/22 14:31, Glenn Washburn wrote:
> On Wed, 21 Dec 2022 20:11:57 +0800
> Zhang Boyang <zhangboyang.id@gmail.com> wrote:
> > +      grub_printf_ (N_("warning: module %.63s has incorrect version:
> > %.63s != %s\n"),
> > +                   mod->name, modver, PACKAGE_VERSION);
>
> I don't quite like this, but I could live with it. I mostly don't like
> it because I don't want to get spammed with a lot of these warning
> messages. But maybe this is the best of the bad set of options.

I sent a V3 patch at 
https://lists.gnu.org/archive/html/grub-devel/2022-12/msg00280.html , in 
which can disable this warning at build time, however I personally don't 
like it.

I think preloading modules is a good solution for you. e.g. run `insmod 
foobar` before switching $root/$prefix. This also eliminate the 
possibility of GRUB crashing because of mismatched modules. For a 
comprehensive list of modules, please see $GRUB_MODULES in 
https://salsa.debian.org/grub-team/grub/-/blob/master/debian/build-efi-images

If you think this solution is good to you, I want to drop V3 and submit 
a improved V2 as V4, because it's cleaner.

> One thing to note is I believe that this will take GRUB out
> of graphical mode and put it into text mode. This doesn't affect me
> (right now) though.

I tested on i386-pc and x86_64-efi and there is no such behavior.

> Another thing is that, for the use case of loading a grub.cfg from a
> different GRUB installation, this message from version mismatched
> modules loaded in the sourcing of the script will be displayed for a
> fraction of a second until the menu from the sourced grub.cfg is
> displayed. So it may not be helpful for the user.

What about adding a 100ms sleep when the warning is displayed? By the 
way, this can also be workaround by preloading modules.

> This isn't likely an issue for loopback.cfg because usually the module
> loading is done implicitly and all the commands are generally inside
> the menu entries. In this case, printing to the screen seems like a
> good idea because directly after the module loading the commands will
> run, which might crash GRUB. So if the crash hangs the machine the user
> will see this message and have a clue.

Best Regards,
Zhang Boyang

> Glenn