Re: [PATCH] selftests/livepatch: filter 'taints' from dmesg comparison

[Miroslav Benes <mbenes@suse.cz>]

On Thu, 7 Nov 2019, Joe Lawrence wrote:

> On 11/7/19 9:53 AM, Miroslav Benes wrote:
> > On Thu, 7 Nov 2019, Joe Lawrence wrote:
> > 
> >> On 11/7/19 3:42 AM, Miroslav Benes wrote:
> >>> On Wed, 6 Nov 2019, Joe Lawrence wrote:
> >>>
> >>>> The livepatch selftests compare expected dmesg output to verify kernel
> >>>> behavior.  They currently filter out "tainting kernel with
> >>>> TAINT_LIVEPATCH" messages which may be logged when loading livepatch
> >>>> modules.
> >>>>
> >>>> Further filter the log to also drop "loading out-of-tree module taints
> >>>> kernel" messages in case the klp_test modules have been build without
> >>>> the in-tree module flag.
> >>>
> >>> That is true, but "tainting kernel with TAINT_LIVEPATCH" should be printed
> >>> out even in this case. check_modinfo_livepatch() is called for all modules
> >>> and relies on MODINFO(livepatch, Y).
> >>>   > So either the bug is elsewhere or I need one more cup of tea.
> > 
> > Ok, the above is not relevant here.
> > 
> > I'm only wondering about the execution steps, because supporting modules
> > lib/livepatch/ should be built as in-tree. No?
> >   
> 
> Ah, I see.  Well as you noted they are modprobed, so theoretically they could
> come from anywhere OOT, right?

Yes.
 
> In my test, I had a kernel tree, but only wanted to build the test modules.
> Once I did a 'make modules SUBDIR=' or 'make M= ...' KBUILD_EXTMOD got flipped
> on and the modules lost in-tree status.  No amount of googling could tell me
> how to build a single in-tree directory of modules :(

"make lib/livepatch/test_klp_livepatch.ko" should do the trick. "make 
lib/livepatch/" only builds the object files and I haven't found a way to 
make it link .ko modules other than specifying them one by one directly.

> And then it seemed that
> opening the tests for OOT modules was reasonable anyway.

That's an interesting idea. If a module is in tree, it is under our 
control. So we know what "testing capabilities" it offers. I guess that 
with OOT testing modules the selftests would have to be smarter.

Miroslav