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

[Joe Lawrence <joe.lawrence@redhat.com>]

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.
 >

I'm only half a cup in this morning myself, but...

In my scenario, I saw in the kernel log:

   % modprobe test_klp_livepatch
   test_klp_livepatch: loading out-of-tree module taints kernel.
   test_klp_livepatch: module verification failed: signature and/or 
required key missing - tainting kernel
   ...

and because check_result() only removes 'tainting' with grep -v, the 
expected log message failed to match with the actual filtered message 
because of the first 'taints' message.

So this change just adds more to the filtered out strings:

   result = dmesg | grep -v <filtered out strings> | grep <interesting 
strings>

BTW, none of the callers of check_result() bother to include either 
taint message since I think they are only ever emitted on the first 
occurance.

-- Joe