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SubjectRe: [PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg
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On 9/9/20 3:49 PM, Kees Cook wrote:
>
> On Fri, Jun 26, 2020 at 01:59:43PM -0700, Kees Cook wrote:
>> Instead of full GNU diff (which smaller boot environments may not have),
>> use "comm" which is more available.
>>
>> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
>> Link: https://lore.kernel.org/lkml/CA+G9fYtHP+Gg+BrR_GkBMxu2oOi-_e9pATtpb6TVRswv1G1r1Q@mail.gmail.com
>> Fixes: f131d9edc29d ("selftests/lkdtm: Don't clear dmesg when running tests")
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>
> Shuah, this really needs to land to fix lkdtm tests on busybox. Can
> you add this to -next? (Or is it better to direct this to Greg for the
> lkdtm tree?)
>
> Thanks!
>
> -Kees
>
>> ---
>> tools/testing/selftests/lkdtm/run.sh | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/lkdtm/run.sh b/tools/testing/selftests/lkdtm/run.sh
>> index 8383eb89d88a..5fe23009ae13 100755
>> --- a/tools/testing/selftests/lkdtm/run.sh
>> +++ b/tools/testing/selftests/lkdtm/run.sh
>> @@ -82,7 +82,7 @@ dmesg > "$DMESG"
>> ($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) || true
>>
>> # Record and dump the results
>> -dmesg | diff --changed-group-format='%>' --unchanged-group-format='' "$DMESG" - > "$LOG" || true
>> +dmesg | comm -13 "$DMESG" - > "$LOG" || true
>>
>> cat "$LOG"
>> # Check for expected output
>> --
>> 2.25.1
>>
>>
>> --
>> Kees Cook
>

Hi Kees,

You may want to consider a similar follow up to the one Miroslav made to
the livepatching equivalent:

https://lore.kernel.org/live-patching/nycvar.YFH.7.76.2008271528000.27422@cbobk.fhfr.pm/T/#m1c17812d2c005dd57e9a299a4a492026a156619e

basically 'comm' will complain if two lines from dmesg have the same
timestamp prefix and their text portions are not sorted.

Regards,

-- Joe

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