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Date:   Tue, 30 Jun 2020 14:53:10 -0400
From:   Joe Lawrence <joe.lawrence@redhat.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Shuah Khan <shuah@kernel.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        Petr Mladek <pmladek@suse.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg
Message-ID: <20200630185310.GA29805@redhat.com>
References: <202006261358.3E8AA623A9@keescook>
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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>
> ---
>  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

I'm not familiar with running lkdtm tests, but I copied the same fixup
for the livepatching selftests and "comm" slides in nicely over there,
so,

Acked-by: Joe Lawrence <joe.lawrence@redhat.com>

-- Joe