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.kamb...@linaro.org>
Link: 
https://lore.kernel.org/lkml/ca+g9fythp+gg+brr_gkbmxu2ooi-_e9pattpb6tvrswv1g1...@mail.gmail.com
Fixes: f131d9edc29d ("selftests/lkdtm: Don't clear dmesg when running tests")
Signed-off-by: Kees Cook <keesc...@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.7.76.2008271528000.27...@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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