Re: [PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg

[Michael Ellerman]

Kees Cook <keescook@xxxxxxxxxxxx> writes:
> Instead of full GNU diff (which smaller boot environments may not have),
> use "comm" which is more available.

Although using "comm" requires CONFIG_PRINTK_TIME=y doesn't it?

Which is probably fine, but should be mentioned.

And I guess for completeness you could add:

diff --git a/tools/testing/selftests/lkdtm/config b/tools/testing/selftests/lkdtm/config
index d874990e442b..ae88bfb163ff 100644
--- a/tools/testing/selftests/lkdtm/config
+++ b/tools/testing/selftests/lkdtm/config
@@ -1 +1,2 @@
 CONFIG_LKDTM=y
+CONFIG_PRINTK_TIME=y


cheers

> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Link: https://lore.kernel.org/lkml/CA+G9fYtHP+Gg+BrR_GkBMxu2oOi-_e9pATtpb6TVRswv1G1r1Q@xxxxxxxxxxxxxx
> Fixes: f131d9edc29d ("selftests/lkdtm: Don't clear dmesg when running tests")
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  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