selftests/lkdtm: Don't clear dmesg when running tests (f131d9ed) · Commits · 戴 / test

It is Very Rude to clear dmesg in test scripts. That's because the script may be part of a larger test run, and clearing dmesg potentially destroys the output of other tests. We can avoid using dmesg -c by saving the content of dmesg before the test, and then using diff to compare that to the dmesg afterward, producing a log with just the added lines. Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au> Acked-by:

Kees Cook <keescook@chromium.org> Signed-off-by:

Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/lkdtm/run.sh

+8 −6

Original line number	Diff line number	Diff line
		@@ -59,23 +59,25 @@ if [ -z "$expect" ]; then
		expect="call trace:"
		fi

		# Clear out dmesg for output reporting
		dmesg -c >/dev/null

		# Prepare log for report checking
		LOG=$(mktemp --tmpdir -t lkdtm-XXXXXX)
		LOG=$(mktemp --tmpdir -t lkdtm-log-XXXXXX)
		DMESG=$(mktemp --tmpdir -t lkdtm-dmesg-XXXXXX)
		cleanup() {
		rm -f "$LOG"
		rm -f "$LOG" "$DMESG"
		}
		trap cleanup EXIT

		# Save existing dmesg so we can detect new content below
		dmesg > "$DMESG"

		# Most shells yell about signals and we're expecting the "cat" process
		# to usually be killed by the kernel. So we have to run it in a sub-shell
		# and silence errors.
		($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) \|\| true

		# Record and dump the results
		dmesg -c >"$LOG"
		dmesg \| diff --changed-group-format='%>' --unchanged-group-format='' "$DMESG" - > "$LOG" \|\| true

		cat "$LOG"
		# Check for expected output
		if egrep -qi "$expect" "$LOG" ; then

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