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selftests/lkdtm: Don't clear dmesg when running tests

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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>
This commit is contained in:
Michael Ellerman 2020-05-08 16:53:55 +10:00 committed by Shuah Khan
parent adb571649c
commit f131d9edc2
1 changed files with 8 additions and 6 deletions
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14
tools/testing/selftests/lkdtm/run.sh
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@ -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