On Mon 2020-06-15 13:27:54, Joe Lawrence wrote:
> The dmesg utility already comes with a command line switch to omit
> kernel timestamps, let's use it instead of applying an extra regex to
> filter them out.
>
> Now without the '[timestamp]: ' prefix at the beginning of the log
> entry, revise the filtering regex to search for the 'livepatch:'
> subsystem prefix at the beginning of the line.
I wanted to push this patchset and run full test after each patch.
Suddenly the tests started to fail, for example:
$/tools/testing/selftests/livepatch> ./test-livepatch.sh
TEST: basic function patching ... ok
TEST: multiple livepatches ... not ok
--- expected
+++ result
@@ -1,3 +1,9 @@
+% echo 0 > /sys/kernel/livepatch/test_klp_livepatch/enabled
+livepatch: 'test_klp_livepatch': initializing unpatching transition
+livepatch: 'test_klp_livepatch': starting unpatching transition
+livepatch: 'test_klp_livepatch': completing unpatching transition
+livepatch: 'test_klp_livepatch': unpatching complete
+% rmmod test_klp_livepatch
% modprobe test_klp_livepatch
livepatch: enabling patch 'test_klp_livepatch'
livepatch: 'test_klp_livepatch': initializing patching transition
@@ -20,9 +26,3 @@ livepatch: 'test_klp_atomic_replace': co
livepatch: 'test_klp_atomic_replace': unpatching complete
% rmmod test_klp_atomic_replace
test_klp_livepatch: this has been live patched
-% echo 0 > /sys/kernel/livepatch/test_klp_livepatch/enabled
-livepatch: 'test_klp_livepatch': initializing unpatching transition
-livepatch: 'test_klp_livepatch': starting unpatching transition
-livepatch: 'test_klp_livepatch': completing unpatching transition
-livepatch: 'test_klp_livepatch': unpatching complete
-% rmmod test_klp_livepatch
ERROR: livepatch kselftest(s) failed
The problem is a combination of:
+ 1st patch that causes that old kernel messages are not cleared
+ 2nd patch that removes time stamps from the diff
+ lost the oldest messages because internal kernel log buffer overflow
+ run the same tests more times
As a result, the diff might match with an incomplete log from
the previous run.
Everything works when this 2nd patch is not commited. The timestamp
helps to distinguish old and new messages. The lost messages
are ignored thanks to the diff parameters:
--changed-group-format='%>' --unchanged-group-format=''
If you agree, I'll solve this problem by not committing this patch
into livepatch.git repo.
It would be great to add a comment that the timestamp is actually
important. But it might be done in a followup patch.
Best Regards,
Petr
> --- a/tools/testing/selftests/livepatch/functions.sh
> +++ b/tools/testing/selftests/livepatch/functions.sh
> @@ -272,9 +272,8 @@ function check_result {
> local expect="$*"
> local result
>
> - result=$(dmesg | diff --changed-group-format='%>' --unchanged-group-format='' "$SAVED_DMESG" - | \
> - grep -v 'tainting' | grep -e 'livepatch:' -e 'test_klp' | \
> - sed 's/^\[[ 0-9.]*\] //')
> + result=$(dmesg --notime | diff --changed-group-format='%>' --unchanged-group-format='' "$SAVED_DMESG" - | \
> + grep -v 'tainting' | grep -e '^livepatch:' -e 'test_klp')
>
> if [[ "$expect" == "$result" ]] ; then
> echo "ok"
> --
> 2.21.3
