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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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Yafang Shao
5d791d3396
CONFIG_DEBUG_KOBJECT makes kobject_add_internal(), kobject_uevent_env(), fill_kobj_path() and friends emit pr_debug() messages, and CONFIG_DEBUG_KOBJECT_RELEASE makes kobject_release() emit a pr_info() for every delayed kobject free. All of these carry the "kobject:" prefix via pr_fmt(), e.g.: # --- expected # +++ result # @@ -1,7 +1,13 @@ # % insmod test_modules/test_klp_livepatch.ko # +kobject: 'test_klp_livepatch' (000000009dbf565e): kobject_add_internal: parent: 'module', set: 'module' # +kobject: 'holders' (000000002856f0ae): kobject_add_internal: parent: 'test_klp_livepatch', set: '<NULL>' # +kobject: 'test_klp_livepatch' (00000000dcae1113): kobject_add_internal: parent: 'livepatch', set: '<NULL>' # +kobject: 'vmlinux' (000000007b8837e6): kobject_add_internal: parent: 'test_klp_livepatch', set: '<NULL>' # livepatch: enabling patch 'test_klp_livepatch' # livepatch: 'test_klp_livepatch': initializing patching transition # livepatch: 'test_klp_livepatch': starting patching transition # +kobject: 'test_klp_livepatch' (000000009dbf565e): kobject_uevent_env # +kobject: 'test_klp_livepatch' (000000009dbf565e): fill_kobj_path: path = '/module/test_klp_livepatch' # livepatch: 'test_klp_livepatch': completing patching transition # livepatch: 'test_klp_livepatch': patching complete # % echo 0 > /sys/kernel/livepatch/test_klp_livepatch/enabled # @@ -9,4 +15,17 @@ livepatch: 'test_klp_livepatch': initial # livepatch: 'test_klp_livepatch': starting unpatching transition # livepatch: 'test_klp_livepatch': completing unpatching transition # livepatch: 'test_klp_livepatch': unpatching complete # +kobject: 'test_klp_livepatch' (00000000dcae1113): kobject_release, parent 00000000f8785d63 (delayed 2000) # +kobject: 'test_klp_livepatch' (00000000dcae1113): kobject_cleanup, parent 00000000f8785d63 # +kobject: 'test_klp_livepatch' (00000000dcae1113): auto cleanup kobject_del # +kobject: 'test_klp_livepatch' (00000000dcae1113): calling ktype release # +kobject: 'test_klp_livepatch': free name # % rmmod test_klp_livepatch # +kobject: 'test_klp_livepatch' (000000009dbf565e): kobject_release, parent 0000000052e5c022 (delayed 3000) # +kobject: 'test_klp_livepatch' (000000009dbf565e): kobject_cleanup, parent 0000000052e5c022 # +kobject: 'test_klp_livepatch' (000000009dbf565e): auto cleanup kobject_del # +kobject: 'test_klp_livepatch' (000000009dbf565e): auto cleanup 'remove' event # +kobject: 'test_klp_livepatch' (000000009dbf565e): kobject_uevent_env # +kobject: 'test_klp_livepatch' (000000009dbf565e): fill_kobj_path: path = '/module/test_klp_livepatch' # +kobject: 'test_klp_livepatch' (000000009dbf565e): calling ktype release # +kobject: 'test_klp_livepatch': free name # # ERROR: livepatch kselftest(s) failed not ok 1 selftests: livepatch: test-livepatch.sh # exit=1 The livepatch test modules' kobjects are named "test_klp_*", so these lines match the check_result() grep for "test_klp" and leak into the result. The extra lines no longer match the expected output, so the selftests fail when either debug config is enabled. Filtering out every "kobject:" line also hides real WARN()s, e.g. the one kobject_get() emits for an object whose refcount was not initialized. Filtering with "dmesg --level=..." is not enough either, since the tests enable livepatch pr_debug() through dynamic_debug/control and expect its messages. Read the log with "dmesg --raw" and drop only the debug-level messages without the "livepatch:" prefix, plus the specific delayed-release info message. Suggested-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Acked-by: Song Liu <song@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Tested-by: Petr Mladek <pmladek@suse.com> Link: https://patch.msgid.link/20260830054857.64758-3-laoar.shao@gmail.com Signed-off-by: Petr Mladek <pmladek@suse.com>
==================== Livepatch Self Tests ==================== This is a small set of sanity tests for the kernel livepatching. The test suite loads and unloads several test kernel modules to verify livepatch behavior. Debug information is logged to the kernel's message buffer and parsed for expected messages. (Note: the tests will compare the message buffer for only the duration of each individual test.) Config ------ Set CONFIG_LIVEPATCH=y option and it's prerequisites. Building the tests ------------------ To only build the tests without running them, run: % make -C tools/testing/selftests/livepatch The command above will compile all test modules and test programs, making them ready to be packaged if so desired. Running the tests ----------------- Test kernel modules are built before running the livepatch selftests. The modules are located under test_modules directory, and are built as out-of-tree modules. This is specially useful since the same sources can be built and tested on systems with different kABI, ensuring they the tests are backwards compatible. The modules will be loaded by the test scripts using insmod. To run the livepatch selftests, from the top of the kernel source tree: % make -C tools/testing/selftests TARGETS=livepatch run_tests or % make kselftest TARGETS=livepatch Adding tests ------------ See the common functions.sh file for the existing collection of utility functions, most importantly setup_config(), start_test() and check_result(). The latter function greps the kernel's ring buffer for "livepatch:" and "test_klp" strings, so tests be sure to include one of those strings for result comparison. Other utility functions include general module loading and livepatch loading helpers (waiting for patch transitions, sysfs entries, etc.)