On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote: > > On Wed, Jul 13, 2022 at 08:24:32AM -0700, Daniel Latypov wrote: > > On Tue, Jul 12, 2022 at 5:52 PM David Gow <davidgow@xxxxxxxxxx> wrote: > > > > > > The new KUnit module handling has KUnit test suites listed in a > > > .kunit_test_suites section of each module. This should be loaded when > > > the module is, but at the moment this only happens if KUnit is built-in. > > > > > > Also load this when KUnit is enabled as a module: it'll not be usable > > > unless KUnit is loaded, but such modules are likely to depend on KUnit > > > anyway, so it's unlikely to ever be loaded needlessly. > > > > This seems reasonable to me. > > > > Question: what happens in this case? > > 1. insmod <test-module> > > 2. insmod kunit > > 3. rmmod <test-module> > > > > I think on 3, we'll call the cleanup code, __kunit_test_suites_exit(), > > for <test-module>, I think? > > But we never called __kunit_test_suites_init(). > > My fear is what breaks as a result of this precondition break. I don't think this should be possible: any module with KUnit tests will depend on the 'kunit' module (or, at least, kunit symbols), so shouldn't load without kunit already present. If modprobe is used, kunit will automatically be loaded. If insmod is used directly, loading the first module should error out with something like: [ 82.393629] list_test: loading test module taints kernel. [ 82.409607] list_test: Unknown symbol kunit_binary_ptr_assert_format (err -2) [ 82.409657] list_test: Unknown symbol kunit_do_failed_assertion (err -2) [ 82.409799] list_test: Unknown symbol kunit_binary_assert_format (err -2) [ 82.409820] list_test: Unknown symbol kunit_unary_assert_format (err -2) insmod: ERROR: could not insert module /lib/modules/5.19.0-rc1-15284-g9ec67db0c271/kernel/lib/list-test.ko: Unknown symbol in module Maybe you could get into some trouble by force-removing modules at various points, but you're in undefined behaviour generally at that point, so I don't think there's much point going out-of-our-way to try to support that. > > > > E.g. In the case that CONFIG_KUNIT_DEBUGFS is enabled, this includes a > > call to kunit_debugfs_destroy_suite() with no previous call to > > kunit_debugfs_create_suite(). > > That will include a call to debugfs_remove_recursive(suite->debugfs), > > where suite->debugfs is an uninitialized pointer. > > > > Maybe we can treat it as "undefined behavior" for now and proceed with > > this patch. > > > > In terms of long-term fixes, perhaps insmod kunit could trigger it to > > 1. run all built-in tests (IIUC, it doesn't right now) > > 2. run all the tests of currently loaded modules > > 3. track which modules already ran so if you rmmod + insmod kunit > > again, it won't rerun tests? > > Let's please address these considerations. > Again, I think the module and Kconfig dependencies should prevent these situations from ever arising. It shouldn't be possible to have any built-in tests if kunit is not itself built-in, so case (1) can't occur. Equally, it shouldn't be possible to load any test modules before the kunit module is loaded, so (2) can't occur. And rmmod kunit will give an error if there are any test modules loaded: "rmmod: ERROR: Module kunit is in use by: list_test", so (3) can't occur. The only similar situation to (3) I can think of is where both the test modules and kunit are rmmod-ed and reloaded. I think we'd want to re-run the tests in that case, so tracking which modules already ran would be counterproductive. In short, I _think_ what we're doing now should be correct, and the cases above are all prevented by module dependencies. But do let me know if I'm missing something... Cheers, -- David
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