| Message ID | 20220713005221.1926290-1-davidgow@google.com |
|---|---|
| State | Accepted |
| Commit | 41a55567b9e31cb852670684404654ec4fd0d8d6 |
| Headers | show |
| Series | module: kunit: Load .kunit_test_suites section when CONFIG_KUNIT=m | expand |
On Wed, Jul 13, 2022 at 08:52:20AM +0800, David Gow 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. > This commit log does not describe what functionality is broken exactly without this commit. What functionality from kunit is provided when .kunit_test_suites is available? > Also load this when KUnit is enabled as a module: it'll not be usable > unless KUnit is loaded, What benefit is there to load a kunit module without kunit? > but such modules are likely to depend on KUnit > anyway, so it's unlikely to ever be loaded needlessly. > > Fixes: 3d6e44623841 ("kunit: unify module and builtin suite definitions") > Signed-off-by: David Gow <davidgow@google.com>
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@google.com> 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. > > 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. Luis
On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@kernel.org> 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@google.com> 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
On Wed, Jul 20, 2022 at 1:57 AM Luis Chamberlain <mcgrof@kernel.org> wrote: > > On Wed, Jul 13, 2022 at 08:52:20AM +0800, David Gow 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. > > > > This commit log does not describe what functionality is broken exactly > without this commit. What functionality from kunit is provided when > .kunit_test_suites is available? > Sorry: the explanation is a bit obtuse, I admit. Basically, when kunit itself is built as a module, no tests run. This is because the code to load the .kunit_test_suites section is compiled out if kunit is not built-in, but it should be present even if kunit is built as a module. > > Also load this when KUnit is enabled as a module: it'll not be usable > > unless KUnit is loaded, > > What benefit is there to load a kunit module without kunit? > None whatsoever, and it should be impossible. This was just rationale for the overhead of loading the section being likely insignificant, but it's worded pretty poorly. > > but such modules are likely to depend on KUnit > > anyway, so it's unlikely to ever be loaded needlessly. > > > > Fixes: 3d6e44623841 ("kunit: unify module and builtin suite definitions") > > Signed-off-by: David Gow <davidgow@google.com> I'll update the commit message when I send a new version of this out. Cheers, -- David
On Wed, Jul 20, 2022 at 05:26:02PM +0800, David Gow wrote: > On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@kernel.org> 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@google.com> 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 This can be fixed with a request_module() call. And since this is a generic requirement, you can have the wrappers do it for you. > 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. You can prevent that by refcounting the kunit module / symbols, by each test. Luis
On Thu, Jul 21, 2022 at 4:29 AM Luis Chamberlain <mcgrof@kernel.org> wrote: > > On Wed, Jul 20, 2022 at 05:26:02PM +0800, David Gow wrote: > > On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@kernel.org> 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@google.com> 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 > > This can be fixed with a request_module() call. And since this is a > generic requirement, you can have the wrappers do it for you. > I'm not convinced that this is worth the trouble, particularly since KUnit needs to be loaded already before any test-specific code in a module is run. _Maybe_ we could put it in the code which looks for the .kunit_test_suites section, but even then it seems like a bit of an ugly hack. Personally, I'm not particularly concerned about test modules failing to load if KUnit isn't already present -- if people want all of a module's dependencies loaded, that's what modprobe is for. That being said, if you feel particularly strongly about it, this is something we can look at. Let's do so in a separate patch though: this one does fix a regression as-is. > > 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. > > You can prevent that by refcounting the kunit module / symbols, by each test. > Again, I don't think KUnit is any more special than any other module here. I don't think we need to do this ourselves, as it shouldn't be possible to remove kunit without first removing any dependent modules. Of course, happy to look into this again if anyone can come up with an actual crash, but I'd rather get this fix in first. At the very least, this patch shouldn't introduce any _new_ issues. Cheers, -- David > Luis
On Thu, Jul 28, 2022 at 4:42 AM David Gow <davidgow@google.com> wrote: > > On Thu, Jul 21, 2022 at 4:29 AM Luis Chamberlain <mcgrof@kernel.org> wrote: > > > > On Wed, Jul 20, 2022 at 05:26:02PM +0800, David Gow wrote: > > > On Wed, Jul 20, 2022 at 1:58 AM Luis Chamberlain <mcgrof@kernel.org> 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@google.com> 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 > > > > This can be fixed with a request_module() call. And since this is a > > generic requirement, you can have the wrappers do it for you. > > > > I'm not convinced that this is worth the trouble, particularly since > KUnit needs to be loaded already before any test-specific code in a > module is run. _Maybe_ we could put it in the code which looks for the > .kunit_test_suites section, but even then it seems like a bit of an > ugly hack. > > Personally, I'm not particularly concerned about test modules failing > to load if KUnit isn't already present -- if people want all of a > module's dependencies loaded, that's what modprobe is for. > > That being said, if you feel particularly strongly about it, this is > something we can look at. Let's do so in a separate patch though: this > one does fix a regression as-is. I agree. We need a fix for 3d6e44623841 to go in for 5.20 - we've gotten several complaints about it. This patch seems to accomplish that. I am not an expert on the module stuff by any means, so I am absolutely open to continuing this discussion in a follow-up patch, but I think we need this fix now. If no one objects, I am going to ask Shuah to take this patch. > > > 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. > > > > You can prevent that by refcounting the kunit module / symbols, by each test. > > > > Again, I don't think KUnit is any more special than any other module > here. I don't think we need to do this ourselves, as it shouldn't be > possible to remove kunit without first removing any dependent modules. > > Of course, happy to look into this again if anyone can come up with an > actual crash, but I'd rather get this fix in first. At the very least, > this patch shouldn't introduce any _new_ issues. Sounds good. I will send my Reviewed-by in a separate email, as per usual. Cheers
diff --git a/kernel/module/main.c b/kernel/module/main.c index 324a770f789c..222a0b7263b6 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2094,7 +2094,7 @@ static int find_module_sections(struct module *mod, struct load_info *info) sizeof(*mod->static_call_sites), &mod->num_static_call_sites); #endif -#ifdef CONFIG_KUNIT +#if IS_ENABLED(CONFIG_KUNIT) mod->kunit_suites = section_objs(info, ".kunit_test_suites", sizeof(*mod->kunit_suites), &mod->num_kunit_suites);
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. Fixes: 3d6e44623841 ("kunit: unify module and builtin suite definitions") Signed-off-by: David Gow <davidgow@google.com> --- kernel/module/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)