+Steve Muckle - since I think this might affect things he is working on. On Thu, Mar 17, 2022 at 10:13 PM David Gow <davidgow@xxxxxxxxxx> wrote: > > When writing tests, it'd often be very useful to be able to intercept > calls to a function in the code being tested and replace it with a > test-specific stub. This has always been an obviously missing piece of > KUnit, and the solutions always involve some tradeoffs with cleanliness, > performance, or impact on non-test code. See the folowing document for > some of the challenges: > https://kunit.dev/mocking.html > > This series consists of two prototype patches which add support for this > sort of redirection to KUnit tests: > > 1: static_stub: Any function which might want to be intercepted adds a > call to a macro which checks if a test has redirected calls to it, and > calls the corresponding replacement. > > 2: ftrace_stub: Functions are intercepted using ftrace and livepatch. > This doesn't require adding a new prologue to each function being > replaced, but does have more dependencies (which restricts it to a small > number of architectures, not including UML), and doesn't work well with > inline functions. > > The API for both implementations is very similar, so it should be easy > to migrate from one to the other if necessary. Both of these > implementations restrict the redirection to the test context: it is > automatically undone after the KUnit test completes, and does not affect > calls in other threads. If CONFIG_KUNIT is not enabled, there should be > no overhead in either implementation. > > Does either (or both) of these features sound useful, and is this > sort-of API the right model? (Personally, I think there's a reasonable > scope for both.) Is anything obviously missing or wrong? Do the names, > descriptions etc. make any sense? > > Note that these patches are definitely still at the "prototype" level, > and things like error-handling, documentation, and testing are still > pretty sparse. There is also quite a bit of room for optimisation. > These'll all be improved for v1 if the concept seems good. > > Cheers, > -- David > > Daniel Latypov (1): > kunit: expose ftrace-based API for stubbing out functions during tests > > David Gow (1): > kunit: Expose 'static stub' API to redirect functions > > include/kunit/ftrace_stub.h | 84 +++++++++++++++++ > include/kunit/static_stub.h | 106 +++++++++++++++++++++ > lib/kunit/Kconfig | 11 +++ > lib/kunit/Makefile | 5 + > lib/kunit/ftrace_stub.c | 138 ++++++++++++++++++++++++++++ > lib/kunit/kunit-example-test.c | 64 +++++++++++++ > lib/kunit/static_stub.c | 125 +++++++++++++++++++++++++ > lib/kunit/stubs_example.kunitconfig | 11 +++ > 8 files changed, 544 insertions(+) > create mode 100644 include/kunit/ftrace_stub.h > create mode 100644 include/kunit/static_stub.h > create mode 100644 lib/kunit/ftrace_stub.c > create mode 100644 lib/kunit/static_stub.c > create mode 100644 lib/kunit/stubs_example.kunitconfig > > -- > 2.35.1.894.gb6a874cedc-goog >
