On Sat, Jan 28, 2023 at 2:49 AM David Gow <davidgow@xxxxxxxxxx> wrote: > > Add a simple way of redirecting calls to functions by including a > special prologue in the "real" function which checks to see if the > replacement function should be called (and, if so, calls it). > > To redirect calls to a function, make the first (non-declaration) line > of the function: > > KUNIT_STATIC_STUB_REDIRECT(function_name, [function arguments]); > > (This will compile away to nothing if KUnit is not enabled, otherwise it > will check if a redirection is active, call the replacement function, > and return. This check is protected by a static branch, so has very > little overhead when there are no KUnit tests running.) > > Calls to the real function can be redirected to a replacement using: > > kunit_activate_static_stub(test, real_fn, replacement_fn); > > The redirection will only affect calls made from within the kthread of > the current test, and will be automatically disabled when the test > completes. It can also be manually disabled with > kunit_deactivate_static_stub(). > > The 'example' KUnit test suite has a more complete example. > > Co-developed-by: Daniel Latypov <dlatypov@xxxxxxxxxx> > Signed-off-by: Daniel Latypov <dlatypov@xxxxxxxxxx> > Signed-off-by: David Gow <davidgow@xxxxxxxxxx> > Reviewed-by: Brendan Higgins <brendanhiggins@xxxxxxxxxx> Still looks good overall to me, but I see one nit: > --- > > This patch depends upon the 'hooks' implementation in > https://lore.kernel.org/linux-kselftest/20230128071007.1134942-1-davidgow@xxxxxxxxxx/ > > Note that checkpatch.pl does warn about control flow in the > KUNIT_STATIC_STUB_REDIRECT() macro. This is an intentional design choice > (we think it makes the feature easier to use), though if there are > strong objections, we can of course reconsider. > > Changes since v1: > https://lore.kernel.org/all/20221208061841.2186447-2-davidgow@xxxxxxxxxx/ > - Adapted to use the "hooks" mechanism > - See: https://lore.kernel.org/linux-kselftest/20230128071007.1134942-1-davidgow@xxxxxxxxxx/ > - Now works when KUnit itself is compiled as a module (CONFIG_KUNIT=m) > > Changes since RFC v2: > https://lore.kernel.org/linux-kselftest/20220910212804.670622-2-davidgow@xxxxxxxxxx/ > - Now uses the kunit_get_current_test() function, which uses the static > key to reduce overhead. > - Thanks Kees for the suggestion. > - Note that this does prevent redirections from working when > CONFIG_KUNIT=m -- this is a restriction of kunit_get_current_test() > which will be removed in a future patch. > - Several tidy-ups to the inline documentation. > > Changes since RFC v1: > https://lore.kernel.org/lkml/20220318021314.3225240-2-davidgow@xxxxxxxxxx/ > - Use typecheck_fn() to fix typechecking in some cases (thanks Brendan) > > --- > include/kunit/static_stub.h | 113 ++++++++++++++++++++++++++++++ > include/kunit/test-bug.h | 1 + > lib/kunit/Makefile | 1 + > lib/kunit/hooks-impl.h | 2 + > lib/kunit/kunit-example-test.c | 38 ++++++++++ > lib/kunit/static_stub.c | 123 +++++++++++++++++++++++++++++++++ > 6 files changed, 278 insertions(+) > create mode 100644 include/kunit/static_stub.h > create mode 100644 lib/kunit/static_stub.c > > diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h > new file mode 100644 > index 000000000000..047b68d65f1a > --- /dev/null > +++ b/include/kunit/static_stub.h > @@ -0,0 +1,113 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * KUnit function redirection (static stubbing) API. > + * > + * Copyright (C) 2022, Google LLC. > + * Author: David Gow <davidgow@xxxxxxxxxx> > + */ > +#ifndef _KUNIT_STATIC_STUB_H > +#define _KUNIT_STATIC_STUB_H > + > +#if !IS_ENABLED(CONFIG_KUNIT) > + > +/* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */ > +#define KUNIT_TRIGGER_STATIC_STUB(real_fn_name, args...) do {} while (0) > + > +#else > + > +#include <kunit/test.h> > +#include <kunit/test-bug.h> > + > +#include <linux/compiler.h> /* for {un,}likely() */ > +#include <linux/sched.h> /* for task_struct */ > + > + > +/** > + * KUNIT_STATIC_STUB_REDIRECT() - call a replacement 'static stub' if one exists > + * @real_fn_name: The name of this function (as an identifier, not a string) > + * @args: All of the arguments passed to this function > + * > + * This is a function prologue which is used to allow calls to the current > + * function to be redirected by a KUnit test. KUnit tests can call > + * kunit_activate_static_stub() to pass a replacement function in. The > + * replacement function will be called by KUNIT_TRIGGER_STATIC_STUB(), which > + * will then return from the function. If the caller is not in a KUnit context, > + * the function will continue execution as normal. > + * > + * Example: > + * > + * .. code-block:: c > + * > + * int real_func(int n) > + * { > + * KUNIT_STATIC_STUB_REDIRECT(real_func, n); > + * return 0; > + * } > + * > + * void replacement_func(int n) nit: Pretty sure the return type should be `int` > + * { > + * return 42; > + * } [...]
