[PATCH v2 0/6] kunit: Add macros to help write more complex tests

[PATCH v2 0/6] kunit: Add macros to help write more complex tests

[Michal Wajdeczko]

v1: https://groups.google.com/g/kunit-dev/c/f4LIMLyofj8
v2: make it more complex and attempt to be thread safe
    s/FIXED_STUB/GLOBAL_STUB (David, Lucas)
    make it little more thread safe (Rae, David)
    wait until stub call finishes before test end (David)
    wait until stub call finishes before changing stub (David)
    allow stub deactivation (Rae)
    prefer kunit log (David)
    add simple selftest (Michal)
    also introduce ONLY_IF_KUNIT macro (Michal)

Sample output from the tests:

    $ tools/testing/kunit/kunit.py run *example*.*global* \
        --kunitconfig lib/kunit/.kunitconfig --raw_output

    KTAP version 1
    1..1
    # example: initializing suite
    KTAP version 1
    # Subtest: example
    # module: kunit_example_test
    1..1
    # example_global_stub_test: initializing
    # example_global_stub_test: add_two: redirecting to subtract_one
    # example_global_stub_test: add_two: redirecting to subtract_one
    # example_global_stub_test: cleaning up
    ok 1 example_global_stub_test
    # example: exiting suite
    ok 1 example

    $ tools/testing/kunit/kunit.py run *global*.*global* \
        --kunitconfig lib/kunit/.kunitconfig --raw_output

    KTAP version 1
    1..1
        KTAP version 1
        # Subtest: kunit_global_stub
        # module: kunit_test
        1..4
        # kunit_global_stub_test_activate: real_void_func: redirecting to replacement_void_func
        # kunit_global_stub_test_activate: real_func: redirecting to replacement_func
        # kunit_global_stub_test_activate: real_func: redirecting to replacement_func
        # kunit_global_stub_test_activate: real_func: redirecting to other_replacement_func
        # kunit_global_stub_test_activate: real_func: redirecting to other_replacement_func
        # kunit_global_stub_test_activate: real_func: redirecting to super_replacement_func
        # kunit_global_stub_test_activate: real_func: redirecting to super_replacement_func
        ok 1 kunit_global_stub_test_activate
        ok 2 kunit_global_stub_test_deactivate
        # kunit_global_stub_test_slow_deactivate: real_func: redirecting to slow_replacement_func
        # kunit_global_stub_test_slow_deactivate: real_func: redirecting to slow_replacement_func
        # kunit_global_stub_test_slow_deactivate: waiting for slow_replacement_func
        # kunit_global_stub_test_slow_deactivate.speed: slow
        ok 3 kunit_global_stub_test_slow_deactivate
        # kunit_global_stub_test_slow_replace: real_func: redirecting to slow_replacement_func
        # kunit_global_stub_test_slow_replace: real_func: redirecting to slow_replacement_func
        # kunit_global_stub_test_slow_replace: waiting for slow_replacement_func
        # kunit_global_stub_test_slow_replace: real_func: redirecting to other_replacement_func
        # kunit_global_stub_test_slow_replace.speed: slow
        ok 4 kunit_global_stub_test_slow_replace
    # kunit_global_stub: pass:4 fail:0 skip:0 total:4
    # Totals: pass:4 fail:0 skip:0 total:4
    ok 1 kunit_global_stub

Cc: Rae Moar <rmoar@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>

Michal Wajdeczko (6):
  kunit: Introduce kunit_is_running()
  kunit: Add macro to conditionally expose declarations to tests
  kunit: Add macro to conditionally expose expressions to tests
  kunit: Allow function redirection outside of the KUnit thread
  kunit: Add example with alternate function redirection method
  kunit: Add some selftests for global stub redirection macros

 include/kunit/static_stub.h    | 158 ++++++++++++++++++++
 include/kunit/test-bug.h       |  12 +-
 include/kunit/visibility.h     |  16 +++
 lib/kunit/kunit-example-test.c |  67 +++++++++
 lib/kunit/kunit-test.c         | 254 ++++++++++++++++++++++++++++++++-
 lib/kunit/static_stub.c        |  49 +++++++
 6 files changed, 553 insertions(+), 3 deletions(-)

-- 
2.43.0

[PATCH v2 1/6] kunit: Introduce kunit_is_running()

[Michal Wajdeczko]

Wrap uses of the static key 'kunit_running' into a helper macro
to allow future checks to be placed in the code residing outside
of the CONFIG_KUNIT. We will start using this in upcoming patch.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: David Gow <davidgow@google.com>
---
 include/kunit/test-bug.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/kunit/test-bug.h b/include/kunit/test-bug.h
index 47aa8f21ccce..e8ea3bab7250 100644
--- a/include/kunit/test-bug.h
+++ b/include/kunit/test-bug.h
@@ -25,6 +25,13 @@ extern struct kunit_hooks_table {
 	void *(*get_static_stub_address)(struct kunit *test, void *real_fn_addr);
 } kunit_hooks;
 
+/**
+ * kunit_is_running() - True, if KUnit test is currently running.
+ *
+ * If CONFIG_KUNIT is not enabled, it will compile down to a false.
+ */
+#define kunit_is_running() static_branch_unlikely(&kunit_running)
+
 /**
  * kunit_get_current_test() - Return a pointer to the currently running
  *			      KUnit test.
@@ -40,7 +47,7 @@ extern struct kunit_hooks_table {
  */
 static inline struct kunit *kunit_get_current_test(void)
 {
-	if (!static_branch_unlikely(&kunit_running))
+	if (!kunit_is_running())
 		return NULL;
 
 	return current->kunit_test;
@@ -53,7 +60,7 @@ static inline struct kunit *kunit_get_current_test(void)
  * If a KUnit test is running in the current task, mark that test as failed.
  */
 #define kunit_fail_current_test(fmt, ...) do {					\
-		if (static_branch_unlikely(&kunit_running)) {			\
+		if (kunit_is_running()) {					\
 			/* Guaranteed to be non-NULL when kunit_running true*/	\
 			kunit_hooks.fail_current_test(__FILE__, __LINE__,	\
 						  fmt, ##__VA_ARGS__);		\
@@ -64,6 +71,7 @@ static inline struct kunit *kunit_get_current_test(void)
 
 static inline struct kunit *kunit_get_current_test(void) { return NULL; }
 
+#define kunit_is_running() false
 #define kunit_fail_current_test(fmt, ...) do {} while (0)
 
 #endif
-- 
2.43.0

[PATCH v2 2/6] kunit: Add macro to conditionally expose declarations to tests

[Michal Wajdeczko]

The DECLARE_IF_KUNIT macro will introduces identifiers only if
CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
no identifiers from the param list will be defined.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
---
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
---
 include/kunit/visibility.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
index 0dfe35feeec6..1c23773f826c 100644
--- a/include/kunit/visibility.h
+++ b/include/kunit/visibility.h
@@ -11,6 +11,13 @@
 #define _KUNIT_VISIBILITY_H
 
 #if IS_ENABLED(CONFIG_KUNIT)
+    /**
+     * DECLARE_IF_KUNIT - A macro that introduces identifiers only if
+     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
+     * no identifiers will be defined.
+     * @body: identifiers to be introduced conditionally
+     */
+    #define DECLARE_IF_KUNIT(body...)	body
     /**
      * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
      * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
@@ -26,6 +33,7 @@
     #define EXPORT_SYMBOL_IF_KUNIT(symbol) EXPORT_SYMBOL_NS(symbol, \
 	    EXPORTED_FOR_KUNIT_TESTING)
 #else
+    #define DECLARE_IF_KUNIT(body...)
     #define VISIBLE_IF_KUNIT static
     #define EXPORT_SYMBOL_IF_KUNIT(symbol)
 #endif
-- 
2.43.0

[PATCH v2 3/6] kunit: Add macro to conditionally expose expressions to tests

[Michal Wajdeczko]

The ONLY_IF_KUNIT macro will add expression statement only if the
CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
it will evaluate always to 0.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
Cc: Rae Moar <rmoar@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
---
 include/kunit/visibility.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
index 1c23773f826c..69c71eacf368 100644
--- a/include/kunit/visibility.h
+++ b/include/kunit/visibility.h
@@ -18,6 +18,13 @@
      * @body: identifiers to be introduced conditionally
      */
     #define DECLARE_IF_KUNIT(body...)	body
+    /**
+     * ONLY_IF_KUNIT - A macro that adds expression statement only if
+     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
+     * it will evaluate always to 0.
+     * @expr: expression to be introduced conditionally
+     */
+    #define ONLY_IF_KUNIT(expr...)	expr
     /**
      * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
      * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
@@ -34,6 +41,7 @@
 	    EXPORTED_FOR_KUNIT_TESTING)
 #else
     #define DECLARE_IF_KUNIT(body...)
+    #define ONLY_IF_KUNIT(expr...) 0
     #define VISIBLE_IF_KUNIT static
     #define EXPORT_SYMBOL_IF_KUNIT(symbol)
 #endif
-- 
2.43.0

[PATCH v2 4/6] kunit: Allow function redirection outside of the KUnit thread

[Michal Wajdeczko]

Currently, the 'static stub' API only allows function redirection
for calls made from the kthread of the current test, which prevents
the use of this functionality when the tested code is also used by
other threads, outside of the KUnit test, like from the workqueue.

Add another set of macros to allow redirection to the replacement
functions, which, unlike the KUNIT_STATIC_STUB_REDIRECT, will
affect all calls done during the test execution.

These new stubs, named 'global', must be declared using dedicated
KUNIT_DECLARE_GLOBAL_STUB() macro and then can be placed either as
global static variables or as part of the other structures.

To properly maintain stubs lifecycle, they can be activated only
from the main KUnit context. Some precaution is taken to avoid
changing or deactivating replacement functions if one is still
used by other thread.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
Cc: Rae Moar <rmoar@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Daniel Latypov <dlatypov@google.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
---
v2: s/FIXED_STUB/GLOBAL_STUB (David, Lucas)
    make it little more thread safe (Rae, David)
    wait until stub call finishes before test end (David)
    wait until stub call finishes before changing stub (David)
    allow stub deactivation (Rae)
    prefer kunit log (David)
---
 include/kunit/static_stub.h | 158 ++++++++++++++++++++++++++++++++++++
 lib/kunit/static_stub.c     |  49 +++++++++++
 2 files changed, 207 insertions(+)

diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h
index bf940322dfc0..42a70dcefb56 100644
--- a/include/kunit/static_stub.h
+++ b/include/kunit/static_stub.h
@@ -12,12 +12,15 @@
 
 /* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */
 #define KUNIT_STATIC_STUB_REDIRECT(real_fn_name, args...) do {} while (0)
+#define KUNIT_GLOBAL_STUB_REDIRECT(stub_name, args...) do {} while (0)
+#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)
 
 #else
 
 #include <kunit/test.h>
 #include <kunit/test-bug.h>
 
+#include <linux/cleanup.h> /* for CLASS */
 #include <linux/compiler.h> /* for {un,}likely() */
 #include <linux/sched.h> /* for task_struct */
 
@@ -109,5 +112,160 @@ void __kunit_activate_static_stub(struct kunit *test,
  */
 void kunit_deactivate_static_stub(struct kunit *test, void *real_fn_addr);
 
+/**
+ * struct kunit_global_stub - Represents a context of global function stub.
+ * @replacement: The address of replacement function.
+ * @owner: The KUnit test that owns the stub, valid only when @busy > 0.
+ * @busy: The stub busyness counter incremented on entry to the replacement
+ *        function, decremented on exit, used to signal if the stub is idle.
+ * @idle: The completion state to indicate when the stub is idle again.
+ *
+ * This structure is for KUnit internal use only.
+ * See KUNIT_DECLARE_GLOBAL_STUB().
+ */
+struct kunit_global_stub {
+	void *replacement;
+	struct kunit *owner;
+	atomic_t busy;
+	struct completion idle;
+};
+
+/**
+ * KUNIT_DECLARE_GLOBAL_STUB() - Declare a global function stub.
+ * @stub_name: The name of the stub, must be a valid identifier
+ * @stub_type: The type of the function that this stub will replace
+ *
+ * This macro will declare new identifier of an anonymous type that will
+ * represent global stub function that could be used by KUnit. It can be stored
+ * outside of the KUnit code. If the CONFIG_KUNIT is not enabled this will
+ * be evaluated to an empty statement.
+ *
+ * The anonymous type introduced by this macro is mostly a wrapper to generic
+ * struct kunit_global_stub but with additional dummy member, that is never
+ * used directly, but is needed to maintain the type of the stub function.
+ */
+#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)				\
+union {										\
+	struct kunit_global_stub base;						\
+	typeof(stub_type) dummy;						\
+} stub_name
+
+/* Internal struct to define guard class */
+struct kunit_global_stub_guard {
+	struct kunit_global_stub *stub;
+	void *active_replacement;
+};
+
+/* Internal class used to guard stub calls */
+DEFINE_CLASS(kunit_global_stub_guard,
+	     struct kunit_global_stub_guard,
+	     ({
+		struct kunit_global_stub *stub = _T.stub;
+		bool active = !!_T.active_replacement;
+
+		if (active && !atomic_dec_return(&stub->busy))
+			complete_all(&stub->idle);
+	     }),
+	     ({
+		class_kunit_global_stub_guard_t guard;
+		bool active = !!atomic_inc_not_zero(&stub->busy);
+
+		guard.stub = stub;
+		guard.active_replacement = active ? READ_ONCE(stub->replacement) : NULL;
+
+		guard;
+	     }),
+	     struct kunit_global_stub *stub)
+
+/**
+ * KUNIT_GLOBAL_STUB_REDIRECT() - Call a fixed function stub if activated.
+ * @stub: The function stub declared using KUNIT_DECLARE_GLOBAL_STUB()
+ * @args: All of the arguments passed to this stub
+ *
+ * This is a function prologue which is used to allow calls to the current
+ * function to be redirected if a KUnit is running. If the KUnit is not
+ * running or stub is not yet activated the function will continue execution
+ * as normal.
+ *
+ * The function stub must be declared with KUNIT_DECLARE_GLOBAL_STUB() that is
+ * stored in a place that is accessible from both the test code, which will
+ * activate this stub using kunit_activate_global_stub(), and from the function,
+ * where we will do this redirection using KUNIT_GLOBAL_STUB_REDIRECT().
+ *
+ * Unlike the KUNIT_STATIC_STUB_REDIRECT(), this redirection will work
+ * even if the caller is not in a KUnit context (like a worker thread).
+ *
+ * Example:
+ *
+ * .. code-block:: c
+ *
+ *	KUNIT_DECLARE_GLOBAL_STUB(func_stub, int (*)(int n));
+ *
+ *	int real_func(int n)
+ *	{
+ *		KUNIT_GLOBAL_STUB_REDIRECT(func_stub, n);
+ *		return n + 1;
+ *	}
+ *
+ *	int replacement_func(int n)
+ *	{
+ *		return n + 100;
+ *	}
+ *
+ *	void example_test(struct kunit *test)
+ *	{
+ *		KUNIT_EXPECT_EQ(test, real_func(1), 2);
+ *		kunit_activate_global_stub(test, func_stub, replacement_func);
+ *		KUNIT_EXPECT_EQ(test, real_func(1), 101);
+ *	}
+ */
+#define KUNIT_GLOBAL_STUB_REDIRECT(stub, args...) do {					\
+	if (kunit_is_running()) {							\
+		typeof(stub) *__stub = &(stub);						\
+		CLASS(kunit_global_stub_guard, guard)(&__stub->base);			\
+		typeof(__stub->dummy) replacement = guard.active_replacement;		\
+		if (unlikely(replacement)) {						\
+			kunit_info(__stub->base.owner, "%s: redirecting to %ps\n",	\
+				   __func__, replacement);				\
+			return replacement(args);					\
+		}									\
+	}										\
+} while (0)
+
+void __kunit_activate_global_stub(struct kunit *test, struct kunit_global_stub *stub,
+				  void *replacement_addr);
+
+/**
+ * kunit_activate_global_stub() - Setup a fixed function stub.
+ * @test: Test case that wants to activate a fixed function stub
+ * @stub: The location of the function stub pointer
+ * @replacement: The replacement function
+ *
+ * This helper setups a function stub with the replacement function.
+ * It will also automatically deactivate the stub at the test end.
+ *
+ * The redirection can be disabled with kunit_deactivate_global_stub().
+ * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
+ */
+#define kunit_activate_global_stub(test, stub, replacement) do {		\
+	typeof(stub) *__stub = &(stub);						\
+	typecheck_fn(typeof(__stub->dummy), (replacement));			\
+	__kunit_activate_global_stub((test), &__stub->base, (replacement));	\
+} while (0)
+
+void __kunit_deactivate_global_stub(struct kunit *test, struct kunit_global_stub *stub);
+
+/**
+ * kunit_deactivate_global_stub() - Disable a fixed function stub.
+ * @test: Test case that wants to deactivate a fixed function stub
+ * @stub: The location of the function stub pointer
+ *
+ * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
+ */
+#define kunit_deactivate_global_stub(test, stub) do {				\
+	typeof(stub) *__stub = &(stub);						\
+	__kunit_deactivate_global_stub((test), &__stub->base);			\
+} while (0)
+
 #endif
 #endif
diff --git a/lib/kunit/static_stub.c b/lib/kunit/static_stub.c
index 92b2cccd5e76..799a7271dc5b 100644
--- a/lib/kunit/static_stub.c
+++ b/lib/kunit/static_stub.c
@@ -121,3 +121,52 @@ void __kunit_activate_static_stub(struct kunit *test,
 	}
 }
 EXPORT_SYMBOL_GPL(__kunit_activate_static_stub);
+
+static void sanitize_global_stub(void *data)
+{
+	struct kunit *test = kunit_get_current_test();
+	struct kunit_global_stub *stub =  data;
+
+	KUNIT_EXPECT_NE(test, 0, atomic_read(&stub->busy));
+	KUNIT_EXPECT_PTR_EQ(test, test, READ_ONCE(stub->owner));
+
+	reinit_completion(&stub->idle);
+	if (!atomic_dec_and_test(&stub->busy)) {
+		kunit_info(test, "waiting for %ps\n", stub->replacement);
+		KUNIT_EXPECT_EQ(test, 0, wait_for_completion_interruptible(&stub->idle));
+	}
+
+	WRITE_ONCE(stub->owner, NULL);
+	WRITE_ONCE(stub->replacement, NULL);
+}
+
+/*
+ * Helper function for kunit_activate_global_stub(). The macro does
+ * typechecking, so use it instead.
+ */
+void __kunit_activate_global_stub(struct kunit *test,
+				  struct kunit_global_stub *stub,
+				  void *replacement_addr)
+{
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stub);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, replacement_addr);
+	if (atomic_read(&stub->busy))
+		kunit_release_action(test, sanitize_global_stub, stub);
+	else
+		init_completion(&stub->idle);
+	WRITE_ONCE(stub->owner, test);
+	WRITE_ONCE(stub->replacement, replacement_addr);
+	KUNIT_ASSERT_EQ(test, 1, atomic_inc_return(&stub->busy));
+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, sanitize_global_stub, stub));
+}
+EXPORT_SYMBOL_GPL(__kunit_activate_global_stub);
+
+/*
+ * Helper function for kunit_deactivate_global_stub(). Use it instead.
+ */
+void __kunit_deactivate_global_stub(struct kunit *test, struct kunit_global_stub *stub)
+{
+	if (atomic_read(&stub->busy))
+		kunit_release_action(test, sanitize_global_stub, stub);
+}
+EXPORT_SYMBOL_GPL(__kunit_deactivate_global_stub);
-- 
2.43.0

[PATCH v2 5/6] kunit: Add example with alternate function redirection method

[Michal Wajdeczko]

Add example how to use KUNIT_FIXED_STUB_REDIRECT and compare its
usage with the KUNIT_STATIC_STUB_REDIRECT. Also show how the
DECLARE_IF_KUNIT macro could be helpful in declaring test data in
the non-test data structures.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rae Moar <rmoar@google.com> #v1
Reviewed-by: David Gow <davidgow@google.com> #v1
---
Cc: Daniel Latypov <dlatypov@google.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
---
v2: add missing testcase description (Rae) and rebase
---
 lib/kunit/kunit-example-test.c | 67 ++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
index 3056d6bc705d..146935a16883 100644
--- a/lib/kunit/kunit-example-test.c
+++ b/lib/kunit/kunit-example-test.c
@@ -6,8 +6,10 @@
  * Author: Brendan Higgins <brendanhiggins@google.com>
  */
 
+#include <linux/workqueue.h>
 #include <kunit/test.h>
 #include <kunit/static_stub.h>
+#include <kunit/visibility.h>
 
 /*
  * This is the most fundamental element of KUnit, the test case. A test case
@@ -221,6 +223,70 @@ static void example_static_stub_using_fn_ptr_test(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, add_one(1), 2);
 }
 
+/* This could be a location of various global stub functions. */
+static struct {
+	KUNIT_DECLARE_GLOBAL_STUB(add_two, int (*)(int i));
+} stubs;
+
+/* This is a function we'll replace with stubs. */
+static int add_two(int i)
+{
+	/* This will trigger the stub if active. */
+	KUNIT_STATIC_STUB_REDIRECT(add_two, i);
+	KUNIT_GLOBAL_STUB_REDIRECT(stubs.add_two, i);
+
+	return i + 2;
+}
+
+struct add_two_async_work {
+	struct work_struct work;
+	int param;
+	int result;
+};
+
+static void add_two_async_func(struct work_struct *work)
+{
+	struct add_two_async_work *w = container_of(work, typeof(*w), work);
+
+	w->result = add_two(w->param);
+}
+
+static int add_two_async(int i)
+{
+	struct add_two_async_work w = { .param = i };
+
+	INIT_WORK_ONSTACK(&w.work, add_two_async_func);
+	schedule_work(&w.work);
+	flush_work(&w.work);
+	destroy_work_on_stack(&w.work);
+
+	return w.result;
+}
+
+/*
+ * This test shows how to use KUNIT_GLOBAL_STUB_REDIRECT and compares its
+ * usage with the KUNIT_STATIC_STUB_REDIRECT.
+ */
+static void example_global_stub_test(struct kunit *test)
+{
+	/* static stub redirection works only for KUnit thread */
+	kunit_activate_static_stub(test, add_two, subtract_one);
+	KUNIT_EXPECT_EQ(test, add_two(1), subtract_one(1));
+	KUNIT_EXPECT_NE_MSG(test, add_two_async(1), subtract_one(1),
+			    "stub shouldn't be active outside KUnit thread!");
+
+	kunit_deactivate_static_stub(test, add_two);
+	KUNIT_EXPECT_EQ(test, add_two(1), add_two(1));
+
+	/* fixed stub redirection works for KUnit and other threads */
+	kunit_activate_global_stub(test, stubs.add_two, subtract_one);
+	KUNIT_EXPECT_EQ(test, add_two(1), subtract_one(1));
+	KUNIT_EXPECT_EQ(test, add_two_async(1), subtract_one(1));
+
+	kunit_deactivate_global_stub(test, stubs.add_two);
+	KUNIT_EXPECT_EQ(test, add_two(1), add_two(1));
+}
+
 static const struct example_param {
 	int value;
 } example_params_array[] = {
@@ -294,6 +360,7 @@ static struct kunit_case example_test_cases[] = {
 	KUNIT_CASE(example_all_expect_macros_test),
 	KUNIT_CASE(example_static_stub_test),
 	KUNIT_CASE(example_static_stub_using_fn_ptr_test),
+	KUNIT_CASE(example_global_stub_test),
 	KUNIT_CASE(example_priv_test),
 	KUNIT_CASE_PARAM(example_params_test, example_gen_params),
 	KUNIT_CASE_SLOW(example_slow_test),
-- 
2.43.0

[PATCH v2 6/6] kunit: Add some selftests for global stub redirection macros

[Michal Wajdeczko]

While we already have few ASSERT() within the implementation,
it's always better to have dedicated test cases. Add tests for:
 - automatic deactivation of the stubs at the test end
 - blocked deactivation until all active stub calls finish
 - blocked stub change until all active stub calls finish
 - safe abuse (deactivation without activation)

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
Cc: Rae Moar <rmoar@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
---
 lib/kunit/kunit-test.c | 254 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 253 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
index 37e02be1e710..eb1bb312ad71 100644
--- a/lib/kunit/kunit-test.c
+++ b/lib/kunit/kunit-test.c
@@ -6,8 +6,10 @@
  * Author: Brendan Higgins <brendanhiggins@google.com>
  */
 #include "linux/gfp_types.h"
+#include <kunit/static_stub.h>
 #include <kunit/test.h>
 #include <kunit/test-bug.h>
+#include <kunit/visibility.h>
 
 #include <linux/device.h>
 #include <kunit/device.h>
@@ -866,10 +868,260 @@ static struct kunit_suite kunit_current_test_suite = {
 	.test_cases = kunit_current_test_cases,
 };
 
+static struct {
+	/* this stub matches the real function */
+	KUNIT_DECLARE_GLOBAL_STUB(first_stub, int (*)(int i));
+	/* this stub matches only return type of the real function */
+	KUNIT_DECLARE_GLOBAL_STUB(second_stub, int (*)(int bit, int data));
+	/* this is an example stub that returns void */
+	KUNIT_DECLARE_GLOBAL_STUB(void_stub, void (*)(void));
+	/* this is an example how to store additional data for use by stubs */
+	DECLARE_IF_KUNIT(int data);
+	DECLARE_IF_KUNIT(int counter);
+} stubs = {
+	DECLARE_IF_KUNIT(.data = 3),
+};
+
+static int real_func(int i)
+{
+	KUNIT_GLOBAL_STUB_REDIRECT(stubs.first_stub, i);
+	KUNIT_GLOBAL_STUB_REDIRECT(stubs.second_stub, BIT(i), stubs.data);
+
+	return i;
+}
+
+struct real_work {
+	struct work_struct work;
+	int param;
+	int result;
+};
+
+static void real_work_func(struct work_struct *work)
+{
+	struct real_work *w = container_of(work, typeof(*w), work);
+
+	w->result = real_func(w->param);
+}
+
+static int real_func_async(int i)
+{
+	struct real_work w = { .param = i, .result = -EINPROGRESS };
+
+	INIT_WORK_ONSTACK(&w.work, real_work_func);
+	schedule_work(&w.work);
+	flush_work(&w.work);
+	destroy_work_on_stack(&w.work);
+
+	return w.result;
+}
+
+static int replacement_func(int i)
+{
+	return i + 1;
+}
+
+static int other_replacement_func(int i)
+{
+	return i + 10;
+}
+
+static int super_replacement_func(int bit, int data)
+{
+	return bit * data;
+}
+
+static int slow_replacement_func(int i)
+{
+	schedule_timeout_interruptible(HZ / 20);
+	return replacement_func(i);
+}
+
+static void real_void_func(void)
+{
+	KUNIT_GLOBAL_STUB_REDIRECT(stubs.void_stub);
+	DECLARE_IF_KUNIT(stubs.counter++);
+}
+
+static void replacement_void_func(void)
+{
+	stubs.counter--;
+}
+
+static void expect_deactivated(void *data)
+{
+	struct kunit *test = kunit_get_current_test();
+
+	KUNIT_EXPECT_NULL(test, stubs.first_stub.base.owner);
+	KUNIT_EXPECT_NULL(test, stubs.first_stub.base.replacement);
+	KUNIT_EXPECT_NULL(test, stubs.second_stub.base.owner);
+	KUNIT_EXPECT_NULL(test, stubs.second_stub.base.replacement);
+	KUNIT_EXPECT_NULL(test, stubs.void_stub.base.owner);
+	KUNIT_EXPECT_NULL(test, stubs.void_stub.base.replacement);
+}
+
+static void kunit_global_stub_test_deactivate(struct kunit *test)
+{
+	/* make sure everything will be deactivated */
+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, expect_deactivated, test));
+
+	/* deactivate without activate */
+	kunit_deactivate_global_stub(test, stubs.first_stub);
+
+	/* deactivate twice */
+	kunit_deactivate_global_stub(test, stubs.first_stub);
+
+	/* allow to skip deactivation (will be tested by expect_deactivated action) */
+	kunit_activate_global_stub(test, stubs.first_stub, replacement_func);
+}
+
+static void kunit_global_stub_test_activate(struct kunit *test)
+{
+	int real, replacement, other, super, i = 2;
+
+	/* prerequisites */
+	real_void_func();
+	KUNIT_ASSERT_EQ(test, stubs.counter, 1);
+	replacement_void_func();
+	KUNIT_ASSERT_EQ(test, stubs.counter, 0);
+
+	/* prerequisites cont'd */
+	KUNIT_ASSERT_EQ(test, real_func(i), real = real_func_async(i));
+	KUNIT_ASSERT_NE(test, real_func(i), replacement = replacement_func(i));
+	KUNIT_ASSERT_NE(test, real_func(i), other = other_replacement_func(i));
+	KUNIT_ASSERT_NE(test, real_func(i), super = super_replacement_func(BIT(i), stubs.data));
+
+	/* make sure everything will be deactivated */
+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, expect_deactivated, test));
+
+	/* allow to activate replacement */
+	kunit_activate_global_stub(test, stubs.void_stub, replacement_void_func);
+	real_void_func();
+	KUNIT_ASSERT_EQ(test, stubs.counter, -1);
+
+	/* allow to activate replacement */
+	kunit_activate_global_stub(test, stubs.first_stub, replacement_func);
+	KUNIT_EXPECT_EQ(test, real_func(i), replacement);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), replacement);
+
+	/* allow to change replacement */
+	kunit_activate_global_stub(test, stubs.first_stub, other_replacement_func);
+	KUNIT_EXPECT_EQ(test, real_func(i), other);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), other);
+
+	/* allow to deactivate replacement */
+	kunit_deactivate_global_stub(test, stubs.first_stub);
+	KUNIT_EXPECT_EQ(test, real_func(i), real);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), real);
+
+	/* allow to activate replacement with different arguments */
+	kunit_activate_global_stub(test, stubs.second_stub, super_replacement_func);
+	KUNIT_EXPECT_EQ(test, real_func(i), super);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), super);
+
+	/* allow to deactivate twice */
+	kunit_deactivate_global_stub(test, stubs.second_stub);
+	kunit_deactivate_global_stub(test, stubs.second_stub);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), real);
+	KUNIT_EXPECT_EQ(test, real_func(i), real);
+}
+
+static void flush_real_work(void *data)
+{
+	struct real_work *w = data;
+
+	flush_work(&w->work);
+}
+
+static void __kunit_global_stub_test_slow(struct kunit *test, bool replace)
+{
+	int real, replacement, other, i = replace ? 3 : 5;
+	struct real_work *w;
+
+	/* prerequisites */
+	KUNIT_ASSERT_EQ(test, real_func(i), real = real_func_async(i));
+	KUNIT_ASSERT_NE(test, real_func(i), replacement = slow_replacement_func(i));
+	KUNIT_ASSERT_NE(test, real_func(i), other = other_replacement_func(i));
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, w = kunit_kzalloc(test, sizeof(*w), GFP_KERNEL));
+	INIT_WORK(&w->work, real_work_func);
+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, flush_real_work, w));
+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, expect_deactivated, test));
+
+	/* allow to activate replacement */
+	kunit_activate_global_stub(test, stubs.first_stub, slow_replacement_func);
+	KUNIT_EXPECT_EQ(test, real_func_async(i), replacement);
+
+	w->param = i;
+	w->result = 0;
+	queue_work(system_long_wq, &w->work);
+
+	/* wait until work starts */
+	while (work_pending(&w->work))
+		schedule_timeout_interruptible(HZ / 100);
+	KUNIT_EXPECT_NE(test, work_busy(&w->work), 0);
+
+	/* wait until work enters the stub */
+	while (atomic_read(&stubs.first_stub.base.busy) < 2)
+		schedule_timeout_interruptible(HZ / 100);
+
+	/* stub should be still busy(2) at this point */
+	KUNIT_EXPECT_EQ(test, 2, atomic_read(&stubs.first_stub.base.busy));
+	KUNIT_EXPECT_EQ(test, w->result, 0);
+
+	if (replace) {
+		/* try replace the stub, it should be just activated(1) */
+		kunit_activate_global_stub(test, stubs.first_stub, other_replacement_func);
+		KUNIT_EXPECT_EQ(test, 1, atomic_read(&stubs.first_stub.base.busy));
+	} else {
+		/* try to deactivate the stub, it should be disabled(0) */
+		kunit_deactivate_global_stub(test, stubs.first_stub);
+		KUNIT_EXPECT_EQ(test, 0, atomic_read(&stubs.first_stub.base.busy));
+	}
+
+	/* and results from the worker should be available */
+	KUNIT_EXPECT_EQ(test, w->result, replacement);
+	KUNIT_EXPECT_NE(test, w->result, real);
+	KUNIT_EXPECT_NE(test, w->result, other);
+
+	if (replace)
+		KUNIT_EXPECT_EQ(test, real_func_async(i), other);
+	else
+		KUNIT_EXPECT_EQ(test, real_func_async(i), real);
+}
+
+static void kunit_global_stub_test_slow_deactivate(struct kunit *test)
+{
+	__kunit_global_stub_test_slow(test, false);
+}
+
+static void kunit_global_stub_test_slow_replace(struct kunit *test)
+{
+	__kunit_global_stub_test_slow(test, true);
+}
+
+static int kunit_global_stub_test_init(struct kunit *test)
+{
+	stubs.counter = 0;
+	return 0;
+}
+
+static struct kunit_case kunit_global_stub_test_cases[] = {
+	KUNIT_CASE(kunit_global_stub_test_activate),
+	KUNIT_CASE(kunit_global_stub_test_deactivate),
+	KUNIT_CASE_SLOW(kunit_global_stub_test_slow_deactivate),
+	KUNIT_CASE_SLOW(kunit_global_stub_test_slow_replace),
+	{}
+};
+
+static struct kunit_suite kunit_global_stub_suite = {
+	.name = "kunit_global_stub",
+	.init = kunit_global_stub_test_init,
+	.test_cases = kunit_global_stub_test_cases,
+};
+
 kunit_test_suites(&kunit_try_catch_test_suite, &kunit_resource_test_suite,
 		  &kunit_log_test_suite, &kunit_status_test_suite,
 		  &kunit_current_test_suite, &kunit_device_test_suite,
-		  &kunit_fault_test_suite);
+		  &kunit_fault_test_suite, &kunit_global_stub_suite);
 
 MODULE_DESCRIPTION("KUnit test for core test infrastructure");
 MODULE_LICENSE("GPL v2");
-- 
2.43.0

Re: [PATCH v2 2/6] kunit: Add macro to conditionally expose declarations to tests

[Lucas De Marchi]

On Tue, Aug 27, 2024 at 12:20:11AM GMT, Michal Wajdeczko wrote:
>The DECLARE_IF_KUNIT macro will introduces identifiers only if
>CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>no identifiers from the param list will be defined.
>
>Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>Reviewed-by: Rae Moar <rmoar@google.com>
>Reviewed-by: David Gow <davidgow@google.com>
>---
>Cc: Lucas De Marchi <lucas.demarchi@intel.com>

up to kunit maintainers, but it doesn't seem the word "DECLARE" is
entirely correct. What it's doing is expanding arg, and it doesn't
matter if it's an expression, definition, declaration.

Looking at patch 3, I think it would be more obvious to the caller if we
have:

IF_KUNIT_ELSE_EMPTY()
IF_KUNIT_ELSE_ZERO()

>---
> include/kunit/visibility.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
>diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
>index 0dfe35feeec6..1c23773f826c 100644
>--- a/include/kunit/visibility.h
>+++ b/include/kunit/visibility.h
>@@ -11,6 +11,13 @@
> #define _KUNIT_VISIBILITY_H
>
> #if IS_ENABLED(CONFIG_KUNIT)
>+    /**
>+     * DECLARE_IF_KUNIT - A macro that introduces identifiers only if
>+     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>+     * no identifiers will be defined.
>+     * @body: identifiers to be introduced conditionally

missing an example here with fields inside a struct

Lucas De Marchi

>+     */
>+    #define DECLARE_IF_KUNIT(body...)	body
>     /**
>      * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
>      * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
>@@ -26,6 +33,7 @@
>     #define EXPORT_SYMBOL_IF_KUNIT(symbol) EXPORT_SYMBOL_NS(symbol, \
> 	    EXPORTED_FOR_KUNIT_TESTING)
> #else
>+    #define DECLARE_IF_KUNIT(body...)
>     #define VISIBLE_IF_KUNIT static
>     #define EXPORT_SYMBOL_IF_KUNIT(symbol)
> #endif
>-- 
>2.43.0
>

Re: [PATCH v2 5/6] kunit: Add example with alternate function redirection method

[Lucas De Marchi]

On Tue, Aug 27, 2024 at 12:20:14AM GMT, Michal Wajdeczko wrote:
>Add example how to use KUNIT_FIXED_STUB_REDIRECT and compare its

s/FIXED/GLOBAL/

>usage with the KUNIT_STATIC_STUB_REDIRECT. Also show how the
>DECLARE_IF_KUNIT macro could be helpful in declaring test data in
>the non-test data structures.
>
>Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>Reviewed-by: Rae Moar <rmoar@google.com> #v1
>Reviewed-by: David Gow <davidgow@google.com> #v1
>---
>Cc: Daniel Latypov <dlatypov@google.com>
>Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>---
>v2: add missing testcase description (Rae) and rebase
>---
> lib/kunit/kunit-example-test.c | 67 ++++++++++++++++++++++++++++++++++
> 1 file changed, 67 insertions(+)
>
>diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
>index 3056d6bc705d..146935a16883 100644
>--- a/lib/kunit/kunit-example-test.c
>+++ b/lib/kunit/kunit-example-test.c
>@@ -6,8 +6,10 @@
>  * Author: Brendan Higgins <brendanhiggins@google.com>
>  */
>
>+#include <linux/workqueue.h>
> #include <kunit/test.h>
> #include <kunit/static_stub.h>
>+#include <kunit/visibility.h>
>
> /*
>  * This is the most fundamental element of KUnit, the test case. A test case
>@@ -221,6 +223,70 @@ static void example_static_stub_using_fn_ptr_test(struct kunit *test)
> 	KUNIT_EXPECT_EQ(test, add_one(1), 2);
> }
>
>+/* This could be a location of various global stub functions. */
>+static struct {
>+	KUNIT_DECLARE_GLOBAL_STUB(add_two, int (*)(int i));
>+} stubs;
>+
>+/* This is a function we'll replace with stubs. */
>+static int add_two(int i)
>+{
>+	/* This will trigger the stub if active. */
>+	KUNIT_STATIC_STUB_REDIRECT(add_two, i);
>+	KUNIT_GLOBAL_STUB_REDIRECT(stubs.add_two, i);

Nice use of an outer storage so we can give it the same name. IMO this
should be encouraged.

>+
>+	return i + 2;
>+}
>+
>+struct add_two_async_work {
>+	struct work_struct work;
>+	int param;
>+	int result;
>+};
>+
>+static void add_two_async_func(struct work_struct *work)
>+{
>+	struct add_two_async_work *w = container_of(work, typeof(*w), work);
>+
>+	w->result = add_two(w->param);
>+}
>+
>+static int add_two_async(int i)
>+{
>+	struct add_two_async_work w = { .param = i };
>+
>+	INIT_WORK_ONSTACK(&w.work, add_two_async_func);
>+	schedule_work(&w.work);
>+	flush_work(&w.work);
>+	destroy_work_on_stack(&w.work);
>+
>+	return w.result;
>+}
>+
>+/*
>+ * This test shows how to use KUNIT_GLOBAL_STUB_REDIRECT and compares its
>+ * usage with the KUNIT_STATIC_STUB_REDIRECT.
>+ */
>+static void example_global_stub_test(struct kunit *test)
>+{
>+	/* static stub redirection works only for KUnit thread */
>+	kunit_activate_static_stub(test, add_two, subtract_one);
>+	KUNIT_EXPECT_EQ(test, add_two(1), subtract_one(1));
>+	KUNIT_EXPECT_NE_MSG(test, add_two_async(1), subtract_one(1),
>+			    "stub shouldn't be active outside KUnit thread!");
>+
>+	kunit_deactivate_static_stub(test, add_two);
>+	KUNIT_EXPECT_EQ(test, add_two(1), add_two(1));
>+
>+	/* fixed stub redirection works for KUnit and other threads */

s/fixed/global/


with those fixes,


Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>

thanks
Lucas De Marchi

>+	kunit_activate_global_stub(test, stubs.add_two, subtract_one);
>+	KUNIT_EXPECT_EQ(test, add_two(1), subtract_one(1));
>+	KUNIT_EXPECT_EQ(test, add_two_async(1), subtract_one(1));
>+
>+	kunit_deactivate_global_stub(test, stubs.add_two);
>+	KUNIT_EXPECT_EQ(test, add_two(1), add_two(1));
>+}
>+
> static const struct example_param {
> 	int value;
> } example_params_array[] = {
>@@ -294,6 +360,7 @@ static struct kunit_case example_test_cases[] = {
> 	KUNIT_CASE(example_all_expect_macros_test),
> 	KUNIT_CASE(example_static_stub_test),
> 	KUNIT_CASE(example_static_stub_using_fn_ptr_test),
>+	KUNIT_CASE(example_global_stub_test),
> 	KUNIT_CASE(example_priv_test),
> 	KUNIT_CASE_PARAM(example_params_test, example_gen_params),
> 	KUNIT_CASE_SLOW(example_slow_test),
>-- 
>2.43.0
>

Re: [PATCH v2 4/6] kunit: Allow function redirection outside of the KUnit thread

[Lucas De Marchi]

On Tue, Aug 27, 2024 at 12:20:13AM GMT, Michal Wajdeczko wrote:
>Currently, the 'static stub' API only allows function redirection
>for calls made from the kthread of the current test, which prevents
>the use of this functionality when the tested code is also used by
>other threads, outside of the KUnit test, like from the workqueue.
>
>Add another set of macros to allow redirection to the replacement
>functions, which, unlike the KUNIT_STATIC_STUB_REDIRECT, will
>affect all calls done during the test execution.
>
>These new stubs, named 'global', must be declared using dedicated
>KUNIT_DECLARE_GLOBAL_STUB() macro and then can be placed either as
>global static variables or as part of the other structures.
>
>To properly maintain stubs lifecycle, they can be activated only
>from the main KUnit context. Some precaution is taken to avoid
>changing or deactivating replacement functions if one is still
>used by other thread.
>
>Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>---
>Cc: Rae Moar <rmoar@google.com>
>Cc: David Gow <davidgow@google.com>
>Cc: Daniel Latypov <dlatypov@google.com>
>Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>---
>v2: s/FIXED_STUB/GLOBAL_STUB (David, Lucas)
>    make it little more thread safe (Rae, David)
>    wait until stub call finishes before test end (David)
>    wait until stub call finishes before changing stub (David)
>    allow stub deactivation (Rae)
>    prefer kunit log (David)
>---
> include/kunit/static_stub.h | 158 ++++++++++++++++++++++++++++++++++++
> lib/kunit/static_stub.c     |  49 +++++++++++
> 2 files changed, 207 insertions(+)
>
>diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h
>index bf940322dfc0..42a70dcefb56 100644
>--- a/include/kunit/static_stub.h
>+++ b/include/kunit/static_stub.h
>@@ -12,12 +12,15 @@
>
> /* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */
> #define KUNIT_STATIC_STUB_REDIRECT(real_fn_name, args...) do {} while (0)
>+#define KUNIT_GLOBAL_STUB_REDIRECT(stub_name, args...) do {} while (0)
>+#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)
>
> #else
>
> #include <kunit/test.h>
> #include <kunit/test-bug.h>
>
>+#include <linux/cleanup.h> /* for CLASS */
> #include <linux/compiler.h> /* for {un,}likely() */
> #include <linux/sched.h> /* for task_struct */
>
>@@ -109,5 +112,160 @@ void __kunit_activate_static_stub(struct kunit *test,
>  */
> void kunit_deactivate_static_stub(struct kunit *test, void *real_fn_addr);
>
>+/**
>+ * struct kunit_global_stub - Represents a context of global function stub.
>+ * @replacement: The address of replacement function.
>+ * @owner: The KUnit test that owns the stub, valid only when @busy > 0.
>+ * @busy: The stub busyness counter incremented on entry to the replacement
>+ *        function, decremented on exit, used to signal if the stub is idle.
>+ * @idle: The completion state to indicate when the stub is idle again.
>+ *
>+ * This structure is for KUnit internal use only.
>+ * See KUNIT_DECLARE_GLOBAL_STUB().
>+ */
>+struct kunit_global_stub {
>+	void *replacement;
>+	struct kunit *owner;
>+	atomic_t busy;
>+	struct completion idle;
>+};
>+
>+/**
>+ * KUNIT_DECLARE_GLOBAL_STUB() - Declare a global function stub.
>+ * @stub_name: The name of the stub, must be a valid identifier
>+ * @stub_type: The type of the function that this stub will replace
>+ *
>+ * This macro will declare new identifier of an anonymous type that will
>+ * represent global stub function that could be used by KUnit. It can be stored
>+ * outside of the KUnit code. If the CONFIG_KUNIT is not enabled this will
>+ * be evaluated to an empty statement.
>+ *
>+ * The anonymous type introduced by this macro is mostly a wrapper to generic
>+ * struct kunit_global_stub but with additional dummy member, that is never
>+ * used directly, but is needed to maintain the type of the stub function.
>+ */
>+#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)				\
>+union {										\
>+	struct kunit_global_stub base;						\
>+	typeof(stub_type) dummy;						\
>+} stub_name
>+
>+/* Internal struct to define guard class */
>+struct kunit_global_stub_guard {
>+	struct kunit_global_stub *stub;
>+	void *active_replacement;
>+};
>+
>+/* Internal class used to guard stub calls */
>+DEFINE_CLASS(kunit_global_stub_guard,
>+	     struct kunit_global_stub_guard,
>+	     ({
>+		struct kunit_global_stub *stub = _T.stub;
>+		bool active = !!_T.active_replacement;

I'd call this `bool active_replacement` as it's not the same thing as
the active below.

>+
>+		if (active && !atomic_dec_return(&stub->busy))
>+			complete_all(&stub->idle);
>+	     }),
>+	     ({
>+		class_kunit_global_stub_guard_t guard;
>+		bool active = !!atomic_inc_not_zero(&stub->busy);
>+
>+		guard.stub = stub;
>+		guard.active_replacement = active ? READ_ONCE(stub->replacement) : NULL;
>+
>+		guard;
>+	     }),
>+	     struct kunit_global_stub *stub)
>+
>+/**
>+ * KUNIT_GLOBAL_STUB_REDIRECT() - Call a fixed function stub if activated.
>+ * @stub: The function stub declared using KUNIT_DECLARE_GLOBAL_STUB()
>+ * @args: All of the arguments passed to this stub
>+ *
>+ * This is a function prologue which is used to allow calls to the current
>+ * function to be redirected if a KUnit is running. If the KUnit is not
>+ * running or stub is not yet activated the function will continue execution
>+ * as normal.
>+ *
>+ * The function stub must be declared with KUNIT_DECLARE_GLOBAL_STUB() that is
>+ * stored in a place that is accessible from both the test code, which will
>+ * activate this stub using kunit_activate_global_stub(), and from the function,
>+ * where we will do this redirection using KUNIT_GLOBAL_STUB_REDIRECT().
>+ *
>+ * Unlike the KUNIT_STATIC_STUB_REDIRECT(), this redirection will work
>+ * even if the caller is not in a KUnit context (like a worker thread).
>+ *
>+ * Example:
>+ *
>+ * .. code-block:: c
>+ *
>+ *	KUNIT_DECLARE_GLOBAL_STUB(func_stub, int (*)(int n));
>+ *
>+ *	int real_func(int n)
>+ *	{
>+ *		KUNIT_GLOBAL_STUB_REDIRECT(func_stub, n);
>+ *		return n + 1;
>+ *	}
>+ *
>+ *	int replacement_func(int n)
>+ *	{
>+ *		return n + 100;
>+ *	}
>+ *
>+ *	void example_test(struct kunit *test)
>+ *	{
>+ *		KUNIT_EXPECT_EQ(test, real_func(1), 2);
>+ *		kunit_activate_global_stub(test, func_stub, replacement_func);
>+ *		KUNIT_EXPECT_EQ(test, real_func(1), 101);
>+ *	}
>+ */
>+#define KUNIT_GLOBAL_STUB_REDIRECT(stub, args...) do {					\
>+	if (kunit_is_running()) {							\
>+		typeof(stub) *__stub = &(stub);						\
>+		CLASS(kunit_global_stub_guard, guard)(&__stub->base);			\
>+		typeof(__stub->dummy) replacement = guard.active_replacement;		\
>+		if (unlikely(replacement)) {						\
>+			kunit_info(__stub->base.owner, "%s: redirecting to %ps\n",	\
>+				   __func__, replacement);				\
>+			return replacement(args);					\
>+		}									\
>+	}										\
>+} while (0)
>+
>+void __kunit_activate_global_stub(struct kunit *test, struct kunit_global_stub *stub,
>+				  void *replacement_addr);
>+
>+/**
>+ * kunit_activate_global_stub() - Setup a fixed function stub.

s/fixed/global/ here and every where else below

>+ * @test: Test case that wants to activate a fixed function stub
>+ * @stub: The location of the function stub pointer
>+ * @replacement: The replacement function
>+ *
>+ * This helper setups a function stub with the replacement function.
>+ * It will also automatically deactivate the stub at the test end.
>+ *
>+ * The redirection can be disabled with kunit_deactivate_global_stub().
>+ * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>+ */
>+#define kunit_activate_global_stub(test, stub, replacement) do {		\
>+	typeof(stub) *__stub = &(stub);						\
>+	typecheck_fn(typeof(__stub->dummy), (replacement));			\
>+	__kunit_activate_global_stub((test), &__stub->base, (replacement));	\
>+} while (0)
>+
>+void __kunit_deactivate_global_stub(struct kunit *test, struct kunit_global_stub *stub);
>+
>+/**
>+ * kunit_deactivate_global_stub() - Disable a fixed function stub.
>+ * @test: Test case that wants to deactivate a fixed function stub
>+ * @stub: The location of the function stub pointer
>+ *
>+ * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>+ */
>+#define kunit_deactivate_global_stub(test, stub) do {				\
>+	typeof(stub) *__stub = &(stub);						\
>+	__kunit_deactivate_global_stub((test), &__stub->base);			\
>+} while (0)
>+
> #endif
> #endif
>diff --git a/lib/kunit/static_stub.c b/lib/kunit/static_stub.c
>index 92b2cccd5e76..799a7271dc5b 100644
>--- a/lib/kunit/static_stub.c
>+++ b/lib/kunit/static_stub.c
>@@ -121,3 +121,52 @@ void __kunit_activate_static_stub(struct kunit *test,
> 	}
> }
> EXPORT_SYMBOL_GPL(__kunit_activate_static_stub);
>+
>+static void sanitize_global_stub(void *data)
>+{
>+	struct kunit *test = kunit_get_current_test();
>+	struct kunit_global_stub *stub =  data;
>+
>+	KUNIT_EXPECT_NE(test, 0, atomic_read(&stub->busy));

shouldn't sanitize_ be unconditional and do nothing in this case?

>+	KUNIT_EXPECT_PTR_EQ(test, test, READ_ONCE(stub->owner));
>+
>+	reinit_completion(&stub->idle);
>+	if (!atomic_dec_and_test(&stub->busy)) {
>+		kunit_info(test, "waiting for %ps\n", stub->replacement);
>+		KUNIT_EXPECT_EQ(test, 0, wait_for_completion_interruptible(&stub->idle));

what's preventing stub->busy going to 1 again after this?

Lucas De Marchi

>+	}
>+
>+	WRITE_ONCE(stub->owner, NULL);
>+	WRITE_ONCE(stub->replacement, NULL);
>+}
>+
>+/*
>+ * Helper function for kunit_activate_global_stub(). The macro does
>+ * typechecking, so use it instead.
>+ */
>+void __kunit_activate_global_stub(struct kunit *test,
>+				  struct kunit_global_stub *stub,
>+				  void *replacement_addr)
>+{
>+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stub);
>+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, replacement_addr);
>+	if (atomic_read(&stub->busy))
>+		kunit_release_action(test, sanitize_global_stub, stub);
>+	else
>+		init_completion(&stub->idle);
>+	WRITE_ONCE(stub->owner, test);
>+	WRITE_ONCE(stub->replacement, replacement_addr);
>+	KUNIT_ASSERT_EQ(test, 1, atomic_inc_return(&stub->busy));
>+	KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test, sanitize_global_stub, stub));
>+}
>+EXPORT_SYMBOL_GPL(__kunit_activate_global_stub);
>+
>+/*
>+ * Helper function for kunit_deactivate_global_stub(). Use it instead.
>+ */
>+void __kunit_deactivate_global_stub(struct kunit *test, struct kunit_global_stub *stub)
>+{
>+	if (atomic_read(&stub->busy))
>+		kunit_release_action(test, sanitize_global_stub, stub);
>+}
>+EXPORT_SYMBOL_GPL(__kunit_deactivate_global_stub);
>-- 
>2.43.0
>

Re: [PATCH v2 3/6] kunit: Add macro to conditionally expose expressions to tests

[Rae Moar]

On Mon, Aug 26, 2024 at 3:20 PM Michal Wajdeczko
<michal.wajdeczko@intel.com> wrote:
>
> The ONLY_IF_KUNIT macro will add expression statement only if the
> CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
> it will evaluate always to 0.
>
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>

Hello!

Thanks for the second version of this patch series!

I definitely could see this new macro as being useful but I currently
don't see an example of its use in the rest of the patch series. How
do you see this macro as being used or do you have a current use case
for this macro?

I would be fine adding this macro without being used as long as
examples on how and why to use it are clearly documented.

Thanks!
-Rae

> ---
> Cc: Rae Moar <rmoar@google.com>
> Cc: David Gow <davidgow@google.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>  include/kunit/visibility.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
> index 1c23773f826c..69c71eacf368 100644
> --- a/include/kunit/visibility.h
> +++ b/include/kunit/visibility.h
> @@ -18,6 +18,13 @@
>       * @body: identifiers to be introduced conditionally
>       */
>      #define DECLARE_IF_KUNIT(body...)  body
> +    /**
> +     * ONLY_IF_KUNIT - A macro that adds expression statement only if
> +     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
> +     * it will evaluate always to 0.
> +     * @expr: expression to be introduced conditionally
> +     */
> +    #define ONLY_IF_KUNIT(expr...)     expr
>      /**
>       * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
>       * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
> @@ -34,6 +41,7 @@
>             EXPORTED_FOR_KUNIT_TESTING)
>  #else
>      #define DECLARE_IF_KUNIT(body...)
> +    #define ONLY_IF_KUNIT(expr...) 0
>      #define VISIBLE_IF_KUNIT static
>      #define EXPORT_SYMBOL_IF_KUNIT(symbol)
>  #endif
> --
> 2.43.0
>

Re: [PATCH v2 3/6] kunit: Add macro to conditionally expose expressions to tests

[Michal Wajdeczko]

On 27.08.2024 21:04, Rae Moar wrote:
> On Mon, Aug 26, 2024 at 3:20 PM Michal Wajdeczko
> <michal.wajdeczko@intel.com> wrote:
>>
>> The ONLY_IF_KUNIT macro will add expression statement only if the
>> CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>> it will evaluate always to 0.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> 
> Hello!
> 
> Thanks for the second version of this patch series!
> 
> I definitely could see this new macro as being useful but I currently
> don't see an example of its use in the rest of the patch series. How
> do you see this macro as being used or do you have a current use case
> for this macro?

in Xe driver we have this macro defined as XE_TEST_ONLY [1]

[1] https://elixir.bootlin.com/linux/v6.11-rc5/A/ident/XE_TEST_ONLY

> 
> I would be fine adding this macro without being used as long as
> examples on how and why to use it are clearly documented.

sure, I'll try to add some usage in the example patch 5/6

> 
> Thanks!
> -Rae
> 
>> ---
>> Cc: Rae Moar <rmoar@google.com>
>> Cc: David Gow <davidgow@google.com>
>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>> ---
>>  include/kunit/visibility.h | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
>> index 1c23773f826c..69c71eacf368 100644
>> --- a/include/kunit/visibility.h
>> +++ b/include/kunit/visibility.h
>> @@ -18,6 +18,13 @@
>>       * @body: identifiers to be introduced conditionally
>>       */
>>      #define DECLARE_IF_KUNIT(body...)  body
>> +    /**
>> +     * ONLY_IF_KUNIT - A macro that adds expression statement only if
>> +     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>> +     * it will evaluate always to 0.
>> +     * @expr: expression to be introduced conditionally
>> +     */
>> +    #define ONLY_IF_KUNIT(expr...)     expr
>>      /**
>>       * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
>>       * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
>> @@ -34,6 +41,7 @@
>>             EXPORTED_FOR_KUNIT_TESTING)
>>  #else
>>      #define DECLARE_IF_KUNIT(body...)
>> +    #define ONLY_IF_KUNIT(expr...) 0
>>      #define VISIBLE_IF_KUNIT static
>>      #define EXPORT_SYMBOL_IF_KUNIT(symbol)
>>  #endif
>> --
>> 2.43.0
>>

Re: [PATCH v2 2/6] kunit: Add macro to conditionally expose declarations to tests

[Michal Wajdeczko]

On 27.08.2024 15:45, Lucas De Marchi wrote:
> On Tue, Aug 27, 2024 at 12:20:11AM GMT, Michal Wajdeczko wrote:
>> The DECLARE_IF_KUNIT macro will introduces identifiers only if
>> CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>> no identifiers from the param list will be defined.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>> Reviewed-by: Rae Moar <rmoar@google.com>
>> Reviewed-by: David Gow <davidgow@google.com>
>> ---
>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> 
> up to kunit maintainers, but it doesn't seem the word "DECLARE" is
> entirely correct. What it's doing is expanding arg, and it doesn't
> matter if it's an expression, definition, declaration.

hmm, while this is true for statement & declarations (as both have
similar notation) but not sure about the expression (that's why we have
patch 3)

> 
> Looking at patch 3, I think it would be more obvious to the caller if we
> have:
> 
> IF_KUNIT_ELSE_EMPTY()
> IF_KUNIT_ELSE_ZERO()

existing macros in this file are named as xxx_IF_KUNIT so maybe we
should try to follow that pattern...

so maybe (like BUILD_BUG_ON_ZERO)

	ONLY_IF_KUNIT(body...)
	ONLY_IF_KUNIT_ZERO(expr...)

> 
>> ---
>> include/kunit/visibility.h | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/include/kunit/visibility.h b/include/kunit/visibility.h
>> index 0dfe35feeec6..1c23773f826c 100644
>> --- a/include/kunit/visibility.h
>> +++ b/include/kunit/visibility.h
>> @@ -11,6 +11,13 @@
>> #define _KUNIT_VISIBILITY_H
>>
>> #if IS_ENABLED(CONFIG_KUNIT)
>> +    /**
>> +     * DECLARE_IF_KUNIT - A macro that introduces identifiers only if
>> +     * CONFIG_KUNIT is enabled. Otherwise if CONFIG_KUNIT is not enabled
>> +     * no identifiers will be defined.
>> +     * @body: identifiers to be introduced conditionally
> 
> missing an example here with fields inside a struct

would this work?

Example:

	struct example {
		int foo;
		/* private: test only */
		DECLARE_IF_KUNIT(int bar);
	};

> 
> Lucas De Marchi
> 
>> +     */
>> +    #define DECLARE_IF_KUNIT(body...)    body
>>     /**
>>      * VISIBLE_IF_KUNIT - A macro that sets symbols to be static if
>>      * CONFIG_KUNIT is not enabled. Otherwise if CONFIG_KUNIT is enabled
>> @@ -26,6 +33,7 @@
>>     #define EXPORT_SYMBOL_IF_KUNIT(symbol) EXPORT_SYMBOL_NS(symbol, \
>>         EXPORTED_FOR_KUNIT_TESTING)
>> #else
>> +    #define DECLARE_IF_KUNIT(body...)
>>     #define VISIBLE_IF_KUNIT static
>>     #define EXPORT_SYMBOL_IF_KUNIT(symbol)
>> #endif
>> -- 
>> 2.43.0
>>

Re: [PATCH v2 4/6] kunit: Allow function redirection outside of the KUnit thread

[Michal Wajdeczko]

On 27.08.2024 16:46, Lucas De Marchi wrote:
> On Tue, Aug 27, 2024 at 12:20:13AM GMT, Michal Wajdeczko wrote:
>> Currently, the 'static stub' API only allows function redirection
>> for calls made from the kthread of the current test, which prevents
>> the use of this functionality when the tested code is also used by
>> other threads, outside of the KUnit test, like from the workqueue.
>>
>> Add another set of macros to allow redirection to the replacement
>> functions, which, unlike the KUNIT_STATIC_STUB_REDIRECT, will
>> affect all calls done during the test execution.
>>
>> These new stubs, named 'global', must be declared using dedicated
>> KUNIT_DECLARE_GLOBAL_STUB() macro and then can be placed either as
>> global static variables or as part of the other structures.
>>
>> To properly maintain stubs lifecycle, they can be activated only
>> from the main KUnit context. Some precaution is taken to avoid
>> changing or deactivating replacement functions if one is still
>> used by other thread.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>> ---
>> Cc: Rae Moar <rmoar@google.com>
>> Cc: David Gow <davidgow@google.com>
>> Cc: Daniel Latypov <dlatypov@google.com>
>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>> ---
>> v2: s/FIXED_STUB/GLOBAL_STUB (David, Lucas)
>>    make it little more thread safe (Rae, David)
>>    wait until stub call finishes before test end (David)
>>    wait until stub call finishes before changing stub (David)
>>    allow stub deactivation (Rae)
>>    prefer kunit log (David)
>> ---
>> include/kunit/static_stub.h | 158 ++++++++++++++++++++++++++++++++++++
>> lib/kunit/static_stub.c     |  49 +++++++++++
>> 2 files changed, 207 insertions(+)
>>
>> diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h
>> index bf940322dfc0..42a70dcefb56 100644
>> --- a/include/kunit/static_stub.h
>> +++ b/include/kunit/static_stub.h
>> @@ -12,12 +12,15 @@
>>
>> /* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */
>> #define KUNIT_STATIC_STUB_REDIRECT(real_fn_name, args...) do {} while (0)
>> +#define KUNIT_GLOBAL_STUB_REDIRECT(stub_name, args...) do {} while (0)
>> +#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)
>>
>> #else
>>
>> #include <kunit/test.h>
>> #include <kunit/test-bug.h>
>>
>> +#include <linux/cleanup.h> /* for CLASS */
>> #include <linux/compiler.h> /* for {un,}likely() */
>> #include <linux/sched.h> /* for task_struct */
>>
>> @@ -109,5 +112,160 @@ void __kunit_activate_static_stub(struct kunit
>> *test,
>>  */
>> void kunit_deactivate_static_stub(struct kunit *test, void
>> *real_fn_addr);
>>
>> +/**
>> + * struct kunit_global_stub - Represents a context of global function
>> stub.
>> + * @replacement: The address of replacement function.
>> + * @owner: The KUnit test that owns the stub, valid only when @busy > 0.
>> + * @busy: The stub busyness counter incremented on entry to the
>> replacement
>> + *        function, decremented on exit, used to signal if the stub
>> is idle.
>> + * @idle: The completion state to indicate when the stub is idle again.
>> + *
>> + * This structure is for KUnit internal use only.
>> + * See KUNIT_DECLARE_GLOBAL_STUB().
>> + */
>> +struct kunit_global_stub {
>> +    void *replacement;
>> +    struct kunit *owner;
>> +    atomic_t busy;
>> +    struct completion idle;
>> +};
>> +
>> +/**
>> + * KUNIT_DECLARE_GLOBAL_STUB() - Declare a global function stub.
>> + * @stub_name: The name of the stub, must be a valid identifier
>> + * @stub_type: The type of the function that this stub will replace
>> + *
>> + * This macro will declare new identifier of an anonymous type that will
>> + * represent global stub function that could be used by KUnit. It can
>> be stored
>> + * outside of the KUnit code. If the CONFIG_KUNIT is not enabled this
>> will
>> + * be evaluated to an empty statement.
>> + *
>> + * The anonymous type introduced by this macro is mostly a wrapper to
>> generic
>> + * struct kunit_global_stub but with additional dummy member, that is
>> never
>> + * used directly, but is needed to maintain the type of the stub
>> function.
>> + */
>> +#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)                \
>> +union {                                        \
>> +    struct kunit_global_stub base;                        \
>> +    typeof(stub_type) dummy;                        \
>> +} stub_name
>> +
>> +/* Internal struct to define guard class */
>> +struct kunit_global_stub_guard {
>> +    struct kunit_global_stub *stub;
>> +    void *active_replacement;
>> +};
>> +
>> +/* Internal class used to guard stub calls */
>> +DEFINE_CLASS(kunit_global_stub_guard,
>> +         struct kunit_global_stub_guard,
>> +         ({
>> +        struct kunit_global_stub *stub = _T.stub;
>> +        bool active = !!_T.active_replacement;
> 
> I'd call this `bool active_replacement` as it's not the same thing as
> the active below.

IMO 'active_replacement' would be even more confusing as by that name we
identify the address and here it's a flag

OTOH the 'active' in both places means more/less the same (in init below
it mean stub was 'activated' and in exit here that we used 'activated'
replacement function)

> 
>> +
>> +        if (active && !atomic_dec_return(&stub->busy))
>> +            complete_all(&stub->idle);
>> +         }),
>> +         ({
>> +        class_kunit_global_stub_guard_t guard;
>> +        bool active = !!atomic_inc_not_zero(&stub->busy);
>> +
>> +        guard.stub = stub;
>> +        guard.active_replacement = active ?
>> READ_ONCE(stub->replacement) : NULL;
>> +
>> +        guard;
>> +         }),
>> +         struct kunit_global_stub *stub)
>> +
>> +/**
>> + * KUNIT_GLOBAL_STUB_REDIRECT() - Call a fixed function stub if
>> activated.
>> + * @stub: The function stub declared using KUNIT_DECLARE_GLOBAL_STUB()
>> + * @args: All of the arguments passed to this stub
>> + *
>> + * This is a function prologue which is used to allow calls to the
>> current
>> + * function to be redirected if a KUnit is running. If the KUnit is not
>> + * running or stub is not yet activated the function will continue
>> execution
>> + * as normal.
>> + *
>> + * The function stub must be declared with
>> KUNIT_DECLARE_GLOBAL_STUB() that is
>> + * stored in a place that is accessible from both the test code,
>> which will
>> + * activate this stub using kunit_activate_global_stub(), and from
>> the function,
>> + * where we will do this redirection using KUNIT_GLOBAL_STUB_REDIRECT().
>> + *
>> + * Unlike the KUNIT_STATIC_STUB_REDIRECT(), this redirection will work
>> + * even if the caller is not in a KUnit context (like a worker thread).
>> + *
>> + * Example:
>> + *
>> + * .. code-block:: c
>> + *
>> + *    KUNIT_DECLARE_GLOBAL_STUB(func_stub, int (*)(int n));
>> + *
>> + *    int real_func(int n)
>> + *    {
>> + *        KUNIT_GLOBAL_STUB_REDIRECT(func_stub, n);
>> + *        return n + 1;
>> + *    }
>> + *
>> + *    int replacement_func(int n)
>> + *    {
>> + *        return n + 100;
>> + *    }
>> + *
>> + *    void example_test(struct kunit *test)
>> + *    {
>> + *        KUNIT_EXPECT_EQ(test, real_func(1), 2);
>> + *        kunit_activate_global_stub(test, func_stub, replacement_func);
>> + *        KUNIT_EXPECT_EQ(test, real_func(1), 101);
>> + *    }
>> + */
>> +#define KUNIT_GLOBAL_STUB_REDIRECT(stub, args...) do
>> {                    \
>> +    if (kunit_is_running()) {                            \
>> +        typeof(stub) *__stub = &(stub);                        \
>> +        CLASS(kunit_global_stub_guard,
>> guard)(&__stub->base);            \
>> +        typeof(__stub->dummy) replacement =
>> guard.active_replacement;        \
>> +        if (unlikely(replacement)) {                        \
>> +            kunit_info(__stub->base.owner, "%s: redirecting to
>> %ps\n",    \
>> +                   __func__, replacement);                \
>> +            return replacement(args);                    \
>> +        }                                    \
>> +    }                                        \
>> +} while (0)
>> +
>> +void __kunit_activate_global_stub(struct kunit *test, struct
>> kunit_global_stub *stub,
>> +                  void *replacement_addr);
>> +
>> +/**
>> + * kunit_activate_global_stub() - Setup a fixed function stub.
> 
> s/fixed/global/ here and every where else below

oops

> 
>> + * @test: Test case that wants to activate a fixed function stub
>> + * @stub: The location of the function stub pointer
>> + * @replacement: The replacement function
>> + *
>> + * This helper setups a function stub with the replacement function.
>> + * It will also automatically deactivate the stub at the test end.
>> + *
>> + * The redirection can be disabled with kunit_deactivate_global_stub().
>> + * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>> + */
>> +#define kunit_activate_global_stub(test, stub, replacement) do
>> {        \
>> +    typeof(stub) *__stub = &(stub);                        \
>> +    typecheck_fn(typeof(__stub->dummy), (replacement));            \
>> +    __kunit_activate_global_stub((test), &__stub->base,
>> (replacement));    \
>> +} while (0)
>> +
>> +void __kunit_deactivate_global_stub(struct kunit *test, struct
>> kunit_global_stub *stub);
>> +
>> +/**
>> + * kunit_deactivate_global_stub() - Disable a fixed function stub.
>> + * @test: Test case that wants to deactivate a fixed function stub
>> + * @stub: The location of the function stub pointer
>> + *
>> + * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>> + */
>> +#define kunit_deactivate_global_stub(test, stub) do {                \
>> +    typeof(stub) *__stub = &(stub);                        \
>> +    __kunit_deactivate_global_stub((test), &__stub->base);            \
>> +} while (0)
>> +
>> #endif
>> #endif
>> diff --git a/lib/kunit/static_stub.c b/lib/kunit/static_stub.c
>> index 92b2cccd5e76..799a7271dc5b 100644
>> --- a/lib/kunit/static_stub.c
>> +++ b/lib/kunit/static_stub.c
>> @@ -121,3 +121,52 @@ void __kunit_activate_static_stub(struct kunit
>> *test,
>>     }
>> }
>> EXPORT_SYMBOL_GPL(__kunit_activate_static_stub);
>> +
>> +static void sanitize_global_stub(void *data)
>> +{
>> +    struct kunit *test = kunit_get_current_test();
>> +    struct kunit_global_stub *stub =  data;
>> +
>> +    KUNIT_EXPECT_NE(test, 0, atomic_read(&stub->busy));
> 
> shouldn't sanitize_ be unconditional and do nothing in this case?

I just didn't like early return here, but maybe it's more correct

> 
>> +    KUNIT_EXPECT_PTR_EQ(test, test, READ_ONCE(stub->owner));
>> +
>> +    reinit_completion(&stub->idle);
>> +    if (!atomic_dec_and_test(&stub->busy)) {
>> +        kunit_info(test, "waiting for %ps\n", stub->replacement);
>> +        KUNIT_EXPECT_EQ(test, 0,
>> wait_for_completion_interruptible(&stub->idle));
> 
> what's preventing stub->busy going to 1 again after this?

at the redirection point in kunit_global_stub_guard we have

	atomic_inc_not_zero(&stub->busy);

and the activation/deactivation can only be done from the main KUnit
thread (which is here)

> 
> Lucas De Marchi
> 
>> +    }
>> +
>> +    WRITE_ONCE(stub->owner, NULL);
>> +    WRITE_ONCE(stub->replacement, NULL);
>> +}
>> +
>> +/*
>> + * Helper function for kunit_activate_global_stub(). The macro does
>> + * typechecking, so use it instead.
>> + */
>> +void __kunit_activate_global_stub(struct kunit *test,
>> +                  struct kunit_global_stub *stub,
>> +                  void *replacement_addr)
>> +{
>> +    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stub);
>> +    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, replacement_addr);
>> +    if (atomic_read(&stub->busy))
>> +        kunit_release_action(test, sanitize_global_stub, stub);
>> +    else
>> +        init_completion(&stub->idle);
>> +    WRITE_ONCE(stub->owner, test);
>> +    WRITE_ONCE(stub->replacement, replacement_addr);
>> +    KUNIT_ASSERT_EQ(test, 1, atomic_inc_return(&stub->busy));
>> +    KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test,
>> sanitize_global_stub, stub));
>> +}
>> +EXPORT_SYMBOL_GPL(__kunit_activate_global_stub);
>> +
>> +/*
>> + * Helper function for kunit_deactivate_global_stub(). Use it instead.
>> + */
>> +void __kunit_deactivate_global_stub(struct kunit *test, struct
>> kunit_global_stub *stub)
>> +{
>> +    if (atomic_read(&stub->busy))
>> +        kunit_release_action(test, sanitize_global_stub, stub);
>> +}
>> +EXPORT_SYMBOL_GPL(__kunit_deactivate_global_stub);
>> -- 
>> 2.43.0
>>

Re: [PATCH v2 4/6] kunit: Allow function redirection outside of the KUnit thread

[Michal Wajdeczko]

On 27.08.2024 22:30, Michal Wajdeczko wrote:
> 
> 
> On 27.08.2024 16:46, Lucas De Marchi wrote:
>> On Tue, Aug 27, 2024 at 12:20:13AM GMT, Michal Wajdeczko wrote:
>>> Currently, the 'static stub' API only allows function redirection
>>> for calls made from the kthread of the current test, which prevents
>>> the use of this functionality when the tested code is also used by
>>> other threads, outside of the KUnit test, like from the workqueue.
>>>
>>> Add another set of macros to allow redirection to the replacement
>>> functions, which, unlike the KUNIT_STATIC_STUB_REDIRECT, will
>>> affect all calls done during the test execution.
>>>
>>> These new stubs, named 'global', must be declared using dedicated
>>> KUNIT_DECLARE_GLOBAL_STUB() macro and then can be placed either as
>>> global static variables or as part of the other structures.
>>>
>>> To properly maintain stubs lifecycle, they can be activated only
>>> from the main KUnit context. Some precaution is taken to avoid
>>> changing or deactivating replacement functions if one is still
>>> used by other thread.
>>>
>>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
>>> ---
>>> Cc: Rae Moar <rmoar@google.com>
>>> Cc: David Gow <davidgow@google.com>
>>> Cc: Daniel Latypov <dlatypov@google.com>
>>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>>> ---
>>> v2: s/FIXED_STUB/GLOBAL_STUB (David, Lucas)
>>>    make it little more thread safe (Rae, David)
>>>    wait until stub call finishes before test end (David)
>>>    wait until stub call finishes before changing stub (David)
>>>    allow stub deactivation (Rae)
>>>    prefer kunit log (David)
>>> ---
>>> include/kunit/static_stub.h | 158 ++++++++++++++++++++++++++++++++++++
>>> lib/kunit/static_stub.c     |  49 +++++++++++
>>> 2 files changed, 207 insertions(+)
>>>
>>> diff --git a/include/kunit/static_stub.h b/include/kunit/static_stub.h
>>> index bf940322dfc0..42a70dcefb56 100644
>>> --- a/include/kunit/static_stub.h
>>> +++ b/include/kunit/static_stub.h
>>> @@ -12,12 +12,15 @@
>>>
>>> /* If CONFIG_KUNIT is not enabled, these stubs quietly disappear. */
>>> #define KUNIT_STATIC_STUB_REDIRECT(real_fn_name, args...) do {} while (0)
>>> +#define KUNIT_GLOBAL_STUB_REDIRECT(stub_name, args...) do {} while (0)
>>> +#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)
>>>
>>> #else
>>>
>>> #include <kunit/test.h>
>>> #include <kunit/test-bug.h>
>>>
>>> +#include <linux/cleanup.h> /* for CLASS */
>>> #include <linux/compiler.h> /* for {un,}likely() */
>>> #include <linux/sched.h> /* for task_struct */
>>>
>>> @@ -109,5 +112,160 @@ void __kunit_activate_static_stub(struct kunit
>>> *test,
>>>  */
>>> void kunit_deactivate_static_stub(struct kunit *test, void
>>> *real_fn_addr);
>>>
>>> +/**
>>> + * struct kunit_global_stub - Represents a context of global function
>>> stub.
>>> + * @replacement: The address of replacement function.
>>> + * @owner: The KUnit test that owns the stub, valid only when @busy > 0.
>>> + * @busy: The stub busyness counter incremented on entry to the
>>> replacement
>>> + *        function, decremented on exit, used to signal if the stub
>>> is idle.
>>> + * @idle: The completion state to indicate when the stub is idle again.
>>> + *
>>> + * This structure is for KUnit internal use only.
>>> + * See KUNIT_DECLARE_GLOBAL_STUB().
>>> + */
>>> +struct kunit_global_stub {
>>> +    void *replacement;
>>> +    struct kunit *owner;
>>> +    atomic_t busy;
>>> +    struct completion idle;
>>> +};
>>> +
>>> +/**
>>> + * KUNIT_DECLARE_GLOBAL_STUB() - Declare a global function stub.
>>> + * @stub_name: The name of the stub, must be a valid identifier
>>> + * @stub_type: The type of the function that this stub will replace
>>> + *
>>> + * This macro will declare new identifier of an anonymous type that will
>>> + * represent global stub function that could be used by KUnit. It can
>>> be stored
>>> + * outside of the KUnit code. If the CONFIG_KUNIT is not enabled this
>>> will
>>> + * be evaluated to an empty statement.
>>> + *
>>> + * The anonymous type introduced by this macro is mostly a wrapper to
>>> generic
>>> + * struct kunit_global_stub but with additional dummy member, that is
>>> never
>>> + * used directly, but is needed to maintain the type of the stub
>>> function.
>>> + */
>>> +#define KUNIT_DECLARE_GLOBAL_STUB(stub_name, stub_type)                \
>>> +union {                                        \
>>> +    struct kunit_global_stub base;                        \
>>> +    typeof(stub_type) dummy;                        \
>>> +} stub_name
>>> +
>>> +/* Internal struct to define guard class */
>>> +struct kunit_global_stub_guard {
>>> +    struct kunit_global_stub *stub;
>>> +    void *active_replacement;
>>> +};
>>> +
>>> +/* Internal class used to guard stub calls */
>>> +DEFINE_CLASS(kunit_global_stub_guard,
>>> +         struct kunit_global_stub_guard,
>>> +         ({
>>> +        struct kunit_global_stub *stub = _T.stub;
>>> +        bool active = !!_T.active_replacement;
>>
>> I'd call this `bool active_replacement` as it's not the same thing as
>> the active below.
> 
> IMO 'active_replacement' would be even more confusing as by that name we
> identify the address and here it's a flag
> 
> OTOH the 'active' in both places means more/less the same (in init below
> it mean stub was 'activated' and in exit here that we used 'activated'
> replacement function)
> 
>>
>>> +
>>> +        if (active && !atomic_dec_return(&stub->busy))
>>> +            complete_all(&stub->idle);
>>> +         }),
>>> +         ({
>>> +        class_kunit_global_stub_guard_t guard;
>>> +        bool active = !!atomic_inc_not_zero(&stub->busy);
>>> +
>>> +        guard.stub = stub;
>>> +        guard.active_replacement = active ?
>>> READ_ONCE(stub->replacement) : NULL;
>>> +
>>> +        guard;
>>> +         }),
>>> +         struct kunit_global_stub *stub)
>>> +
>>> +/**
>>> + * KUNIT_GLOBAL_STUB_REDIRECT() - Call a fixed function stub if
>>> activated.
>>> + * @stub: The function stub declared using KUNIT_DECLARE_GLOBAL_STUB()
>>> + * @args: All of the arguments passed to this stub
>>> + *
>>> + * This is a function prologue which is used to allow calls to the
>>> current
>>> + * function to be redirected if a KUnit is running. If the KUnit is not
>>> + * running or stub is not yet activated the function will continue
>>> execution
>>> + * as normal.
>>> + *
>>> + * The function stub must be declared with
>>> KUNIT_DECLARE_GLOBAL_STUB() that is
>>> + * stored in a place that is accessible from both the test code,
>>> which will
>>> + * activate this stub using kunit_activate_global_stub(), and from
>>> the function,
>>> + * where we will do this redirection using KUNIT_GLOBAL_STUB_REDIRECT().
>>> + *
>>> + * Unlike the KUNIT_STATIC_STUB_REDIRECT(), this redirection will work
>>> + * even if the caller is not in a KUnit context (like a worker thread).
>>> + *
>>> + * Example:
>>> + *
>>> + * .. code-block:: c
>>> + *
>>> + *    KUNIT_DECLARE_GLOBAL_STUB(func_stub, int (*)(int n));
>>> + *
>>> + *    int real_func(int n)
>>> + *    {
>>> + *        KUNIT_GLOBAL_STUB_REDIRECT(func_stub, n);
>>> + *        return n + 1;
>>> + *    }
>>> + *
>>> + *    int replacement_func(int n)
>>> + *    {
>>> + *        return n + 100;
>>> + *    }
>>> + *
>>> + *    void example_test(struct kunit *test)
>>> + *    {
>>> + *        KUNIT_EXPECT_EQ(test, real_func(1), 2);
>>> + *        kunit_activate_global_stub(test, func_stub, replacement_func);
>>> + *        KUNIT_EXPECT_EQ(test, real_func(1), 101);
>>> + *    }
>>> + */
>>> +#define KUNIT_GLOBAL_STUB_REDIRECT(stub, args...) do
>>> {                    \
>>> +    if (kunit_is_running()) {                            \
>>> +        typeof(stub) *__stub = &(stub);                        \
>>> +        CLASS(kunit_global_stub_guard,
>>> guard)(&__stub->base);            \
>>> +        typeof(__stub->dummy) replacement =
>>> guard.active_replacement;        \
>>> +        if (unlikely(replacement)) {                        \
>>> +            kunit_info(__stub->base.owner, "%s: redirecting to
>>> %ps\n",    \
>>> +                   __func__, replacement);                \
>>> +            return replacement(args);                    \
>>> +        }                                    \
>>> +    }                                        \
>>> +} while (0)
>>> +
>>> +void __kunit_activate_global_stub(struct kunit *test, struct
>>> kunit_global_stub *stub,
>>> +                  void *replacement_addr);
>>> +
>>> +/**
>>> + * kunit_activate_global_stub() - Setup a fixed function stub.
>>
>> s/fixed/global/ here and every where else below
> 
> oops
> 
>>
>>> + * @test: Test case that wants to activate a fixed function stub
>>> + * @stub: The location of the function stub pointer
>>> + * @replacement: The replacement function
>>> + *
>>> + * This helper setups a function stub with the replacement function.
>>> + * It will also automatically deactivate the stub at the test end.
>>> + *
>>> + * The redirection can be disabled with kunit_deactivate_global_stub().
>>> + * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>>> + */
>>> +#define kunit_activate_global_stub(test, stub, replacement) do
>>> {        \
>>> +    typeof(stub) *__stub = &(stub);                        \
>>> +    typecheck_fn(typeof(__stub->dummy), (replacement));            \
>>> +    __kunit_activate_global_stub((test), &__stub->base,
>>> (replacement));    \
>>> +} while (0)
>>> +
>>> +void __kunit_deactivate_global_stub(struct kunit *test, struct
>>> kunit_global_stub *stub);
>>> +
>>> +/**
>>> + * kunit_deactivate_global_stub() - Disable a fixed function stub.
>>> + * @test: Test case that wants to deactivate a fixed function stub
>>> + * @stub: The location of the function stub pointer
>>> + *
>>> + * The stub must be declared using KUNIT_DECLARE_GLOBAL_STUB().
>>> + */
>>> +#define kunit_deactivate_global_stub(test, stub) do {                \
>>> +    typeof(stub) *__stub = &(stub);                        \
>>> +    __kunit_deactivate_global_stub((test), &__stub->base);            \
>>> +} while (0)
>>> +
>>> #endif
>>> #endif
>>> diff --git a/lib/kunit/static_stub.c b/lib/kunit/static_stub.c
>>> index 92b2cccd5e76..799a7271dc5b 100644
>>> --- a/lib/kunit/static_stub.c
>>> +++ b/lib/kunit/static_stub.c
>>> @@ -121,3 +121,52 @@ void __kunit_activate_static_stub(struct kunit
>>> *test,
>>>     }
>>> }
>>> EXPORT_SYMBOL_GPL(__kunit_activate_static_stub);
>>> +
>>> +static void sanitize_global_stub(void *data)
>>> +{
>>> +    struct kunit *test = kunit_get_current_test();
>>> +    struct kunit_global_stub *stub =  data;
>>> +
>>> +    KUNIT_EXPECT_NE(test, 0, atomic_read(&stub->busy));
>>
>> shouldn't sanitize_ be unconditional and do nothing in this case?
> 
> I just didn't like early return here, but maybe it's more correct

hmm, in fact we don't need to check stub->busy prior to calling
kunit_release_action() since our goal is to detect whether stub was
activated, but this action will be released/called only if we have added
this action after the stub activation, so we can just rely on the action
management code and just keep the EXPECT_NE here as a guard

> 
>>
>>> +    KUNIT_EXPECT_PTR_EQ(test, test, READ_ONCE(stub->owner));
>>> +
>>> +    reinit_completion(&stub->idle);
>>> +    if (!atomic_dec_and_test(&stub->busy)) {
>>> +        kunit_info(test, "waiting for %ps\n", stub->replacement);
>>> +        KUNIT_EXPECT_EQ(test, 0,
>>> wait_for_completion_interruptible(&stub->idle));
>>
>> what's preventing stub->busy going to 1 again after this?
> 
> at the redirection point in kunit_global_stub_guard we have
> 
> 	atomic_inc_not_zero(&stub->busy);
> 
> and the activation/deactivation can only be done from the main KUnit
> thread (which is here)
> 
>>
>> Lucas De Marchi
>>
>>> +    }
>>> +
>>> +    WRITE_ONCE(stub->owner, NULL);
>>> +    WRITE_ONCE(stub->replacement, NULL);
>>> +}
>>> +
>>> +/*
>>> + * Helper function for kunit_activate_global_stub(). The macro does
>>> + * typechecking, so use it instead.
>>> + */
>>> +void __kunit_activate_global_stub(struct kunit *test,
>>> +                  struct kunit_global_stub *stub,
>>> +                  void *replacement_addr)
>>> +{
>>> +    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stub);
>>> +    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, replacement_addr);
>>> +    if (atomic_read(&stub->busy))
>>> +        kunit_release_action(test, sanitize_global_stub, stub);
>>> +    else
>>> +        init_completion(&stub->idle);
>>> +    WRITE_ONCE(stub->owner, test);
>>> +    WRITE_ONCE(stub->replacement, replacement_addr);
>>> +    KUNIT_ASSERT_EQ(test, 1, atomic_inc_return(&stub->busy));
>>> +    KUNIT_ASSERT_EQ(test, 0, kunit_add_action_or_reset(test,
>>> sanitize_global_stub, stub));
>>> +}
>>> +EXPORT_SYMBOL_GPL(__kunit_activate_global_stub);
>>> +
>>> +/*
>>> + * Helper function for kunit_deactivate_global_stub(). Use it instead.
>>> + */
>>> +void __kunit_deactivate_global_stub(struct kunit *test, struct
>>> kunit_global_stub *stub)
>>> +{
>>> +    if (atomic_read(&stub->busy))
>>> +        kunit_release_action(test, sanitize_global_stub, stub);
>>> +}
>>> +EXPORT_SYMBOL_GPL(__kunit_deactivate_global_stub);
>>> -- 
>>> 2.43.0
>>>