KUnit aborts the current thread when an assertion fails. Currently, this
is done conditionally as part of the kunit_do_failed_assertion()
function, but this hides the kunit_abort() call from the compiler
(particularly if it's in another module). This, in turn, can lead to
both suboptimal code generation (the compiler can't know if
kunit_do_failed_assertion() will return), and to static analysis tools
like smatch giving false positives.

Moving the kunit_abort() call into the macro should give the compiler
and tools a better chance at understanding what's going on. Doing so
requires exporting kunit_abort(), though it's recommended to continue to
use assertions in lieu of aborting directly.

In addition, kunit_abort() and kunit_do_failed_assertion() are renamed
to make it clear they they're intended for internal KUnit use, to:
__kunit_do_failed_assertion() and __kunit_abort()

Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: David Gow <davidgow@google.com>
---

Changes since RFCv1:
https://lore.kernel.org/linux-kselftest/20230526075355.586335-1-davidgow@google.com/
- Add missing MODULE_EXPORT_GPL() (Thanks kernel test robot)
- Rename kunit_abort() and kunit_do_failed_assertion() to make it clear
  they're intended for internal use.
  - Thanks Daniel Latypov!

---
 include/kunit/test.h | 20 ++++++++++++--------
 lib/kunit/test.c     | 10 ++++------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 2f23d6efa505..f40e65adfb1f 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -481,7 +481,9 @@ void __printf(2, 3) kunit_log_append(char *log, const char *fmt, ...);
  */
 #define KUNIT_SUCCEED(test) do {} while (0)
 
-void kunit_do_failed_assertion(struct kunit *test,
+void __noreturn __kunit_abort(struct kunit *test);
+
+void __kunit_do_failed_assertion(struct kunit *test,
 			       const struct kunit_loc *loc,
 			       enum kunit_assert_type type,
 			       const struct kunit_assert *assert,
@@ -491,13 +493,15 @@ void kunit_do_failed_assertion(struct kunit *test,
 #define _KUNIT_FAILED(test, assert_type, assert_class, assert_format, INITIALIZER, fmt, ...) do { \
 	static const struct kunit_loc __loc = KUNIT_CURRENT_LOC;	       \
 	const struct assert_class __assertion = INITIALIZER;		       \
-	kunit_do_failed_assertion(test,					       \
-				  &__loc,				       \
-				  assert_type,				       \
-				  &__assertion.assert,			       \
-				  assert_format,			       \
-				  fmt,					       \
-				  ##__VA_ARGS__);			       \
+	__kunit_do_failed_assertion(test,				       \
+				    &__loc,				       \
+				    assert_type,			       \
+				    &__assertion.assert,		       \
+				    assert_format,			       \
+				    fmt,				       \
+				    ##__VA_ARGS__);			       \
+	if (assert_type == KUNIT_ASSERTION)				       \
+		__kunit_abort(test);					       \
 } while (0)
 
 
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index d3fb93a23ccc..e652ab0d9996 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -310,7 +310,7 @@ static void kunit_fail(struct kunit *test, const struct kunit_loc *loc,
 	string_stream_destroy(stream);
 }
 
-static void __noreturn kunit_abort(struct kunit *test)
+void __noreturn __kunit_abort(struct kunit *test)
 {
 	kunit_try_catch_throw(&test->try_catch); /* Does not return. */
 
@@ -322,8 +322,9 @@ static void __noreturn kunit_abort(struct kunit *test)
 	 */
 	WARN_ONCE(true, "Throw could not abort from test!\n");
 }
+EXPORT_SYMBOL_GPL(__kunit_abort);
 
-void kunit_do_failed_assertion(struct kunit *test,
+void __kunit_do_failed_assertion(struct kunit *test,
 			       const struct kunit_loc *loc,
 			       enum kunit_assert_type type,
 			       const struct kunit_assert *assert,
@@ -340,11 +341,8 @@ void kunit_do_failed_assertion(struct kunit *test,
 	kunit_fail(test, loc, type, assert, assert_format, &message);
 
 	va_end(args);
-
-	if (type == KUNIT_ASSERTION)
-		kunit_abort(test);
 }
-EXPORT_SYMBOL_GPL(kunit_do_failed_assertion);
+EXPORT_SYMBOL_GPL(__kunit_do_failed_assertion);
 
 void kunit_init_test(struct kunit *test, const char *name, char *log)
 {
-- 
2.41.0.rc0.172.g3f132b7071-goog

On Tue, May 30, 2023 at 10:22 PM David Gow <davidgow@google.com> wrote:
>
> KUnit aborts the current thread when an assertion fails. Currently, this
> is done conditionally as part of the kunit_do_failed_assertion()
> function, but this hides the kunit_abort() call from the compiler
> (particularly if it's in another module). This, in turn, can lead to
> both suboptimal code generation (the compiler can't know if
> kunit_do_failed_assertion() will return), and to static analysis tools
> like smatch giving false positives.
>
> Moving the kunit_abort() call into the macro should give the compiler
> and tools a better chance at understanding what's going on. Doing so
> requires exporting kunit_abort(), though it's recommended to continue to
> use assertions in lieu of aborting directly.
>
> In addition, kunit_abort() and kunit_do_failed_assertion() are renamed
> to make it clear they they're intended for internal KUnit use, to:
> __kunit_do_failed_assertion() and __kunit_abort()
>
> Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
> Signed-off-by: David Gow <davidgow@google.com>

Reviewed-by: Daniel Latypov <dlatypov@google.com>

Minor note, there's a reference to the old `kunit_abort` name still.

Documentation/dev-tools/kunit/architecture.rst
122:              ``void __noreturn kunit_abort(struct kunit *)``.
124:            - ``kunit_abort`` calls the function:

Note that this comes from commit bc145b370c11 ("Documentation: KUnit:
Added KUnit Architecture").
I had forgotten this existed until now.

On Wed, May 31, 2023 at 7:22 AM David Gow <davidgow@google.com> wrote:
>
> KUnit aborts the current thread when an assertion fails. Currently, this
> is done conditionally as part of the kunit_do_failed_assertion()
> function, but this hides the kunit_abort() call from the compiler
> (particularly if it's in another module). This, in turn, can lead to
> both suboptimal code generation (the compiler can't know if
> kunit_do_failed_assertion() will return), and to static analysis tools
> like smatch giving false positives.
>
> Moving the kunit_abort() call into the macro should give the compiler
> and tools a better chance at understanding what's going on. Doing so
> requires exporting kunit_abort(), though it's recommended to continue to
> use assertions in lieu of aborting directly.
>
> In addition, kunit_abort() and kunit_do_failed_assertion() are renamed
> to make it clear they they're intended for internal KUnit use, to:
> __kunit_do_failed_assertion() and __kunit_abort()
>
> Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
> Signed-off-by: David Gow <davidgow@google.com>

Reviewed-by: Miguel Ojeda <ojeda@kernel.org>

Also tested on top of the Rust doctests KUnit changes with [1].

Thanks!

Cheers,
Miguel

[1]

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 48adb992da936..3fae6284abbc2 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -61,7 +61,7 @@ macro_rules! kunit_assert {
             //     next test runs, that test failures should be fixed
and that KUnit is explicitly
             //     documented as not suitable for production
environments, we feel it is reasonable.
             unsafe {
-                $crate::bindings::kunit_do_failed_assertion(
+                $crate::bindings::__kunit_do_failed_assertion(
                     $test,
                     core::ptr::addr_of!(LOCATION.0),
                     $crate::bindings::kunit_assert_type_KUNIT_ASSERTION,
@@ -70,6 +70,13 @@ macro_rules! kunit_assert {
                     core::ptr::null(),
                 );
             }
+
+            // SAFETY: FFI call; the `test` pointer is valid because
this hidden macro should only
+            // be called by the generated documentation tests which
forward the test pointer given
+            // by KUnit.
+            unsafe {
+                $crate::bindings::__kunit_abort($test);
+            }
         }
     }};
 }

On Wed, May 31, 2023 at 01:21:57PM +0800, David Gow wrote:
> KUnit aborts the current thread when an assertion fails. Currently, this
> is done conditionally as part of the kunit_do_failed_assertion()
> function, but this hides the kunit_abort() call from the compiler
> (particularly if it's in another module). This, in turn, can lead to
> both suboptimal code generation (the compiler can't know if
> kunit_do_failed_assertion() will return), and to static analysis tools
> like smatch giving false positives.
> 
> Moving the kunit_abort() call into the macro should give the compiler
> and tools a better chance at understanding what's going on. Doing so
> requires exporting kunit_abort(), though it's recommended to continue to
> use assertions in lieu of aborting directly.
> 
> In addition, kunit_abort() and kunit_do_failed_assertion() are renamed
> to make it clear they they're intended for internal KUnit use, to:
> __kunit_do_failed_assertion() and __kunit_abort()
> 
> Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
> Signed-off-by: David Gow <davidgow@google.com>

Fantastic!  Thanks so much!

regards,
dan carpenter