Re: [PATCH v2] lib: overflow: Convert to Kunit

[Daniel Latypov]

On Wed, Mar 23, 2022 at 10:29 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Wed, Feb 23, 2022 at 09:48:25PM -0800, Kees Cook wrote:
> > Convert overflow unit tests to KUnit, for better integration into the
> > kernel self test framework. Includes a rename of test_overflow.c to
> > overflow_kunit.c, and CONFIG_TEST_OVERFLOW to CONFIG_OVERFLOW_KUNIT_TEST.
> >
>
> This patch results in lots of test build failures
> due to large frame sizes.
>
> Building i386:allyesconfig ... failed
> --------------
> Error log:
> lib/overflow_kunit.c: In function 'overflow_size_helpers_test':
> lib/overflow_kunit.c:644:1: error: the frame size of 2480 bytes is larger than 2048 bytes

This is somewhat expected and should hopefully be fixed soon.


More detail:
Unless optimized away by the compiler, each KUNIT_EXPECT_* use will
add a struct to the stack.
I have a number of pending patches that will decrease that stack usage.
On UML (x86_64), they cut it down from 88 bytes => 32 bytes per
KUNIT_EXPECT_EQ/GT/etc.

Shuah sent a PR to Linus which contains these patches,
https://lore.kernel.org/all/d138a93a-997f-bfb6-6119-83aa2c00a49d@xxxxxxxxxxxxxxxxxxx/
Once those are in, hopefully all these warnings go away as we're not
over the 2048 limit by that much.

Daniel