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From:   Daniel Latypov <dlatypov@google.com>
Date:   Fri, 13 Jan 2023 17:38:17 -0800
Message-ID: <CAGS_qxoeKishaVvHk-HCvstWJrZ8gXRrQipGd-sz=ONrPjteZw@mail.gmail.com>
Subject: Re: [PATCH] kunit: memcpy: Split slow memcpy tests into MEMCPY_SLOW_KUNIT_TEST
To:     Kees Cook <keescook@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Nick Desaulniers <ndesaulniers@google.com>,
        David Gow <davidgow@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        linux-hardening@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Miguel Ojeda <ojeda@kernel.org>,
        Isabella Basso <isabbasso@riseup.net>,
        Dan Williams <dan.j.williams@intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-kernel@vger.kernel.org
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Precedence: bulk

On Fri, Jan 13, 2023 at 4:54 PM Kees Cook <keescook@chromium.org> wrote:
> diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c
> index 89128551448d..5a545e1b5dbb 100644
> --- a/lib/memcpy_kunit.c
> +++ b/lib/memcpy_kunit.c
> @@ -307,8 +307,12 @@ static void set_random_nonzero(struct kunit *test, u8 *byte)
>         }
>  }
>
> -static void init_large(struct kunit *test)
> +static int init_large(struct kunit *test)
>  {
> +       if (!IS_ENABLED(CONFIG_MEMCPY_SLOW_KUNIT_TEST)) {
> +               kunit_skip(test, "Slow test skipped. Enable with CONFIG_MEMCPY_SLOW_KUNIT_TEST=y");
> +               return -EBUSY;

Note: kunit_skip() here means you don't need explicit returns in the test cases.
kunit_skip() is basically
  kunit_mark_skipped(test, "reason");
  kthread_complete_and_exit(...);

So the diff in this file could be reduced down to just these 2 lines
  if (!IS_ENABLED(...))
      kunit_skip(test, "...")

But I can see the appeal of being more explicit about the control flow.
In that case, you could switch kunit_mark_skipped(), which just sets
the status and doesn't affect control flow at all.

Daniel