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SubjectRe: [PATCH] kunit: memcpy: Split slow memcpy tests into MEMCPY_SLOW_KUNIT_TEST
On Sat, 14 Jan 2023 at 08:54, Kees Cook <keescook@chromium.org> wrote:
>
> Since the long memcpy tests may stall a system for tens of seconds
> in virtualized architecture environments, split those tests off under
> CONFIG_MEMCPY_SLOW_KUNIT_TEST so they can be separately disabled.
>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Link: https://lore.kernel.org/lkml/20221226195206.GA2626419@roeck-us.net
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-and-tested-by: Guenter Roeck <linux@roeck-us.net>
> Reviewed-by: David Gow <davidgow@google.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---

Thanks: this is okay as-is, but I left a few suggestions below, having
tried it out a bit more.

Daniel's comment about kunit_skip() aborting the test is the only real
fix, but depending on how easy you'd want to make turning these tests
off, there are a couple of possible tweaks to the Kconfig option.

Cheers,
-- David

> v2: fix tristate to bool
> v1: https://lore.kernel.org/lkml/20230107040203.never.112-kees@kernel.org
> ---
> lib/Kconfig.debug | 9 +++++++++
> lib/memcpy_kunit.c | 15 ++++++++++++---
> 2 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c2c78d0e761c..f90637171453 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2621,6 +2621,15 @@ config MEMCPY_KUNIT_TEST
>
> If unsure, say N.
>
> +config MEMCPY_SLOW_KUNIT_TEST
> + bool "Include exhaustive memcpy tests" if !KUNIT_ALL_TESTS

I think it'd be better to not include the "if !KUNIT_ALL_TESTS" here,
because it's very convenient to be able to use:
./tools/testing/kunit/kunit.py run memcpy --kconfig_add
CONFIG_MEMCPY_SLOW_KUNIT_TEST=n
to override it.

That does undermine the way KUNIT_ALL_TESTS works a bit, though it
depends if you want to consider this a new set of tests, or just an
option for the existing ones.

> + depends on MEMCPY_KUNIT_TEST
> + default KUNIT_ALL_TESTS

Does this default work for everyone? Personally, I think these tests
aren't slow enough that we'd want them disabled from an "all tests"
build by default. So I'd keep it as-is.

> + help
> + Some memcpy tests are quite exhaustive in checking for overlaps
> + and bit ranges. These can be very slow, so they are split out
> + as a separate config.
> +
> config IS_SIGNED_TYPE_KUNIT_TEST
> tristate "Test is_signed_type() macro" if !KUNIT_ALL_TESTS
> depends on KUNIT
> 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;

As Daniel notes, it shouldn't be necessary to return here, as
kunit_skip() will abort the test. (It's a macro, so isn't marked
__noreturn itself, but kunit_try_catch_throw(), which it uses, is.)

> + }
>
> /* Get many bit patterns. */
> get_random_bytes(large_src, ARRAY_SIZE(large_src));
> @@ -319,6 +323,8 @@ static void init_large(struct kunit *test)
>
> /* Explicitly zero the entire destination. */
> memset(large_dst, 0, ARRAY_SIZE(large_dst));
> +
> + return 0;
> }
>
> /*
> @@ -327,7 +333,9 @@ static void init_large(struct kunit *test)
> */
> static void copy_large_test(struct kunit *test, bool use_memmove)
> {
> - init_large(test);
> +
> + if (init_large(test))
> + return;
>
> /* Copy a growing number of non-overlapping bytes ... */
> for (int bytes = 1; bytes <= ARRAY_SIZE(large_src); bytes++) {
> @@ -472,7 +480,8 @@ static void memmove_overlap_test(struct kunit *test)
> static const int bytes_start = 1;
> static const int bytes_end = ARRAY_SIZE(large_src) + 1;
>
> - init_large(test);
> + if (init_large(test))
> + return;
>
> /* Copy a growing number of overlapping bytes ... */
> for (int bytes = bytes_start; bytes < bytes_end;
> --
> 2.34.1
>
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