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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Fri, 7 Oct 2022 13:44:19 -0700
Message-ID: <CAKwvOdkhAQx3gxbRFfd3jU0G9Dox+0McDyOcr=174Mv4c7Y8rA@mail.gmail.com>
Subject: Re: [PATCH] overflow: Refactor test skips for Clang-specific issues
To:     Kees Cook <keescook@chromium.org>
Cc:     Nathan Chancellor <nathan@kernel.org>, Tom Rix <trix@redhat.com>,
        Daniel Latypov <dlatypov@google.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>,
        llvm@lists.linux.dev, Vitor Massaru Iha <vitor@massaru.org>,
        kernel test robot <lkp@intel.com>,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
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On Thu, Oct 6, 2022 at 4:00 PM Kees Cook <keescook@chromium.org> wrote:
>
> Convert test exclusion into test skipping. This brings the logic for
> why a test is being skipped into the test itself, instead of having to
> spread ifdefs around the code. This will make cleanup easier as minimum
> tests get raised. Drop __maybe_unused so missed tests will be noticed
> again and clean up whitespace.
>
> For example, clang-11 on i386:
>
> [15:52:32] ================== overflow (18 subtests) ==================
> [15:52:32] [PASSED] u8_u8__u8_overflow_test
> [15:52:32] [PASSED] s8_s8__s8_overflow_test
> [15:52:32] [PASSED] u16_u16__u16_overflow_test
> [15:52:32] [PASSED] s16_s16__s16_overflow_test
> [15:52:32] [PASSED] u32_u32__u32_overflow_test
> [15:52:32] [PASSED] s32_s32__s32_overflow_test
> [15:52:32] [SKIPPED] u64_u64__u64_overflow_test
> [15:52:32] [SKIPPED] s64_s64__s64_overflow_test
> [15:52:32] [SKIPPED] u32_u32__int_overflow_test
> [15:52:32] [PASSED] u32_u32__u8_overflow_test
> [15:52:32] [PASSED] u8_u8__int_overflow_test
> [15:52:32] [PASSED] int_int__u8_overflow_test
> [15:52:32] [PASSED] shift_sane_test
> [15:52:32] [PASSED] shift_overflow_test
> [15:52:32] [PASSED] shift_truncate_test
> [15:52:32] [PASSED] shift_nonsense_test
> [15:52:32] [PASSED] overflow_allocation_test
> [15:52:32] [PASSED] overflow_size_helpers_test
> [15:52:32] ==================== [PASSED] overflow =====================
> [15:52:32] ============================================================
> [15:52:32] Testing complete. Ran 18 tests: passed: 15, skipped: 3
>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Tom Rix <trix@redhat.com>
> Cc: Daniel Latypov <dlatypov@google.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> Cc: llvm@lists.linux.dev
> Signed-off-by: Kees Cook <keescook@chromium.org>

Thanks; much nicer!

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

I ran the following tests:
$ ./tools/testing/kunit/kunit.py run --arch=i386 --make_options LLVM=1 overflow
$ ./tools/testing/kunit/kunit.py run --arch=arm --make_options LLVM=1 overflow
$ make LLVM=1 -j128 defconfig
$ ./scripts/config -e KUNIT -e KUNIT_ALL_TESTS
$ make LLVM=1 -j128 olddefconfig lib/overflow_kunit.o W=1

> ---
>  lib/overflow_kunit.c | 52 +++++++++++++++++++++++++++++---------------
>  1 file changed, 35 insertions(+), 17 deletions(-)
>
> diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c
> index 2914c9d36b0f..3062b33e4bb1 100644
> --- a/lib/overflow_kunit.c
> +++ b/lib/overflow_kunit.c
> @@ -16,6 +16,34 @@
>  #include <linux/types.h>
>  #include <linux/vmalloc.h>
>
> +#define SKIP(cond, reason)             do {                    \
> +       if (cond) {                                             \
> +               kunit_skip(test, reason);                       \
> +               return;                                         \
> +       }                                                       \
> +} while (0)
> +
> +/*
> + * Clang 11 and earlier generate unwanted libcalls for signed output
> + * on unsigned input.
> + */
> +#if defined(CONFIG_CC_IS_CLANG) && __clang_major__ <= 11
> +# define SKIP_SIGN_MISMATCH(t) SKIP(t, "Clang 11 unwanted libcalls")
> +#else
> +# define SKIP_SIGN_MISMATCH(t) do { } while (0)
> +#endif
> +
> +/*
> + * Clang 13 and earlier generate unwanted libcalls for 64-bit tests on
> + * 32-bit hosts.
> + */
> +#if defined(CONFIG_CC_IS_CLANG) && __clang_major__ <= 13 &&    \
> +    BITS_PER_LONG != 64
> +# define SKIP_64_ON_32(t)      SKIP(t, "Clang 13 unwanted libcalls")
> +#else
> +# define SKIP_64_ON_32(t)      do { } while (0)
> +#endif
> +
>  #define DEFINE_TEST_ARRAY_TYPED(t1, t2, t)                     \
>         static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \
>                 t1 a;                                           \
> @@ -94,7 +122,6 @@ DEFINE_TEST_ARRAY(u32) = {
>         {-4U, 5U, 1U, -9U, -20U, true, false, true},
>  };
>
> -#if BITS_PER_LONG == 64
>  DEFINE_TEST_ARRAY(u64) = {
>         {0, 0, 0, 0, 0, false, false, false},
>         {1, 1, 2, 0, 1, false, false, false},
> @@ -118,7 +145,6 @@ DEFINE_TEST_ARRAY(u64) = {
>          false, true, false},
>         {-15ULL, 10ULL, -5ULL, -25ULL, -150ULL, false, false, true},
>  };
> -#endif
>
>  DEFINE_TEST_ARRAY(s8) = {
>         {0, 0, 0, 0, 0, false, false, false},
> @@ -194,7 +220,6 @@ DEFINE_TEST_ARRAY(s32) = {
>         {S32_MAX, S32_MAX, -2, 0, 1, true, false, true},
>  };
>
> -#if BITS_PER_LONG == 64
>  DEFINE_TEST_ARRAY(s64) = {
>         {0, 0, 0, 0, 0, false, false, false},
>
> @@ -223,7 +248,6 @@ DEFINE_TEST_ARRAY(s64) = {
>         {-128, -1, -129, -127, 128, false, false, false},
>         {0, -S64_MAX, -S64_MAX, S64_MAX, 0, false, false, false},
>  };
> -#endif
>
>  #define check_one_op(t, fmt, op, sym, a, b, r, of) do {                        \
>         int _a_orig = a, _a_bump = a + 1;                               \
> @@ -246,7 +270,7 @@ DEFINE_TEST_ARRAY(s64) = {
>
>  #define DEFINE_TEST_FUNC_TYPED(n, t, fmt)                              \
>  static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \
> -{                                                                      \
> +{                                                                      \
>         check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of);    \
>         check_one_op(t, fmt, add, "+", p->b, p->a, p->sum, p->s_of);    \
>         check_one_op(t, fmt, sub, "-", p->a, p->b, p->diff, p->d_of);   \
> @@ -254,10 +278,15 @@ static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \
>         check_one_op(t, fmt, mul, "*", p->b, p->a, p->prod, p->p_of);   \
>  }                                                                      \
>                                                                         \
> -__maybe_unused                                                         \
>  static void n ## _overflow_test(struct kunit *test) {                  \
>         unsigned i;                                                     \
>                                                                         \
> +       SKIP_64_ON_32(__same_type(t, u64));                             \
> +       SKIP_64_ON_32(__same_type(t, s64));                             \
> +       SKIP_SIGN_MISMATCH(__same_type(n ## _tests[0].a, u32) &&        \
> +                          __same_type(n ## _tests[0].b, u32) &&        \
> +                          __same_type(n ## _tests[0].sum, int));       \
> +                                                                       \
>         for (i = 0; i < ARRAY_SIZE(n ## _tests); ++i)                   \
>                 do_test_ ## n(test, &n ## _tests[i]);                   \
>         kunit_info(test, "%zu %s arithmetic tests finished\n",          \
> @@ -273,10 +302,8 @@ DEFINE_TEST_FUNC(u16, "%d");
>  DEFINE_TEST_FUNC(s16, "%d");
>  DEFINE_TEST_FUNC(u32, "%u");
>  DEFINE_TEST_FUNC(s32, "%d");
> -#if BITS_PER_LONG == 64
>  DEFINE_TEST_FUNC(u64, "%llu");
>  DEFINE_TEST_FUNC(s64, "%lld");
> -#endif
>
>  DEFINE_TEST_ARRAY_TYPED(u32, u32, u8) = {
>         {0, 0, 0, 0, 0, false, false, false},
> @@ -716,18 +743,9 @@ static struct kunit_case overflow_test_cases[] = {
>         KUNIT_CASE(s16_s16__s16_overflow_test),
>         KUNIT_CASE(u32_u32__u32_overflow_test),
>         KUNIT_CASE(s32_s32__s32_overflow_test),
> -/* Clang 13 and earlier generate unwanted libcalls on 32-bit. */
> -#if BITS_PER_LONG == 64
>         KUNIT_CASE(u64_u64__u64_overflow_test),
>         KUNIT_CASE(s64_s64__s64_overflow_test),
> -#endif
> -/*
> - * Clang 11 and earlier generate unwanted libcalls for signed output, unsigned
> - * input.
> - */
> -#if !(defined(CONFIG_CC_IS_CLANG) && __clang_major__ <= 11)
>         KUNIT_CASE(u32_u32__int_overflow_test),
> -#endif
>         KUNIT_CASE(u32_u32__u8_overflow_test),
>         KUNIT_CASE(u8_u8__int_overflow_test),
>         KUNIT_CASE(int_int__u8_overflow_test),
> --
> 2.34.1
>


-- 
Thanks,
~Nick Desaulniers