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Mon, 18 May 2026 06:14:44 -0700 (PDT) From: Milan Tripkovic To: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, kees@kernel.org, andy@kernel.org, linux-hardening@vger.kernel.org, Dusan.Stojkovic@rt-rk.com, Milan Tripkovic Subject: [PATCH v4 2/2] lib/string_kunit: extend benchmarks and unit test to memcmp() Date: Mon, 18 May 2026 15:14:07 +0200 Message-ID: <20260518131407.1026049-3-milant2002@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260518131407.1026049-1-milant2002@gmail.com> References: <20260518131407.1026049-1-milant2002@gmail.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Milan Tripkovic Extend the string benchmarking suite to include memcmp(). Extend the string unit test to include memcmp(). Signed-off-by: Milan Tripkovic --- lib/tests/string_kunit.c | 120 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c index 0819ace5b..48b1fd068 100644 --- a/lib/tests/string_kunit.c +++ b/lib/tests/string_kunit.c @@ -881,6 +881,124 @@ static void string_bench_strrchr(struct kunit *test) STRING_BENCH_BUF(test, buf, len, strrchr, buf, '\0'); } +static void string_test_memcmp(struct kunit *test) +{ + const unsigned int max_offset = 16; + const unsigned int max_len = 32; + const unsigned int buf_size = max_offset + max_len + 32; + u8 *buf1, *buf2; + unsigned int i, j, len, k; + int res; + + buf1 = kunit_kzalloc(test, buf_size, GFP_KERNEL); + buf2 = kunit_kzalloc(test, buf_size, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf1); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf2); + + for (i = 0; i < max_offset; i++) { + for (j = 0; j < max_offset; j++) { + for (len = 0; len <= max_len; len++) { + memset(buf1, 'A', buf_size); + memset(buf2, 'A', buf_size); + KUNIT_EXPECT_EQ_MSG(test, memcmp(buf1 + i, buf2 + j, len), 0, + "Should be equal: i:%u j:%u len:%u", i, j, len); + for (k = 0; k < len; k++) { + memset(buf1, 'A', buf_size); + memset(buf2, 'A', buf_size); + buf2[j + k] = 'B'; + res = memcmp(buf1 + i, buf2 + j, len); + KUNIT_EXPECT_NE_MSG(test, res, 0, + "Should detect difference at k:%u (i:%u j:%u len:%u)", + k, i, j, len); + if (buf1[i + k] < buf2[j + k]) + KUNIT_EXPECT_LT(test, res, 0); + else + KUNIT_EXPECT_GT(test, res, 0); + } + } + } + } +} + +#ifndef STRING_BENCH +#define STRING_BENCH(...) 0 +#endif + +static void do_string_bench_memcmp(struct kunit *test) +{ + char *buf1 = NULL; + char *buf2 = NULL; + const u64 lengths[] = { 1, 7, 8, 16, 32, 64, 128, 512, 1024, 4096}; + const int offsets[] = { 0, 1, 3, 7}; + const u64 max_len = 4096 + 64; + unsigned int w, o, i; + unsigned int off; + u64 len; + char *p1; + char *p2; + u64 iterations; + u64 elapsed; + u64 ns_per_call; + u64 mbps; + u64 j; + + buf1 = vmalloc(max_len); + buf2 = vmalloc(max_len); + + if (!buf1 || !buf2) { + vfree(buf1); + vfree(buf2); + kunit_err(test, "vmalloc failed\n"); + return; + } + + memset(buf1, 'A', max_len); + memset(buf2, 'A', max_len); + + for (w = 0; w < 100000U; w++) + (void)memcmp(buf1, buf2, 4096); + + for (o = 0; o < ARRAY_SIZE(offsets); o++) { + off = offsets[o]; + + for (i = 0; i < ARRAY_SIZE(lengths); i++) { + len = lengths[i]; + p1 = buf1; + p2 = buf2 + off; + iterations = (len < 512) ? 100000ULL : 10000ULL; + + for (j = 0; j < iterations; j++) { + (void)memcmp(p1, p2, len); + barrier(); + } + + elapsed = STRING_BENCH(iterations, memcmp, p1, p2, len); + ns_per_call = div_u64(elapsed, iterations); + mbps = len ? div_u64(iterations * len * (NSEC_PER_SEC / MEGA), elapsed) : 0; + + if (off == 0) { + kunit_info(test, "bench_memcmp_aligned: len=%-4llu: %llu MB/s (%llu ns/call)\n", + len, mbps, ns_per_call); + } else { + kunit_info(test, "bench_memcmp_unaligned(off=%u): len=%-4llu: %llu MB/s (%llu ns/call)\n", + off, len, mbps, ns_per_call); + } + } + } + + vfree(buf1); + vfree(buf2); +} + +static void string_bench_memcmp(struct kunit *test) +{ + if (!IS_ENABLED(CONFIG_STRING_KUNIT_BENCH)) { + kunit_skip(test, "CONFIG_STRING_KUNIT_BENCH not enabled"); + return; + } + do_string_bench_memcmp(test); +} + static struct kunit_case string_test_cases[] = { KUNIT_CASE(string_test_memset16), KUNIT_CASE(string_test_memset32), @@ -910,6 +1028,8 @@ static struct kunit_case string_test_cases[] = { KUNIT_CASE(string_bench_strnlen), KUNIT_CASE(string_bench_strchr), KUNIT_CASE(string_bench_strrchr), + KUNIT_CASE(string_test_memcmp), + KUNIT_CASE_SLOW(string_bench_memcmp), {} }; -- 2.43.0