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Tue, 21 Sep 2021 09:33:31 -0700 (PDT) Date: Tue, 21 Sep 2021 09:33:23 -0700 In-Reply-To: <20210921163323.944352-1-axelrasmussen@google.com> Message-Id: <20210921163323.944352-3-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210921163323.944352-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.33.0.464.g1972c5931b-goog Subject: [PATCH 3/3] userfaultfd/selftests: don't rely on GNU extensions for random numbers From: Axel Rasmussen To: Andrew Morton , Peter Xu , Shuah Khan Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Axel Rasmussen Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E6C9A10DFED1 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Wf+QnXwZ; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf13.hostedemail.com: domain of 3WwlKYQ0KCKYGdKRXGYSaYYKTMUUMRK.IUSROTad-SSQbGIQ.UXM@flex--axelrasmussen.bounces.google.com designates 209.85.222.201 as permitted sender) smtp.mailfrom=3WwlKYQ0KCKYGdKRXGYSaYYKTMUUMRK.IUSROTad-SSQbGIQ.UXM@flex--axelrasmussen.bounces.google.com X-Stat-Signature: 7qdihganz176u539fdjsb85qz1br37yh X-HE-Tag: 1632242011-568897 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000007, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Two arguments for doing this: First, and maybe most importantly, the resulting code is significantly shorter / simpler. Then, we avoid using GNU libc extensions. Why does this matter? It makes testing userfaultfd with the selftest easier e.g. on distros which use something other than glibc (e.g., Alpine, which uses musl); basically, it makes the test more portable. Signed-off-by: Axel Rasmussen --- tools/testing/selftests/vm/userfaultfd.c | 26 ++++-------------------- 1 file changed, 4 insertions(+), 22 deletions(-) diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c index aad5211f5012..9d9f60e71524 100644 --- a/tools/testing/selftests/vm/userfaultfd.c +++ b/tools/testing/selftests/vm/userfaultfd.c @@ -57,6 +57,7 @@ #include #include #include +#include #include "../kselftest.h" @@ -528,22 +529,10 @@ static void continue_range(int ufd, __u64 start, __u64 len) static void *locking_thread(void *arg) { unsigned long cpu = (unsigned long) arg; - struct random_data rand; unsigned long page_nr = *(&(page_nr)); /* uninitialized warning */ - int32_t rand_nr; unsigned long long count; - char randstate[64]; - unsigned int seed; - if (bounces & BOUNCE_RANDOM) { - seed = (unsigned int) time(NULL) - bounces; - if (!(bounces & BOUNCE_RACINGFAULTS)) - seed += cpu; - bzero(&rand, sizeof(rand)); - bzero(&randstate, sizeof(randstate)); - if (initstate_r(seed, randstate, sizeof(randstate), &rand)) - err("initstate_r failed"); - } else { + if (!(bounces & BOUNCE_RANDOM)) { page_nr = -bounces; if (!(bounces & BOUNCE_RACINGFAULTS)) page_nr += cpu * nr_pages_per_cpu; @@ -551,15 +540,8 @@ static void *locking_thread(void *arg) while (!finished) { if (bounces & BOUNCE_RANDOM) { - if (random_r(&rand, &rand_nr)) - err("random_r failed"); - page_nr = rand_nr; - if (sizeof(page_nr) > sizeof(rand_nr)) { - if (random_r(&rand, &rand_nr)) - err("random_r failed"); - page_nr |= (((unsigned long) rand_nr) << 16) << - 16; - } + if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr)) + err("getrandom failed"); } else page_nr += 1; page_nr %= nr_pages; -- 2.33.0.464.g1972c5931b-goog