From 1c10e674b35e2c2566b621ceca74064817c249f0 Mon Sep 17 00:00:00 2001 From: Axel Rasmussen Date: Fri, 5 Nov 2021 13:42:07 -0700 Subject: [PATCH] userfaultfd/selftests: don't rely on GNU extensions for random numbers Patch series "Small userfaultfd selftest fixups", v2. This patch (of 3): 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. Link: https://lkml.kernel.org/r/20210930212309.4001967-2-axelrasmussen@google.com Signed-off-by: Axel Rasmussen Reviewed-by: Peter Xu Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 60aa1a4..d2acab4 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" @@ -518,22 +519,10 @@ 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; @@ -541,15 +530,8 @@ 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; -- 2.7.4