[PATCH v2 1/3] userfaultfd/selftests: don't rely on GNU extensions for random numbers
From: Axel Rasmussen <axelrasmussen@google.com>
Date: 2021-09-30 21:23:24
Also in:
linux-kselftest, lkml
Subsystem:
kernel selftest framework, the rest · Maintainers:
Shuah Khan, Linus Torvalds
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. Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> --- 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 10ab56c2484a..2a71a91559a7 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c@@ -57,6 +57,7 @@ #include <assert.h> #include <inttypes.h> #include <stdint.h> +#include <sys/random.h> #include "../kselftest.h"
@@ -501,22 +502,10 @@ 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;
@@ -524,15 +513,8 @@ 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;
--
2.33.0.800.g4c38ced690-goog