diff mbox series

[3/3] userfaultfd/selftests: don't rely on GNU extensions for random numbers

Message ID 20210921163323.944352-3-axelrasmussen@google.com (mailing list archive)
State New
Headers show
Series [1/3] userfaultfd/selftests: fix feature support detection | expand

Commit Message

Axel Rasmussen Sept. 21, 2021, 4:33 p.m. UTC 
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 <axelrasmussen@google.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 26 ++++--------------------
 1 file changed, 4 insertions(+), 22 deletions(-)

Comments

Peter Xu Sept. 21, 2021, 6:03 p.m. UTC | #1 
On Tue, Sep 21, 2021 at 09:33:23AM -0700, Axel Rasmussen wrote:
> 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 <axelrasmussen@google.com>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

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 <assert.h>
 #include <inttypes.h>
 #include <stdint.h>
+#include <sys/random.h>
 
 #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;