linux-kernel - [PATCH v2 3/6] userfaultfd: selftests: modify selftest to use /dev/userfaultfd

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Date:   Fri, 22 Apr 2022 14:29:42 -0700
From:   Axel Rasmussen <axelrasmussen@...gle.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Charan Teja Reddy <charante@...eaurora.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Dmitry V . Levin" <ldv@...linux.org>,
        Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>,
        Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
        Peter Xu <peterx@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, zhangyi <yi.zhang@...wei.com>
Cc:     Axel Rasmussen <axelrasmussen@...gle.com>,
        linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH v2 3/6] userfaultfd: selftests: modify selftest to use /dev/userfaultfd

We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
working into the future, so just run the test twice, using each
interface.

Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 31 ++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 92a4516f8f0d..12ae742a9981 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -77,6 +77,9 @@ static int bounces;
 #define TEST_SHMEM	3
 static int test_type;
 
+/* test using /dev/userfaultfd, instead of userfaultfd(2) */
+static bool test_dev_userfaultfd;
+
 /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
 #define ALARM_INTERVAL_SECS 10
 static volatile bool test_uffdio_copy_eexist = true;
@@ -383,13 +386,31 @@ static void assert_expected_ioctls_present(uint64_t mode, uint64_t ioctls)
 	}
 }
 
+static void __userfaultfd_open_dev(void)
+{
+	int fd;
+
+	uffd = -1;
+	fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return;
+
+	uffd = ioctl(fd, USERFAULTFD_IOC_NEW,
+		     O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+	close(fd);
+}
+
 static void userfaultfd_open(uint64_t *features)
 {
 	struct uffdio_api uffdio_api;
 
-	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+	if (test_dev_userfaultfd)
+		__userfaultfd_open_dev();
+	else
+		uffd = syscall(__NR_userfaultfd,
+			       O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
 	if (uffd < 0)
-		err("userfaultfd syscall not available in this kernel");
+		err("creating userfaultfd failed");
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);
 
 	uffdio_api.api = UFFD_API;
@@ -1698,6 +1719,12 @@ int main(int argc, char **argv)
 	}
 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
 	       nr_pages, nr_pages_per_cpu);
+
+	test_dev_userfaultfd = false;
+	if (userfaultfd_stress())
+		return 1;
+
+	test_dev_userfaultfd = true;
 	return userfaultfd_stress();
 }
 
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog