[PATCH v3 3/6] userfaultfd: selftests: modify selftest to use /dev/userfaultfd

From: Axel Rasmussen
Date: Wed Jun 01 2022 - 17:11:01 EST


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@xxxxxxxxxx>
---
tools/testing/selftests/vm/userfaultfd.c | 37 +++++++++++++++++++++---
1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 0bdfc1955229..1badb5d31bf9 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;
@@ -154,12 +157,14 @@ static void usage(void)
ret, __LINE__); \
} while (0)

-#define err(fmt, ...) \
+#define errexit(exitcode, fmt, ...) \
do { \
_err(fmt, ##__VA_ARGS__); \
- exit(1); \
+ exit(exitcode); \
} while (0)

+#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
+
static void uffd_stats_reset(struct uffd_stats *uffd_stats,
unsigned long n_cpus)
{
@@ -383,13 +388,31 @@ 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");
+ errexit(KSFT_SKIP, "creating userfaultfd failed");
uffd_flags = fcntl(uffd, F_GETFD, NULL);

uffdio_api.api = UFFD_API;
@@ -1691,6 +1714,12 @@ 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();
}

--
2.36.1.255.ge46751e96f-goog