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

On Wed, Jun 01, 2022 at 02:09:48PM -0700, Axel Rasmussen wrote:

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@google.com

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();
  

I can understand uffd is a global var, but still AFAICT that's trivially easy to do the return to match the syscall case..

uffd = __userfaultfd_open_dev();

And since at it, it'll be great to make a macro:

#define UFFD_FLAGS (O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)

Thanks,

• 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