On Tue, Apr 26, 2022 at 9:16 AM Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On 4/22/22 3:29 PM, 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@xxxxxxxxxx>
> > ---
> > 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");
>
> This isn't an error as in test failure. This will be a skip because of
> unmet dependencies. Also if this test requires root access, please check
> for that and make that a skip as well.
Testing with the userfaultfd syscall doesn't require any special
permissions (root or otherwise).
But testing with /dev/userfaultfd will require access to that device
node, which is root:root by default, but the system administrator may
have changed this. In general I think this will only fail due to a)
lack of kernel support or b) lack of permissions though, so always
exiting with KSFT_SKIP here seems reasonable. I'll make that change in
v3.
>
> > 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();
> > }
> >
> >
>
> thanks,
> -- Shuah
