Skip userfaultfd selftest if the syscall isn't available

Userfaultfd kernel feature was backported into android kernel since
android12-5.4. Subsequently, the userfaultfd selftest was enabled in
VTS. However, sometimes when the test is run on older kernel, it leads
to failures.

This CL makes the test return KSFT_PASS, which is interpreted as
'passed', if userfaultfd syscall isn't available. Eventually, when VTS
starts supporting 'skipped' tests, we should change the test to return
KSFT_SKIP instead.

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Test: atest vts_linux_kselftest_arm_64:vm_userfaultfd_shmem_arm_64
Bug: 206503000
Change-Id: I17579e1c0a14330539187edadd0be91b35398029
2 files changed