Prefer this new interface, but if using it fails for any reason just
fall back to using userfaultfd(2) as before.
Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
---
tools/testing/selftests/vm/userfaultfd.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 92a4516f8f0d..a50c430f036c 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -383,13 +383,32 @@ 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);
+ __userfaultfd_open_dev();
+ if (uffd < 0) {
+ printf("/dev/userfaultfd failed, fallback to userfaultfd(2)\n");
+ uffd = syscall(__NR_userfaultfd,
+ O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+ }
if (uffd < 0)
- err("userfaultfd syscall not available in this kernel");
+ err("userfaultfd syscall failed");
uffd_flags = fcntl(uffd, F_GETFD, NULL);
uffdio_api.api = UFFD_API;
--
2.35.1.1178.g4f1659d476-goog
