[PATCH v5 10/10] userfaultfd/selftests: exercise minor fault handling shmem support

Axel Rasmussen
2021-04-27T22:53:16Z

Enable test_uffdio_minor for test_type == TEST_SHMEM, and modify the
test slightly to pass in / check for the right feature flags.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
tools/testing/selftests/vm/userfaultfd.c | 29 ++++++++++++++++++++----
1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 3fbc69f513dc..a7ecc9993439 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -474,6 +474,7 @@ static void wp_range(int ufd, __u64 start, __u64 len, bool wp)
static void continue_range(int ufd, __u64 start, __u64 len)
{
struct uffdio_continue req;
+ int ret;

req.range.start = start;
req.range.len = len;
@@ -482,6 +483,17 @@ static void continue_range(int ufd, __u64 start, __u64 len)
if (ioctl(ufd, UFFDIO_CONTINUE, &req))
err("UFFDIO_CONTINUE failed for address 0x%" PRIx64,
(uint64_t)start);
+
+ /*
+ * Error handling within the kernel for continue is subtly different
+ * from copy or zeropage, so it may be a source of bugs. Trigger an
+ * error (-EEXIST) on purpose, to verify doing so doesn't cause a BUG.
+ */
+ req.mapped = 0;
+ ret = ioctl(ufd, UFFDIO_CONTINUE, &req);
+ if (ret >= 0 || req.mapped != -EEXIST)
+ err("failed to exercise UFFDIO_CONTINUE error handling, ret=%d, mapped=%" PRId64,
+ ret, (int64_t) req.mapped);
}

static void *locking_thread(void *arg)
@@ -1182,7 +1194,7 @@ static int userfaultfd_minor_test(void)
void *expected_page;
char c;
struct uffd_stats stats = { 0 };
- uint64_t features = UFFD_FEATURE_MINOR_HUGETLBFS;
+ uint64_t req_features, features_out;

if (!test_uffdio_minor)
return 0;
@@ -1190,9 +1202,17 @@ static int userfaultfd_minor_test(void)
printf("testing minor faults: ");
fflush(stdout);

- uffd_test_ctx_init_ext(&features);
- /* If kernel reports the feature isn't supported, skip the test. */
- if (!(features & UFFD_FEATURE_MINOR_HUGETLBFS)) {
+ if (test_type == TEST_HUGETLB)
+ req_features = UFFD_FEATURE_MINOR_HUGETLBFS;
+ else if (test_type == TEST_SHMEM)
+ req_features = UFFD_FEATURE_MINOR_SHMEM;
+ else
+ return 1;
+
+ features_out = req_features;
+ uffd_test_ctx_init_ext(&features_out);
+ /* If kernel reports required features aren't supported, skip test. */
+ if ((features_out & req_features) != req_features) {
printf("skipping test due to lack of feature support\n");
fflush(stdout);
return 0;
@@ -1426,6 +1446,7 @@ static void set_test_type(const char *type)
map_shared = true;
test_type = TEST_SHMEM;
uffd_test_ops = &shmem_uffd_test_ops;
+ test_uffdio_minor = true;
} else {
err("Unknown test type: %s", type);
}
--
2.31.1.498.g6c1eba8ee3d-goog