userfaultfd/selftests: exercise minor fault handling shmem support

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

Link: https://lkml.kernel.org/r/20210503180737.2487560-11-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Wang Qing <wangqing@vivo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index f78816130c7ff71d63d6450332cae08095cbdcb2..e363bdaff59d4e0efdc1155b287c2119ec5b0ccb 100644 (file)
--- 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;
@@ -1575,6 +1595,7 @@ 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);
        }