userfaultfd/selftests: create alias mappings in the shmem test

Previously, we just allocated two shm areas: area_src and area_dst.  With
this commit, change this so we also allocate area_src_alias, and
area_dst_alias.

area_*_alias and area_* (respectively) point to the same underlying
physical pages, but are different VMAs.  In a future commit in this
series, we'll leverage this setup to exercise minor fault handling support
for shmem, just like we do in the hugetlb_shared test.

Link: https://lkml.kernel.org/r/20210503180737.2487560-9-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 7495834180cecf38bb242a82c904c4ed542f34be..1f8e2bee8f8da9ce1178861cf03674e605002c6d 100644 (file)
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -278,13 +278,29 @@ static void shmem_release_pages(char *rel_area)
 
 static void shmem_allocate_area(void **alloc_area)
 {
-       unsigned long offset =
-               alloc_area == (void **)&area_src ? 0 : nr_pages * page_size;
+       void *area_alias = NULL;
+       bool is_src = alloc_area == (void **)&area_src;
+       unsigned long offset = is_src ? 0 : nr_pages * page_size;
 
        *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                           MAP_SHARED, shm_fd, offset);
        if (*alloc_area == MAP_FAILED)
                err("mmap of memfd failed");
+
+       area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
+                         MAP_SHARED, shm_fd, offset);
+       if (area_alias == MAP_FAILED)
+               err("mmap of memfd alias failed");
+
+       if (is_src)
+               area_src_alias = area_alias;
+       else
+               area_dst_alias = area_alias;
+}
+
+static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
+{
+       *start = (unsigned long)area_dst_alias + offset;
 }
 
 struct uffd_test_ops {
@@ -314,7 +330,7 @@ static struct uffd_test_ops shmem_uffd_test_ops = {
        .expected_ioctls = SHMEM_EXPECTED_IOCTLS,
        .allocate_area  = shmem_allocate_area,
        .release_pages  = shmem_release_pages,
-       .alias_mapping = noop_alias_mapping,
+       .alias_mapping = shmem_alias_mapping,
 };
 
 static struct uffd_test_ops hugetlb_uffd_test_ops = {