userfaultfd/selftests: add pagemap uffd-wp test

Add one anonymous specific test to start using pagemap.  With pagemap
support, we can directly read the uffd-wp bit from pgtable without
triggering any fault, so it's easier to do sanity checks in unit tests.

Meanwhile this test also leverages the newly introduced MADV_PAGEOUT
madvise function to test swap ptes with uffd-wp bit set, and across
fork()s.

Link: https://lkml.kernel.org/r/20210428225030.9708-7-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.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 6339aeaeeff8b1966ed8790afee23d6d50c0dfa0..93eae095b61e60ef7892a884fbd095636d2845cf 100644 (file)
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -1170,6 +1170,144 @@ static int userfaultfd_minor_test(void)
        return stats.missing_faults != 0 || stats.minor_faults != nr_pages;
 }
 
+#define BIT_ULL(nr)                   (1ULL << (nr))
+#define PM_SOFT_DIRTY                 BIT_ULL(55)
+#define PM_MMAP_EXCLUSIVE             BIT_ULL(56)
+#define PM_UFFD_WP                    BIT_ULL(57)
+#define PM_FILE                       BIT_ULL(61)
+#define PM_SWAP                       BIT_ULL(62)
+#define PM_PRESENT                    BIT_ULL(63)
+
+static int pagemap_open(void)
+{
+       int fd = open("/proc/self/pagemap", O_RDONLY);
+
+       if (fd < 0)
+               err("open pagemap");
+
+       return fd;
+}
+
+static uint64_t pagemap_read_vaddr(int fd, void *vaddr)
+{
+       uint64_t value;
+       int ret;
+
+       ret = pread(fd, &value, sizeof(uint64_t),
+                   ((uint64_t)vaddr >> 12) * sizeof(uint64_t));
+       if (ret != sizeof(uint64_t))
+               err("pread() on pagemap failed");
+
+       return value;
+}
+
+/* This macro let __LINE__ works in err() */
+#define  pagemap_check_wp(value, wp) do {                              \
+               if (!!(value & PM_UFFD_WP) != wp)                       \
+                       err("pagemap uffd-wp bit error: 0x%"PRIx64, value); \
+       } while (0)
+
+static int pagemap_test_fork(bool present)
+{
+       pid_t child = fork();
+       uint64_t value;
+       int fd, result;
+
+       if (!child) {
+               /* Open the pagemap fd of the child itself */
+               fd = pagemap_open();
+               value = pagemap_read_vaddr(fd, area_dst);
+               /*
+                * After fork() uffd-wp bit should be gone as long as we're
+                * without UFFD_FEATURE_EVENT_FORK
+                */
+               pagemap_check_wp(value, false);
+               /* Succeed */
+               exit(0);
+       }
+       waitpid(child, &result, 0);
+       return result;
+}
+
+static void userfaultfd_pagemap_test(unsigned int test_pgsize)
+{
+       struct uffdio_register uffdio_register;
+       int pagemap_fd;
+       uint64_t value;
+
+       /* Pagemap tests uffd-wp only */
+       if (!test_uffdio_wp)
+               return;
+
+       /* Not enough memory to test this page size */
+       if (test_pgsize > nr_pages * page_size)
+               return;
+
+       printf("testing uffd-wp with pagemap (pgsize=%u): ", test_pgsize);
+       /* Flush so it doesn't flush twice in parent/child later */
+       fflush(stdout);
+
+       uffd_test_ops->release_pages(area_dst);
+
+       if (test_pgsize > page_size) {
+               /* This is a thp test */
+               if (madvise(area_dst, nr_pages * page_size, MADV_HUGEPAGE))
+                       err("madvise(MADV_HUGEPAGE) failed");
+       } else if (test_pgsize == page_size) {
+               /* This is normal page test; force no thp */
+               if (madvise(area_dst, nr_pages * page_size, MADV_NOHUGEPAGE))
+                       err("madvise(MADV_NOHUGEPAGE) failed");
+       }
+
+       if (userfaultfd_open(0))
+               err("userfaultfd_open");
+
+       uffdio_register.range.start = (unsigned long) area_dst;
+       uffdio_register.range.len = nr_pages * page_size;
+       uffdio_register.mode = UFFDIO_REGISTER_MODE_WP;
+       if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+               err("register failed");
+
+       pagemap_fd = pagemap_open();
+
+       /* Touch the page */
+       *area_dst = 1;
+       wp_range(uffd, (uint64_t)area_dst, test_pgsize, true);
+       value = pagemap_read_vaddr(pagemap_fd, area_dst);
+       pagemap_check_wp(value, true);
+       /* Make sure uffd-wp bit dropped when fork */
+       if (pagemap_test_fork(true))
+               err("Detected stall uffd-wp bit in child");
+
+       /* Exclusive required or PAGEOUT won't work */
+       if (!(value & PM_MMAP_EXCLUSIVE))
+               err("multiple mapping detected: 0x%"PRIx64, value);
+
+       if (madvise(area_dst, test_pgsize, MADV_PAGEOUT))
+               err("madvise(MADV_PAGEOUT) failed");
+
+       /* Uffd-wp should persist even swapped out */
+       value = pagemap_read_vaddr(pagemap_fd, area_dst);
+       pagemap_check_wp(value, true);
+       /* Make sure uffd-wp bit dropped when fork */
+       if (pagemap_test_fork(false))
+               err("Detected stall uffd-wp bit in child");
+
+       /* Unprotect; this tests swap pte modifications */
+       wp_range(uffd, (uint64_t)area_dst, page_size, false);
+       value = pagemap_read_vaddr(pagemap_fd, area_dst);
+       pagemap_check_wp(value, false);
+
+       /* Fault in the page from disk */
+       *area_dst = 2;
+       value = pagemap_read_vaddr(pagemap_fd, area_dst);
+       pagemap_check_wp(value, false);
+
+       close(pagemap_fd);
+       close(uffd);
+       printf("done\n");
+}
+
 static int userfaultfd_stress(void)
 {
        void *area;
@@ -1341,6 +1479,22 @@ static int userfaultfd_stress(void)
        }
 
        close(uffd);
+
+       if (test_type == TEST_ANON) {
+               /*
+                * shmem/hugetlb won't be able to run since they have different
+                * behavior on fork() (file-backed memory normally drops ptes
+                * directly when fork), meanwhile the pagemap test will verify
+                * pgtable entry of fork()ed child.
+                */
+               userfaultfd_pagemap_test(page_size);
+               /*
+                * Hard-code for x86_64 for now for 2M THP, as x86_64 is
+                * currently the only one that supports uffd-wp
+                */
+               userfaultfd_pagemap_test(page_size * 512);
+       }
+
        return userfaultfd_zeropage_test() || userfaultfd_sig_test()
                || userfaultfd_events_test() || userfaultfd_minor_test();
 }