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Date: Wed, 28 Apr 2021 18:50:30 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Mike Kravetz <mike.kravetz@...cle.com>, peterx@...hat.com,
Mike Rapoport <rppt@...ux.vnet.ibm.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Andrew Morton <akpm@...ux-foundation.org>,
Jerome Glisse <jglisse@...hat.com>
Subject: [PATCH 6/6] 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.
Signed-off-by: Peter Xu <peterx@...hat.com>
---
tools/testing/selftests/vm/userfaultfd.c | 154 +++++++++++++++++++++++
1 file changed, 154 insertions(+)
diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 6339aeaeeff8b..93eae095b61e6 100644
--- 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();
}
--
2.26.2
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