From cff294582798dce6ca2b2d08051f563c0f7a09c8 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Mon, 17 Apr 2023 15:53:15 -0400 Subject: [PATCH] selftests/mm: extend and rename uffd pagemap test MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Extend it to all types of mem, meanwhile add one parallel test when EVENT_FORK is enabled, where uffd-wp bits should be persisted rather than dropped. Since at it, rename the test to "wp-fork" to better show what it means. Making the new test called "wp-fork-with-event". Before: Testing pagemap on anon... done After: Testing wp-fork on anon... done Testing wp-fork on shmem... done Testing wp-fork on shmem-private... done Testing wp-fork on hugetlb... done Testing wp-fork on hugetlb-private... done Testing wp-fork-with-event on anon... done Testing wp-fork-with-event on shmem... done Testing wp-fork-with-event on shmem-private... done Testing wp-fork-with-event on hugetlb... done Testing wp-fork-with-event on hugetlb-private... done Link: https://lkml.kernel.org/r/20230417195317.898696-5-peterx@redhat.com Signed-off-by: Peter Xu Cc: Andrea Arcangeli Cc: Axel Rasmussen Cc: David Hildenbrand Cc: Mika Penttilä Cc: Mike Kravetz Cc: Nadav Amit Signed-off-by: Andrew Morton --- tools/testing/selftests/mm/uffd-unit-tests.c | 130 +++++++++++++++---- 1 file changed, 106 insertions(+), 24 deletions(-) diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index 452ca05a829d..739fc4d30342 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -227,25 +227,65 @@ static int pagemap_open(void) err("pagemap uffd-wp bit error: 0x%"PRIx64, value); \ } while (0) -static int pagemap_test_fork(bool present) +typedef struct { + int parent_uffd, child_uffd; +} fork_event_args; + +static void *fork_event_consumer(void *data) { - pid_t child = fork(); + fork_event_args *args = data; + struct uffd_msg msg = { 0 }; + + /* Read until a full msg received */ + while (uffd_read_msg(args->parent_uffd, &msg)); + + if (msg.event != UFFD_EVENT_FORK) + err("wrong message: %u\n", msg.event); + + /* Just to be properly freed later */ + args->child_uffd = msg.arg.fork.ufd; + return NULL; +} + +static int pagemap_test_fork(int uffd, bool with_event) +{ + fork_event_args args = { .parent_uffd = uffd, .child_uffd = -1 }; + pthread_t thread; + pid_t child; uint64_t value; int fd, result; + /* Prepare a thread to resolve EVENT_FORK */ + if (with_event) { + if (pthread_create(&thread, NULL, fork_event_consumer, &args)) + err("pthread_create()"); + } + + child = fork(); if (!child) { /* Open the pagemap fd of the child itself */ fd = pagemap_open(); value = pagemap_get_entry(fd, area_dst); /* - * After fork() uffd-wp bit should be gone as long as we're - * without UFFD_FEATURE_EVENT_FORK + * After fork(), we should handle uffd-wp bit differently: + * + * (1) when with EVENT_FORK, it should persist + * (2) when without EVENT_FORK, it should be dropped */ - pagemap_check_wp(value, false); + pagemap_check_wp(value, with_event); /* Succeed */ exit(0); } waitpid(child, &result, 0); + + if (with_event) { + if (pthread_join(thread, NULL)) + err("pthread_join()"); + if (args.child_uffd < 0) + err("Didn't receive child uffd"); + close(args.child_uffd); + } + return result; } @@ -295,7 +335,8 @@ static void uffd_wp_unpopulated_test(uffd_test_args_t *args) uffd_test_pass(); } -static void uffd_pagemap_test(uffd_test_args_t *args) +static void uffd_wp_fork_test_common(uffd_test_args_t *args, + bool with_event) { int pagemap_fd; uint64_t value; @@ -311,23 +352,42 @@ static void uffd_pagemap_test(uffd_test_args_t *args) wp_range(uffd, (uint64_t)area_dst, page_size, true); value = pagemap_get_entry(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"); + if (pagemap_test_fork(uffd, with_event)) { + uffd_test_fail("Detected %s uffd-wp bit in child in present pte", + with_event ? "missing" : "stall"); + goto out; + } - /* Exclusive required or PAGEOUT won't work */ - if (!(value & PM_MMAP_EXCLUSIVE)) - err("multiple mapping detected: 0x%"PRIx64, value); - - if (madvise(area_dst, page_size, MADV_PAGEOUT)) - err("madvise(MADV_PAGEOUT) failed"); + /* + * This is an attempt for zapping the pgtable so as to test the + * markers. + * + * For private mappings, PAGEOUT will only work on exclusive ptes + * (PM_MMAP_EXCLUSIVE) which we should satisfy. + * + * For shared, PAGEOUT may not work. Use DONTNEED instead which + * plays a similar role of zapping (rather than freeing the page) + * to expose pte markers. + */ + if (args->mem_type->shared) { + if (madvise(area_dst, page_size, MADV_DONTNEED)) + err("MADV_DONTNEED"); + } else { + /* + * NOTE: ignore retval because private-hugetlb doesn't yet + * support swapping, so it could fail. + */ + madvise(area_dst, page_size, MADV_PAGEOUT); + } /* Uffd-wp should persist even swapped out */ value = pagemap_get_entry(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"); + if (pagemap_test_fork(uffd, with_event)) { + uffd_test_fail("Detected %s uffd-wp bit in child in zapped pte", + with_event ? "missing" : "stall"); + goto out; + } /* Unprotect; this tests swap pte modifications */ wp_range(uffd, (uint64_t)area_dst, page_size, false); @@ -338,9 +398,21 @@ static void uffd_pagemap_test(uffd_test_args_t *args) *area_dst = 2; value = pagemap_get_entry(pagemap_fd, area_dst); pagemap_check_wp(value, false); - - close(pagemap_fd); uffd_test_pass(); +out: + if (uffd_unregister(uffd, area_dst, nr_pages * page_size)) + err("unregister failed"); + close(pagemap_fd); +} + +static void uffd_wp_fork_test(uffd_test_args_t *args) +{ + uffd_wp_fork_test_common(args, false); +} + +static void uffd_wp_fork_with_event_test(uffd_test_args_t *args) +{ + uffd_wp_fork_test_common(args, true); } static void check_memory_contents(char *p) @@ -836,10 +908,20 @@ uffd_test_case_t uffd_tests[] = { .uffd_feature_required = 0, }, { - .name = "pagemap", - .uffd_fn = uffd_pagemap_test, - .mem_targets = MEM_ANON, - .uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP, + .name = "wp-fork", + .uffd_fn = uffd_wp_fork_test, + .mem_targets = MEM_ALL, + .uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP | + UFFD_FEATURE_WP_HUGETLBFS_SHMEM, + }, + { + .name = "wp-fork-with-event", + .uffd_fn = uffd_wp_fork_with_event_test, + .mem_targets = MEM_ALL, + .uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP | + UFFD_FEATURE_WP_HUGETLBFS_SHMEM | + /* when set, child process should inherit uffd-wp bits */ + UFFD_FEATURE_EVENT_FORK, }, { .name = "wp-unpopulated",