Commit eb3b2e00 authored by Peter Xu's avatar Peter Xu Committed by Linus Torvalds
Browse files

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: default avatarPeter 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fb8e37f3

tools/testing/selftests/vm/userfaultfd.c

+154 −0
Original line number Diff line number Diff line
@@ -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();

}