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userfaultfd/selftests: add pagemap uffd-wp test

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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>
This commit is contained in:
Peter Xu 2021-06-30 18:49:13 -07:00 committed by Linus Torvalds
parent fb8e37f35a
commit eb3b2e0039
1 changed files with 154 additions and 0 deletions
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154
tools/testing/selftests/vm/userfaultfd.c
View File

@ -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();
}